Version abc71001

50 files changed, 19472 insertions, 0 deletions

diff --git a/src/sat/bsat/module.make b/src/sat/bsat/module.make
new file mode 100644
index 00000000..563c8dfc
--- /dev/null
+++ b/src/sat/bsat/module.make
@@ -0,0 +1,6 @@
+SRC +=  src/sat/bsat/satMem.c \
+    src/sat/bsat/satInter.c \
+    src/sat/bsat/satSolver.c \
+    src/sat/bsat/satStore.c \
+    src/sat/bsat/satTrace.c \
+    src/sat/bsat/satUtil.c
diff --git a/src/sat/bsat/satInter.c b/src/sat/bsat/satInter.c
new file mode 100644
index 00000000..8759aa09
--- /dev/null
+++ b/src/sat/bsat/satInter.c
@@ -0,0 +1,991 @@
+/**CFile****************************************************************
+
+  FileName    [satInter.c]
+
+  SystemName  [ABC: Logic synthesis and verification system.]
+
+  PackageName [SAT sat_solver.]
+
+  Synopsis    [Interpolation package.]
+
+  Author      [Alan Mishchenko]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - June 20, 2005.]
+
+  Revision    [$Id: satInter.c,v 1.4 2005/09/16 22:55:03 casem Exp $]
+
+***********************************************************************/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <time.h>
+#include "satStore.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+// variable assignments 
+static const lit    LIT_UNDEF = 0xffffffff;
+
+// interpolation manager
+struct Int_Man_t_
+{
+    // clauses of the problems
+    Sto_Man_t *     pCnf;         // the set of CNF clauses for A and B
+    // various parameters
+    int             fVerbose;     // verbosiness flag
+    int             fProofVerif;  // verifies the proof
+    int             fProofWrite;  // writes the proof file
+    int             nVarsAlloc;   // the allocated size of var arrays
+    int             nClosAlloc;   // the allocated size of clause arrays
+    // internal BCP
+    int             nRootSize;    // the number of root level assignments
+    int             nTrailSize;   // the number of assignments made 
+    lit *           pTrail;       // chronological order of assignments (size nVars)
+    lit *           pAssigns;     // assignments by variable (size nVars) 
+    char *          pSeens;       // temporary mark (size nVars)
+    Sto_Cls_t **    pReasons;     // reasons for each assignment (size nVars)          
+    Sto_Cls_t **    pWatches;     // watched clauses for each literal (size 2*nVars)          
+    // interpolation data
+    int             nVarsAB;      // the number of global variables
+    char *          pVarTypes;    // variable type (size nVars) [1=A, 0=B, <0=AB]
+    unsigned *      pInters;      // storage for interpolants as truth tables (size nClauses)
+    int             nIntersAlloc; // the allocated size of truth table array
+    int             nWords;       // the number of words in the truth table
+    // proof recording
+    int             Counter;      // counter of resolved clauses
+    int *           pProofNums;   // the proof numbers for each clause (size nClauses)
+    FILE *          pFile;        // the file for proof recording
+    // internal verification
+    lit *           pResLits;     // the literals of the resolvent   
+    int             nResLits;     // the number of literals of the resolvent
+    int             nResLitsAlloc;// the number of literals of the resolvent
+    // runtime stats
+    int             timeBcp;      // the runtime for BCP
+    int             timeTrace;    // the runtime of trace construction
+    int             timeTotal;    // the total runtime of interpolation
+};
+
+// procedure to get hold of the clauses' truth table 
+static inline unsigned * Int_ManTruthRead( Int_Man_t * p, Sto_Cls_t * pCls )          { return p->pInters + pCls->Id * p->nWords;                 }
+static inline void       Int_ManTruthClear( unsigned * p, int nWords )                { int i; for ( i = nWords - 1; i >= 0; i-- ) p[i]  =  0;    }
+static inline void       Int_ManTruthFill( unsigned * p, int nWords )                 { int i; for ( i = nWords - 1; i >= 0; i-- ) p[i]  = ~0;    }
+static inline void       Int_ManTruthCopy( unsigned * p, unsigned * q, int nWords )   { int i; for ( i = nWords - 1; i >= 0; i-- ) p[i]  =  q[i]; }
+static inline void       Int_ManTruthAnd( unsigned * p, unsigned * q, int nWords )    { int i; for ( i = nWords - 1; i >= 0; i-- ) p[i] &=  q[i]; }
+static inline void       Int_ManTruthOr( unsigned * p, unsigned * q, int nWords )     { int i; for ( i = nWords - 1; i >= 0; i-- ) p[i] |=  q[i]; }
+static inline void       Int_ManTruthOrNot( unsigned * p, unsigned * q, int nWords )  { int i; for ( i = nWords - 1; i >= 0; i-- ) p[i] |= ~q[i]; }
+
+// reading/writing the proof for a clause
+static inline int        Int_ManProofGet( Int_Man_t * p, Sto_Cls_t * pCls )           { return p->pProofNums[pCls->Id];  }
+static inline void       Int_ManProofSet( Int_Man_t * p, Sto_Cls_t * pCls, int n )    { p->pProofNums[pCls->Id] = n;     }
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Allocate proof manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Int_Man_t * Int_ManAlloc( int nVarsAlloc )
+{
+    Int_Man_t * p;
+    // allocate the manager
+    p = (Int_Man_t *)malloc( sizeof(Int_Man_t) );
+    memset( p, 0, sizeof(Int_Man_t) );
+    // verification
+    p->nResLitsAlloc = (1<<16);
+    p->pResLits = malloc( sizeof(lit) * p->nResLitsAlloc );
+    // parameters
+    p->fProofWrite = 0;
+    p->fProofVerif = 1;
+    return p;    
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Count common variables in the clauses of A and B.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Int_ManGlobalVars( Int_Man_t * p )
+{
+    Sto_Cls_t * pClause;
+    int Var, nVarsAB, v;
+
+    // mark the variable encountered in the clauses of A
+    Sto_ManForEachClauseRoot( p->pCnf, pClause )
+    {
+        if ( !pClause->fA )
+            break;
+        for ( v = 0; v < (int)pClause->nLits; v++ )
+            p->pVarTypes[lit_var(pClause->pLits[v])] = 1;
+    }
+
+    // check variables that appear in clauses of B
+    nVarsAB = 0;
+    Sto_ManForEachClauseRoot( p->pCnf, pClause )
+    {
+        if ( pClause->fA )
+            continue;
+        for ( v = 0; v < (int)pClause->nLits; v++ )
+        {
+            Var = lit_var(pClause->pLits[v]);
+            if ( p->pVarTypes[Var] == 1 ) // var of A
+            {
+                // change it into a global variable
+                nVarsAB++;
+                p->pVarTypes[Var] = -1;
+            }
+        }
+    }
+
+    // order global variables
+    nVarsAB = 0;
+    for ( v = 0; v < p->pCnf->nVars; v++ )
+        if ( p->pVarTypes[v] == -1 )
+            p->pVarTypes[v] -= nVarsAB++;
+//printf( "There are %d global variables.\n", nVarsAB );
+    return nVarsAB;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Resize proof manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Int_ManResize( Int_Man_t * p )
+{
+    // check if resizing is needed
+    if ( p->nVarsAlloc < p->pCnf->nVars )
+    {
+        // find the new size
+        if ( p->nVarsAlloc == 0 )
+            p->nVarsAlloc = 1;
+        while ( p->nVarsAlloc < p->pCnf->nVars ) 
+            p->nVarsAlloc *= 2;
+        // resize the arrays
+        p->pTrail    = (lit *)       realloc( p->pTrail,    sizeof(lit) * p->nVarsAlloc );
+        p->pAssigns  = (lit *)       realloc( p->pAssigns,  sizeof(lit) * p->nVarsAlloc );
+        p->pSeens    = (char *)      realloc( p->pSeens,    sizeof(char) * p->nVarsAlloc );
+        p->pVarTypes = (char *)      realloc( p->pVarTypes, sizeof(char) * p->nVarsAlloc );
+        p->pReasons  = (Sto_Cls_t **)realloc( p->pReasons,  sizeof(Sto_Cls_t *) * p->nVarsAlloc );
+        p->pWatches  = (Sto_Cls_t **)realloc( p->pWatches,  sizeof(Sto_Cls_t *) * p->nVarsAlloc*2 );
+    }
+
+    // clean the free space
+    memset( p->pAssigns , 0xff, sizeof(lit) * p->pCnf->nVars );
+    memset( p->pSeens   , 0,    sizeof(char) * p->pCnf->nVars );
+    memset( p->pVarTypes, 0,    sizeof(char) * p->pCnf->nVars );
+    memset( p->pReasons , 0,    sizeof(Sto_Cls_t *) * p->pCnf->nVars );
+    memset( p->pWatches , 0,    sizeof(Sto_Cls_t *) * p->pCnf->nVars*2 );
+
+    // compute the number of common variables
+    p->nVarsAB = Int_ManGlobalVars( p );
+    // compute the number of words in the truth table
+    p->nWords = (p->nVarsAB <= 5 ? 1 : (1 << (p->nVarsAB - 5)));
+
+    // check if resizing of clauses is needed
+    if ( p->nClosAlloc < p->pCnf->nClauses )
+    {
+        // find the new size
+        if ( p->nClosAlloc == 0 )
+            p->nClosAlloc = 1;
+        while ( p->nClosAlloc < p->pCnf->nClauses ) 
+            p->nClosAlloc *= 2;
+        // resize the arrays
+        p->pProofNums = (int *) realloc( p->pProofNums,  sizeof(int) * p->nClosAlloc );
+    }
+    memset( p->pProofNums, 0, sizeof(int) * p->pCnf->nClauses );
+
+    // check if resizing of truth tables is needed
+    if ( p->nIntersAlloc < p->nWords * p->pCnf->nClauses )
+    {
+        p->nIntersAlloc = p->nWords * p->pCnf->nClauses;
+        p->pInters = (unsigned *) realloc( p->pInters, sizeof(unsigned) * p->nIntersAlloc );
+    }
+//    memset( p->pInters, 0, sizeof(unsigned) * p->nWords * p->pCnf->nClauses );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Deallocate proof manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Int_ManFree( Int_Man_t * p )
+{
+/*
+    printf( "Runtime stats:\n" );
+PRT( "BCP     ", p->timeBcp   );
+PRT( "Trace   ", p->timeTrace );
+PRT( "TOTAL   ", p->timeTotal );
+*/
+    free( p->pInters );
+    free( p->pProofNums );
+    free( p->pTrail );
+    free( p->pAssigns );
+    free( p->pSeens );
+    free( p->pVarTypes );
+    free( p->pReasons );
+    free( p->pWatches );
+    free( p->pResLits );
+    free( p );
+}
+
+
+
+
+/**Function*************************************************************
+
+  Synopsis    [Prints the clause.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Int_ManPrintClause( Int_Man_t * p, Sto_Cls_t * pClause )
+{
+    int i;
+    printf( "Clause ID = %d. Proof = %d. {", pClause->Id, Int_ManProofGet(p, pClause) );
+    for ( i = 0; i < (int)pClause->nLits; i++ )
+        printf( " %d", pClause->pLits[i] );
+    printf( " }\n" );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Prints the resolvent.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Int_ManPrintResolvent( lit * pResLits, int nResLits )
+{
+    int i;
+    printf( "Resolvent: {" );
+    for ( i = 0; i < nResLits; i++ )
+        printf( " %d", pResLits[i] );
+    printf( " }\n" );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Records the proof.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Extra_PrintBinary__( FILE * pFile, unsigned Sign[], int nBits )
+{
+    int Remainder, nWords;
+    int w, i;
+
+    Remainder = (nBits%(sizeof(unsigned)*8));
+    nWords    = (nBits/(sizeof(unsigned)*8)) + (Remainder>0);
+
+    for ( w = nWords-1; w >= 0; w-- )
+        for ( i = ((w == nWords-1 && Remainder)? Remainder-1: 31); i >= 0; i-- )
+            fprintf( pFile, "%c", '0' + (int)((Sign[w] & (1<<i)) > 0) );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Prints the interpolant for one clause.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Int_ManPrintInterOne( Int_Man_t * p, Sto_Cls_t * pClause )
+{
+    printf( "Clause %2d :  ", pClause->Id );
+    Extra_PrintBinary__( stdout, Int_ManTruthRead(p, pClause), (1 << p->nVarsAB) );
+    printf( "\n" );
+}
+
+
+
+/**Function*************************************************************
+
+  Synopsis    [Adds one clause to the watcher list.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+static inline void Int_ManWatchClause( Int_Man_t * p, Sto_Cls_t * pClause, lit Lit )
+{
+    assert( lit_check(Lit, p->pCnf->nVars) );
+    if ( pClause->pLits[0] == Lit )
+        pClause->pNext0 = p->pWatches[lit_neg(Lit)];  
+    else
+    {
+        assert( pClause->pLits[1] == Lit );
+        pClause->pNext1 = p->pWatches[lit_neg(Lit)];  
+    }
+    p->pWatches[lit_neg(Lit)] = pClause;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Records implication.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+static inline int Int_ManEnqueue( Int_Man_t * p, lit Lit, Sto_Cls_t * pReason )
+{
+    int Var = lit_var(Lit);
+    if ( p->pAssigns[Var] != LIT_UNDEF )
+        return p->pAssigns[Var] == Lit;
+    p->pAssigns[Var] = Lit;
+    p->pReasons[Var] = pReason;
+    p->pTrail[p->nTrailSize++] = Lit;
+//printf( "assigning var %d value %d\n", Var, !lit_sign(Lit) );
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Records implication.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+static inline void Int_ManCancelUntil( Int_Man_t * p, int Level )
+{
+    lit Lit;
+    int i, Var;
+    for ( i = p->nTrailSize - 1; i >= Level; i-- )
+    {
+        Lit = p->pTrail[i];
+        Var = lit_var( Lit );
+        p->pReasons[Var] = NULL;
+        p->pAssigns[Var] = LIT_UNDEF;
+//printf( "cancelling var %d\n", Var );
+    }
+    p->nTrailSize = Level;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Propagate one assignment.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+static inline Sto_Cls_t * Int_ManPropagateOne( Int_Man_t * p, lit Lit )
+{
+    Sto_Cls_t ** ppPrev, * pCur, * pTemp;
+    lit LitF = lit_neg(Lit);
+    int i;
+    // iterate through the literals
+    ppPrev = p->pWatches + Lit;
+    for ( pCur = p->pWatches[Lit]; pCur; pCur = *ppPrev )
+    {
+        // make sure the false literal is in the second literal of the clause
+        if ( pCur->pLits[0] == LitF )
+        {
+            pCur->pLits[0] = pCur->pLits[1];
+            pCur->pLits[1] = LitF;
+            pTemp = pCur->pNext0;
+            pCur->pNext0 = pCur->pNext1;
+            pCur->pNext1 = pTemp;
+        }
+        assert( pCur->pLits[1] == LitF );
+
+        // if the first literal is true, the clause is satisfied
+        if ( pCur->pLits[0] == p->pAssigns[lit_var(pCur->pLits[0])] )
+        {
+            ppPrev = &pCur->pNext1;
+            continue;
+        }
+
+        // look for a new literal to watch
+        for ( i = 2; i < (int)pCur->nLits; i++ )
+        {
+            // skip the case when the literal is false
+            if ( lit_neg(pCur->pLits[i]) == p->pAssigns[lit_var(pCur->pLits[i])] )
+                continue;
+            // the literal is either true or unassigned - watch it
+            pCur->pLits[1] = pCur->pLits[i];
+            pCur->pLits[i] = LitF;
+            // remove this clause from the watch list of Lit
+            *ppPrev = pCur->pNext1;
+            // add this clause to the watch list of pCur->pLits[i] (now it is pCur->pLits[1])
+            Int_ManWatchClause( p, pCur, pCur->pLits[1] );
+            break;
+        }
+        if ( i < (int)pCur->nLits ) // found new watch
+            continue;
+
+        // clause is unit - enqueue new implication
+        if ( Int_ManEnqueue(p, pCur->pLits[0], pCur) )
+        {
+            ppPrev = &pCur->pNext1;
+            continue;
+        }
+
+        // conflict detected - return the conflict clause
+        return pCur;
+    }
+    return NULL;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Propagate the current assignments.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Sto_Cls_t * Int_ManPropagate( Int_Man_t * p, int Start )
+{
+    Sto_Cls_t * pClause;
+    int i;
+    int clk = clock();
+    for ( i = Start; i < p->nTrailSize; i++ )
+    {
+        pClause = Int_ManPropagateOne( p, p->pTrail[i] );
+        if ( pClause )
+        {
+p->timeBcp += clock() - clk;
+            return pClause;
+        }
+    }
+p->timeBcp += clock() - clk;
+    return NULL;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Writes one root clause into a file.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Int_ManProofWriteOne( Int_Man_t * p, Sto_Cls_t * pClause )
+{
+    Int_ManProofSet( p, pClause, ++p->Counter );
+
+    if ( p->fProofWrite )
+    {
+        int v;
+        fprintf( p->pFile, "%d", Int_ManProofGet(p, pClause) );
+        for ( v = 0; v < (int)pClause->nLits; v++ )
+            fprintf( p->pFile, " %d", lit_print(pClause->pLits[v]) );
+        fprintf( p->pFile, " 0 0\n" );
+    }
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Traces the proof for one clause.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Int_ManProofTraceOne( Int_Man_t * p, Sto_Cls_t * pConflict, Sto_Cls_t * pFinal )
+{
+    Sto_Cls_t * pReason;
+    int i, v, Var, PrevId;
+    int fPrint = 0;
+    int clk = clock();
+
+    // collect resolvent literals
+    if ( p->fProofVerif )
+    {
+        assert( (int)pConflict->nLits <= p->nResLitsAlloc );
+        memcpy( p->pResLits, pConflict->pLits, sizeof(lit) * pConflict->nLits );
+        p->nResLits = pConflict->nLits;
+    }
+
+    // mark all the variables in the conflict as seen
+    for ( v = 0; v < (int)pConflict->nLits; v++ )
+        p->pSeens[lit_var(pConflict->pLits[v])] = 1;
+
+    // start the anticedents
+//    pFinal->pAntis = Vec_PtrAlloc( 32 );
+//    Vec_PtrPush( pFinal->pAntis, pConflict );
+
+    if ( p->pCnf->nClausesA )
+        Int_ManTruthCopy( Int_ManTruthRead(p, pFinal), Int_ManTruthRead(p, pConflict), p->nWords );
+
+    // follow the trail backwards
+    PrevId = Int_ManProofGet(p, pConflict);
+    for ( i = p->nTrailSize - 1; i >= 0; i-- )
+    {
+        // skip literals that are not involved
+        Var = lit_var(p->pTrail[i]);
+        if ( !p->pSeens[Var] )
+            continue;
+        p->pSeens[Var] = 0;
+
+        // skip literals of the resulting clause
+        pReason = p->pReasons[Var];
+        if ( pReason == NULL )
+            continue;
+        assert( p->pTrail[i] == pReason->pLits[0] );
+
+        // add the variables to seen
+        for ( v = 1; v < (int)pReason->nLits; v++ )
+            p->pSeens[lit_var(pReason->pLits[v])] = 1;
+
+
+        // record the reason clause
+        assert( Int_ManProofGet(p, pReason) > 0 );
+        p->Counter++;
+        if ( p->fProofWrite )
+            fprintf( p->pFile, "%d * %d %d 0\n", p->Counter, PrevId, Int_ManProofGet(p, pReason) );
+        PrevId = p->Counter;
+
+        if ( p->pCnf->nClausesA )
+        {
+            if ( p->pVarTypes[Var] == 1 ) // var of A
+                Int_ManTruthOr( Int_ManTruthRead(p, pFinal), Int_ManTruthRead(p, pReason), p->nWords );
+            else
+                Int_ManTruthAnd( Int_ManTruthRead(p, pFinal), Int_ManTruthRead(p, pReason), p->nWords );
+        }
+ 
+        // resolve the temporary resolvent with the reason clause
+        if ( p->fProofVerif )
+        {
+            int v1, v2; 
+            if ( fPrint )
+                Int_ManPrintResolvent( p->pResLits, p->nResLits );
+            // check that the var is present in the resolvent
+            for ( v1 = 0; v1 < p->nResLits; v1++ )
+                if ( lit_var(p->pResLits[v1]) == Var )
+                    break;
+            if ( v1 == p->nResLits )
+                printf( "Recording clause %d: Cannot find variable %d in the temporary resolvent.\n", pFinal->Id, Var );
+            if ( p->pResLits[v1] != lit_neg(pReason->pLits[0]) )
+                printf( "Recording clause %d: The resolved variable %d is in the wrong polarity.\n", pFinal->Id, Var );
+            // remove this variable from the resolvent
+            assert( lit_var(p->pResLits[v1]) == Var );
+            p->nResLits--;
+            for ( ; v1 < p->nResLits; v1++ )
+                p->pResLits[v1] = p->pResLits[v1+1];
+            // add variables of the reason clause
+            for ( v2 = 1; v2 < (int)pReason->nLits; v2++ )
+            {
+                for ( v1 = 0; v1 < p->nResLits; v1++ )
+                    if ( lit_var(p->pResLits[v1]) == lit_var(pReason->pLits[v2]) )
+                        break;
+                // if it is a new variable, add it to the resolvent
+                if ( v1 == p->nResLits ) 
+                {
+                    if ( p->nResLits == p->nResLitsAlloc )
+                        printf( "Recording clause %d: Ran out of space for intermediate resolvent.\n", pFinal->Id );
+                    p->pResLits[ p->nResLits++ ] = pReason->pLits[v2];
+                    continue;
+                }
+                // if the variable is the same, the literal should be the same too
+                if ( p->pResLits[v1] == pReason->pLits[v2] )
+                    continue;
+                // the literal is different
+                printf( "Recording clause %d: Trying to resolve the clause with more than one opposite literal.\n", pFinal->Id );
+            }
+        }
+
+//        Vec_PtrPush( pFinal->pAntis, pReason );
+    }
+
+    // unmark all seen variables
+//    for ( i = p->nTrailSize - 1; i >= 0; i-- )
+//        p->pSeens[lit_var(p->pTrail[i])] = 0;
+    // check that the literals are unmarked
+//    for ( i = p->nTrailSize - 1; i >= 0; i-- )
+//        assert( p->pSeens[lit_var(p->pTrail[i])] == 0 );
+
+    // use the resulting clause to check the correctness of resolution
+    if ( p->fProofVerif )
+    {
+        int v1, v2; 
+        if ( fPrint )
+            Int_ManPrintResolvent( p->pResLits, p->nResLits );
+        for ( v1 = 0; v1 < p->nResLits; v1++ )
+        {
+            for ( v2 = 0; v2 < (int)pFinal->nLits; v2++ )
+                if ( pFinal->pLits[v2] == p->pResLits[v1] )
+                    break;
+            if ( v2 < (int)pFinal->nLits )
+                continue;
+            break;
+        }
+        if ( v1 < p->nResLits )
+        {
+            printf( "Recording clause %d: The final resolvent is wrong.\n", pFinal->Id );
+            Int_ManPrintClause( p, pConflict );
+            Int_ManPrintResolvent( p->pResLits, p->nResLits );
+            Int_ManPrintClause( p, pFinal );
+        }
+    }
+p->timeTrace += clock() - clk;
+
+    // return the proof pointer 
+    if ( p->pCnf->nClausesA )
+    {
+//        Int_ManPrintInterOne( p, pFinal );
+    }
+    Int_ManProofSet( p, pFinal, p->Counter );
+    return p->Counter;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Records the proof for one clause.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Int_ManProofRecordOne( Int_Man_t * p, Sto_Cls_t * pClause )
+{
+    Sto_Cls_t * pConflict;
+    int i;
+
+    // empty clause never ends up there
+    assert( pClause->nLits > 0 );
+    if ( pClause->nLits == 0 )
+        printf( "Error: Empty clause is attempted.\n" );
+
+    // add assumptions to the trail
+    assert( !pClause->fRoot );
+    assert( p->nTrailSize == p->nRootSize );
+    for ( i = 0; i < (int)pClause->nLits; i++ )
+        if ( !Int_ManEnqueue( p, lit_neg(pClause->pLits[i]), NULL ) )
+        {
+            assert( 0 ); // impossible
+            return 0;
+        }
+
+    // propagate the assumptions
+    pConflict = Int_ManPropagate( p, p->nRootSize );
+    if ( pConflict == NULL )
+    {
+        assert( 0 ); // cannot prove
+        return 0;
+    }
+
+    // construct the proof
+    Int_ManProofTraceOne( p, pConflict, pClause );
+
+    // undo to the root level
+    Int_ManCancelUntil( p, p->nRootSize );
+
+    // add large clauses to the watched lists
+    if ( pClause->nLits > 1 )
+    {
+        Int_ManWatchClause( p, pClause, pClause->pLits[0] );
+        Int_ManWatchClause( p, pClause, pClause->pLits[1] );
+        return 1;
+    }
+    assert( pClause->nLits == 1 );
+
+    // if the clause proved is unit, add it and propagate
+    if ( !Int_ManEnqueue( p, pClause->pLits[0], pClause ) )
+    {
+        assert( 0 ); // impossible
+        return 0;
+    }
+
+    // propagate the assumption
+    pConflict = Int_ManPropagate( p, p->nRootSize );
+    if ( pConflict )
+    {
+        // construct the proof
+        Int_ManProofTraceOne( p, pConflict, p->pCnf->pEmpty );
+        if ( p->fVerbose )
+            printf( "Found last conflict after adding unit clause number %d!\n", pClause->Id );
+        return 0;
+    }
+
+    // update the root level
+    p->nRootSize = p->nTrailSize;
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Propagate the root clauses.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Int_ManProcessRoots( Int_Man_t * p )
+{
+    Sto_Cls_t * pClause;
+    int Counter;
+
+    // make sure the root clauses are preceeding the learnt clauses
+    Counter = 0;
+    Sto_ManForEachClause( p->pCnf, pClause )
+    {
+        assert( (int)pClause->fA    == (Counter < (int)p->pCnf->nClausesA) );
+        assert( (int)pClause->fRoot == (Counter < (int)p->pCnf->nRoots)    );
+        Counter++;
+    }
+    assert( p->pCnf->nClauses == Counter );
+
+    // make sure the last clause if empty
+    assert( p->pCnf->pTail->nLits == 0 );
+
+    // go through the root unit clauses
+    p->nTrailSize = 0;
+    Sto_ManForEachClauseRoot( p->pCnf, pClause )
+    {
+        // create watcher lists for the root clauses
+        if ( pClause->nLits > 1 )
+        {
+            Int_ManWatchClause( p, pClause, pClause->pLits[0] );
+            Int_ManWatchClause( p, pClause, pClause->pLits[1] );
+        }
+        // empty clause and large clauses
+        if ( pClause->nLits != 1 )
+            continue;
+        // unit clause
+        assert( lit_check(pClause->pLits[0], p->pCnf->nVars) );
+        if ( !Int_ManEnqueue( p, pClause->pLits[0], pClause ) )
+        {
+            // detected root level conflict
+            printf( "Error in Int_ManProcessRoots(): Detected a root-level conflict too early!\n" );
+            assert( 0 );
+            return 0;
+        }
+    }
+
+    // propagate the root unit clauses
+    pClause = Int_ManPropagate( p, 0 );
+    if ( pClause )
+    {
+        // detected root level conflict
+        Int_ManProofTraceOne( p, pClause, p->pCnf->pEmpty );
+        if ( p->fVerbose )
+            printf( "Found root level conflict!\n" );
+        return 0;
+    }
+
+    // set the root level
+    p->nRootSize = p->nTrailSize;
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Records the proof.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Int_ManPrepareInter( Int_Man_t * p )
+{
+    // elementary truth tables
+    unsigned uTruths[8][8] = {
+        { 0xAAAAAAAA,0xAAAAAAAA,0xAAAAAAAA,0xAAAAAAAA,0xAAAAAAAA,0xAAAAAAAA,0xAAAAAAAA,0xAAAAAAAA },
+        { 0xCCCCCCCC,0xCCCCCCCC,0xCCCCCCCC,0xCCCCCCCC,0xCCCCCCCC,0xCCCCCCCC,0xCCCCCCCC,0xCCCCCCCC },
+        { 0xF0F0F0F0,0xF0F0F0F0,0xF0F0F0F0,0xF0F0F0F0,0xF0F0F0F0,0xF0F0F0F0,0xF0F0F0F0,0xF0F0F0F0 },
+        { 0xFF00FF00,0xFF00FF00,0xFF00FF00,0xFF00FF00,0xFF00FF00,0xFF00FF00,0xFF00FF00,0xFF00FF00 },
+        { 0xFFFF0000,0xFFFF0000,0xFFFF0000,0xFFFF0000,0xFFFF0000,0xFFFF0000,0xFFFF0000,0xFFFF0000 }, 
+        { 0x00000000,0xFFFFFFFF,0x00000000,0xFFFFFFFF,0x00000000,0xFFFFFFFF,0x00000000,0xFFFFFFFF }, 
+        { 0x00000000,0x00000000,0xFFFFFFFF,0xFFFFFFFF,0x00000000,0x00000000,0xFFFFFFFF,0xFFFFFFFF }, 
+        { 0x00000000,0x00000000,0x00000000,0x00000000,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF } 
+    };
+    Sto_Cls_t * pClause;
+    int Var, VarAB, v;
+    assert( p->nVarsAB <= 8 );
+
+    // set interpolants for root clauses
+    Sto_ManForEachClauseRoot( p->pCnf, pClause )
+    {
+        if ( !pClause->fA ) // clause of B
+        {
+            Int_ManTruthFill( Int_ManTruthRead(p, pClause), p->nWords );
+//            Int_ManPrintInterOne( p, pClause );
+            continue;
+        }
+        // clause of A
+        Int_ManTruthClear( Int_ManTruthRead(p, pClause), p->nWords );
+        for ( v = 0; v < (int)pClause->nLits; v++ )
+        {
+            Var = lit_var(pClause->pLits[v]);
+            if ( p->pVarTypes[Var] < 0 ) // global var
+            {
+                VarAB = -p->pVarTypes[Var]-1;
+                assert( VarAB >= 0 && VarAB < p->nVarsAB );
+                if ( lit_sign(pClause->pLits[v]) ) // negative var
+                    Int_ManTruthOrNot( Int_ManTruthRead(p, pClause), uTruths[VarAB], p->nWords );
+                else
+                    Int_ManTruthOr( Int_ManTruthRead(p, pClause), uTruths[VarAB], p->nWords );
+            }
+        }
+//        Int_ManPrintInterOne( p, pClause );
+    }
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Computes interpolant for the given CNF.]
+
+  Description [Returns the number of common variable found and interpolant.
+  Returns 0, if something did not work.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Int_ManInterpolate( Int_Man_t * p, Sto_Man_t * pCnf, int fVerbose, unsigned ** ppResult )
+{
+    Sto_Cls_t * pClause;
+    int RetValue = 1;
+    int clkTotal = clock();
+
+    // check that the CNF makes sense
+    assert( pCnf->nVars > 0 && pCnf->nClauses > 0 );
+    p->pCnf = pCnf;
+    p->fVerbose = fVerbose;
+    *ppResult = NULL;
+
+    // adjust the manager
+    Int_ManResize( p );
+
+    // prepare the interpolant computation
+    Int_ManPrepareInter( p );
+
+    // construct proof for each clause
+    // start the proof
+    if ( p->fProofWrite )
+    {
+        p->pFile = fopen( "proof.cnf_", "w" );
+        p->Counter = 0;
+    }
+
+    // write the root clauses
+    Sto_ManForEachClauseRoot( p->pCnf, pClause )
+        Int_ManProofWriteOne( p, pClause );
+
+    // propagate root level assignments
+    if ( Int_ManProcessRoots( p ) )
+    {
+        // if there is no conflict, consider learned clauses
+        Sto_ManForEachClause( p->pCnf, pClause )
+        {
+            if ( pClause->fRoot )
+                continue;
+            if ( !Int_ManProofRecordOne( p, pClause ) )
+            {
+                RetValue = 0;
+                break;
+            }
+        }
+    }
+
+    // stop the proof
+    if ( p->fProofWrite )
+    {
+        fclose( p->pFile );
+        p->pFile = NULL;    
+    }
+
+    if ( fVerbose )
+    {
+    printf( "Vars = %d. Roots = %d. Learned = %d. Resol steps = %d.  Ave = %.2f.  Mem = %.2f Mb\n", 
+        p->pCnf->nVars, p->pCnf->nRoots, p->pCnf->nClauses-p->pCnf->nRoots, p->Counter,  
+        1.0*(p->Counter-p->pCnf->nRoots)/(p->pCnf->nClauses-p->pCnf->nRoots), 
+        1.0*Sto_ManMemoryReport(p->pCnf)/(1<<20) );
+p->timeTotal += clock() - clkTotal;
+    }
+
+    *ppResult = Int_ManTruthRead( p, p->pCnf->pTail );
+    return p->nVarsAB;
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/bsat/satMem.c b/src/sat/bsat/satMem.c
new file mode 100644
index 00000000..7fa1a824
--- /dev/null
+++ b/src/sat/bsat/satMem.c
@@ -0,0 +1,527 @@
+/**CFile****************************************************************
+
+  FileName    [satMem.c]
+
+  PackageName [SAT solver.]
+
+  Synopsis    [Memory management.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - January 1, 2004.]
+
+  Revision    [$Id: satMem.c,v 1.0 2004/01/01 1:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include "satMem.h"
+#include "vec.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+struct Sat_MmFixed_t_
+{
+    // information about individual entries
+    int           nEntrySize;    // the size of one entry
+    int           nEntriesAlloc; // the total number of entries allocated
+    int           nEntriesUsed;  // the number of entries in use
+    int           nEntriesMax;   // the max number of entries in use
+    char *        pEntriesFree;  // the linked list of free entries
+
+    // this is where the memory is stored
+    int           nChunkSize;    // the size of one chunk
+    int           nChunksAlloc;  // the maximum number of memory chunks 
+    int           nChunks;       // the current number of memory chunks 
+    char **       pChunks;       // the allocated memory
+
+    // statistics
+    int           nMemoryUsed;   // memory used in the allocated entries
+    int           nMemoryAlloc;  // memory allocated
+};
+
+struct Sat_MmFlex_t_
+{
+    // information about individual entries
+    int           nEntriesUsed;  // the number of entries allocated
+    char *        pCurrent;      // the current pointer to free memory
+    char *        pEnd;          // the first entry outside the free memory
+
+    // this is where the memory is stored
+    int           nChunkSize;    // the size of one chunk
+    int           nChunksAlloc;  // the maximum number of memory chunks 
+    int           nChunks;       // the current number of memory chunks 
+    char **       pChunks;       // the allocated memory
+
+    // statistics
+    int           nMemoryUsed;   // memory used in the allocated entries
+    int           nMemoryAlloc;  // memory allocated
+};
+
+struct Sat_MmStep_t_
+{
+    int                nMems;    // the number of fixed memory managers employed
+    Sat_MmFixed_t **  pMems;    // memory managers: 2^1 words, 2^2 words, etc
+    int                nMapSize; // the size of the memory array
+    Sat_MmFixed_t **  pMap;     // maps the number of bytes into its memory manager
+};
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Allocates memory pieces of fixed size.]
+
+  Description [The size of the chunk is computed as the minimum of
+  1024 entries and 64K. Can only work with entry size at least 4 byte long.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Sat_MmFixed_t * Sat_MmFixedStart( int nEntrySize )
+{
+    Sat_MmFixed_t * p;
+
+    p = ALLOC( Sat_MmFixed_t, 1 );
+    memset( p, 0, sizeof(Sat_MmFixed_t) );
+
+    p->nEntrySize    = nEntrySize;
+    p->nEntriesAlloc = 0;
+    p->nEntriesUsed  = 0;
+    p->pEntriesFree  = NULL;
+
+    if ( nEntrySize * (1 << 10) < (1<<16) )
+        p->nChunkSize = (1 << 10);
+    else
+        p->nChunkSize = (1<<16) / nEntrySize;
+    if ( p->nChunkSize < 8 )
+        p->nChunkSize = 8;
+
+    p->nChunksAlloc  = 64;
+    p->nChunks       = 0;
+    p->pChunks       = ALLOC( char *, p->nChunksAlloc );
+
+    p->nMemoryUsed   = 0;
+    p->nMemoryAlloc  = 0;
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Sat_MmFixedStop( Sat_MmFixed_t * p, int fVerbose )
+{
+    int i;
+    if ( p == NULL )
+        return;
+    if ( fVerbose )
+    {
+        printf( "Fixed memory manager: Entry = %5d. Chunk = %5d. Chunks used = %5d.\n",
+            p->nEntrySize, p->nChunkSize, p->nChunks );
+        printf( "   Entries used = %8d. Entries peak = %8d. Memory used = %8d. Memory alloc = %8d.\n",
+            p->nEntriesUsed, p->nEntriesMax, p->nEntrySize * p->nEntriesUsed, p->nMemoryAlloc );
+    }
+    for ( i = 0; i < p->nChunks; i++ )
+        free( p->pChunks[i] );
+    free( p->pChunks );
+    free( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+char * Sat_MmFixedEntryFetch( Sat_MmFixed_t * p )
+{
+    char * pTemp;
+    int i;
+
+    // check if there are still free entries
+    if ( p->nEntriesUsed == p->nEntriesAlloc )
+    { // need to allocate more entries
+        assert( p->pEntriesFree == NULL );
+        if ( p->nChunks == p->nChunksAlloc )
+        {
+            p->nChunksAlloc *= 2;
+            p->pChunks = REALLOC( char *, p->pChunks, p->nChunksAlloc ); 
+        }
+        p->pEntriesFree = ALLOC( char, p->nEntrySize * p->nChunkSize );
+        p->nMemoryAlloc += p->nEntrySize * p->nChunkSize;
+        // transform these entries into a linked list
+        pTemp = p->pEntriesFree;
+        for ( i = 1; i < p->nChunkSize; i++ )
+        {
+            *((char **)pTemp) = pTemp + p->nEntrySize;
+            pTemp += p->nEntrySize;
+        }
+        // set the last link
+        *((char **)pTemp) = NULL;
+        // add the chunk to the chunk storage
+        p->pChunks[ p->nChunks++ ] = p->pEntriesFree;
+        // add to the number of entries allocated
+        p->nEntriesAlloc += p->nChunkSize;
+    }
+    // incrememt the counter of used entries
+    p->nEntriesUsed++;
+    if ( p->nEntriesMax < p->nEntriesUsed )
+        p->nEntriesMax = p->nEntriesUsed;
+    // return the first entry in the free entry list
+    pTemp = p->pEntriesFree;
+    p->pEntriesFree = *((char **)pTemp);
+    return pTemp;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Sat_MmFixedEntryRecycle( Sat_MmFixed_t * p, char * pEntry )
+{
+    // decrement the counter of used entries
+    p->nEntriesUsed--;
+    // add the entry to the linked list of free entries
+    *((char **)pEntry) = p->pEntriesFree;
+    p->pEntriesFree = pEntry;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description [Relocates all the memory except the first chunk.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Sat_MmFixedRestart( Sat_MmFixed_t * p )
+{
+    int i;
+    char * pTemp;
+
+    // deallocate all chunks except the first one
+    for ( i = 1; i < p->nChunks; i++ )
+        free( p->pChunks[i] );
+    p->nChunks = 1;
+    // transform these entries into a linked list
+    pTemp = p->pChunks[0];
+    for ( i = 1; i < p->nChunkSize; i++ )
+    {
+        *((char **)pTemp) = pTemp + p->nEntrySize;
+        pTemp += p->nEntrySize;
+    }
+    // set the last link
+    *((char **)pTemp) = NULL;
+    // set the free entry list
+    p->pEntriesFree  = p->pChunks[0];
+    // set the correct statistics
+    p->nMemoryAlloc  = p->nEntrySize * p->nChunkSize;
+    p->nMemoryUsed   = 0;
+    p->nEntriesAlloc = p->nChunkSize;
+    p->nEntriesUsed  = 0;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Sat_MmFixedReadMemUsage( Sat_MmFixed_t * p )
+{
+    return p->nMemoryAlloc;
+}
+
+
+
+/**Function*************************************************************
+
+  Synopsis    [Allocates entries of flexible size.]
+
+  Description [Can only work with entry size at least 4 byte long.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Sat_MmFlex_t * Sat_MmFlexStart()
+{
+    Sat_MmFlex_t * p;
+
+    p = ALLOC( Sat_MmFlex_t, 1 );
+    memset( p, 0, sizeof(Sat_MmFlex_t) );
+
+    p->nEntriesUsed  = 0;
+    p->pCurrent      = NULL;
+    p->pEnd          = NULL;
+
+    p->nChunkSize    = (1 << 12);
+    p->nChunksAlloc  = 64;
+    p->nChunks       = 0;
+    p->pChunks       = ALLOC( char *, p->nChunksAlloc );
+
+    p->nMemoryUsed   = 0;
+    p->nMemoryAlloc  = 0;
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Sat_MmFlexStop( Sat_MmFlex_t * p, int fVerbose )
+{
+    int i;
+    if ( p == NULL )
+        return;
+    if ( fVerbose )
+    {
+        printf( "Flexible memory manager: Chunk size = %d. Chunks used = %d.\n",
+            p->nChunkSize, p->nChunks );
+        printf( "   Entries used = %d. Memory used = %d. Memory alloc = %d.\n",
+            p->nEntriesUsed, p->nMemoryUsed, p->nMemoryAlloc );
+    }
+    for ( i = 0; i < p->nChunks; i++ )
+        free( p->pChunks[i] );
+    free( p->pChunks );
+    free( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+char * Sat_MmFlexEntryFetch( Sat_MmFlex_t * p, int nBytes )
+{
+    char * pTemp;
+    // check if there are still free entries
+    if ( p->pCurrent == NULL || p->pCurrent + nBytes > p->pEnd )
+    { // need to allocate more entries
+        if ( p->nChunks == p->nChunksAlloc )
+        {
+            p->nChunksAlloc *= 2;
+            p->pChunks = REALLOC( char *, p->pChunks, p->nChunksAlloc ); 
+        }
+        if ( nBytes > p->nChunkSize )
+        {
+            // resize the chunk size if more memory is requested than it can give
+            // (ideally, this should never happen)
+            p->nChunkSize = 2 * nBytes;
+        }
+        p->pCurrent = ALLOC( char, p->nChunkSize );
+        p->pEnd     = p->pCurrent + p->nChunkSize;
+        p->nMemoryAlloc += p->nChunkSize;
+        // add the chunk to the chunk storage
+        p->pChunks[ p->nChunks++ ] = p->pCurrent;
+    }
+    assert( p->pCurrent + nBytes <= p->pEnd );
+    // increment the counter of used entries
+    p->nEntriesUsed++;
+    // keep track of the memory used
+    p->nMemoryUsed += nBytes;
+    // return the next entry
+    pTemp = p->pCurrent;
+    p->pCurrent += nBytes;
+    return pTemp;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Sat_MmFlexReadMemUsage( Sat_MmFlex_t * p )
+{
+    return p->nMemoryAlloc;
+}
+
+
+
+
+
+/**Function*************************************************************
+
+  Synopsis    [Starts the hierarchical memory manager.]
+
+  Description [This manager can allocate entries of any size.
+  Iternally they are mapped into the entries with the number of bytes
+  equal to the power of 2. The smallest entry size is 8 bytes. The
+  next one is 16 bytes etc. So, if the user requests 6 bytes, he gets 
+  8 byte entry. If we asks for 25 bytes, he gets 32 byte entry etc.
+  The input parameters "nSteps" says how many fixed memory managers
+  are employed internally. Calling this procedure with nSteps equal
+  to 10 results in 10 hierarchically arranged internal memory managers, 
+  which can allocate up to 4096 (1Kb) entries. Requests for larger 
+  entries are handed over to malloc() and then free()ed.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Sat_MmStep_t * Sat_MmStepStart( int nSteps )
+{
+    Sat_MmStep_t * p;
+    int i, k;
+    p = ALLOC( Sat_MmStep_t, 1 );
+    p->nMems = nSteps;
+    // start the fixed memory managers
+    p->pMems = ALLOC( Sat_MmFixed_t *, p->nMems );
+    for ( i = 0; i < p->nMems; i++ )
+        p->pMems[i] = Sat_MmFixedStart( (8<<i) );
+    // set up the mapping of the required memory size into the corresponding manager
+    p->nMapSize = (4<<p->nMems);
+    p->pMap = ALLOC( Sat_MmFixed_t *, p->nMapSize+1 );
+    p->pMap[0] = NULL;
+    for ( k = 1; k <= 4; k++ )
+        p->pMap[k] = p->pMems[0];
+    for ( i = 0; i < p->nMems; i++ )
+        for ( k = (4<<i)+1; k <= (8<<i); k++ )
+            p->pMap[k] = p->pMems[i];
+//for ( i = 1; i < 100; i ++ )
+//printf( "%10d: size = %10d\n", i, p->pMap[i]->nEntrySize );
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Stops the memory manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Sat_MmStepStop( Sat_MmStep_t * p, int fVerbose )
+{
+    int i;
+    for ( i = 0; i < p->nMems; i++ )
+        Sat_MmFixedStop( p->pMems[i], fVerbose );
+    free( p->pMems );
+    free( p->pMap );
+    free( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Creates the entry.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+char * Sat_MmStepEntryFetch( Sat_MmStep_t * p, int nBytes )
+{
+    if ( nBytes == 0 )
+        return NULL;
+    if ( nBytes > p->nMapSize )
+    {
+//        printf( "Allocating %d bytes.\n", nBytes );
+        return ALLOC( char, nBytes );
+    }
+    return Sat_MmFixedEntryFetch( p->pMap[nBytes] );
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Recycles the entry.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Sat_MmStepEntryRecycle( Sat_MmStep_t * p, char * pEntry, int nBytes )
+{
+    if ( nBytes == 0 )
+        return;
+    if ( nBytes > p->nMapSize )
+    {
+        free( pEntry );
+        return;
+    }
+    Sat_MmFixedEntryRecycle( p->pMap[nBytes], pEntry );
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Sat_MmStepReadMemUsage( Sat_MmStep_t * p )
+{
+    int i, nMemTotal = 0;
+    for ( i = 0; i < p->nMems; i++ )
+        nMemTotal += p->pMems[i]->nMemoryAlloc;
+    return nMemTotal;
+}
diff --git a/src/sat/bsat/satMem.h b/src/sat/bsat/satMem.h
new file mode 100644
index 00000000..22b7a87c
--- /dev/null
+++ b/src/sat/bsat/satMem.h
@@ -0,0 +1,80 @@
+/**CFile****************************************************************
+
+  FileName    [satMem.h]
+
+  PackageName [SAT solver.]
+
+  Synopsis    [Memory management.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - January 1, 2004.]
+
+  Revision    [$Id: satMem.h,v 1.0 2004/01/01 1:00:00 alanmi Exp $]
+
+***********************************************************************/
+ 
+#ifndef __SAT_MEM_H__
+#define __SAT_MEM_H__
+
+////////////////////////////////////////////////////////////////////////
+///                          INCLUDES                                ///
+////////////////////////////////////////////////////////////////////////
+
+//#include "leaks.h"       
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+////////////////////////////////////////////////////////////////////////
+///                         PARAMETERS                               ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                    STRUCTURE DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+typedef struct Sat_MmFixed_t_ Sat_MmFixed_t;
+typedef struct Sat_MmFlex_t_  Sat_MmFlex_t;
+typedef struct Sat_MmStep_t_  Sat_MmStep_t;
+
+////////////////////////////////////////////////////////////////////////
+///                       GLOBAL VARIABLES                           ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                       MACRO DEFINITIONS                          ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DECLARATIONS                        ///
+////////////////////////////////////////////////////////////////////////
+
+// fixed-size-block memory manager
+extern Sat_MmFixed_t *     Sat_MmFixedStart( int nEntrySize );
+extern void                Sat_MmFixedStop( Sat_MmFixed_t * p, int fVerbose );
+extern char *              Sat_MmFixedEntryFetch( Sat_MmFixed_t * p );
+extern void                Sat_MmFixedEntryRecycle( Sat_MmFixed_t * p, char * pEntry );
+extern void                Sat_MmFixedRestart( Sat_MmFixed_t * p );
+extern int                 Sat_MmFixedReadMemUsage( Sat_MmFixed_t * p );
+// flexible-size-block memory manager
+extern Sat_MmFlex_t *      Sat_MmFlexStart();
+extern void                Sat_MmFlexStop( Sat_MmFlex_t * p, int fVerbose );
+extern char *              Sat_MmFlexEntryFetch( Sat_MmFlex_t * p, int nBytes );
+extern int                 Sat_MmFlexReadMemUsage( Sat_MmFlex_t * p );
+// hierarchical memory manager
+extern Sat_MmStep_t *      Sat_MmStepStart( int nSteps );
+extern void                Sat_MmStepStop( Sat_MmStep_t * p, int fVerbose );
+extern char *              Sat_MmStepEntryFetch( Sat_MmStep_t * p, int nBytes );
+extern void                Sat_MmStepEntryRecycle( Sat_MmStep_t * p, char * pEntry, int nBytes );
+extern int                 Sat_MmStepReadMemUsage( Sat_MmStep_t * p );
+
+#endif
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
diff --git a/src/sat/bsat/satSolver.c b/src/sat/bsat/satSolver.c
new file mode 100644
index 00000000..fbc9874d
--- /dev/null
+++ b/src/sat/bsat/satSolver.c
@@ -0,0 +1,1358 @@
+/**************************************************************************************************
+MiniSat -- Copyright (c) 2005, Niklas Sorensson
+http://www.cs.chalmers.se/Cs/Research/FormalMethods/MiniSat/
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute,
+sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or
+substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+**************************************************************************************************/
+// Modified to compile with MS Visual Studio 6.0 by Alan Mishchenko
+
+#include <stdio.h>
+#include <assert.h>
+#include <string.h>
+#include <math.h>
+
+#include "satSolver.h"
+
+//#define SAT_USE_SYSTEM_MEMORY_MANAGEMENT
+
+//=================================================================================================
+// Debug:
+
+//#define VERBOSEDEBUG
+
+// For derivation output (verbosity level 2)
+#define L_IND    "%-*d"
+#define L_ind    sat_solver_dlevel(s)*3+3,sat_solver_dlevel(s)
+#define L_LIT    "%sx%d"
+#define L_lit(p) lit_sign(p)?"~":"", (lit_var(p))
+
+// Just like 'assert()' but expression will be evaluated in the release version as well.
+static inline void check(int expr) { assert(expr); }
+
+static void printlits(lit* begin, lit* end)
+{
+    int i;
+    for (i = 0; i < end - begin; i++)
+        printf(L_LIT" ",L_lit(begin[i]));
+}
+
+//=================================================================================================
+// Random numbers:
+
+
+// Returns a random float 0 <= x < 1. Seed must never be 0.
+static inline double drand(double* seed) {
+    int q;
+    *seed *= 1389796;
+    q = (int)(*seed / 2147483647);
+    *seed -= (double)q * 2147483647;
+    return *seed / 2147483647; }
+
+
+// Returns a random integer 0 <= x < size. Seed must never be 0.
+static inline int irand(double* seed, int size) {
+    return (int)(drand(seed) * size); }
+
+
+//=================================================================================================
+// Predeclarations:
+
+static void sat_solver_sort(void** array, int size, int(*comp)(const void *, const void *));
+
+//=================================================================================================
+// Clause datatype + minor functions:
+
+struct clause_t
+{
+    int size_learnt;
+    lit lits[0];
+};
+
+static inline int   clause_size       (clause* c)          { return c->size_learnt >> 1; }
+static inline lit*  clause_begin      (clause* c)          { return c->lits; }
+static inline int   clause_learnt     (clause* c)          { return c->size_learnt & 1; }
+static inline float clause_activity   (clause* c)          { return *((float*)&c->lits[c->size_learnt>>1]); }
+static inline void  clause_setactivity(clause* c, float a) { *((float*)&c->lits[c->size_learnt>>1]) = a; }
+
+//=================================================================================================
+// Encode literals in clause pointers:
+
+static inline clause* clause_from_lit (lit l)     { return (clause*)((unsigned long)l + (unsigned long)l + 1);  }
+static inline bool    clause_is_lit   (clause* c) { return ((unsigned long)c & 1);                              }
+static inline lit     clause_read_lit (clause* c) { return (lit)((unsigned long)c >> 1);                        }
+
+//=================================================================================================
+// Simple helpers:
+
+static inline int     sat_solver_dlevel(sat_solver* s)            { return veci_size(&s->trail_lim); }
+static inline vecp*   sat_solver_read_wlist(sat_solver* s, lit l) { return &s->wlists[l]; }
+static inline void    vecp_remove(vecp* v, void* e)
+{
+    void** ws = vecp_begin(v);
+    int    j  = 0;
+    for (; ws[j] != e  ; j++);
+    assert(j < vecp_size(v));
+    for (; j < vecp_size(v)-1; j++) ws[j] = ws[j+1];
+    vecp_resize(v,vecp_size(v)-1);
+}
+
+//=================================================================================================
+// Variable order functions:
+
+static inline void order_update(sat_solver* s, int v) // updateorder
+{
+    int*    orderpos = s->orderpos;
+    double* activity = s->activity;
+    int*    heap     = veci_begin(&s->order);
+    int     i        = orderpos[v];
+    int     x        = heap[i];
+    int     parent   = (i - 1) / 2;
+
+    assert(s->orderpos[v] != -1);
+
+    while (i != 0 && activity[x] > activity[heap[parent]]){
+        heap[i]           = heap[parent];
+        orderpos[heap[i]] = i;
+        i                 = parent;
+        parent            = (i - 1) / 2;
+    }
+    heap[i]     = x;
+    orderpos[x] = i;
+}
+
+static inline void order_assigned(sat_solver* s, int v) 
+{
+}
+
+static inline void order_unassigned(sat_solver* s, int v) // undoorder
+{
+    int* orderpos = s->orderpos;
+    if (orderpos[v] == -1){
+        orderpos[v] = veci_size(&s->order);
+        veci_push(&s->order,v);
+        order_update(s,v);
+//printf( "+%d ", v );
+    }
+}
+
+static inline int  order_select(sat_solver* s, float random_var_freq) // selectvar
+{
+    int*    heap;
+    double* activity;
+    int*    orderpos;
+
+    lbool* values = s->assigns;
+
+    // Random decision:
+    if (drand(&s->random_seed) < random_var_freq){
+        int next = irand(&s->random_seed,s->size);
+        assert(next >= 0 && next < s->size);
+        if (values[next] == l_Undef)
+            return next;
+    }
+
+    // Activity based decision:
+
+    heap     = veci_begin(&s->order);
+    activity = s->activity;
+    orderpos = s->orderpos;
+
+
+    while (veci_size(&s->order) > 0){
+        int    next  = heap[0];
+        int    size  = veci_size(&s->order)-1;
+        int    x     = heap[size];
+
+        veci_resize(&s->order,size);
+
+        orderpos[next] = -1;
+
+        if (size > 0){
+            double act   = activity[x];
+
+            int    i     = 0;
+            int    child = 1;
+
+
+            while (child < size){
+                if (child+1 < size && activity[heap[child]] < activity[heap[child+1]])
+                    child++;
+
+                assert(child < size);
+
+                if (act >= activity[heap[child]])
+                    break;
+
+                heap[i]           = heap[child];
+                orderpos[heap[i]] = i;
+                i                 = child;
+                child             = 2 * child + 1;
+            }
+            heap[i]           = x;
+            orderpos[heap[i]] = i;
+        }
+
+//printf( "-%d ", next );
+        if (values[next] == l_Undef)
+            return next;
+    }
+
+    return var_Undef;
+}
+
+//=================================================================================================
+// Activity functions:
+
+static inline void act_var_rescale(sat_solver* s) {
+    double* activity = s->activity;
+    int i;
+    for (i = 0; i < s->size; i++)
+        activity[i] *= 1e-100;
+    s->var_inc *= 1e-100;
+}
+
+static inline void act_var_bump(sat_solver* s, int v) {
+    s->activity[v] += s->var_inc;
+    if (s->activity[v] > 1e100)
+        act_var_rescale(s);
+    //printf("bump %d %f\n", v-1, activity[v]);
+    if (s->orderpos[v] != -1)
+        order_update(s,v);
+}
+
+static inline void act_var_bump_factor(sat_solver* s, int v) {
+    s->activity[v] += (s->var_inc * s->factors[v]);
+    if (s->activity[v] > 1e100)
+        act_var_rescale(s);
+    //printf("bump %d %f\n", v-1, activity[v]);
+    if (s->orderpos[v] != -1)
+        order_update(s,v);
+}
+
+static inline void act_var_decay(sat_solver* s) { s->var_inc *= s->var_decay; }
+
+static inline void act_clause_rescale(sat_solver* s) {
+    clause** cs = (clause**)vecp_begin(&s->learnts);
+    int i;
+    for (i = 0; i < vecp_size(&s->learnts); i++){
+        float a = clause_activity(cs[i]);
+        clause_setactivity(cs[i], a * (float)1e-20);
+    }
+    s->cla_inc *= (float)1e-20;
+}
+
+
+static inline void act_clause_bump(sat_solver* s, clause *c) {
+    float a = clause_activity(c) + s->cla_inc;
+    clause_setactivity(c,a);
+    if (a > 1e20) act_clause_rescale(s);
+}
+
+static inline void act_clause_decay(sat_solver* s) { s->cla_inc *= s->cla_decay; }
+
+//=================================================================================================
+// Clause functions:
+
+/* pre: size > 1 && no variable occurs twice
+ */
+static clause* clause_new(sat_solver* s, lit* begin, lit* end, int learnt)
+{
+    int size;
+    clause* c;
+    int i;
+
+    assert(end - begin > 1);
+    assert(learnt >= 0 && learnt < 2);
+    size           = end - begin;
+//    c              = (clause*)malloc(sizeof(clause) + sizeof(lit) * size + learnt * sizeof(float));
+#ifdef SAT_USE_SYSTEM_MEMORY_MANAGEMENT
+    c = (clause*)malloc(sizeof(clause) + sizeof(lit) * size + learnt * sizeof(float));
+#else
+    c = (clause*)Sat_MmStepEntryFetch( s->pMem, sizeof(clause) + sizeof(lit) * size + learnt * sizeof(float) );
+#endif
+
+    c->size_learnt = (size << 1) | learnt;
+    assert(((unsigned long)c & 1) == 0);
+
+    for (i = 0; i < size; i++)
+        c->lits[i] = begin[i];
+
+    if (learnt)
+        *((float*)&c->lits[size]) = 0.0;
+
+    assert(begin[0] >= 0);
+    assert(begin[0] < s->size*2);
+    assert(begin[1] >= 0);
+    assert(begin[1] < s->size*2);
+
+    assert(lit_neg(begin[0]) < s->size*2);
+    assert(lit_neg(begin[1]) < s->size*2);
+
+    //vecp_push(sat_solver_read_wlist(s,lit_neg(begin[0])),(void*)c);
+    //vecp_push(sat_solver_read_wlist(s,lit_neg(begin[1])),(void*)c);
+
+    vecp_push(sat_solver_read_wlist(s,lit_neg(begin[0])),(void*)(size > 2 ? c : clause_from_lit(begin[1])));
+    vecp_push(sat_solver_read_wlist(s,lit_neg(begin[1])),(void*)(size > 2 ? c : clause_from_lit(begin[0])));
+
+    return c;
+}
+
+
+static void clause_remove(sat_solver* s, clause* c)
+{
+    lit* lits = clause_begin(c);
+    assert(lit_neg(lits[0]) < s->size*2);
+    assert(lit_neg(lits[1]) < s->size*2);
+
+    //vecp_remove(sat_solver_read_wlist(s,lit_neg(lits[0])),(void*)c);
+    //vecp_remove(sat_solver_read_wlist(s,lit_neg(lits[1])),(void*)c);
+
+    assert(lits[0] < s->size*2);
+    vecp_remove(sat_solver_read_wlist(s,lit_neg(lits[0])),(void*)(clause_size(c) > 2 ? c : clause_from_lit(lits[1])));
+    vecp_remove(sat_solver_read_wlist(s,lit_neg(lits[1])),(void*)(clause_size(c) > 2 ? c : clause_from_lit(lits[0])));
+
+    if (clause_learnt(c)){
+        s->stats.learnts--;
+        s->stats.learnts_literals -= clause_size(c);
+    }else{
+        s->stats.clauses--;
+        s->stats.clauses_literals -= clause_size(c);
+    }
+
+#ifdef SAT_USE_SYSTEM_MEMORY_MANAGEMENT
+    free(c);
+#else
+    Sat_MmStepEntryRecycle( s->pMem, (char *)c, sizeof(clause) + sizeof(lit) * clause_size(c) + clause_learnt(c) * sizeof(float) );
+#endif
+}
+
+
+static lbool clause_simplify(sat_solver* s, clause* c)
+{
+    lit*   lits   = clause_begin(c);
+    lbool* values = s->assigns;
+    int i;
+
+    assert(sat_solver_dlevel(s) == 0);
+
+    for (i = 0; i < clause_size(c); i++){
+        lbool sig = !lit_sign(lits[i]); sig += sig - 1;
+        if (values[lit_var(lits[i])] == sig)
+            return l_True;
+    }
+    return l_False;
+}
+
+//=================================================================================================
+// Minor (solver) functions:
+
+void sat_solver_setnvars(sat_solver* s,int n)
+{
+    int var;
+
+    if (s->cap < n){
+
+        while (s->cap < n) s->cap = s->cap*2+1;
+
+        s->wlists    = (vecp*)   realloc(s->wlists,   sizeof(vecp)*s->cap*2);
+        s->activity  = (double*) realloc(s->activity, sizeof(double)*s->cap);
+        s->factors   = (double*) realloc(s->factors,  sizeof(double)*s->cap);
+        s->assigns   = (lbool*)  realloc(s->assigns,  sizeof(lbool)*s->cap);
+        s->orderpos  = (int*)    realloc(s->orderpos, sizeof(int)*s->cap);
+        s->reasons   = (clause**)realloc(s->reasons,  sizeof(clause*)*s->cap);
+        s->levels    = (int*)    realloc(s->levels,   sizeof(int)*s->cap);
+        s->tags      = (lbool*)  realloc(s->tags,     sizeof(lbool)*s->cap);
+        s->trail     = (lit*)    realloc(s->trail,    sizeof(lit)*s->cap);
+    }
+
+    for (var = s->size; var < n; var++){
+        vecp_new(&s->wlists[2*var]);
+        vecp_new(&s->wlists[2*var+1]);
+        s->activity [var] = 0;
+        s->factors  [var] = 0;
+        s->assigns  [var] = l_Undef;
+        s->orderpos [var] = veci_size(&s->order);
+        s->reasons  [var] = (clause*)0;
+        s->levels   [var] = 0;
+        s->tags     [var] = l_Undef;
+        
+        /* does not hold because variables enqueued at top level will not be reinserted in the heap
+           assert(veci_size(&s->order) == var); 
+         */
+        veci_push(&s->order,var);
+        order_update(s, var);
+    }
+
+    s->size = n > s->size ? n : s->size;
+}
+
+
+static inline bool enqueue(sat_solver* s, lit l, clause* from)
+{
+    lbool* values = s->assigns;
+    int    v      = lit_var(l);
+    lbool  val    = values[v];
+#ifdef VERBOSEDEBUG
+    printf(L_IND"enqueue("L_LIT")\n", L_ind, L_lit(l));
+#endif
+
+    lbool sig = !lit_sign(l); sig += sig - 1;
+    if (val != l_Undef){
+        return val == sig;
+    }else{
+        // New fact -- store it.
+#ifdef VERBOSEDEBUG
+        printf(L_IND"bind("L_LIT")\n", L_ind, L_lit(l));
+#endif
+        int*     levels  = s->levels;
+        clause** reasons = s->reasons;
+
+        values [v] = sig;
+        levels [v] = sat_solver_dlevel(s);
+        reasons[v] = from;
+        s->trail[s->qtail++] = l;
+
+        order_assigned(s, v);
+        return true;
+    }
+}
+
+
+static inline void assume(sat_solver* s, lit l){
+    assert(s->qtail == s->qhead);
+    assert(s->assigns[lit_var(l)] == l_Undef);
+#ifdef VERBOSEDEBUG
+    printf(L_IND"assume("L_LIT")\n", L_ind, L_lit(l));
+#endif
+    veci_push(&s->trail_lim,s->qtail);
+    enqueue(s,l,(clause*)0);
+}
+
+
+static void sat_solver_canceluntil(sat_solver* s, int level) {
+    lit*     trail;   
+    lbool*   values;  
+    clause** reasons; 
+    int      bound;
+    int      c;
+    
+    if (sat_solver_dlevel(s) <= level)
+        return;
+
+    trail   = s->trail;
+    values  = s->assigns;
+    reasons = s->reasons;
+    bound   = (veci_begin(&s->trail_lim))[level];
+
+    ////////////////////////////////////////
+    // added to cancel all assignments
+//    if ( level == -1 )
+//        bound = 0;
+    ////////////////////////////////////////
+
+    for (c = s->qtail-1; c >= bound; c--) {
+        int     x  = lit_var(trail[c]);
+        values [x] = l_Undef;
+        reasons[x] = (clause*)0;
+    }
+
+    for (c = s->qhead-1; c >= bound; c--)
+        order_unassigned(s,lit_var(trail[c]));
+
+    s->qhead = s->qtail = bound;
+    veci_resize(&s->trail_lim,level);
+}
+
+static void sat_solver_record(sat_solver* s, veci* cls)
+{
+    lit*    begin = veci_begin(cls);
+    lit*    end   = begin + veci_size(cls);
+    clause* c     = (veci_size(cls) > 1) ? clause_new(s,begin,end,1) : (clause*)0;
+    enqueue(s,*begin,c);
+
+    ///////////////////////////////////
+    // add clause to internal storage
+    if ( s->pStore )
+    {
+        extern int Sto_ManAddClause( void * p, lit * pBeg, lit * pEnd );
+        int RetValue = Sto_ManAddClause( s->pStore, begin, end );
+        assert( RetValue );
+    }
+    ///////////////////////////////////
+
+    assert(veci_size(cls) > 0);
+
+    if (c != 0) {
+        vecp_push(&s->learnts,c);
+        act_clause_bump(s,c);
+        s->stats.learnts++;
+        s->stats.learnts_literals += veci_size(cls);
+    }
+}
+
+
+static double sat_solver_progress(sat_solver* s)
+{
+    lbool*  values = s->assigns;
+    int*    levels = s->levels;
+    int     i;
+
+    double  progress = 0;
+    double  F        = 1.0 / s->size;
+    for (i = 0; i < s->size; i++)
+        if (values[i] != l_Undef)
+            progress += pow(F, levels[i]);
+    return progress / s->size;
+}
+
+//=================================================================================================
+// Major methods:
+
+static bool sat_solver_lit_removable(sat_solver* s, lit l, int minl)
+{
+    lbool*   tags    = s->tags;
+    clause** reasons = s->reasons;
+    int*     levels  = s->levels;
+    int      top     = veci_size(&s->tagged);
+
+    assert(lit_var(l) >= 0 && lit_var(l) < s->size);
+    assert(reasons[lit_var(l)] != 0);
+    veci_resize(&s->stack,0);
+    veci_push(&s->stack,lit_var(l));
+
+    while (veci_size(&s->stack) > 0){
+        clause* c;
+        int v = veci_begin(&s->stack)[veci_size(&s->stack)-1];
+        assert(v >= 0 && v < s->size);
+        veci_resize(&s->stack,veci_size(&s->stack)-1);
+        assert(reasons[v] != 0);
+        c    = reasons[v];
+
+        if (clause_is_lit(c)){
+            int v = lit_var(clause_read_lit(c));
+            if (tags[v] == l_Undef && levels[v] != 0){
+                if (reasons[v] != 0 && ((1 << (levels[v] & 31)) & minl)){
+                    veci_push(&s->stack,v);
+                    tags[v] = l_True;
+                    veci_push(&s->tagged,v);
+                }else{
+                    int* tagged = veci_begin(&s->tagged);
+                    int j;
+                    for (j = top; j < veci_size(&s->tagged); j++)
+                        tags[tagged[j]] = l_Undef;
+                    veci_resize(&s->tagged,top);
+                    return false;
+                }
+            }
+        }else{
+            lit*    lits = clause_begin(c);
+            int     i, j;
+
+            for (i = 1; i < clause_size(c); i++){
+                int v = lit_var(lits[i]);
+                if (tags[v] == l_Undef && levels[v] != 0){
+                    if (reasons[v] != 0 && ((1 << (levels[v] & 31)) & minl)){
+
+                        veci_push(&s->stack,lit_var(lits[i]));
+                        tags[v] = l_True;
+                        veci_push(&s->tagged,v);
+                    }else{
+                        int* tagged = veci_begin(&s->tagged);
+                        for (j = top; j < veci_size(&s->tagged); j++)
+                            tags[tagged[j]] = l_Undef;
+                        veci_resize(&s->tagged,top);
+                        return false;
+                    }
+                }
+            }
+        }
+    }
+
+    return true;
+}
+
+static void sat_solver_analyze(sat_solver* s, clause* c, veci* learnt)
+{
+    lit*     trail   = s->trail;
+    lbool*   tags    = s->tags;
+    clause** reasons = s->reasons;
+    int*     levels  = s->levels;
+    int      cnt     = 0;
+    lit      p       = lit_Undef;
+    int      ind     = s->qtail-1;
+    lit*     lits;
+    int      i, j, minl;
+    int*     tagged;
+
+    veci_push(learnt,lit_Undef);
+
+    do{
+        assert(c != 0);
+
+        if (clause_is_lit(c)){
+            lit q = clause_read_lit(c);
+            assert(lit_var(q) >= 0 && lit_var(q) < s->size);
+            if (tags[lit_var(q)] == l_Undef && levels[lit_var(q)] > 0){
+                tags[lit_var(q)] = l_True;
+                veci_push(&s->tagged,lit_var(q));
+                act_var_bump(s,lit_var(q));
+                if (levels[lit_var(q)] == sat_solver_dlevel(s))
+                    cnt++;
+                else
+                    veci_push(learnt,q);
+            }
+        }else{
+
+            if (clause_learnt(c))
+                act_clause_bump(s,c);
+
+            lits = clause_begin(c);
+            //printlits(lits,lits+clause_size(c)); printf("\n");
+            for (j = (p == lit_Undef ? 0 : 1); j < clause_size(c); j++){
+                lit q = lits[j];
+                assert(lit_var(q) >= 0 && lit_var(q) < s->size);
+                if (tags[lit_var(q)] == l_Undef && levels[lit_var(q)] > 0){
+                    tags[lit_var(q)] = l_True;
+                    veci_push(&s->tagged,lit_var(q));
+                    act_var_bump(s,lit_var(q));
+                    if (levels[lit_var(q)] == sat_solver_dlevel(s))
+                        cnt++;
+                    else
+                        veci_push(learnt,q);
+                }
+            }
+        }
+
+        while (tags[lit_var(trail[ind--])] == l_Undef);
+
+        p = trail[ind+1];
+        c = reasons[lit_var(p)];
+        cnt--;
+
+    }while (cnt > 0);
+
+    *veci_begin(learnt) = lit_neg(p);
+
+    lits = veci_begin(learnt);
+    minl = 0;
+    for (i = 1; i < veci_size(learnt); i++){
+        int lev = levels[lit_var(lits[i])];
+        minl    |= 1 << (lev & 31);
+    }
+
+    // simplify (full)
+    for (i = j = 1; i < veci_size(learnt); i++){
+        if (reasons[lit_var(lits[i])] == 0 || !sat_solver_lit_removable(s,lits[i],minl))
+            lits[j++] = lits[i];
+    }
+
+    // update size of learnt + statistics
+    s->stats.max_literals += veci_size(learnt);
+    veci_resize(learnt,j);
+    s->stats.tot_literals += j;
+
+    // clear tags
+    tagged = veci_begin(&s->tagged);
+    for (i = 0; i < veci_size(&s->tagged); i++)
+        tags[tagged[i]] = l_Undef;
+    veci_resize(&s->tagged,0);
+
+#ifdef DEBUG
+    for (i = 0; i < s->size; i++)
+        assert(tags[i] == l_Undef);
+#endif
+
+#ifdef VERBOSEDEBUG
+    printf(L_IND"Learnt {", L_ind);
+    for (i = 0; i < veci_size(learnt); i++) printf(" "L_LIT, L_lit(lits[i]));
+#endif
+    if (veci_size(learnt) > 1){
+        int max_i = 1;
+        int max   = levels[lit_var(lits[1])];
+        lit tmp;
+
+        for (i = 2; i < veci_size(learnt); i++)
+            if (levels[lit_var(lits[i])] > max){
+                max   = levels[lit_var(lits[i])];
+                max_i = i;
+            }
+
+        tmp         = lits[1];
+        lits[1]     = lits[max_i];
+        lits[max_i] = tmp;
+    }
+#ifdef VERBOSEDEBUG
+    {
+        int lev = veci_size(learnt) > 1 ? levels[lit_var(lits[1])] : 0;
+        printf(" } at level %d\n", lev);
+    }
+#endif
+}
+
+
+clause* sat_solver_propagate(sat_solver* s)
+{
+    lbool*  values = s->assigns;
+    clause* confl  = (clause*)0;
+    lit*    lits;
+
+    //printf("sat_solver_propagate\n");
+    while (confl == 0 && s->qtail - s->qhead > 0){
+        lit  p  = s->trail[s->qhead++];
+        vecp* ws = sat_solver_read_wlist(s,p);
+        clause **begin = (clause**)vecp_begin(ws);
+        clause **end   = begin + vecp_size(ws);
+        clause **i, **j;
+
+        s->stats.propagations++;
+        s->simpdb_props--;
+
+        //printf("checking lit %d: "L_LIT"\n", veci_size(ws), L_lit(p));
+        for (i = j = begin; i < end; ){
+            if (clause_is_lit(*i)){
+//                s->stats.inspects2++;
+                *j++ = *i;
+                if (!enqueue(s,clause_read_lit(*i),clause_from_lit(p))){
+                    confl = s->binary;
+                    (clause_begin(confl))[1] = lit_neg(p);
+                    (clause_begin(confl))[0] = clause_read_lit(*i++);
+                    // Copy the remaining watches:
+//                    s->stats.inspects2 += end - i;
+                    while (i < end)
+                        *j++ = *i++;
+                }
+            }else{
+                lit false_lit;
+                lbool sig;
+
+                lits = clause_begin(*i);
+
+                // Make sure the false literal is data[1]:
+                false_lit = lit_neg(p);
+                if (lits[0] == false_lit){
+                    lits[0] = lits[1];
+                    lits[1] = false_lit;
+                }
+                assert(lits[1] == false_lit);
+                //printf("checking clause: "); printlits(lits, lits+clause_size(*i)); printf("\n");
+
+                // If 0th watch is true, then clause is already satisfied.
+                sig = !lit_sign(lits[0]); sig += sig - 1;
+                if (values[lit_var(lits[0])] == sig){
+                    *j++ = *i;
+                }else{
+                    // Look for new watch:
+                    lit* stop = lits + clause_size(*i);
+                    lit* k;
+                    for (k = lits + 2; k < stop; k++){
+                        lbool sig = lit_sign(*k); sig += sig - 1;
+                        if (values[lit_var(*k)] != sig){
+                            lits[1] = *k;
+                            *k = false_lit;
+                            vecp_push(sat_solver_read_wlist(s,lit_neg(lits[1])),*i);
+                            goto next; }
+                    }
+
+                    *j++ = *i;
+                    // Clause is unit under assignment:
+                    if (!enqueue(s,lits[0], *i)){
+                        confl = *i++;
+                        // Copy the remaining watches:
+//                        s->stats.inspects2 += end - i;
+                        while (i < end)
+                            *j++ = *i++;
+                    }
+                }
+            }
+        next:
+            i++;
+        }
+
+        s->stats.inspects += j - (clause**)vecp_begin(ws);
+        vecp_resize(ws,j - (clause**)vecp_begin(ws));
+    }
+
+    return confl;
+}
+
+static inline int clause_cmp (const void* x, const void* y) {
+    return clause_size((clause*)x) > 2 && (clause_size((clause*)y) == 2 || clause_activity((clause*)x) < clause_activity((clause*)y)) ? -1 : 1; }
+
+void sat_solver_reducedb(sat_solver* s)
+{
+    int      i, j;
+    double   extra_lim = s->cla_inc / vecp_size(&s->learnts); // Remove any clause below this activity
+    clause** learnts = (clause**)vecp_begin(&s->learnts);
+    clause** reasons = s->reasons;
+
+    sat_solver_sort(vecp_begin(&s->learnts), vecp_size(&s->learnts), &clause_cmp);
+
+    for (i = j = 0; i < vecp_size(&s->learnts) / 2; i++){
+        if (clause_size(learnts[i]) > 2 && reasons[lit_var(*clause_begin(learnts[i]))] != learnts[i])
+            clause_remove(s,learnts[i]);
+        else
+            learnts[j++] = learnts[i];
+    }
+    for (; i < vecp_size(&s->learnts); i++){
+        if (clause_size(learnts[i]) > 2 && reasons[lit_var(*clause_begin(learnts[i]))] != learnts[i] && clause_activity(learnts[i]) < extra_lim)
+            clause_remove(s,learnts[i]);
+        else
+            learnts[j++] = learnts[i];
+    }
+
+    //printf("reducedb deleted %d\n", vecp_size(&s->learnts) - j);
+
+
+    vecp_resize(&s->learnts,j);
+}
+
+static lbool sat_solver_search(sat_solver* s, sint64 nof_conflicts, sint64 nof_learnts)
+{
+    int*    levels          = s->levels;
+    double  var_decay       = 0.95;
+    double  clause_decay    = 0.999;
+    double  random_var_freq = 0.02;
+
+    sint64  conflictC       = 0;
+    veci    learnt_clause;
+    int     i;
+
+    assert(s->root_level == sat_solver_dlevel(s));
+
+    s->nRestarts++;
+    s->stats.starts++;
+    s->var_decay = (float)(1 / var_decay   );
+    s->cla_decay = (float)(1 / clause_decay);
+    veci_resize(&s->model,0);
+    veci_new(&learnt_clause);
+
+    // use activity factors in every even restart
+    if ( (s->nRestarts & 1) && veci_size(&s->act_vars) > 0 )
+        for ( i = 0; i < s->act_vars.size; i++ )
+            act_var_bump_factor(s, s->act_vars.ptr[i]);
+
+    for (;;){
+        clause* confl = sat_solver_propagate(s);
+        if (confl != 0){
+            // CONFLICT
+            int blevel;
+
+#ifdef VERBOSEDEBUG
+            printf(L_IND"**CONFLICT**\n", L_ind);
+#endif
+            s->stats.conflicts++; conflictC++;
+            if (sat_solver_dlevel(s) == s->root_level){
+                veci_delete(&learnt_clause);
+                return l_False;
+            }
+
+            veci_resize(&learnt_clause,0);
+            sat_solver_analyze(s, confl, &learnt_clause);
+            blevel = veci_size(&learnt_clause) > 1 ? levels[lit_var(veci_begin(&learnt_clause)[1])] : s->root_level;
+            blevel = s->root_level > blevel ? s->root_level : blevel;
+            sat_solver_canceluntil(s,blevel);
+            sat_solver_record(s,&learnt_clause);
+            act_var_decay(s);
+            act_clause_decay(s);
+
+        }else{
+            // NO CONFLICT
+            int next;
+
+            if (nof_conflicts >= 0 && conflictC >= nof_conflicts){
+                // Reached bound on number of conflicts:
+                s->progress_estimate = sat_solver_progress(s);
+                sat_solver_canceluntil(s,s->root_level);
+                veci_delete(&learnt_clause);
+                return l_Undef; }
+
+            if ( (s->nConfLimit && s->stats.conflicts > s->nConfLimit) ||
+                 (s->nInsLimit  && s->stats.inspects  > s->nInsLimit) )
+            {
+                // Reached bound on number of conflicts:
+                s->progress_estimate = sat_solver_progress(s);
+                sat_solver_canceluntil(s,s->root_level);
+                veci_delete(&learnt_clause);
+                return l_Undef; 
+            }
+
+            if (sat_solver_dlevel(s) == 0 && !s->fSkipSimplify)
+                // Simplify the set of problem clauses:
+                sat_solver_simplify(s);
+
+            if (nof_learnts >= 0 && vecp_size(&s->learnts) - s->qtail >= nof_learnts)
+                // Reduce the set of learnt clauses:
+                sat_solver_reducedb(s);
+
+            // New variable decision:
+            s->stats.decisions++;
+            next = order_select(s,(float)random_var_freq);
+
+            if (next == var_Undef){
+                // Model found:
+                lbool* values = s->assigns;
+                int i;
+                veci_resize(&s->model, 0);
+                for (i = 0; i < s->size; i++) 
+                    veci_push(&s->model,(int)values[i]);
+                sat_solver_canceluntil(s,s->root_level);
+                veci_delete(&learnt_clause);
+
+                /*
+                veci apa; veci_new(&apa);
+                for (i = 0; i < s->size; i++) 
+                    veci_push(&apa,(int)(s->model.ptr[i] == l_True ? toLit(i) : lit_neg(toLit(i))));
+                printf("model: "); printlits((lit*)apa.ptr, (lit*)apa.ptr + veci_size(&apa)); printf("\n");
+                veci_delete(&apa);
+                */
+
+                return l_True;
+            }
+
+            assume(s,lit_neg(toLit(next)));
+        }
+    }
+
+    return l_Undef; // cannot happen
+}
+
+//=================================================================================================
+// External solver functions:
+
+sat_solver* sat_solver_new(void)
+{
+    sat_solver* s = (sat_solver*)malloc(sizeof(sat_solver));
+    memset( s, 0, sizeof(sat_solver) );
+
+    // initialize vectors
+    vecp_new(&s->clauses);
+    vecp_new(&s->learnts);
+    veci_new(&s->order);
+    veci_new(&s->trail_lim);
+    veci_new(&s->tagged);
+    veci_new(&s->stack);
+    veci_new(&s->model);
+    veci_new(&s->act_vars);
+
+    // initialize arrays
+    s->wlists    = 0;
+    s->activity  = 0;
+    s->factors   = 0;
+    s->assigns   = 0;
+    s->orderpos  = 0;
+    s->reasons   = 0;
+    s->levels    = 0;
+    s->tags      = 0;
+    s->trail     = 0;
+
+
+    // initialize other vars
+    s->size                   = 0;
+    s->cap                    = 0;
+    s->qhead                  = 0;
+    s->qtail                  = 0;
+    s->cla_inc                = 1;
+    s->cla_decay              = 1;
+    s->var_inc                = 1;
+    s->var_decay              = 1;
+    s->root_level             = 0;
+    s->simpdb_assigns         = 0;
+    s->simpdb_props           = 0;
+    s->random_seed            = 91648253;
+    s->progress_estimate      = 0;
+    s->binary                 = (clause*)malloc(sizeof(clause) + sizeof(lit)*2);
+    s->binary->size_learnt    = (2 << 1);
+    s->verbosity              = 0;
+
+    s->stats.starts           = 0;
+    s->stats.decisions        = 0;
+    s->stats.propagations     = 0;
+    s->stats.inspects         = 0;
+    s->stats.conflicts        = 0;
+    s->stats.clauses          = 0;
+    s->stats.clauses_literals = 0;
+    s->stats.learnts          = 0;
+    s->stats.learnts_literals = 0;
+    s->stats.max_literals     = 0;
+    s->stats.tot_literals     = 0;
+
+#ifdef SAT_USE_SYSTEM_MEMORY_MANAGEMENT
+    s->pMem = NULL;
+#else
+    s->pMem = Sat_MmStepStart( 10 );
+#endif
+    return s;
+}
+
+
+void sat_solver_delete(sat_solver* s)
+{
+
+#ifdef SAT_USE_SYSTEM_MEMORY_MANAGEMENT
+    int i;
+    for (i = 0; i < vecp_size(&s->clauses); i++)
+        free(vecp_begin(&s->clauses)[i]);
+    for (i = 0; i < vecp_size(&s->learnts); i++)
+        free(vecp_begin(&s->learnts)[i]);
+#else
+    Sat_MmStepStop( s->pMem, 0 );
+#endif
+
+    // delete vectors
+    vecp_delete(&s->clauses);
+    vecp_delete(&s->learnts);
+    veci_delete(&s->order);
+    veci_delete(&s->trail_lim);
+    veci_delete(&s->tagged);
+    veci_delete(&s->stack);
+    veci_delete(&s->model);
+    veci_delete(&s->act_vars);
+    free(s->binary);
+
+    // delete arrays
+    if (s->wlists != 0){
+        int i;
+        for (i = 0; i < s->size*2; i++)
+            vecp_delete(&s->wlists[i]);
+
+        // if one is different from null, all are
+        free(s->wlists   );
+        free(s->activity );
+        free(s->factors  );
+        free(s->assigns  );
+        free(s->orderpos );
+        free(s->reasons  );
+        free(s->levels   );
+        free(s->trail    );
+        free(s->tags     );
+    }
+
+    sat_solver_store_free(s);
+    free(s);
+}
+
+
+bool sat_solver_addclause(sat_solver* s, lit* begin, lit* end)
+{
+    lit *i,*j;
+    int maxvar;
+    lbool* values;
+    lit last;
+
+    if (begin == end) return false;
+
+    //printlits(begin,end); printf("\n");
+    // insertion sort
+    maxvar = lit_var(*begin);
+    for (i = begin + 1; i < end; i++){
+        lit l = *i;
+        maxvar = lit_var(l) > maxvar ? lit_var(l) : maxvar;
+        for (j = i; j > begin && *(j-1) > l; j--)
+            *j = *(j-1);
+        *j = l;
+    }
+    sat_solver_setnvars(s,maxvar+1);
+//    sat_solver_setnvars(s, lit_var(*(end-1))+1 );
+
+    //printlits(begin,end); printf("\n");
+    values = s->assigns;
+
+    // delete duplicates
+    last = lit_Undef;
+    for (i = j = begin; i < end; i++){
+        //printf("lit: "L_LIT", value = %d\n", L_lit(*i), (lit_sign(*i) ? -values[lit_var(*i)] : values[lit_var(*i)]));
+        lbool sig = !lit_sign(*i); sig += sig - 1;
+        if (*i == lit_neg(last) || sig == values[lit_var(*i)])
+            return true;   // tautology
+        else if (*i != last && values[lit_var(*i)] == l_Undef)
+            last = *j++ = *i;
+    }
+
+    //printf("final: "); printlits(begin,j); printf("\n");
+
+    if (j == begin)          // empty clause
+        return false;
+
+    ///////////////////////////////////
+    // add clause to internal storage
+    if ( s->pStore )
+    {
+        extern int Sto_ManAddClause( void * p, lit * pBeg, lit * pEnd );
+        int RetValue = Sto_ManAddClause( s->pStore, begin, j );
+        assert( RetValue );
+    }
+    ///////////////////////////////////
+
+    if (j - begin == 1) // unit clause
+        return enqueue(s,*begin,(clause*)0);
+
+    // create new clause
+    vecp_push(&s->clauses,clause_new(s,begin,j,0));
+
+
+    s->stats.clauses++;
+    s->stats.clauses_literals += j - begin;
+
+    return true;
+}
+
+
+bool sat_solver_simplify(sat_solver* s)
+{
+    clause** reasons;
+    int type;
+
+    assert(sat_solver_dlevel(s) == 0);
+
+    if (sat_solver_propagate(s) != 0)
+        return false;
+
+    if (s->qhead == s->simpdb_assigns || s->simpdb_props > 0)
+        return true;
+
+    reasons = s->reasons;
+    for (type = 0; type < 2; type++){
+        vecp*    cs  = type ? &s->learnts : &s->clauses;
+        clause** cls = (clause**)vecp_begin(cs);
+
+        int i, j;
+        for (j = i = 0; i < vecp_size(cs); i++){
+            if (reasons[lit_var(*clause_begin(cls[i]))] != cls[i] &&
+                clause_simplify(s,cls[i]) == l_True)
+                clause_remove(s,cls[i]);
+            else
+                cls[j++] = cls[i];
+        }
+        vecp_resize(cs,j);
+    }
+
+    s->simpdb_assigns = s->qhead;
+    // (shouldn't depend on 'stats' really, but it will do for now)
+    s->simpdb_props   = (int)(s->stats.clauses_literals + s->stats.learnts_literals);
+
+    return true;
+}
+
+
+int sat_solver_solve(sat_solver* s, lit* begin, lit* end, sint64 nConfLimit, sint64 nInsLimit, sint64 nConfLimitGlobal, sint64 nInsLimitGlobal)
+{
+    sint64  nof_conflicts = 100;
+    sint64  nof_learnts   = sat_solver_nclauses(s) / 3;
+    lbool   status        = l_Undef;
+    lbool*  values        = s->assigns;
+    lit*    i;
+
+    // set the external limits
+    s->nCalls++;
+    s->nRestarts  = 0;
+    s->nConfLimit = 0;
+    s->nInsLimit  = 0;
+    if ( nConfLimit )
+        s->nConfLimit = s->stats.conflicts + nConfLimit;
+    if ( nInsLimit )
+        s->nInsLimit = s->stats.inspects + nInsLimit;
+    if ( nConfLimitGlobal && (s->nConfLimit == 0 || s->nConfLimit > nConfLimitGlobal) )
+        s->nConfLimit = nConfLimitGlobal;
+    if ( nInsLimitGlobal && (s->nInsLimit == 0 || s->nInsLimit > nInsLimitGlobal) )
+        s->nInsLimit = nInsLimitGlobal;
+
+    //printf("solve: "); printlits(begin, end); printf("\n");
+    for (i = begin; i < end; i++){
+        switch (lit_sign(*i) ? -values[lit_var(*i)] : values[lit_var(*i)]){
+        case 1: /* l_True: */
+            break;
+        case 0: /* l_Undef */
+            assume(s, *i);
+            if (sat_solver_propagate(s) == NULL)
+                break;
+            // fallthrough
+        case -1: /* l_False */
+            sat_solver_canceluntil(s, 0);
+            return l_False;
+        }
+    }
+    s->nCalls2++;
+
+    s->root_level = sat_solver_dlevel(s);
+
+    if (s->verbosity >= 1){
+        printf("==================================[MINISAT]===================================\n");
+        printf("| Conflicts |     ORIGINAL     |              LEARNT              | Progress |\n");
+        printf("|           | Clauses Literals |   Limit Clauses Literals  Lit/Cl |          |\n");
+        printf("==============================================================================\n");
+    }
+
+    while (status == l_Undef){
+        double Ratio = (s->stats.learnts == 0)? 0.0 :
+            s->stats.learnts_literals / (double)s->stats.learnts;
+
+        if (s->verbosity >= 1)
+        {
+            printf("| %9.0f | %7.0f %8.0f | %7.0f %7.0f %8.0f %7.1f | %6.3f %% |\n", 
+                (double)s->stats.conflicts,
+                (double)s->stats.clauses, 
+                (double)s->stats.clauses_literals,
+                (double)nof_learnts, 
+                (double)s->stats.learnts, 
+                (double)s->stats.learnts_literals,
+                Ratio,
+                s->progress_estimate*100);
+            fflush(stdout);
+        }
+        status = sat_solver_search(s, nof_conflicts, nof_learnts);
+        nof_conflicts = nof_conflicts * 3 / 2; //*= 1.5;
+        nof_learnts   = nof_learnts * 11 / 10; //*= 1.1;
+
+        // quit the loop if reached an external limit
+        if ( s->nConfLimit && s->stats.conflicts > s->nConfLimit )
+        {
+//            printf( "Reached the limit on the number of conflicts (%d).\n", s->nConfLimit );
+            break;
+        }
+        if ( s->nInsLimit  && s->stats.inspects > s->nInsLimit )
+        {
+//            printf( "Reached the limit on the number of implications (%d).\n", s->nInsLimit );
+            break;
+        }
+    }
+    if (s->verbosity >= 1)
+        printf("==============================================================================\n");
+
+    sat_solver_canceluntil(s,0);
+
+    ////////////////////////////////////////////////
+    if ( status == l_False && s->pStore )
+    {
+        extern int Sto_ManAddClause( void * p, lit * pBeg, lit * pEnd );
+        int RetValue = Sto_ManAddClause( s->pStore, NULL, NULL );
+        assert( RetValue );
+    }
+    ////////////////////////////////////////////////
+    return status;
+}
+
+
+int sat_solver_nvars(sat_solver* s)
+{
+    return s->size;
+}
+
+
+int sat_solver_nclauses(sat_solver* s)
+{
+    return vecp_size(&s->clauses);
+}
+
+
+int sat_solver_nconflicts(sat_solver* s)
+{
+    return (int)s->stats.conflicts;
+}
+
+//=================================================================================================
+// Clause storage functions:
+
+void sat_solver_store_alloc( sat_solver * s )
+{
+    extern void * Sto_ManAlloc();
+    assert( s->pStore == NULL );
+    s->pStore = Sto_ManAlloc();
+}
+
+void sat_solver_store_write( sat_solver * s, char * pFileName )
+{
+    extern void Sto_ManDumpClauses( void * p, char * pFileName );
+    if ( s->pStore ) Sto_ManDumpClauses( s->pStore, pFileName );
+}
+
+void sat_solver_store_free( sat_solver * s )
+{
+    extern void Sto_ManFree( void * p );
+    if ( s->pStore ) Sto_ManFree( s->pStore );
+    s->pStore = NULL;
+}
+ 
+void sat_solver_store_mark_roots( sat_solver * s )
+{
+    extern void Sto_ManMarkRoots( void * p );
+    if ( s->pStore ) Sto_ManMarkRoots( s->pStore );
+}
+
+void sat_solver_store_mark_clauses_a( sat_solver * s )
+{
+    extern void Sto_ManMarkClausesA( void * p );
+    if ( s->pStore ) Sto_ManMarkClausesA( s->pStore );
+}
+
+void * sat_solver_store_release( sat_solver * s )
+{
+    void * pTemp;
+    if ( s->pStore == NULL )
+        return NULL;
+    pTemp = s->pStore;
+    s->pStore = NULL;
+    return pTemp;
+}
+
+//=================================================================================================
+// Sorting functions (sigh):
+
+static inline void selectionsort(void** array, int size, int(*comp)(const void *, const void *))
+{
+    int     i, j, best_i;
+    void*   tmp;
+
+    for (i = 0; i < size-1; i++){
+        best_i = i;
+        for (j = i+1; j < size; j++){
+            if (comp(array[j], array[best_i]) < 0)
+                best_i = j;
+        }
+        tmp = array[i]; array[i] = array[best_i]; array[best_i] = tmp;
+    }
+}
+
+
+static void sortrnd(void** array, int size, int(*comp)(const void *, const void *), double* seed)
+{
+    if (size <= 15)
+        selectionsort(array, size, comp);
+
+    else{
+        void*       pivot = array[irand(seed, size)];
+        void*       tmp;
+        int         i = -1;
+        int         j = size;
+
+        for(;;){
+            do i++; while(comp(array[i], pivot)<0);
+            do j--; while(comp(pivot, array[j])<0);
+
+            if (i >= j) break;
+
+            tmp = array[i]; array[i] = array[j]; array[j] = tmp;
+        }
+
+        sortrnd(array    , i     , comp, seed);
+        sortrnd(&array[i], size-i, comp, seed);
+    }
+}
+
+void sat_solver_sort(void** array, int size, int(*comp)(const void *, const void *))
+{
+    double seed = 91648253;
+    sortrnd(array,size,comp,&seed);
+}
diff --git a/src/sat/bsat/satSolver.h b/src/sat/bsat/satSolver.h
new file mode 100644
index 00000000..542b9895
--- /dev/null
+++ b/src/sat/bsat/satSolver.h
@@ -0,0 +1,191 @@
+/**************************************************************************************************
+MiniSat -- Copyright (c) 2005, Niklas Sorensson
+http://www.cs.chalmers.se/Cs/Research/FormalMethods/MiniSat/
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute,
+sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or
+substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+**************************************************************************************************/
+// Modified to compile with MS Visual Studio 6.0 by Alan Mishchenko
+
+#ifndef satSolver_h
+#define satSolver_h
+
+#ifdef _WIN32
+#define inline __inline // compatible with MS VS 6.0
+#endif
+
+#include "satVec.h"
+#include "satMem.h"
+
+//=================================================================================================
+// Simple types:
+
+// does not work for c++
+//typedef int                   bool;
+#ifndef __cplusplus
+#ifndef bool
+#define bool int
+#endif
+#endif
+
+static const bool  true      = 1;
+static const bool  false     = 0;
+
+typedef int                lit;
+typedef char               lbool;
+
+#ifndef SINT64
+#define SINT64
+
+#ifdef _WIN32
+typedef signed __int64     sint64;   // compatible with MS VS 6.0
+#else
+typedef long long          sint64;
+#endif
+
+#endif
+
+static const int   var_Undef = -1;
+static const lit   lit_Undef = -2;
+
+static const lbool l_Undef   =  0;
+static const lbool l_True    =  1;
+static const lbool l_False   = -1;
+
+static inline lit  toLit    (int v)        { return v + v; }
+static inline lit  toLitCond(int v, int c) { return v + v + (c != 0); }
+static inline lit  lit_neg  (lit l)        { return l ^ 1; }
+static inline int  lit_var  (lit l)        { return l >> 1; }
+static inline int  lit_sign (lit l)        { return l & 1; }
+static inline int  lit_print(lit l)        { return lit_sign(l)? -lit_var(l)-1 : lit_var(l)+1; }
+static inline lit  lit_read (int s)        { return s > 0 ? toLit(s-1) : lit_neg(toLit(-s-1)); }
+
+
+//=================================================================================================
+// Public interface:
+
+struct sat_solver_t;
+typedef struct sat_solver_t sat_solver;
+
+extern sat_solver* sat_solver_new(void);
+extern void        sat_solver_delete(sat_solver* s);
+
+extern bool        sat_solver_addclause(sat_solver* s, lit* begin, lit* end);
+extern bool        sat_solver_simplify(sat_solver* s);
+extern int         sat_solver_solve(sat_solver* s, lit* begin, lit* end, sint64 nConfLimit, sint64 nInsLimit, sint64 nConfLimitGlobal, sint64 nInsLimitGlobal);
+
+extern int         sat_solver_nvars(sat_solver* s);
+extern int         sat_solver_nclauses(sat_solver* s);
+extern int         sat_solver_nconflicts(sat_solver* s);
+
+extern void        sat_solver_setnvars(sat_solver* s,int n);
+
+struct stats_t
+{
+    sint64   starts, decisions, propagations, inspects, conflicts;
+    sint64   clauses, clauses_literals, learnts, learnts_literals, max_literals, tot_literals;
+};
+typedef struct stats_t stats;
+
+extern void        Sat_SolverWriteDimacs( sat_solver * p, char * pFileName, lit* assumptionsBegin, lit* assumptionsEnd, int incrementVars );
+extern void        Sat_SolverPrintStats( FILE * pFile, sat_solver * p );
+extern int *       Sat_SolverGetModel( sat_solver * p, int * pVars, int nVars );
+extern void        Sat_SolverDoubleClauses( sat_solver * p, int iVar );
+
+// trace recording
+extern void        Sat_SolverTraceStart( sat_solver * pSat, char * pName );
+extern void        Sat_SolverTraceStop( sat_solver * pSat );
+extern void        Sat_SolverTraceWrite( sat_solver * pSat, int * pBeg, int * pEnd, int fRoot );
+
+// clause storage
+extern void        sat_solver_store_alloc( sat_solver * s );
+extern void        sat_solver_store_write( sat_solver * s, char * pFileName );
+extern void        sat_solver_store_free( sat_solver * s );
+extern void        sat_solver_store_mark_roots( sat_solver * s );
+extern void        sat_solver_store_mark_clauses_a( sat_solver * s );
+extern void *      sat_solver_store_release( sat_solver * s ); 
+
+//=================================================================================================
+// Solver representation:
+
+struct clause_t;
+typedef struct clause_t clause;
+
+struct sat_solver_t
+{
+    int      size;          // nof variables
+    int      cap;           // size of varmaps
+    int      qhead;         // Head index of queue.
+    int      qtail;         // Tail index of queue.
+
+    // clauses
+    vecp     clauses;       // List of problem constraints. (contains: clause*)
+    vecp     learnts;       // List of learnt clauses. (contains: clause*)
+
+    // activities
+    double   var_inc;       // Amount to bump next variable with.
+    double   var_decay;     // INVERSE decay factor for variable activity: stores 1/decay. 
+    float    cla_inc;       // Amount to bump next clause with.
+    float    cla_decay;     // INVERSE decay factor for clause activity: stores 1/decay.
+
+    vecp*    wlists;        // 
+    double*  activity;      // A heuristic measurement of the activity of a variable.
+    lbool*   assigns;       // Current values of variables.
+    int*     orderpos;      // Index in variable order.
+    clause** reasons;       //
+    int*     levels;        //
+    lit*     trail;
+
+    clause*  binary;        // A temporary binary clause
+    lbool*   tags;          //
+    veci     tagged;        // (contains: var)
+    veci     stack;         // (contains: var)
+
+    veci     order;         // Variable order. (heap) (contains: var)
+    veci     trail_lim;     // Separator indices for different decision levels in 'trail'. (contains: int)
+    veci     model;         // If problem is solved, this vector contains the model (contains: lbool).
+
+    int      root_level;    // Level of first proper decision.
+    int      simpdb_assigns;// Number of top-level assignments at last 'simplifyDB()'.
+    int      simpdb_props;  // Number of propagations before next 'simplifyDB()'.
+    double   random_seed;
+    double   progress_estimate;
+    int      verbosity;     // Verbosity level. 0=silent, 1=some progress report, 2=everything
+
+    stats    stats;
+
+    sint64   nConfLimit;    // external limit on the number of conflicts
+    sint64   nInsLimit;     // external limit on the number of implications
+
+    veci     act_vars;      // variables whose activity has changed
+    double*  factors;       // the activity factors
+    int      nRestarts;     // the number of local restarts
+    int      nCalls;        // the number of local restarts
+    int      nCalls2;        // the number of local restarts
+ 
+    Sat_MmStep_t * pMem;
+
+    int      fSkipSimplify; // set to one to skip simplification of the clause database
+
+    // clause store
+    void *   pStore;
+
+    // trace recording
+    FILE *   pFile;
+    int      nClauses;
+    int      nRoots;
+};
+
+#endif
diff --git a/src/sat/bsat/satStore.c b/src/sat/bsat/satStore.c
new file mode 100644
index 00000000..f968162e
--- /dev/null
+++ b/src/sat/bsat/satStore.c
@@ -0,0 +1,437 @@
+/**CFile****************************************************************
+
+  FileName    [satStore.c]
+
+  SystemName  [ABC: Logic synthesis and verification system.]
+
+  PackageName [SAT solver.]
+
+  Synopsis    [Records the trace of SAT solving in the CNF form.]
+
+  Author      [Alan Mishchenko]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - June 20, 2005.]
+
+  Revision    [$Id: satStore.c,v 1.4 2005/09/16 22:55:03 casem Exp $]
+
+***********************************************************************/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <time.h>
+#include "satStore.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Fetches memory.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+char * Sto_ManMemoryFetch( Sto_Man_t * p, int nBytes )
+{
+    char * pMem;
+    if ( p->pChunkLast == NULL || nBytes > p->nChunkSize - p->nChunkUsed )
+    {
+        pMem = (char *)malloc( p->nChunkSize );
+        *(char **)pMem = p->pChunkLast;
+        p->pChunkLast = pMem;
+        p->nChunkUsed = sizeof(char *);
+    }
+    pMem = p->pChunkLast + p->nChunkUsed;
+    p->nChunkUsed += nBytes;
+    return pMem;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Frees memory manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Sto_ManMemoryStop( Sto_Man_t * p )
+{
+    char * pMem, * pNext;
+    if ( p->pChunkLast == NULL )
+        return;
+    for ( pMem = p->pChunkLast; (pNext = *(char **)pMem); pMem = pNext )
+        free( pMem );
+    free( pMem );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Reports memory usage in bytes.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Sto_ManMemoryReport( Sto_Man_t * p )
+{
+    int Total;
+    char * pMem, * pNext;
+    if ( p->pChunkLast == NULL )
+        return 0;
+    Total = p->nChunkUsed; 
+    for ( pMem = p->pChunkLast; (pNext = *(char **)pMem); pMem = pNext )
+        Total += p->nChunkSize;
+    return Total;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Allocate proof manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Sto_Man_t * Sto_ManAlloc()
+{
+    Sto_Man_t * p;
+    // allocate the manager
+    p = (Sto_Man_t *)malloc( sizeof(Sto_Man_t) );
+    memset( p, 0, sizeof(Sto_Man_t) );
+    // memory management
+    p->nChunkSize = (1<<16); // use 64K chunks
+    return p;    
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Deallocate proof manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Sto_ManFree( Sto_Man_t * p )
+{
+    Sto_ManMemoryStop( p );
+    free( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Adds one clause to the manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Sto_ManAddClause( Sto_Man_t * p, lit * pBeg, lit * pEnd )
+{
+    Sto_Cls_t * pClause;
+    lit Lit, * i, * j;
+    int nSize;
+
+    // process the literals
+    if ( pBeg < pEnd )
+    {
+        // insertion sort
+        for ( i = pBeg + 1; i < pEnd; i++ )
+        {
+            Lit = *i;
+            for ( j = i; j > pBeg && *(j-1) > Lit; j-- )
+                *j = *(j-1);
+            *j = Lit;
+        }
+        // make sure there is no duplicated variables
+        for ( i = pBeg + 1; i < pEnd; i++ )
+            if ( lit_var(*(i-1)) == lit_var(*i) )
+            {
+                printf( "The clause contains two literals of the same variable: %d and %d.\n", *(i-1), *i );
+                return 0;
+            }
+        // check the largest var size
+        p->nVars = STO_MAX( p->nVars, lit_var(*(pEnd-1)) + 1 );
+    }
+
+    // get memory for the clause
+    nSize = sizeof(Sto_Cls_t) + sizeof(lit) * (pEnd - pBeg);
+    pClause = (Sto_Cls_t *)Sto_ManMemoryFetch( p, nSize );
+    memset( pClause, 0, sizeof(Sto_Cls_t) );
+
+    // assign the clause
+    pClause->Id = p->nClauses++;
+    pClause->nLits = pEnd - pBeg;
+    memcpy( pClause->pLits, pBeg, sizeof(lit) * (pEnd - pBeg) );
+
+    // add the clause to the list
+    if ( p->pHead == NULL )
+        p->pHead = pClause;
+    if ( p->pTail == NULL )
+        p->pTail = pClause;
+    else
+    {
+        p->pTail->pNext = pClause;
+        p->pTail = pClause;
+    }
+
+    // add the empty clause
+    if ( pClause->nLits == 0 )
+    {
+        if ( p->pEmpty )
+        {
+            printf( "More than one empty clause!\n" );
+            return 0;
+        }
+        p->pEmpty = pClause;
+    }
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Mark all clauses added so far as root clauses.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Sto_ManMarkRoots( Sto_Man_t * p )
+{
+    Sto_Cls_t * pClause;
+    p->nRoots = 0;
+    Sto_ManForEachClause( p, pClause )
+    {
+        pClause->fRoot = 1;
+        p->nRoots++;
+    }
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Mark all clauses added so far as clause of A.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Sto_ManMarkClausesA( Sto_Man_t * p )
+{
+    Sto_Cls_t * pClause;
+    p->nClausesA = 0;
+    Sto_ManForEachClause( p, pClause )
+    {
+        pClause->fA = 1;
+        p->nClausesA++;
+    }
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Writes the stored clauses into a file.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Sto_ManDumpClauses( Sto_Man_t * p, char * pFileName )
+{
+    FILE * pFile;
+    Sto_Cls_t * pClause;
+    int i;
+    // start the file
+    pFile = fopen( pFileName, "w" );
+    if ( pFile == NULL )
+    {
+        printf( "Error: Cannot open output file (%s).\n", pFileName );
+        return;
+    }
+    // write the data
+    fprintf( pFile, "p %d %d %d %d\n", p->nVars, p->nClauses, p->nRoots, p->nClausesA );
+    Sto_ManForEachClause( p, pClause )
+    {
+        for ( i = 0; i < (int)pClause->nLits; i++ )
+            fprintf( pFile, " %d", lit_print(pClause->pLits[i]) );
+        fprintf( pFile, "\n" );
+    }
+    fprintf( pFile, " 0\n" );
+    fclose( pFile );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Reads one literal from file.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Sto_ManLoadNumber( FILE * pFile, int * pNumber )
+{
+    int Char, Number = 0, Sign = 0;
+    // skip space-like chars
+    do {
+        Char = fgetc( pFile );
+        if ( Char == EOF )
+            return 0;
+    } while ( Char == ' ' || Char == '\t' || Char == '\r' || Char == '\n' );
+    // read the literal
+    while ( 1 )
+    {
+        // get the next character
+        Char = fgetc( pFile );
+        if ( Char == ' ' || Char == '\t' || Char == '\r' || Char == '\n' )
+            break;
+        // check that the char is a digit
+        if ( (Char < '0' || Char > '9') && Char != '-' )
+        {
+            printf( "Error: Wrong char (%c) in the input file.\n", Char );
+            return 0;
+        }
+        // check if this is a minus
+        if ( Char == '-' )
+            Sign = 1;
+        else
+            Number = 10 * Number + Char;
+    }
+    // return the number
+    *pNumber = Sign? -Number : Number;
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Reads CNF from file.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Sto_Man_t * Sto_ManLoadClauses( char * pFileName )
+{
+    FILE * pFile;
+    Sto_Man_t * p;
+    Sto_Cls_t * pClause;
+    char pBuffer[1024];
+    int nLits, nLitsAlloc, Counter, Number;
+    lit * pLits;
+
+    // start the file
+    pFile = fopen( pFileName, "r" );
+    if ( pFile == NULL )
+    {
+        printf( "Error: Cannot open input file (%s).\n", pFileName );
+        return NULL;
+    }
+
+    // create the manager
+    p = Sto_ManAlloc();
+
+    // alloc the array of literals
+    nLitsAlloc = 1024;
+    pLits = (lit *)malloc( sizeof(lit) * nLitsAlloc );
+
+    // read file header
+    p->nVars = p->nClauses = p->nRoots = p->nClausesA = 0;
+    while ( fgets( pBuffer, 1024, pFile ) )
+    {
+        if ( pBuffer[0] == 'c' )
+            continue;
+        if ( pBuffer[0] == 'p' )
+        {
+            sscanf( pBuffer + 1, "%d %d %d %d", &p->nVars, &p->nClauses, &p->nRoots, &p->nClausesA );
+            break;
+        }
+        printf( "Warning: Skipping line: \"%s\"\n", pBuffer );
+    }
+
+    // read the clauses
+    nLits = 0;
+    while ( Sto_ManLoadNumber(pFile, &Number) )
+    {
+        if ( Number == 0 )
+        {
+            int RetValue;
+            RetValue = Sto_ManAddClause( p, pLits, pLits + nLits );
+            assert( RetValue );
+            nLits = 0;
+            continue;
+        }
+        if ( nLits == nLitsAlloc )
+        {
+            nLitsAlloc *= 2;
+            pLits = (lit *)realloc( pLits, sizeof(lit) * nLitsAlloc );
+        }
+        pLits[ nLits++ ] = lit_read(Number);
+    }
+    if ( nLits > 0 )
+        printf( "Error: The last clause was not saved.\n" );
+
+    // count clauses
+    Counter = 0;
+    Sto_ManForEachClause( p, pClause )
+        Counter++;
+
+    // check the number of clauses
+    if ( p->nClauses != Counter )
+    {
+        printf( "Error: The actual number of clauses (%d) is different than declared (%d).\n", Counter, p->nClauses );
+        Sto_ManFree( p );
+        return NULL;
+    }
+
+    free( pLits );
+    fclose( pFile );
+    return p;
+}
+
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/bsat/satStore.h b/src/sat/bsat/satStore.h
new file mode 100644
index 00000000..346b59df
--- /dev/null
+++ b/src/sat/bsat/satStore.h
@@ -0,0 +1,137 @@
+/**CFile****************************************************************
+
+  FileName    [pr.h]
+
+  SystemName  [ABC: Logic synthesis and verification system.]
+
+  PackageName [Proof recording.]
+
+  Synopsis    [External declarations.]
+
+  Author      [Alan Mishchenko]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - June 20, 2005.]
+
+  Revision    [$Id: pr.h,v 1.00 2005/06/20 00:00:00 alanmi Exp $]
+
+***********************************************************************/
+ 
+#ifndef __PR_H__
+#define __PR_H__
+
+/*
+    The trace of SAT solving contains the original clause of the problem
+    along with the learned clauses derived during SAT solving.
+    The first line of the resulting file contains 3 numbers instead of 2:
+    c <num_vars> <num_all_clauses> <num_root_clauses>
+*/
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifdef _WIN32
+#define inline __inline // compatible with MS VS 6.0
+#endif
+
+#ifndef PRT
+#define PRT(a,t)  printf("%s = ", (a)); printf("%6.2f sec\n", (float)(t)/(float)(CLOCKS_PER_SEC))
+#endif
+
+#define STO_MAX(a,b)  ((a) > (b) ? (a) : (b))
+
+////////////////////////////////////////////////////////////////////////
+///                          INCLUDES                                ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                         PARAMETERS                               ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                         BASIC TYPES                              ///
+////////////////////////////////////////////////////////////////////////
+
+typedef unsigned lit;
+
+typedef struct Sto_Cls_t_ Sto_Cls_t;
+struct Sto_Cls_t_
+{
+    Sto_Cls_t *     pNext;        // the next clause
+    Sto_Cls_t *     pNext0;       // the next 0-watch
+    Sto_Cls_t *     pNext1;       // the next 0-watch
+    int             Id;           // the clause ID
+    unsigned        fA     :  1;  // belongs to A
+    unsigned        fRoot  :  1;  // original clause
+    unsigned        fVisit :  1;  // visited clause
+    unsigned        nLits  : 24;  // the number of literals
+    lit             pLits[0];     // literals of this clause
+};
+
+typedef struct Sto_Man_t_ Sto_Man_t;
+struct Sto_Man_t_
+{
+    // general data
+    int             nVars;        // the number of variables
+    int             nRoots;       // the number of root clauses
+    int             nClauses;     // the number of all clauses
+    int             nClausesA;    // the number of clauses of A 
+    Sto_Cls_t *     pHead;        // the head clause
+    Sto_Cls_t *     pTail;        // the tail clause
+    Sto_Cls_t *     pEmpty;       // the empty clause
+    // memory management
+    int             nChunkSize;   // the number of bytes in a chunk
+    int             nChunkUsed;   // the number of bytes used in the last chunk
+    char *          pChunkLast;   // the last memory chunk
+};
+
+// variable/literal conversions (taken from MiniSat)
+static inline lit   toLit    (int v)        { return v + v;  }
+static inline lit   toLitCond(int v, int c) { return v + v + (c != 0); }
+static inline lit   lit_neg  (lit l)        { return l ^ 1;  }
+static inline int   lit_var  (lit l)        { return l >> 1; }
+static inline int   lit_sign (lit l)        { return l & 1;  }
+static inline int   lit_print(lit l)        { return lit_sign(l)? -lit_var(l)-1 : lit_var(l)+1; }
+static inline lit   lit_read (int s)        { return s > 0 ? toLit(s-1) : lit_neg(toLit(-s-1)); }
+static inline int   lit_check(lit l, int n) { return l >= 0 && lit_var(l) < n;                  }
+
+// iterators through the clauses
+#define Sto_ManForEachClause( p, pCls )      for( pCls = p->pHead; pCls; pCls = pCls->pNext )
+#define Sto_ManForEachClauseRoot( p, pCls )  for( pCls = p->pHead; pCls && pCls->fRoot; pCls = pCls->pNext )
+
+////////////////////////////////////////////////////////////////////////
+///                      MACRO DEFINITIONS                           ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                    FUNCTION DECLARATIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/*=== satStore.c ==========================================================*/
+extern Sto_Man_t *  Sto_ManAlloc();
+extern void         Sto_ManFree( Sto_Man_t * p );
+extern int          Sto_ManAddClause( Sto_Man_t * p, lit * pBeg, lit * pEnd );
+extern int          Sto_ManMemoryReport( Sto_Man_t * p );
+extern void         Sto_ManMarkRoots( Sto_Man_t * p );
+extern void         Sto_ManMarkClausesA( Sto_Man_t * p );
+extern void         Sto_ManDumpClauses( Sto_Man_t * p, char * pFileName );
+extern Sto_Man_t *  Sto_ManLoadClauses( char * pFileName );
+
+/*=== satInter.c ==========================================================*/
+typedef struct Int_Man_t_ Int_Man_t;
+extern Int_Man_t *  Int_ManAlloc( int nVarsAlloc );
+extern void         Int_ManFree( Int_Man_t * p );
+extern int          Int_ManInterpolate( Int_Man_t * p, Sto_Man_t * pCnf, int fVerbose, unsigned ** ppResult );
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
diff --git a/src/sat/bsat/satTrace.c b/src/sat/bsat/satTrace.c
new file mode 100644
index 00000000..111e8dfb
--- /dev/null
+++ b/src/sat/bsat/satTrace.c
@@ -0,0 +1,109 @@
+/**CFile****************************************************************
+
+  FileName    [satTrace.c]
+
+  SystemName  [ABC: Logic synthesis and verification system.]
+
+  PackageName [SAT sat_solver.]
+
+  Synopsis    [Records the trace of SAT solving in the CNF form.]
+
+  Author      [Alan Mishchenko]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - June 20, 2005.]
+
+  Revision    [$Id: satTrace.c,v 1.4 2005/09/16 22:55:03 casem Exp $]
+
+***********************************************************************/
+
+#include <stdio.h>
+#include <assert.h>
+#include "satSolver.h"
+
+/*
+    The trace of SAT solving contains the original clause of the problem
+    along with the learned clauses derived during SAT solving.
+    The first line of the resulting file contains 3 numbers instead of 2:
+    c <num_vars> <num_all_clauses> <num_root_clauses>
+*/
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Start the trace recording.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Sat_SolverTraceStart( sat_solver * pSat, char * pName )
+{
+    assert( pSat->pFile == NULL );
+    pSat->pFile = fopen( pName, "w" );
+    fprintf( pSat->pFile, "                                        \n" );
+    pSat->nClauses = 0;
+    pSat->nRoots = 0;
+}   
+
+/**Function*************************************************************
+
+  Synopsis    [Stops the trace recording.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Sat_SolverTraceStop( sat_solver * pSat )
+{
+    if ( pSat->pFile == NULL )
+        return;
+    rewind( pSat->pFile );
+    fprintf( pSat->pFile, "p %d %d %d", sat_solver_nvars(pSat), pSat->nClauses, pSat->nRoots );
+    fclose( pSat->pFile );
+    pSat->pFile = NULL;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Writes one clause into the trace file.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Sat_SolverTraceWrite( sat_solver * pSat, int * pBeg, int * pEnd, int fRoot )
+{
+    if ( pSat->pFile == NULL )
+        return;
+    pSat->nClauses++;
+    pSat->nRoots += fRoot;
+    for ( ; pBeg < pEnd ; pBeg++ )
+        fprintf( pSat->pFile, " %d", lit_print(*pBeg) );
+    fprintf( pSat->pFile, " 0\n" );
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/bsat/satUtil.c b/src/sat/bsat/satUtil.c
new file mode 100644
index 00000000..3961cf7e
--- /dev/null
+++ b/src/sat/bsat/satUtil.c
@@ -0,0 +1,234 @@
+/**CFile****************************************************************
+
+  FileName    [satUtil.c]
+
+  SystemName  [ABC: Logic synthesis and verification system.]
+
+  PackageName [C-language MiniSat solver.]
+
+  Synopsis    [Additional SAT solver procedures.]
+
+  Author      [Alan Mishchenko]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - June 20, 2005.]
+
+  Revision    [$Id: satUtil.c,v 1.4 2005/09/16 22:55:03 casem Exp $]
+
+***********************************************************************/
+
+#include <stdio.h>
+#include <assert.h>
+#include "satSolver.h"
+#include "vec.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+struct clause_t
+{
+    int size_learnt;
+    lit lits[0];
+};
+
+static inline int  clause_size( clause* c )  { return c->size_learnt >> 1; }
+static inline lit* clause_begin( clause* c ) { return c->lits;             }
+
+static void Sat_SolverClauseWriteDimacs( FILE * pFile, clause * pC, bool fIncrement );
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Write the clauses in the solver into a file in DIMACS format.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Sat_SolverWriteDimacs( sat_solver * p, char * pFileName, lit* assumptionsBegin, lit* assumptionsEnd, int incrementVars )
+{
+    FILE * pFile;
+    void ** pClauses;
+    int nClauses, i;
+
+    // count the number of clauses
+    nClauses = p->clauses.size + p->learnts.size;
+    for ( i = 0; i < p->size; i++ )
+        if ( p->levels[i] == 0 && p->assigns[i] != l_Undef )
+            nClauses++;
+
+    // start the file
+    pFile = fopen( pFileName, "wb" );
+    if ( pFile == NULL )
+    {
+        printf( "Sat_SolverWriteDimacs(): Cannot open the ouput file.\n" );
+        return;
+    }
+//    fprintf( pFile, "c CNF generated by ABC on %s\n", Extra_TimeStamp() );
+    fprintf( pFile, "p cnf %d %d\n", p->size, nClauses );
+
+    // write the original clauses
+    nClauses = p->clauses.size;
+    pClauses = p->clauses.ptr;
+    for ( i = 0; i < nClauses; i++ )
+        Sat_SolverClauseWriteDimacs( pFile, pClauses[i], incrementVars );
+
+    // write the learned clauses
+    nClauses = p->learnts.size;
+    pClauses = p->learnts.ptr;
+    for ( i = 0; i < nClauses; i++ )
+        Sat_SolverClauseWriteDimacs( pFile, pClauses[i], incrementVars );
+
+    // write zero-level assertions
+    for ( i = 0; i < p->size; i++ )
+        if ( p->levels[i] == 0 && p->assigns[i] != l_Undef )
+            fprintf( pFile, "%s%d%s\n",
+                     (p->assigns[i] == l_False)? "-": "",
+                     i + (int)(incrementVars>0),
+                     (incrementVars) ? " 0" : "");
+
+    // write the assumptions
+    if (assumptionsBegin) {
+        for (; assumptionsBegin != assumptionsEnd; assumptionsBegin++) {
+            fprintf( pFile, "%s%d%s\n",
+                     lit_sign(*assumptionsBegin)? "-": "",
+                     lit_var(*assumptionsBegin) + (int)(incrementVars>0),
+                     (incrementVars) ? " 0" : "");
+        }
+    }
+
+    fprintf( pFile, "\n" );
+    fclose( pFile );
+}   
+
+/**Function*************************************************************
+
+  Synopsis    [Writes the given clause in a file in DIMACS format.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Sat_SolverClauseWriteDimacs( FILE * pFile, clause * pC, bool fIncrement )
+{
+    lit * pLits = clause_begin(pC);
+    int nLits = clause_size(pC);
+    int i;
+
+    for ( i = 0; i < nLits; i++ )
+        fprintf( pFile, "%s%d ", (lit_sign(pLits[i])? "-": ""),  lit_var(pLits[i]) + (int)(fIncrement>0) );
+    if ( fIncrement )
+        fprintf( pFile, "0" );
+    fprintf( pFile, "\n" );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Writes the given clause in a file in DIMACS format.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Sat_SolverPrintStats( FILE * pFile, sat_solver * p )
+{
+//    printf( "calls         : %8d (%d)\n", (int)p->nCalls, (int)p->nCalls2 );
+    printf( "starts        : %8d\n", (int)p->stats.starts );
+    printf( "conflicts     : %8d\n", (int)p->stats.conflicts );
+    printf( "decisions     : %8d\n", (int)p->stats.decisions );
+    printf( "propagations  : %8d\n", (int)p->stats.propagations );
+    printf( "inspects      : %8d\n", (int)p->stats.inspects );
+//    printf( "inspects2     : %8d\n", (int)p->stats.inspects2 );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Returns a counter-example.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int * Sat_SolverGetModel( sat_solver * p, int * pVars, int nVars )
+{
+    int * pModel;
+    int i;
+    pModel = ALLOC( int, nVars );
+    for ( i = 0; i < nVars; i++ )
+    {
+        assert( pVars[i] >= 0 && pVars[i] < p->size );
+        pModel[i] = (int)(p->model.ptr[pVars[i]] == l_True);
+    }
+    return pModel;    
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Duplicates all clauses, complements unit clause of the given var.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Sat_SolverDoubleClauses( sat_solver * p, int iVar )
+{
+    clause * pClause;
+    lit Lit, * pLits;
+    int RetValue, nClauses, nVarsOld, nLitsOld, nLits, c, v;
+    // get the number of variables
+    nVarsOld = p->size;
+    nLitsOld = 2 * p->size;
+    // extend the solver to depend on two sets of variables
+    sat_solver_setnvars( p, 2 * p->size );
+    // duplicate implications
+    for ( v = 0; v < nVarsOld; v++ )
+        if ( p->assigns[v] != l_Undef )
+        {
+            Lit = nLitsOld + toLitCond( v, p->assigns[v]==l_False );
+            if ( v == iVar )
+                Lit = lit_neg(Lit);
+            RetValue = sat_solver_addclause( p, &Lit, &Lit + 1 );
+            assert( RetValue );
+        }
+    // duplicate clauses
+    nClauses = vecp_size(&p->clauses);
+    for ( c = 0; c < nClauses; c++ )
+    {
+        pClause = p->clauses.ptr[c];
+        nLits = clause_size(pClause);
+        pLits = clause_begin(pClause);
+        for ( v = 0; v < nLits; v++ )
+            pLits[v] += nLitsOld;
+        RetValue = sat_solver_addclause( p, pLits, pLits + nLits );
+        assert( RetValue );
+        for ( v = 0; v < nLits; v++ )
+            pLits[v] -= nLitsOld;
+    }
+}
+
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/bsat/satVec.h b/src/sat/bsat/satVec.h
new file mode 100644
index 00000000..d7fce5c0
--- /dev/null
+++ b/src/sat/bsat/satVec.h
@@ -0,0 +1,83 @@
+/**************************************************************************************************
+MiniSat -- Copyright (c) 2005, Niklas Sorensson
+http://www.cs.chalmers.se/Cs/Research/FormalMethods/MiniSat/
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute,
+sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or
+substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+**************************************************************************************************/
+// Modified to compile with MS Visual Studio 6.0 by Alan Mishchenko
+
+#ifndef satVec_h
+#define satVec_h
+
+#include <stdlib.h>
+
+// vector of 32-bit intergers (added for 64-bit portability)
+struct veci_t {
+    int    size;
+    int    cap;
+    int*   ptr;
+};
+typedef struct veci_t veci;
+
+static inline void veci_new (veci* v) {
+    v->size = 0;
+    v->cap  = 4;
+    v->ptr  = (int*)malloc(sizeof(int)*v->cap);
+}
+
+static inline void   veci_delete (veci* v)          { free(v->ptr);   }
+static inline int*   veci_begin  (veci* v)          { return v->ptr;  }
+static inline int    veci_size   (veci* v)          { return v->size; }
+static inline void   veci_resize (veci* v, int k)   { v->size = k;    } // only safe to shrink !!
+static inline void   veci_push   (veci* v, int e)
+{
+    if (v->size == v->cap) {
+        int newsize = v->cap * 2;//+1;
+        v->ptr = (int*)realloc(v->ptr,sizeof(int)*newsize);
+        v->cap = newsize; }
+    v->ptr[v->size++] = e;
+}
+
+
+// vector of 32- or 64-bit pointers
+struct vecp_t {
+    int    size;
+    int    cap;
+    void** ptr;
+};
+typedef struct vecp_t vecp;
+
+static inline void vecp_new (vecp* v) {
+    v->size = 0;
+    v->cap  = 4;
+    v->ptr  = (void**)malloc(sizeof(void*)*v->cap);
+}
+
+static inline void   vecp_delete (vecp* v)          { free(v->ptr);   }
+static inline void** vecp_begin  (vecp* v)          { return v->ptr;  }
+static inline int    vecp_size   (vecp* v)          { return v->size; }
+static inline void   vecp_resize (vecp* v, int   k) { v->size = k;    } // only safe to shrink !!
+static inline void   vecp_push   (vecp* v, void* e)
+{
+    if (v->size == v->cap) {
+        int newsize = v->cap * 2;//+1;
+        v->ptr = (void**)realloc(v->ptr,sizeof(void*)*newsize);
+        v->cap = newsize; }
+    v->ptr[v->size++] = e;
+}
+
+
+#endif
diff --git a/src/sat/csat/csat_apis.c b/src/sat/csat/csat_apis.c
new file mode 100644
index 00000000..5872f5bc
--- /dev/null
+++ b/src/sat/csat/csat_apis.c
@@ -0,0 +1,769 @@
+/**CFile****************************************************************
+
+  FileName    [csat_apis.h]
+
+  PackageName [Interface to CSAT.]
+
+  Synopsis    [APIs, enums, and data structures expected from the use of CSAT.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - August 28, 2005]
+
+  Revision    [$Id: csat_apis.h,v 1.00 2005/08/28 00:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include "abc.h"
+#include "fraig.h"
+#include "csat_apis.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+#define ABC_DEFAULT_CONF_LIMIT     0   // limit on conflicts
+#define ABC_DEFAULT_IMP_LIMIT      0   // limit on implications
+
+
+struct ABC_ManagerStruct_t
+{
+    // information about the problem
+    stmm_table *          tName2Node;    // the hash table mapping names to nodes
+    stmm_table *          tNode2Name;    // the hash table mapping nodes to names
+    Abc_Ntk_t *           pNtk;          // the starting ABC network
+    Abc_Ntk_t *           pTarget;       // the AIG representing the target
+    char *                pDumpFileName; // the name of the file to dump the target network
+    Extra_MmFlex_t *      pMmNames;      // memory manager for signal names
+    // solving parameters
+    int                   mode;          // 0 = resource-aware integration; 1 = brute-force SAT
+    Prove_Params_t        Params;        // integrated CEC parameters
+    // information about the target 
+    int                   nog;           // the numbers of gates in the target
+    Vec_Ptr_t *           vNodes;        // the gates in the target
+    Vec_Int_t *           vValues;       // the values of gate's outputs in the target
+    // solution
+    CSAT_Target_ResultT * pResult;       // the result of solving the target
+};
+
+static CSAT_Target_ResultT * ABC_TargetResAlloc( int nVars );
+static char * ABC_GetNodeName( ABC_Manager mng, Abc_Obj_t * pNode );
+
+// procedures to start and stop the ABC framework
+extern void  Abc_Start();
+extern void  Abc_Stop();
+
+// some external procedures
+extern int Io_WriteBench( Abc_Ntk_t * pNtk, char * FileName );
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Creates a new manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+ABC_Manager ABC_InitManager()
+{
+    ABC_Manager_t * mng;
+    Abc_Start();
+    mng = ALLOC( ABC_Manager_t, 1 );
+    memset( mng, 0, sizeof(ABC_Manager_t) );
+    mng->pNtk = Abc_NtkAlloc( ABC_NTK_LOGIC, ABC_FUNC_SOP, 1 );
+    mng->pNtk->pName = Extra_UtilStrsav("csat_network");
+    mng->tName2Node = stmm_init_table(strcmp, stmm_strhash);
+    mng->tNode2Name = stmm_init_table(stmm_ptrcmp, stmm_ptrhash);
+    mng->pMmNames   = Extra_MmFlexStart();
+    mng->vNodes     = Vec_PtrAlloc( 100 );
+    mng->vValues    = Vec_IntAlloc( 100 );
+    mng->mode       = 0; // set "resource-aware integration" as the default mode
+    // set default parameters for CEC
+    Prove_ParamsSetDefault( &mng->Params );
+    // set infinite resource limit for the final mitering
+//    mng->Params.nMiteringLimitLast = ABC_INFINITY;
+    return mng;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Deletes the manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void ABC_ReleaseManager( ABC_Manager mng )
+{
+    CSAT_Target_ResultT * p_res = ABC_Get_Target_Result( mng,0 );
+    ABC_TargetResFree(p_res);
+    if ( mng->tNode2Name ) stmm_free_table( mng->tNode2Name );
+    if ( mng->tName2Node ) stmm_free_table( mng->tName2Node );
+    if ( mng->pMmNames )   Extra_MmFlexStop( mng->pMmNames );
+    if ( mng->pNtk )       Abc_NtkDelete( mng->pNtk );
+    if ( mng->pTarget )    Abc_NtkDelete( mng->pTarget );
+    if ( mng->vNodes )     Vec_PtrFree( mng->vNodes );
+    if ( mng->vValues )    Vec_IntFree( mng->vValues );
+    FREE( mng->pDumpFileName );
+    free( mng );
+    Abc_Stop();
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Sets solver options for learning.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void ABC_SetSolveOption( ABC_Manager mng, enum CSAT_OptionT option )
+{
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Sets solving mode by brute-force SAT.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void ABC_UseOnlyCoreSatSolver( ABC_Manager mng )
+{
+    mng->mode = 1;  // switch to "brute-force SAT" as the solving option
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Adds a gate to the circuit.]
+
+  Description [The meaning of the parameters are:
+    type: the type of the gate to be added
+    name: the name of the gate to be added, name should be unique in a circuit.
+    nofi: number of fanins of the gate to be added;
+    fanins: the name array of fanins of the gate to be added.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int ABC_AddGate( ABC_Manager mng, enum GateType type, char * name, int nofi, char ** fanins, int dc_attr )
+{
+    Abc_Obj_t * pObj, * pFanin;
+    char * pSop, * pNewName;
+    int i;
+
+    // save the name in the local memory manager
+    pNewName = Extra_MmFlexEntryFetch( mng->pMmNames, strlen(name) + 1 );
+    strcpy( pNewName, name );
+    name = pNewName;
+
+    // consider different cases, create the node, and map the node into the name
+    switch( type )
+    {
+    case CSAT_BPI:
+    case CSAT_BPPI:
+        if ( nofi != 0 )
+            { printf( "ABC_AddGate: The PI/PPI gate \"%s\" has fanins.\n", name ); return 0; }
+        // create the PI
+        pObj = Abc_NtkCreatePi( mng->pNtk );
+        stmm_insert( mng->tNode2Name, (char *)pObj, name );
+        break;
+    case CSAT_CONST:
+    case CSAT_BAND:
+    case CSAT_BNAND:
+    case CSAT_BOR:
+    case CSAT_BNOR:
+    case CSAT_BXOR:
+    case CSAT_BXNOR:
+    case CSAT_BINV:
+    case CSAT_BBUF:
+        // create the node
+        pObj = Abc_NtkCreateNode( mng->pNtk );
+        // create the fanins
+        for ( i = 0; i < nofi; i++ )
+        {
+            if ( !stmm_lookup( mng->tName2Node, fanins[i], (char **)&pFanin ) )
+                { printf( "ABC_AddGate: The fanin gate \"%s\" is not in the network.\n", fanins[i] ); return 0; }
+            Abc_ObjAddFanin( pObj, pFanin );
+        }
+        // create the node function
+        switch( type )
+        {
+            case CSAT_CONST:
+                if ( nofi != 0 )
+                    { printf( "ABC_AddGate: The constant gate \"%s\" has fanins.\n", name ); return 0; }
+                pSop = Abc_SopCreateConst1( mng->pNtk->pManFunc );
+                break;
+            case CSAT_BAND:
+                if ( nofi < 1 )
+                    { printf( "ABC_AddGate: The AND gate \"%s\" no fanins.\n", name ); return 0; }
+                pSop = Abc_SopCreateAnd( mng->pNtk->pManFunc, nofi, NULL );
+                break;
+            case CSAT_BNAND:
+                if ( nofi < 1 )
+                    { printf( "ABC_AddGate: The NAND gate \"%s\" no fanins.\n", name ); return 0; }
+                pSop = Abc_SopCreateNand( mng->pNtk->pManFunc, nofi );
+                break;
+            case CSAT_BOR:
+                if ( nofi < 1 )
+                    { printf( "ABC_AddGate: The OR gate \"%s\" no fanins.\n", name ); return 0; }
+                pSop = Abc_SopCreateOr( mng->pNtk->pManFunc, nofi, NULL );
+                break;
+            case CSAT_BNOR:
+                if ( nofi < 1 )
+                    { printf( "ABC_AddGate: The NOR gate \"%s\" no fanins.\n", name ); return 0; }
+                pSop = Abc_SopCreateNor( mng->pNtk->pManFunc, nofi );
+                break;
+            case CSAT_BXOR:
+                if ( nofi < 1 )
+                    { printf( "ABC_AddGate: The XOR gate \"%s\" no fanins.\n", name ); return 0; }
+                if ( nofi > 2 )
+                    { printf( "ABC_AddGate: The XOR gate \"%s\" has more than two fanins.\n", name ); return 0; }
+                pSop = Abc_SopCreateXor( mng->pNtk->pManFunc, nofi );
+                break;
+            case CSAT_BXNOR:
+                if ( nofi < 1 )
+                    { printf( "ABC_AddGate: The XNOR gate \"%s\" no fanins.\n", name ); return 0; }
+                if ( nofi > 2 )
+                    { printf( "ABC_AddGate: The XNOR gate \"%s\" has more than two fanins.\n", name ); return 0; }
+                pSop = Abc_SopCreateNxor( mng->pNtk->pManFunc, nofi );
+                break;
+            case CSAT_BINV:
+                if ( nofi != 1 )
+                    { printf( "ABC_AddGate: The inverter gate \"%s\" does not have exactly one fanin.\n", name ); return 0; }
+                pSop = Abc_SopCreateInv( mng->pNtk->pManFunc );
+                break;
+            case CSAT_BBUF:
+                if ( nofi != 1 )
+                    { printf( "ABC_AddGate: The buffer gate \"%s\" does not have exactly one fanin.\n", name ); return 0; }
+                pSop = Abc_SopCreateBuf( mng->pNtk->pManFunc );
+                break;
+            default :
+                break;
+        }
+        Abc_ObjSetData( pObj, pSop );
+        break;
+    case CSAT_BPPO:
+    case CSAT_BPO:
+        if ( nofi != 1 )
+            { printf( "ABC_AddGate: The PO/PPO gate \"%s\" does not have exactly one fanin.\n", name ); return 0; }
+        // create the PO
+        pObj = Abc_NtkCreatePo( mng->pNtk );
+        stmm_insert( mng->tNode2Name, (char *)pObj, name );
+        // connect to the PO fanin
+        if ( !stmm_lookup( mng->tName2Node, fanins[0], (char **)&pFanin ) )
+            { printf( "ABC_AddGate: The fanin gate \"%s\" is not in the network.\n", fanins[0] ); return 0; }
+        Abc_ObjAddFanin( pObj, pFanin );
+        break;
+    default:
+        printf( "ABC_AddGate: Unknown gate type.\n" );
+        break;
+    }
+
+    // map the name into the node
+    if ( stmm_insert( mng->tName2Node, name, (char *)pObj ) )
+        { printf( "ABC_AddGate: The same gate \"%s\" is added twice.\n", name ); return 0; }
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [This procedure also finalizes construction of the ABC network.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void ABC_Network_Finalize( ABC_Manager mng )
+{
+    Abc_Ntk_t * pNtk = mng->pNtk;
+    Abc_Obj_t * pObj;
+    int i;
+    Abc_NtkForEachPi( pNtk, pObj, i )
+        Abc_ObjAssignName( pObj, ABC_GetNodeName(mng, pObj), NULL );
+    Abc_NtkForEachPo( pNtk, pObj, i )
+        Abc_ObjAssignName( pObj, ABC_GetNodeName(mng, pObj), NULL );
+    assert( Abc_NtkLatchNum(pNtk) == 0 );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Checks integraty of the manager.]
+
+  Description [Checks if there are gates that are not used by any primary output.
+  If no such gates exist, return 1 else return 0.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int ABC_Check_Integrity( ABC_Manager mng )
+{
+    Abc_Ntk_t * pNtk = mng->pNtk;
+    Abc_Obj_t * pObj;
+    int i;
+
+    // check that there are no dangling nodes
+    Abc_NtkForEachNode( pNtk, pObj, i )
+    {
+        if ( i == 0 ) 
+            continue;
+        if ( Abc_ObjFanoutNum(pObj) == 0 )
+        {
+//            printf( "ABC_Check_Integrity: The network has dangling nodes.\n" );
+            return 0;
+        }
+    }
+
+    // make sure everything is okay with the network structure
+    if ( !Abc_NtkDoCheck( pNtk ) )
+    {
+        printf( "ABC_Check_Integrity: The internal network check has failed.\n" );
+        return 0;
+    }
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Sets time limit for solving a target.]
+
+  Description [Runtime: time limit (in second).]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void ABC_SetTimeLimit( ABC_Manager mng, int runtime )
+{
+//    printf( "ABC_SetTimeLimit: The resource limit is not implemented (warning).\n" );
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void ABC_SetLearnLimit( ABC_Manager mng, int num )
+{
+//    printf( "ABC_SetLearnLimit: The resource limit is not implemented (warning).\n" );
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void ABC_SetLearnBacktrackLimit( ABC_Manager mng, int num )
+{
+//    printf( "ABC_SetLearnBacktrackLimit: The resource limit is not implemented (warning).\n" );
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void ABC_SetSolveBacktrackLimit( ABC_Manager mng, int num )
+{
+    mng->Params.nMiteringLimitLast = num;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void ABC_SetSolveImplicationLimit( ABC_Manager mng, int num )
+{
+//    printf( "ABC_SetSolveImplicationLimit: The resource limit is not implemented (warning).\n" );
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void ABC_SetTotalBacktrackLimit( ABC_Manager mng, uint64 num )
+{
+    mng->Params.nTotalBacktrackLimit = num;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void ABC_SetTotalInspectLimit( ABC_Manager mng, uint64 num )
+{
+    mng->Params.nTotalInspectLimit = num;
+}
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+uint64 ABC_GetTotalBacktracksMade( ABC_Manager mng )
+{
+    return mng->Params.nTotalBacktracksMade;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+uint64 ABC_GetTotalInspectsMade( ABC_Manager mng )
+{
+    return mng->Params.nTotalInspectsMade;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Sets the file name to dump the structurally hashed network used for solving.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void ABC_EnableDump( ABC_Manager mng, char * dump_file )
+{
+    FREE( mng->pDumpFileName );
+    mng->pDumpFileName = Extra_UtilStrsav( dump_file );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Adds a new target to the manager.]
+
+  Description [The meaning of the parameters are:
+    nog: number of gates that are in the targets,
+    names: name array of gates,
+    values: value array of the corresponding gates given in "names" to be solved. 
+    The relation of them is AND.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int ABC_AddTarget( ABC_Manager mng, int nog, char ** names, int * values )
+{
+    Abc_Obj_t * pObj;
+    int i;
+    if ( nog < 1 )
+        { printf( "ABC_AddTarget: The target has no gates.\n" ); return 0; }
+    // clear storage for the target
+    mng->nog = 0;
+    Vec_PtrClear( mng->vNodes );
+    Vec_IntClear( mng->vValues );
+    // save the target
+    for ( i = 0; i < nog; i++ )
+    {
+        if ( !stmm_lookup( mng->tName2Node, names[i], (char **)&pObj ) )
+            { printf( "ABC_AddTarget: The target gate \"%s\" is not in the network.\n", names[i] ); return 0; }
+        Vec_PtrPush( mng->vNodes, pObj );
+        if ( values[i] < 0 || values[i] > 1 )
+            { printf( "ABC_AddTarget: The value of gate \"%s\" is not 0 or 1.\n", names[i] ); return 0; }
+        Vec_IntPush( mng->vValues, values[i] );
+    }
+    mng->nog = nog;
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Initialize the solver internal data structure.]
+
+  Description [Prepares the solver to work on one specific target
+  set by calling ABC_AddTarget before.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void ABC_SolveInit( ABC_Manager mng )
+{
+    // check if the target is available
+    assert( mng->nog == Vec_PtrSize(mng->vNodes) );
+    if ( mng->nog == 0 )
+        { printf( "ABC_SolveInit: Target is not specified by ABC_AddTarget().\n" ); return; }
+
+    // free the previous target network if present
+    if ( mng->pTarget ) Abc_NtkDelete( mng->pTarget );
+
+    // set the new target network
+//    mng->pTarget = Abc_NtkCreateTarget( mng->pNtk, mng->vNodes, mng->vValues );
+    mng->pTarget = Abc_NtkStrash( mng->pNtk, 0, 1, 0 );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Currently not implemented.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void ABC_AnalyzeTargets( ABC_Manager mng )
+{
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Solves the targets added by ABC_AddTarget().]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+enum CSAT_StatusT ABC_Solve( ABC_Manager mng )
+{
+    Prove_Params_t * pParams = &mng->Params;
+    int RetValue, i;
+
+    // check if the target network is available
+    if ( mng->pTarget == NULL )
+        { printf( "ABC_Solve: Target network is not derived by ABC_SolveInit().\n" ); return UNDETERMINED; }
+
+    // try to prove the miter using a number of techniques
+    if ( mng->mode )
+        RetValue = Abc_NtkMiterSat( mng->pTarget, (sint64)pParams->nMiteringLimitLast, (sint64)0, 0, NULL, NULL );
+    else
+//        RetValue = Abc_NtkMiterProve( &mng->pTarget, pParams ); // old CEC engine
+        RetValue = Abc_NtkIvyProve( &mng->pTarget, pParams ); // new CEC engine
+
+    // analyze the result
+    mng->pResult = ABC_TargetResAlloc( Abc_NtkCiNum(mng->pTarget) );
+    if ( RetValue == -1 )
+        mng->pResult->status = UNDETERMINED;
+    else if ( RetValue == 1 )
+        mng->pResult->status = UNSATISFIABLE;
+    else if ( RetValue == 0 )
+    {
+        mng->pResult->status = SATISFIABLE;
+        // create the array of PI names and values
+        for ( i = 0; i < mng->pResult->no_sig; i++ )
+        {
+            mng->pResult->names[i]  = Extra_UtilStrsav( ABC_GetNodeName(mng, Abc_NtkCi(mng->pNtk, i)) ); 
+            mng->pResult->values[i] = mng->pTarget->pModel[i];
+        }
+        FREE( mng->pTarget->pModel );
+    }
+    else assert( 0 );
+
+    // delete the target
+    Abc_NtkDelete( mng->pTarget );
+    mng->pTarget = NULL;
+    // return the status
+    return mng->pResult->status;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Gets the solve status of a target.]
+
+  Description [TargetID: the target id returned by ABC_AddTarget().]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+CSAT_Target_ResultT * ABC_Get_Target_Result( ABC_Manager mng, int TargetID )
+{
+    return mng->pResult;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Dumps the original network into the BENCH file.]
+
+  Description [This procedure should be modified to dump the target.]
+               
+  SideEffects []
+
+  SeeAlso     [] 
+
+***********************************************************************/
+void ABC_Dump_Bench_File( ABC_Manager mng )
+{
+    Abc_Ntk_t * pNtkTemp, * pNtkAig;
+    char * pFileName;
+ 
+    // derive the netlist
+    pNtkAig = Abc_NtkStrash( mng->pNtk, 0, 0, 0 );
+    pNtkTemp = Abc_NtkToNetlistBench( pNtkAig );
+    Abc_NtkDelete( pNtkAig );
+    if ( pNtkTemp == NULL ) 
+        { printf( "ABC_Dump_Bench_File: Dumping BENCH has failed.\n" ); return; }
+    pFileName = mng->pDumpFileName? mng->pDumpFileName: "abc_test.bench";
+    Io_WriteBench( pNtkTemp, pFileName );
+    Abc_NtkDelete( pNtkTemp );
+}
+
+
+
+/**Function*************************************************************
+
+  Synopsis    [Allocates the target result.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+CSAT_Target_ResultT * ABC_TargetResAlloc( int nVars )
+{
+    CSAT_Target_ResultT * p;
+    p = ALLOC( CSAT_Target_ResultT, 1 );
+    memset( p, 0, sizeof(CSAT_Target_ResultT) );
+    p->no_sig = nVars;
+    p->names = ALLOC( char *, nVars );
+    p->values = ALLOC( int, nVars );
+    memset( p->names, 0, sizeof(char *) * nVars );
+    memset( p->values, 0, sizeof(int) * nVars );
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Deallocates the target result.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void ABC_TargetResFree( CSAT_Target_ResultT * p )
+{
+    if ( p == NULL )
+        return;
+    if( p->names )
+    {
+        int i = 0;
+        for ( i = 0; i < p->no_sig; i++ )
+        {
+            FREE(p->names[i]);
+        }
+    }
+    FREE( p->names );
+    FREE( p->values );
+    free( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Dumps the target AIG into the BENCH file.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+char * ABC_GetNodeName( ABC_Manager mng, Abc_Obj_t * pNode )
+{
+    char * pName = NULL;
+    if ( !stmm_lookup( mng->tNode2Name, (char *)pNode, (char **)&pName ) )
+    {
+        assert( 0 );
+    }
+    return pName;
+}
+
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/csat/csat_apis.h b/src/sat/csat/csat_apis.h
new file mode 100644
index 00000000..b80eddbf
--- /dev/null
+++ b/src/sat/csat/csat_apis.h
@@ -0,0 +1,222 @@
+/**CFile****************************************************************
+
+  FileName    [csat_apis.h]
+
+  PackageName [Interface to CSAT.]
+
+  Synopsis    [APIs, enums, and data structures expected from the use of CSAT.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - August 28, 2005]
+
+  Revision    [$Id: csat_apis.h,v 1.5 2005/12/30 10:54:40 rmukherj Exp $]
+
+***********************************************************************/
+
+#ifndef __ABC_APIS_H__
+#define __ABC_APIS_H__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+////////////////////////////////////////////////////////////////////////
+///                          INCLUDES                                ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                         PARAMETERS                               ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                    STRUCTURE DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+
+typedef struct ABC_ManagerStruct_t     ABC_Manager_t;
+typedef struct ABC_ManagerStruct_t *   ABC_Manager;
+
+
+// GateType defines the gate type that can be added to circuit by
+// ABC_AddGate();
+#ifndef _ABC_GATE_TYPE_
+#define _ABC_GATE_TYPE_
+enum GateType
+{
+    CSAT_CONST = 0,  // constant gate
+    CSAT_BPI,    // boolean PI
+    CSAT_BPPI,   // bit level PSEUDO PRIMARY INPUT
+    CSAT_BAND,   // bit level AND
+    CSAT_BNAND,  // bit level NAND
+    CSAT_BOR,    // bit level OR
+    CSAT_BNOR,   // bit level NOR
+    CSAT_BXOR,   // bit level XOR
+    CSAT_BXNOR,  // bit level XNOR
+    CSAT_BINV,   // bit level INVERTER
+    CSAT_BBUF,   // bit level BUFFER
+    CSAT_BMUX,   // bit level MUX --not supported 
+    CSAT_BDFF,   // bit level D-type FF
+    CSAT_BSDFF,  // bit level scan FF --not supported 
+    CSAT_BTRIH,  // bit level TRISTATE gate with active high control --not supported 
+    CSAT_BTRIL,  // bit level TRISTATE gate with active low control --not supported 
+    CSAT_BBUS,   // bit level BUS --not supported 
+    CSAT_BPPO,   // bit level PSEUDO PRIMARY OUTPUT
+    CSAT_BPO,    // boolean PO
+    CSAT_BCNF,   // boolean constraint
+    CSAT_BDC,    // boolean don't care gate (2 input)
+};
+#endif
+
+
+//CSAT_StatusT defines the return value by ABC_Solve();
+#ifndef _ABC_STATUS_
+#define _ABC_STATUS_
+enum CSAT_StatusT 
+{
+    UNDETERMINED = 0,
+    UNSATISFIABLE,
+    SATISFIABLE,
+    TIME_OUT,
+    FRAME_OUT,
+    NO_TARGET,
+    ABORTED,
+    SEQ_SATISFIABLE     
+};
+#endif
+
+
+// to identify who called the CSAT solver
+#ifndef _ABC_CALLER_
+#define _ABC_CALLER_
+enum CSAT_CallerT
+{
+    BLS = 0,
+    SATORI,
+    NONE
+};
+#endif
+
+
+// CSAT_OptionT defines the solver option about learning
+// which is used by ABC_SetSolveOption();
+#ifndef _ABC_OPTION_
+#define _ABC_OPTION_
+enum CSAT_OptionT
+{
+    BASE_LINE = 0,
+    IMPLICT_LEARNING, //default
+    EXPLICT_LEARNING
+};
+#endif
+
+
+#ifndef _ABC_Target_Result
+#define _ABC_Target_Result
+typedef struct _CSAT_Target_ResultT CSAT_Target_ResultT;
+struct _CSAT_Target_ResultT
+{
+    enum CSAT_StatusT status; // solve status of the target
+    int num_dec;              // num of decisions to solve the target
+    int num_imp;              // num of implications to solve the target
+    int num_cftg;             // num of conflict gates learned 
+    int num_cfts;             // num of conflict signals in conflict gates
+    double time;              // time(in second) used to solve the target
+    int no_sig;               // if "status" is SATISFIABLE, "no_sig" is the number of 
+                              // primary inputs, if the "status" is TIME_OUT, "no_sig" is the
+                              // number of constant signals found.
+    char** names;             // if the "status" is SATISFIABLE, "names" is the name array of
+                              // primary inputs, "values" is the value array of primary 
+                              // inputs that satisfy the target. 
+                              // if the "status" is TIME_OUT, "names" is the name array of
+                              // constant signals found (signals at the root of decision 
+                              // tree), "values" is the value array of constant signals found.
+    int* values;
+};
+#endif
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+// create a new manager
+extern ABC_Manager          ABC_InitManager(void);
+
+// release a manager
+extern void ABC_ReleaseManager(ABC_Manager mng);
+
+// set solver options for learning
+extern void                  ABC_SetSolveOption(ABC_Manager mng, enum CSAT_OptionT option);
+
+// enable checking by brute-force SAT solver (MiniSat-1.14)
+extern void                  ABC_UseOnlyCoreSatSolver(ABC_Manager mng);
+
+
+// add a gate to the circuit
+// the meaning of the parameters are:
+// type: the type of the gate to be added
+// name: the name of the gate to be added, name should be unique in a circuit.
+// nofi: number of fanins of the gate to be added;
+// fanins: the name array of fanins of the gate to be added
+extern int                   ABC_AddGate(ABC_Manager mng,
+                     enum GateType type,
+                     char* name,
+                     int nofi,
+                     char** fanins,
+                     int dc_attr);
+
+// check if there are gates that are not used by any primary ouput.
+// if no such gates exist, return 1 else return 0;
+extern int                   ABC_Check_Integrity(ABC_Manager mng);
+
+// THIS PROCEDURE SHOULD BE CALLED AFTER THE NETWORK IS CONSTRUCTED!!!
+extern void                  ABC_Network_Finalize( ABC_Manager mng );
+
+// set time limit for solving a target.
+// runtime: time limit (in second).
+extern void                  ABC_SetTimeLimit(ABC_Manager mng, int runtime);
+extern void                  ABC_SetLearnLimit(ABC_Manager mng, int num);
+extern void                  ABC_SetSolveBacktrackLimit(ABC_Manager mng, int num);
+extern void                  ABC_SetLearnBacktrackLimit(ABC_Manager mng, int num);
+extern void                  ABC_EnableDump(ABC_Manager mng, char* dump_file);
+
+extern void                  ABC_SetTotalBacktrackLimit( ABC_Manager mng, uint64 num );
+extern void                  ABC_SetTotalInspectLimit( ABC_Manager mng, uint64 num );
+extern uint64                ABC_GetTotalBacktracksMade( ABC_Manager mng );
+extern uint64                ABC_GetTotalInspectsMade( ABC_Manager mng );
+
+// the meaning of the parameters are:
+// nog: number of gates that are in the targets
+// names: name array of gates
+// values: value array of the corresponding gates given in "names" to be
+// solved. the relation of them is AND.
+extern int                   ABC_AddTarget(ABC_Manager mng, int nog, char**names, int* values);
+
+// initialize the solver internal data structure.
+extern void                  ABC_SolveInit(ABC_Manager mng);
+extern void                  ABC_AnalyzeTargets(ABC_Manager mng);
+
+// solve the targets added by ABC_AddTarget()
+extern enum CSAT_StatusT     ABC_Solve(ABC_Manager mng);
+
+// get the solve status of a target
+// TargetID: the target id returned by  ABC_AddTarget().
+extern CSAT_Target_ResultT * ABC_Get_Target_Result(ABC_Manager mng, int TargetID);
+extern void                  ABC_Dump_Bench_File(ABC_Manager mng);
+
+// ADDED PROCEDURES:
+extern void                  ABC_TargetResFree( CSAT_Target_ResultT * p );
+
+extern void CSAT_SetCaller(ABC_Manager mng, enum CSAT_CallerT caller);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
diff --git a/src/sat/csat/module.make b/src/sat/csat/module.make
new file mode 100644
index 00000000..5b71a03c
--- /dev/null
+++ b/src/sat/csat/module.make
@@ -0,0 +1 @@
+SRC +=  src/sat/csat/csat_apis.c
diff --git a/src/sat/fraig/fraig.h b/src/sat/fraig/fraig.h
new file mode 100644
index 00000000..1dad21e2
--- /dev/null
+++ b/src/sat/fraig/fraig.h
@@ -0,0 +1,267 @@
+/**CFile****************************************************************
+
+  FileName    [fraig.h]
+
+  PackageName [FRAIG: Functionally reduced AND-INV graphs.]
+
+  Synopsis    [External declarations of the FRAIG package.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 2.0. Started - October 1, 2004]
+
+  Revision    [$Id: fraig.h,v 1.18 2005/07/08 01:01:30 alanmi Exp $]
+
+***********************************************************************/
+
+#ifndef __FRAIG_H__
+#define __FRAIG_H__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+////////////////////////////////////////////////////////////////////////
+///                          INCLUDES                                ///
+////////////////////////////////////////////////////////////////////////
+
+#ifndef SINT64
+#define SINT64
+
+#ifdef _WIN32
+typedef signed __int64     sint64;   // compatible with MS VS 6.0
+#else
+typedef long long          sint64;
+#endif
+
+#endif
+
+////////////////////////////////////////////////////////////////////////
+///                         PARAMETERS                               ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                    STRUCTURE DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+typedef struct Fraig_ManStruct_t_         Fraig_Man_t;
+typedef struct Fraig_NodeStruct_t_        Fraig_Node_t;
+typedef struct Fraig_NodeVecStruct_t_     Fraig_NodeVec_t;
+typedef struct Fraig_HashTableStruct_t_   Fraig_HashTable_t;
+typedef struct Fraig_ParamsStruct_t_      Fraig_Params_t;
+typedef struct Fraig_PatternsStruct_t_    Fraig_Patterns_t;
+typedef struct Prove_ParamsStruct_t_      Prove_Params_t;
+
+struct Fraig_ParamsStruct_t_
+{
+    int  nPatsRand;     // the number of words of random simulation info
+    int  nPatsDyna;     // the number of words of dynamic simulation info
+    int  nBTLimit;      // the max number of backtracks to perform
+    int  nSeconds;      // the timeout for the final proof
+    int  fFuncRed;      // performs only one level hashing
+    int  fFeedBack;     // enables solver feedback
+    int  fDist1Pats;    // enables distance-1 patterns
+    int  fDoSparse;     // performs equiv tests for sparse functions 
+    int  fChoicing;     // enables recording structural choices
+    int  fTryProve;     // tries to solve the final miter
+    int  fVerbose;      // the verbosiness flag
+    int  fVerboseP;     // the verbosiness flag (for proof reporting)
+    int  fInternal;     // is set to 1 for internal fraig calls
+    int  nConfLimit;    // the limit on the number of conflicts
+    sint64 nInspLimit;  // the limit on the number of inspections
+};
+
+struct Prove_ParamsStruct_t_
+{
+    // general parameters
+    int     fUseFraiging;          // enables fraiging
+    int     fUseRewriting;         // enables rewriting
+    int     fUseBdds;              // enables BDD construction when other methods fail
+    int     fVerbose;              // prints verbose stats
+    // iterations
+    int     nItersMax;             // the number of iterations
+    // mitering 
+    int     nMiteringLimitStart;   // starting mitering limit
+    float   nMiteringLimitMulti;   // multiplicative coefficient to increase the limit in each iteration
+    // rewriting 
+    int     nRewritingLimitStart;  // the number of rewriting iterations
+    float   nRewritingLimitMulti;  // multiplicative coefficient to increase the limit in each iteration
+    // fraiging 
+    int     nFraigingLimitStart;   // starting backtrack(conflict) limit
+    float   nFraigingLimitMulti;   // multiplicative coefficient to increase the limit in each iteration
+    // last-gasp BDD construction
+    int     nBddSizeLimit;         // the number of BDD nodes when construction is aborted
+    int     fBddReorder;           // enables dynamic BDD variable reordering
+    // last-gasp mitering
+    int     nMiteringLimitLast;    // final mitering limit
+    // global SAT solver limits
+    sint64  nTotalBacktrackLimit;  // global limit on the number of backtracks
+    sint64  nTotalInspectLimit;    // global limit on the number of clause inspects
+    // global resources applied
+    sint64  nTotalBacktracksMade;  // the total number of backtracks made
+    sint64  nTotalInspectsMade;    // the total number of inspects made
+};
+
+////////////////////////////////////////////////////////////////////////
+///                       GLOBAL VARIABLES                           ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                       MACRO DEFINITIONS                          ///
+////////////////////////////////////////////////////////////////////////
+ 
+// macros working with complemented attributes of the nodes
+#define Fraig_IsComplement(p)    (((int)((unsigned long) (p) & 01)))
+#define Fraig_Regular(p)         ((Fraig_Node_t *)((unsigned long)(p) & ~01)) 
+#define Fraig_Not(p)             ((Fraig_Node_t *)((unsigned long)(p) ^ 01)) 
+#define Fraig_NotCond(p,c)       ((Fraig_Node_t *)((unsigned long)(p) ^ (c)))
+
+// these are currently not used
+#define Fraig_Ref(p)              
+#define Fraig_Deref(p)            
+#define Fraig_RecursiveDeref(p,c)
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/*=== fraigApi.c =============================================================*/
+extern Fraig_NodeVec_t *   Fraig_ManReadVecInputs( Fraig_Man_t * p );
+extern Fraig_NodeVec_t *   Fraig_ManReadVecOutputs( Fraig_Man_t * p );    
+extern Fraig_NodeVec_t *   Fraig_ManReadVecNodes( Fraig_Man_t * p );      
+extern Fraig_Node_t **     Fraig_ManReadInputs ( Fraig_Man_t * p );       
+extern Fraig_Node_t **     Fraig_ManReadOutputs( Fraig_Man_t * p );       
+extern Fraig_Node_t **     Fraig_ManReadNodes( Fraig_Man_t * p );         
+extern int                 Fraig_ManReadInputNum ( Fraig_Man_t * p );     
+extern int                 Fraig_ManReadOutputNum( Fraig_Man_t * p );     
+extern int                 Fraig_ManReadNodeNum( Fraig_Man_t * p );       
+extern Fraig_Node_t *      Fraig_ManReadConst1 ( Fraig_Man_t * p );       
+extern Fraig_Node_t *      Fraig_ManReadIthVar( Fraig_Man_t * p, int i ); 
+extern Fraig_Node_t *      Fraig_ManReadIthNode( Fraig_Man_t * p, int i );
+extern char **             Fraig_ManReadInputNames( Fraig_Man_t * p );    
+extern char **             Fraig_ManReadOutputNames( Fraig_Man_t * p );   
+extern char *              Fraig_ManReadVarsInt( Fraig_Man_t * p );       
+extern char *              Fraig_ManReadSat( Fraig_Man_t * p );           
+extern int                 Fraig_ManReadFuncRed( Fraig_Man_t * p );       
+extern int                 Fraig_ManReadFeedBack( Fraig_Man_t * p );      
+extern int                 Fraig_ManReadDoSparse( Fraig_Man_t * p );      
+extern int                 Fraig_ManReadChoicing( Fraig_Man_t * p );      
+extern int                 Fraig_ManReadVerbose( Fraig_Man_t * p );       
+extern int *               Fraig_ManReadModel( Fraig_Man_t * p );
+extern int                 Fraig_ManReadPatternNumRandom( Fraig_Man_t * p );
+extern int                 Fraig_ManReadPatternNumDynamic( Fraig_Man_t * p );
+extern int                 Fraig_ManReadPatternNumDynamicFiltered( Fraig_Man_t * p );
+extern int                 Fraig_ManReadSatFails( Fraig_Man_t * p );      
+extern int                 Fraig_ManReadConflicts( Fraig_Man_t * p );      
+extern int                 Fraig_ManReadInspects( Fraig_Man_t * p );      
+
+extern void                Fraig_ManSetFuncRed( Fraig_Man_t * p, int fFuncRed );        
+extern void                Fraig_ManSetFeedBack( Fraig_Man_t * p, int fFeedBack );      
+extern void                Fraig_ManSetDoSparse( Fraig_Man_t * p, int fDoSparse );      
+extern void                Fraig_ManSetChoicing( Fraig_Man_t * p, int fChoicing ); 
+extern void                Fraig_ManSetTryProve( Fraig_Man_t * p, int fTryProve );
+extern void                Fraig_ManSetVerbose( Fraig_Man_t * p, int fVerbose );        
+extern void                Fraig_ManSetTimeToGraph( Fraig_Man_t * p, int Time );        
+extern void                Fraig_ManSetTimeToNet( Fraig_Man_t * p, int Time );          
+extern void                Fraig_ManSetTimeTotal( Fraig_Man_t * p, int Time );          
+extern void                Fraig_ManSetOutputNames( Fraig_Man_t * p, char ** ppNames ); 
+extern void                Fraig_ManSetInputNames( Fraig_Man_t * p, char ** ppNames );  
+extern void                Fraig_ManSetPo( Fraig_Man_t * p, Fraig_Node_t * pNode );
+
+extern Fraig_Node_t *      Fraig_NodeReadData0( Fraig_Node_t * p );                     
+extern Fraig_Node_t *      Fraig_NodeReadData1( Fraig_Node_t * p );                     
+extern int                 Fraig_NodeReadNum( Fraig_Node_t * p );                       
+extern Fraig_Node_t *      Fraig_NodeReadOne( Fraig_Node_t * p );                       
+extern Fraig_Node_t *      Fraig_NodeReadTwo( Fraig_Node_t * p );                       
+extern Fraig_Node_t *      Fraig_NodeReadNextE( Fraig_Node_t * p );                     
+extern Fraig_Node_t *      Fraig_NodeReadRepr( Fraig_Node_t * p );                      
+extern int                 Fraig_NodeReadNumRefs( Fraig_Node_t * p );                   
+extern int                 Fraig_NodeReadNumFanouts( Fraig_Node_t * p );                
+extern int                 Fraig_NodeReadSimInv( Fraig_Node_t * p );                    
+extern int                 Fraig_NodeReadNumOnes( Fraig_Node_t * p );
+extern unsigned *          Fraig_NodeReadPatternsRandom( Fraig_Node_t * p );
+extern unsigned *          Fraig_NodeReadPatternsDynamic( Fraig_Node_t * p );
+
+extern void                Fraig_NodeSetData0( Fraig_Node_t * p, Fraig_Node_t * pData );
+extern void                Fraig_NodeSetData1( Fraig_Node_t * p, Fraig_Node_t * pData );
+
+extern int                 Fraig_NodeIsConst( Fraig_Node_t * p );
+extern int                 Fraig_NodeIsVar( Fraig_Node_t * p );
+extern int                 Fraig_NodeIsAnd( Fraig_Node_t * p );
+extern int                 Fraig_NodeComparePhase( Fraig_Node_t * p1, Fraig_Node_t * p2 );
+
+extern Fraig_Node_t *      Fraig_NodeOr( Fraig_Man_t * p, Fraig_Node_t * p1, Fraig_Node_t * p2 );
+extern Fraig_Node_t *      Fraig_NodeAnd( Fraig_Man_t * p, Fraig_Node_t * p1, Fraig_Node_t * p2 );
+extern Fraig_Node_t *      Fraig_NodeOr( Fraig_Man_t * p, Fraig_Node_t * p1, Fraig_Node_t * p2 );
+extern Fraig_Node_t *      Fraig_NodeExor( Fraig_Man_t * p, Fraig_Node_t * p1, Fraig_Node_t * p2 );
+extern Fraig_Node_t *      Fraig_NodeMux( Fraig_Man_t * p, Fraig_Node_t * pNode, Fraig_Node_t * pNodeT, Fraig_Node_t * pNodeE );
+extern void                Fraig_NodeSetChoice( Fraig_Man_t * pMan, Fraig_Node_t * pNodeOld, Fraig_Node_t * pNodeNew );
+
+/*=== fraigMan.c =============================================================*/
+extern void                Prove_ParamsSetDefault( Prove_Params_t * pParams );
+extern void                Fraig_ParamsSetDefault( Fraig_Params_t * pParams );
+extern void                Fraig_ParamsSetDefaultFull( Fraig_Params_t * pParams );
+extern Fraig_Man_t *       Fraig_ManCreate( Fraig_Params_t * pParams );
+extern void                Fraig_ManFree( Fraig_Man_t * pMan );
+extern void                Fraig_ManPrintStats( Fraig_Man_t * p );
+extern Fraig_NodeVec_t *   Fraig_ManGetSimInfo( Fraig_Man_t * p );
+extern int                 Fraig_ManCheckClauseUsingSimInfo( Fraig_Man_t * p, Fraig_Node_t * pNode1, Fraig_Node_t * pNode2 );
+extern void                Fraig_ManAddClause( Fraig_Man_t * p, Fraig_Node_t ** ppNodes, int nNodes );
+
+/*=== fraigDfs.c =============================================================*/
+extern Fraig_NodeVec_t *   Fraig_Dfs( Fraig_Man_t * pMan, int fEquiv );
+extern Fraig_NodeVec_t *   Fraig_DfsOne( Fraig_Man_t * pMan, Fraig_Node_t * pNode, int fEquiv );
+extern Fraig_NodeVec_t *   Fraig_DfsNodes( Fraig_Man_t * pMan, Fraig_Node_t ** ppNodes, int nNodes, int fEquiv );
+extern Fraig_NodeVec_t *   Fraig_DfsReverse( Fraig_Man_t * pMan );
+extern int                 Fraig_CountNodes( Fraig_Man_t * pMan, int fEquiv );
+extern int                 Fraig_CheckTfi( Fraig_Man_t * pMan, Fraig_Node_t * pOld, Fraig_Node_t * pNew );
+extern int                 Fraig_CountLevels( Fraig_Man_t * pMan );
+
+/*=== fraigSat.c =============================================================*/
+extern int                 Fraig_NodesAreEqual( Fraig_Man_t * p, Fraig_Node_t * pNode1, Fraig_Node_t * pNode2, int nBTLimit, int nTimeLimit );
+extern int                 Fraig_NodeIsEquivalent( Fraig_Man_t * p, Fraig_Node_t * pOld, Fraig_Node_t * pNew, int nBTLimit, int nTimeLimit );
+extern void                Fraig_ManProveMiter( Fraig_Man_t * p );
+extern int                 Fraig_ManCheckMiter( Fraig_Man_t * p );
+extern int                 Fraig_ManCheckClauseUsingSat( Fraig_Man_t * p, Fraig_Node_t * pNode1, Fraig_Node_t * pNode2, int nBTLimit );
+
+/*=== fraigVec.c ===============================================================*/
+extern Fraig_NodeVec_t *   Fraig_NodeVecAlloc( int nCap );
+extern void                Fraig_NodeVecFree( Fraig_NodeVec_t * p );
+extern Fraig_NodeVec_t *   Fraig_NodeVecDup( Fraig_NodeVec_t * p );
+extern Fraig_Node_t **     Fraig_NodeVecReadArray( Fraig_NodeVec_t * p );
+extern int                 Fraig_NodeVecReadSize( Fraig_NodeVec_t * p );
+extern void                Fraig_NodeVecGrow( Fraig_NodeVec_t * p, int nCapMin );
+extern void                Fraig_NodeVecShrink( Fraig_NodeVec_t * p, int nSizeNew );
+extern void                Fraig_NodeVecClear( Fraig_NodeVec_t * p );
+extern void                Fraig_NodeVecPush( Fraig_NodeVec_t * p, Fraig_Node_t * Entry );
+extern int                 Fraig_NodeVecPushUnique( Fraig_NodeVec_t * p, Fraig_Node_t * Entry );
+extern void                Fraig_NodeVecPushOrder( Fraig_NodeVec_t * p, Fraig_Node_t * pNode );
+extern int                 Fraig_NodeVecPushUniqueOrder( Fraig_NodeVec_t * p, Fraig_Node_t * pNode );
+extern void                Fraig_NodeVecPushOrderByLevel( Fraig_NodeVec_t * p, Fraig_Node_t * pNode );
+extern int                 Fraig_NodeVecPushUniqueOrderByLevel( Fraig_NodeVec_t * p, Fraig_Node_t * pNode );
+extern Fraig_Node_t *      Fraig_NodeVecPop( Fraig_NodeVec_t * p );
+extern void                Fraig_NodeVecRemove( Fraig_NodeVec_t * p, Fraig_Node_t * Entry );
+extern void                Fraig_NodeVecWriteEntry( Fraig_NodeVec_t * p, int i, Fraig_Node_t * Entry );
+extern Fraig_Node_t *      Fraig_NodeVecReadEntry( Fraig_NodeVec_t * p, int i );
+extern void                Fraig_NodeVecSortByLevel( Fraig_NodeVec_t * p, int fIncreasing );
+extern void                Fraig_NodeVecSortByNumber( Fraig_NodeVec_t * p );
+
+/*=== fraigUtil.c ===============================================================*/
+extern void                Fraig_ManMarkRealFanouts( Fraig_Man_t * p );
+extern int                 Fraig_ManCheckConsistency( Fraig_Man_t * p );
+extern int                 Fraig_GetMaxLevel( Fraig_Man_t * pMan );
+extern void                Fraig_ManReportChoices( Fraig_Man_t * pMan );
+extern void                Fraig_MappingSetChoiceLevels( Fraig_Man_t * pMan, int fMaximum );
+extern Fraig_NodeVec_t *   Fraig_CollectSupergate( Fraig_Node_t * pNode, int fStopAtMux );
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+ 
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/src/sat/fraig/fraigApi.c b/src/sat/fraig/fraigApi.c
new file mode 100644
index 00000000..79a7c224
--- /dev/null
+++ b/src/sat/fraig/fraigApi.c
@@ -0,0 +1,297 @@
+/**CFile****************************************************************
+
+  FileName    [fraigApi.c]
+
+  PackageName [FRAIG: Functionally reduced AND-INV graphs.]
+
+  Synopsis    [Access APIs for the FRAIG manager and node.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 2.0. Started - October 1, 2004]
+
+  Revision    [$Id: fraigApi.c,v 1.2 2005/07/08 01:01:30 alanmi Exp $]
+
+***********************************************************************/
+
+#include "fraigInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Access functions to read the data members of the manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_NodeVec_t * Fraig_ManReadVecInputs( Fraig_Man_t * p )                   { return p->vInputs;            }
+Fraig_NodeVec_t * Fraig_ManReadVecOutputs( Fraig_Man_t * p )                  { return p->vOutputs;           }
+Fraig_NodeVec_t * Fraig_ManReadVecNodes( Fraig_Man_t * p )                    { return p->vNodes;             }
+Fraig_Node_t **   Fraig_ManReadInputs ( Fraig_Man_t * p )                     { return p->vInputs->pArray;    }
+Fraig_Node_t **   Fraig_ManReadOutputs( Fraig_Man_t * p )                     { return p->vOutputs->pArray;   }
+Fraig_Node_t **   Fraig_ManReadNodes( Fraig_Man_t * p )                       { return p->vNodes->pArray;     }
+int               Fraig_ManReadInputNum ( Fraig_Man_t * p )                   { return p->vInputs->nSize;     }
+int               Fraig_ManReadOutputNum( Fraig_Man_t * p )                   { return p->vOutputs->nSize;    }
+int               Fraig_ManReadNodeNum( Fraig_Man_t * p )                     { return p->vNodes->nSize;      }
+Fraig_Node_t *    Fraig_ManReadConst1 ( Fraig_Man_t * p )                     { return p->pConst1;            }
+Fraig_Node_t *    Fraig_ManReadIthNode( Fraig_Man_t * p, int i )              { assert ( i < p->vNodes->nSize  ); return p->vNodes->pArray[i];  }
+char **           Fraig_ManReadInputNames( Fraig_Man_t * p )                  { return p->ppInputNames;       }
+char **           Fraig_ManReadOutputNames( Fraig_Man_t * p )                 { return p->ppOutputNames;      }
+char *            Fraig_ManReadVarsInt( Fraig_Man_t * p )                     { return (char *)p->vVarsInt;   }
+char *            Fraig_ManReadSat( Fraig_Man_t * p )                         { return (char *)p->pSat;       }
+int               Fraig_ManReadFuncRed( Fraig_Man_t * p )                     { return p->fFuncRed;   }
+int               Fraig_ManReadFeedBack( Fraig_Man_t * p )                    { return p->fFeedBack;  }
+int               Fraig_ManReadDoSparse( Fraig_Man_t * p )                    { return p->fDoSparse;  }
+int               Fraig_ManReadChoicing( Fraig_Man_t * p )                    { return p->fChoicing;  }
+int               Fraig_ManReadVerbose( Fraig_Man_t * p )                     { return p->fVerbose;   }
+int *             Fraig_ManReadModel( Fraig_Man_t * p )                       { return p->pModel;     }
+// returns the number of patterns used for random simulation (this number is fixed for the FRAIG run)
+int               Fraig_ManReadPatternNumRandom( Fraig_Man_t * p )            { return p->nWordsRand * 32;  }
+// returns the number of dynamic patterns accumulated at runtime (include SAT solver counter-examples and distance-1 patterns derived from them)
+int               Fraig_ManReadPatternNumDynamic( Fraig_Man_t * p )           { return p->iWordStart * 32;  }
+// returns the number of dynamic patterns proved useful to distinquish some FRAIG nodes (this number is more than 0 after the first garbage collection of patterns)
+int               Fraig_ManReadPatternNumDynamicFiltered( Fraig_Man_t * p )   { return p->iPatsPerm;        }
+// returns the number of times FRAIG package timed out
+int               Fraig_ManReadSatFails( Fraig_Man_t * p )                    { return p->nSatFailsReal;    }      
+// returns the number of conflicts in the SAT solver
+int               Fraig_ManReadConflicts( Fraig_Man_t * p )                   { return p->pSat? Msat_SolverReadBackTracks(p->pSat) : 0; }      
+// returns the number of inspections in the SAT solver
+int               Fraig_ManReadInspects( Fraig_Man_t * p )                    { return p->pSat? Msat_SolverReadInspects(p->pSat) : 0;   }            
+
+/**Function*************************************************************
+
+  Synopsis    [Access functions to set the data members of the manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void            Fraig_ManSetFuncRed( Fraig_Man_t * p, int fFuncRed )        { p->fFuncRed  = fFuncRed;  }
+void            Fraig_ManSetFeedBack( Fraig_Man_t * p, int fFeedBack )      { p->fFeedBack = fFeedBack; }
+void            Fraig_ManSetDoSparse( Fraig_Man_t * p, int fDoSparse )      { p->fDoSparse = fDoSparse; }
+void            Fraig_ManSetChoicing( Fraig_Man_t * p, int fChoicing )      { p->fChoicing = fChoicing; }
+void            Fraig_ManSetTryProve( Fraig_Man_t * p, int fTryProve )      { p->fTryProve = fTryProve; }
+void            Fraig_ManSetVerbose( Fraig_Man_t * p, int fVerbose )        { p->fVerbose  = fVerbose;  }
+void            Fraig_ManSetTimeToGraph( Fraig_Man_t * p, int Time )        { p->timeToAig = Time;      }
+void            Fraig_ManSetTimeToNet( Fraig_Man_t * p, int Time )          { p->timeToNet = Time;      }
+void            Fraig_ManSetTimeTotal( Fraig_Man_t * p, int Time )          { p->timeTotal = Time;      }
+void            Fraig_ManSetOutputNames( Fraig_Man_t * p, char ** ppNames ) { p->ppOutputNames = ppNames; }
+void            Fraig_ManSetInputNames( Fraig_Man_t * p, char ** ppNames )  { p->ppInputNames  = ppNames; }
+
+/**Function*************************************************************
+
+  Synopsis    [Access functions to read the data members of the node.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_Node_t *  Fraig_NodeReadData0( Fraig_Node_t * p )                   { return p->pData0;    }
+Fraig_Node_t *  Fraig_NodeReadData1( Fraig_Node_t * p )                   { return p->pData1;    }
+int             Fraig_NodeReadNum( Fraig_Node_t * p )                     { return p->Num;       }
+Fraig_Node_t *  Fraig_NodeReadOne( Fraig_Node_t * p )                     { assert (!Fraig_IsComplement(p)); return p->p1; }
+Fraig_Node_t *  Fraig_NodeReadTwo( Fraig_Node_t * p )                     { assert (!Fraig_IsComplement(p)); return p->p2; }
+Fraig_Node_t *  Fraig_NodeReadNextE( Fraig_Node_t * p )                   { return p->pNextE;    }
+Fraig_Node_t *  Fraig_NodeReadRepr( Fraig_Node_t * p )                    { return p->pRepr;     }
+int             Fraig_NodeReadNumRefs( Fraig_Node_t * p )                 { return p->nRefs;     }
+int             Fraig_NodeReadNumFanouts( Fraig_Node_t * p )              { return p->nFanouts;  }
+int             Fraig_NodeReadSimInv( Fraig_Node_t * p )                  { return p->fInv;      }
+int             Fraig_NodeReadNumOnes( Fraig_Node_t * p )                 { return p->nOnes;     }
+// returns the pointer to the random simulation patterns (their number is returned by Fraig_ManReadPatternNumRandom)
+// memory pointed to by this and the following procedure is maintained by the FRAIG package and exists as long as the package runs
+unsigned *      Fraig_NodeReadPatternsRandom( Fraig_Node_t * p )          { return p->puSimR;    }
+// returns the pointer to the dynamic simulation patterns (their number is returned by Fraig_ManReadPatternNumDynamic or Fraig_ManReadPatternNumDynamicFiltered)
+// if the number of patterns is not evenly divisible by 32, the patterns beyond the given number contain garbage
+unsigned *      Fraig_NodeReadPatternsDynamic( Fraig_Node_t * p )         { return p->puSimD;    }
+
+/**Function*************************************************************
+
+  Synopsis    [Access functions to set the data members of the node.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void            Fraig_NodeSetData0( Fraig_Node_t * p, Fraig_Node_t * pData )      { p->pData0  = pData;  }
+void            Fraig_NodeSetData1( Fraig_Node_t * p, Fraig_Node_t * pData )      { p->pData1  = pData;  }
+
+/**Function*************************************************************
+
+  Synopsis    [Checks the type of the node.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int             Fraig_NodeIsConst( Fraig_Node_t * p )    {  return (Fraig_Regular(p))->Num   == 0;  }
+int             Fraig_NodeIsVar( Fraig_Node_t * p )      {  return (Fraig_Regular(p))->NumPi >= 0;  }
+int             Fraig_NodeIsAnd( Fraig_Node_t * p )      {  return (Fraig_Regular(p))->NumPi <  0 && (Fraig_Regular(p))->Num > 0;  }
+int             Fraig_NodeComparePhase( Fraig_Node_t * p1, Fraig_Node_t * p2 ) { assert( !Fraig_IsComplement(p1) ); assert( !Fraig_IsComplement(p2) ); return p1->fInv ^ p2->fInv; }
+
+/**Function*************************************************************
+
+  Synopsis    [Returns a new primary input node.]
+
+  Description [If the node with this number does not exist, 
+  create a new PI node with this number.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_Node_t * Fraig_ManReadIthVar( Fraig_Man_t * p, int i )
+{
+    int k;
+    if ( i < 0 )
+    {
+        printf( "Requesting a PI with a negative number\n" );
+        return NULL;
+    }
+    // create the PIs to fill in the interval
+    if ( i >= p->vInputs->nSize )
+        for ( k = p->vInputs->nSize; k <= i; k++ )
+            Fraig_NodeCreatePi( p ); 
+    return p->vInputs->pArray[i];
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Creates a new PO node.]
+
+  Description [This procedure may take a complemented node.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_ManSetPo( Fraig_Man_t * p, Fraig_Node_t * pNode )
+{
+    // internal node may be a PO two times
+    Fraig_Regular(pNode)->fNodePo = 1;
+    Fraig_NodeVecPush( p->vOutputs, pNode );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Perfoms the AND operation with functional hashing.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_Node_t * Fraig_NodeAnd( Fraig_Man_t * p, Fraig_Node_t * p1, Fraig_Node_t * p2 )
+{
+    return Fraig_NodeAndCanon( p, p1, p2 );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Perfoms the OR operation with functional hashing.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_Node_t * Fraig_NodeOr( Fraig_Man_t * p, Fraig_Node_t * p1, Fraig_Node_t * p2 )
+{
+    return Fraig_Not( Fraig_NodeAndCanon( p, Fraig_Not(p1), Fraig_Not(p2) ) );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Perfoms the EXOR operation with functional hashing.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_Node_t * Fraig_NodeExor( Fraig_Man_t * p, Fraig_Node_t * p1, Fraig_Node_t * p2 )
+{
+    return Fraig_NodeMux( p, p1, Fraig_Not(p2), p2 );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Perfoms the MUX operation with functional hashing.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_Node_t * Fraig_NodeMux( Fraig_Man_t * p, Fraig_Node_t * pC, Fraig_Node_t * pT, Fraig_Node_t * pE )
+{
+    Fraig_Node_t * pAnd1, * pAnd2, * pRes;
+    pAnd1 = Fraig_NodeAndCanon( p, pC,          pT );     Fraig_Ref( pAnd1 );
+    pAnd2 = Fraig_NodeAndCanon( p, Fraig_Not(pC), pE );   Fraig_Ref( pAnd2 );
+    pRes  = Fraig_NodeOr( p, pAnd1, pAnd2 ); 
+    Fraig_RecursiveDeref( p, pAnd1 );
+    Fraig_RecursiveDeref( p, pAnd2 );
+    Fraig_Deref( pRes );
+    return pRes;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Sets the node to be equivalent to the given one.]
+
+  Description [This procedure is a work-around for the equivalence check.
+  Does not verify the equivalence. Use at the user's risk.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_NodeSetChoice( Fraig_Man_t * pMan, Fraig_Node_t * pNodeOld, Fraig_Node_t * pNodeNew )
+{
+//    assert( pMan->fChoicing );
+    pNodeNew->pNextE = pNodeOld->pNextE;
+    pNodeOld->pNextE = pNodeNew;
+    pNodeNew->pRepr  = pNodeOld;
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/fraig/fraigCanon.c b/src/sat/fraig/fraigCanon.c
new file mode 100644
index 00000000..89bc924f
--- /dev/null
+++ b/src/sat/fraig/fraigCanon.c
@@ -0,0 +1,218 @@
+/**CFile****************************************************************
+
+  FileName    [fraigCanon.c]
+
+  PackageName [FRAIG: Functionally reduced AND-INV graphs.]
+
+  Synopsis    [AND-node creation and elementary AND-operation.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 2.0. Started - October 1, 2004]
+
+  Revision    [$Id: fraigCanon.c,v 1.4 2005/07/08 01:01:31 alanmi Exp $]
+
+***********************************************************************/
+
+#include <limits.h>
+#include "fraigInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [The internal AND operation for the two FRAIG nodes.]
+
+  Description [This procedure is the core of the FRAIG package, because
+  it performs the two-step canonicization of FRAIG nodes. The first step
+  involves the lookup in the structural hash table (which hashes two ANDs 
+  into a node that has them as fanins, if such a node exists). If the node 
+  is not found in the structural hash table, an attempt is made to find a 
+  functionally equivalent node in another hash table (which hashes the 
+  simulation info into the nodes, which has this simulation info). Some 
+  tricks used on the way are described in the comments to the code and
+  in the paper "FRAIGs: Functionally reduced AND-INV graphs".]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_Node_t * Fraig_NodeAndCanon( Fraig_Man_t * pMan, Fraig_Node_t * p1, Fraig_Node_t * p2 )
+{
+    Fraig_Node_t * pNodeNew, * pNodeOld, * pNodeRepr;
+    int fUseSatCheck;
+//    int RetValue;
+
+    // check for trivial cases
+    if ( p1 == p2 )
+        return p1;
+    if ( p1 == Fraig_Not(p2) )
+        return Fraig_Not(pMan->pConst1);
+    if ( Fraig_NodeIsConst(p1) )
+    {
+        if ( p1 == pMan->pConst1 )
+            return p2;
+        return Fraig_Not(pMan->pConst1);
+    }
+    if ( Fraig_NodeIsConst(p2) )
+    {
+        if ( p2 == pMan->pConst1 )
+            return p1;
+        return Fraig_Not(pMan->pConst1);
+    }
+/*
+    // check for less trivial cases
+    if ( Fraig_IsComplement(p1) )
+    {
+        if ( RetValue = Fraig_NodeIsInSupergate( Fraig_Regular(p1), p2 ) )
+        {
+            if ( RetValue == -1 )
+                pMan->nImplies0++;
+            else
+                pMan->nImplies1++;
+
+            if ( RetValue == -1 )
+                return p2;
+        }
+    }
+    else
+    {
+        if ( RetValue = Fraig_NodeIsInSupergate( p1, p2 ) )
+        {
+            if ( RetValue == 1 )
+                pMan->nSimplifies1++;
+            else
+                pMan->nSimplifies0++;
+
+            if ( RetValue == 1 )
+                return p1;
+            return Fraig_Not(pMan->pConst1);
+        }
+    }
+ 
+    if ( Fraig_IsComplement(p2) )
+    {
+        if ( RetValue = Fraig_NodeIsInSupergate( Fraig_Regular(p2), p1 ) )
+        {
+            if ( RetValue == -1 )
+                pMan->nImplies0++;
+            else
+                pMan->nImplies1++;
+
+            if ( RetValue == -1 )
+                return p1;
+        }
+    }
+    else
+    {
+        if ( RetValue = Fraig_NodeIsInSupergate( p2, p1 ) )
+        {
+            if ( RetValue == 1 )
+                pMan->nSimplifies1++;
+            else
+                pMan->nSimplifies0++;
+
+            if ( RetValue == 1 )
+                return p2;
+            return Fraig_Not(pMan->pConst1);
+        }
+    }
+*/
+    // perform level-one structural hashing
+    if ( Fraig_HashTableLookupS( pMan, p1, p2, &pNodeNew ) ) // the node with these children is found
+    {
+        // if the existent node is part of the cone of unused logic
+        // (that is logic feeding the node which is equivalent to the given node)
+        // return the canonical representative of this node
+        // determine the phase of the given node, with respect to its canonical form
+        pNodeRepr = Fraig_Regular(pNodeNew)->pRepr;
+        if ( pMan->fFuncRed && pNodeRepr )
+            return Fraig_NotCond( pNodeRepr, Fraig_IsComplement(pNodeNew) ^ Fraig_NodeComparePhase(Fraig_Regular(pNodeNew), pNodeRepr) );
+        // otherwise, the node is itself a canonical representative, return it
+        return pNodeNew;
+    }
+    // the same node is not found, but the new one is created
+
+    // if one level hashing is requested (without functionality hashing), return
+    if ( !pMan->fFuncRed )
+        return pNodeNew;
+
+    // check if the new node is unique using the simulation info
+    if ( pNodeNew->nOnes == 0 || pNodeNew->nOnes == (unsigned)pMan->nWordsRand * 32 )
+    {
+        pMan->nSatZeros++;
+        if ( !pMan->fDoSparse ) // if we do not do sparse functions, skip
+            return pNodeNew;
+        // check the sparse function simulation hash table
+        pNodeOld = Fraig_HashTableLookupF0( pMan, pNodeNew );
+        if ( pNodeOld == NULL ) // the node is unique (it is added to the table)
+            return pNodeNew;
+    }
+    else
+    {
+        // check the simulation hash table
+        pNodeOld = Fraig_HashTableLookupF( pMan, pNodeNew );
+        if ( pNodeOld == NULL ) // the node is unique
+            return pNodeNew;
+    }
+    assert( pNodeOld->pRepr == 0 );
+    // there is another node which looks the same according to simulation
+
+    // use SAT to resolve the ambiguity
+    fUseSatCheck = (pMan->nInspLimit == 0 || Fraig_ManReadInspects(pMan) < pMan->nInspLimit); 
+    if ( fUseSatCheck && Fraig_NodeIsEquivalent( pMan, pNodeOld, pNodeNew, pMan->nBTLimit, 1000000 ) )
+    {
+        // set the node to be equivalent with this node
+        // to prevent loops, only set if the old node is not in the TFI of the new node
+        // the loop may happen in the following case: suppose 
+        // NodeC = AND(NodeA, NodeB) and at the same time NodeA => NodeB
+        // in this case, NodeA and NodeC are functionally equivalent
+        // however, NodeA is a fanin of node NodeC (this leads to the loop)
+        // add the node to the list of equivalent nodes or dereference it
+        if ( pMan->fChoicing && !Fraig_CheckTfi( pMan, pNodeOld, pNodeNew ) )
+        { 
+            // if the old node is not in the TFI of the new node and choicing 
+            // is enabled, add the new node to the list of equivalent ones
+            pNodeNew->pNextE = pNodeOld->pNextE;
+            pNodeOld->pNextE = pNodeNew;
+        }
+        // set the canonical representative of this node
+        pNodeNew->pRepr = pNodeOld;
+        // return the equivalent node
+        return Fraig_NotCond( pNodeOld, Fraig_NodeComparePhase(pNodeOld, pNodeNew) );
+    }
+
+    // now we add another member to this simulation class
+    if ( pNodeNew->nOnes == 0 || pNodeNew->nOnes == (unsigned)pMan->nWordsRand * 32 )
+    {
+        Fraig_Node_t * pNodeTemp;
+        assert( pMan->fDoSparse );
+        pNodeTemp = Fraig_HashTableLookupF0( pMan, pNodeNew );
+//        assert( pNodeTemp == NULL );
+//        Fraig_HashTableInsertF0( pMan, pNodeNew );
+    }
+    else
+    {
+        pNodeNew->pNextD = pNodeOld->pNextD;
+        pNodeOld->pNextD = pNodeNew;
+    }
+    // return the new node
+    assert( pNodeNew->pRepr == 0 );
+    return pNodeNew;
+}
+
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/fraig/fraigChoice.c b/src/sat/fraig/fraigChoice.c
new file mode 100644
index 00000000..896e5d2d
--- /dev/null
+++ b/src/sat/fraig/fraigChoice.c
@@ -0,0 +1,241 @@
+/**CFile****************************************************************
+
+  FileName    [fraigTrans.c]
+
+  PackageName [MVSIS 1.3: Multi-valued logic synthesis system.]
+
+  Synopsis    [Adds the additive and distributive choices to the AIG.]
+
+  Author      [MVSIS Group]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - February 1, 2003.]
+
+  Revision    [$Id: fraigTrans.c,v 1.1 2005/02/28 05:34:34 alanmi Exp $]
+
+***********************************************************************/
+
+#include "fraigInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFITIONS                           ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Adds choice nodes based on associativity.]
+
+  Description [Make nLimit big AND gates and add all decompositions
+               to the Fraig.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_ManAddChoices( Fraig_Man_t * pMan, int fVerbose, int nLimit )
+{
+//    ProgressBar * pProgress;
+    char Buffer[100];
+    int clkTotal = clock();
+    int i, nNodesBefore, nNodesAfter, nInputs, nMaxNodes;
+    int /*nMaxLevel,*/ nDistributive;
+    Fraig_Node_t *pNode, *pRepr;
+    Fraig_Node_t *pX, *pA, *pB, *pC, /* *pD,*/ *pN, /* *pQ, *pR,*/ *pT;
+    int fShortCut = 0;
+
+    nDistributive = 0;
+
+//    Fraig_ManSetApprox( pMan, 1 );
+
+    // NO functional reduction
+    if (fShortCut) Fraig_ManSetFuncRed( pMan, 0 );
+
+    // First we mark critical functions i.e. compute those
+    // nodes which lie on the critical path. Note that this
+    // doesn't update the required times on any choice nodes
+    // which are not the representatives
+/*
+    nMaxLevel = Fraig_GetMaxLevel( pMan );
+    for ( i = 0; i < pMan->nOutputs; i++ )
+    {
+        Fraig_SetNodeRequired( pMan, pMan->pOutputs[i], nMaxLevel );
+    }
+*/
+    nNodesBefore = Fraig_ManReadNodeNum( pMan );
+    nInputs      = Fraig_ManReadInputNum( pMan );
+    nMaxNodes    = nInputs + nLimit * ( nNodesBefore - nInputs );
+
+    printf ("Limit = %d, Before = %d\n", nMaxNodes, nNodesBefore );
+
+    if (0) 
+    {
+        char buffer[128];
+        sprintf (buffer, "test" );
+//        Fraig_MappingShow( pMan, buffer );
+    }
+
+//    pProgress = Extra_ProgressBarStart( stdout, nMaxNodes );
+Fraig_ManCheckConsistency( pMan );
+
+    for ( i = nInputs+1; (i < Fraig_ManReadNodeNum( pMan )) 
+            && (nMaxNodes > Fraig_ManReadNodeNum( pMan )); ++i )
+    {
+//        if ( i == nNodesBefore )
+//            break;
+
+        pNode = Fraig_ManReadIthNode( pMan, i );
+        assert ( pNode );
+
+        pRepr = pNode->pRepr ? pNode->pRepr : pNode;
+        //printf ("Slack: %d\n", Fraig_NodeReadSlack( pRepr ));
+        
+        // All the new associative choices we add will have huge slack
+        // since we do not redo timing, and timing doesnt handle choices
+        // well anyway. However every newly added node is a choice of an
+        // existing critical node, so they are considered critical.
+//        if ( (Fraig_NodeReadSlack( pRepr ) > 3) && (i < nNodesBefore)  )     
+//            continue;
+
+//        if ( pNode->pRepr )
+//            continue;
+
+        // Try ((ab)c), x = ab -> (a(bc)) and (b(ac))
+        pX = Fraig_NodeReadOne(pNode);
+        pC = Fraig_NodeReadTwo(pNode);
+        if (Fraig_NodeIsAnd(pX) && !Fraig_IsComplement(pX))
+        {
+            pA = Fraig_NodeReadOne(Fraig_Regular(pX));
+            pB = Fraig_NodeReadTwo(Fraig_Regular(pX));
+
+//            pA = Fraig_NodeGetRepr( pA );
+//            pB = Fraig_NodeGetRepr( pB );
+//            pC = Fraig_NodeGetRepr( pC );
+
+            if (fShortCut) 
+            {
+                pT = Fraig_NodeAnd(pMan, pB, pC);
+                if ( !pT->pRepr )
+                {
+                    pN = Fraig_NodeAnd(pMan, pA, pT);
+//                    Fraig_NodeAddChoice( pMan, pNode, pN );
+                }
+            }
+            else
+                pN = Fraig_NodeAnd(pMan, pA, Fraig_NodeAnd(pMan, pB, pC));
+            // assert ( Fraig_NodesEqual(pN, pNode) );
+
+
+            if (fShortCut) 
+            {
+                pT = Fraig_NodeAnd(pMan, pA, pC);
+                if ( !pT->pRepr )
+                {
+                    pN = Fraig_NodeAnd(pMan, pB, pT);
+//                    Fraig_NodeAddChoice( pMan, pNode, pN );
+                }
+            }
+            else
+                pN = Fraig_NodeAnd(pMan, pB, Fraig_NodeAnd(pMan, pA, pC));
+            // assert ( Fraig_NodesEqual(pN, pNode) );
+        }
+
+
+        // Try (a(bc)), x = bc -> ((ab)c) and ((ac)b)
+        pA = Fraig_NodeReadOne(pNode);
+        pX = Fraig_NodeReadTwo(pNode);
+        if (Fraig_NodeIsAnd(pX) && !Fraig_IsComplement(pX))
+        {
+            pB = Fraig_NodeReadOne(Fraig_Regular(pX));
+            pC = Fraig_NodeReadTwo(Fraig_Regular(pX));
+
+//            pA = Fraig_NodeGetRepr( pA );
+//            pB = Fraig_NodeGetRepr( pB );
+//            pC = Fraig_NodeGetRepr( pC );
+
+            if (fShortCut) 
+            {
+                pT = Fraig_NodeAnd(pMan, pA, pB);
+                if ( !pT->pRepr )
+                {
+                    pN = Fraig_NodeAnd(pMan, pC, pT);
+//                    Fraig_NodeAddChoice( pMan, pNode, pN );
+                }
+            }
+            else
+                pN = Fraig_NodeAnd(pMan, Fraig_NodeAnd(pMan, pA, pB), pC);
+            // assert ( Fraig_NodesEqual(pN, pNode) );
+
+            if (fShortCut) 
+            {
+                pT = Fraig_NodeAnd(pMan, pA, pC);
+                if ( !pT->pRepr )
+                {
+                    pN = Fraig_NodeAnd(pMan, pB, pT);
+//                    Fraig_NodeAddChoice( pMan, pNode, pN );
+                }
+            }
+            else
+                pN = Fraig_NodeAnd(pMan, Fraig_NodeAnd(pMan, pA, pC), pB);
+            // assert ( Fraig_NodesEqual(pN, pNode) );
+        }
+
+
+/*
+        // Try distributive transform
+        pQ = Fraig_NodeReadOne(pNode);
+        pR = Fraig_NodeReadTwo(pNode);
+        if ( (Fraig_IsComplement(pQ) && Fraig_NodeIsAnd(pQ))
+             && (Fraig_IsComplement(pR) && Fraig_NodeIsAnd(pR)) )
+        {
+            pA = Fraig_NodeReadOne(Fraig_Regular(pQ));
+            pB = Fraig_NodeReadTwo(Fraig_Regular(pQ));
+            pC = Fraig_NodeReadOne(Fraig_Regular(pR));
+            pD = Fraig_NodeReadTwo(Fraig_Regular(pR));
+
+            // Now detect the !(xy + xz) pattern, store 
+            // x in pA, y in pB and z in pC and set pD = 0 to indicate
+            // pattern was found
+            assert (pD != 0);
+            if (pA == pC) { pC = pD;                   pD = 0; } 
+            if (pA == pD) {                            pD = 0; } 
+            if (pB == pC) { pB = pA; pA = pC; pC = pD; pD = 0; }
+            if (pB == pD) { pB = pA; pA = pD;          pD = 0; }
+            if (pD == 0)
+            {
+                nDistributive++;
+                pN = Fraig_Not(Fraig_NodeAnd(pMan, pA, 
+                        Fraig_NodeOr(pMan, pB, pC)));
+                if (fShortCut) Fraig_NodeAddChoice( pMan, pNode, pN );
+                // assert ( Fraig_NodesEqual(pN, pNode) );
+            }
+        }
+*/            
+        if ( i % 1000 == 0 )
+        {
+            sprintf( Buffer, "Adding choice %6d...", i - nNodesBefore );
+//            Extra_ProgressBarUpdate( pProgress, i, Buffer );
+        }
+    }
+
+//    Extra_ProgressBarStop( pProgress );
+
+Fraig_ManCheckConsistency( pMan );
+
+    nNodesAfter = Fraig_ManReadNodeNum( pMan );
+    printf ( "Nodes before = %6d. Nodes with associative choices = %6d. Increase = %4.2f %%.\n", 
+            nNodesBefore, nNodesAfter, ((float)(nNodesAfter - nNodesBefore)) * 100.0/(nNodesBefore - nInputs) );
+    printf ( "Distributive = %d\n", nDistributive );
+
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/fraig/fraigFanout.c b/src/sat/fraig/fraigFanout.c
new file mode 100644
index 00000000..789bffca
--- /dev/null
+++ b/src/sat/fraig/fraigFanout.c
@@ -0,0 +1,175 @@
+/**CFile****************************************************************
+
+  FileName    [fraigFanout.c]
+
+  PackageName [FRAIG: Functionally reduced AND-INV graphs.]
+
+  Synopsis    [Procedures to manipulate fanouts of the FRAIG nodes.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 2.0. Started - October 1, 2004]
+
+  Revision    [$Id: fraigFanout.c,v 1.5 2005/07/08 01:01:31 alanmi Exp $]
+
+***********************************************************************/
+
+#include "fraigInt.h"
+
+#ifdef FRAIG_ENABLE_FANOUTS
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Add the fanout to the node.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_NodeAddFaninFanout( Fraig_Node_t * pFanin, Fraig_Node_t * pFanout )
+{
+    Fraig_Node_t * pPivot;
+
+    // pFanins is a fanin of pFanout
+    assert( !Fraig_IsComplement(pFanin) );
+    assert( !Fraig_IsComplement(pFanout) );
+    assert( Fraig_Regular(pFanout->p1) == pFanin || Fraig_Regular(pFanout->p2) == pFanin );
+
+    pPivot = pFanin->pFanPivot;
+    if ( pPivot == NULL )
+    {
+        pFanin->pFanPivot = pFanout;
+        return;
+    }
+
+    if ( Fraig_Regular(pPivot->p1) == pFanin )
+    {
+        if ( Fraig_Regular(pFanout->p1) == pFanin )
+        {
+            pFanout->pFanFanin1 = pPivot->pFanFanin1;
+            pPivot->pFanFanin1  = pFanout;
+        }
+        else // if ( Fraig_Regular(pFanout->p2) == pFanin )
+        {
+            pFanout->pFanFanin2 = pPivot->pFanFanin1;
+            pPivot->pFanFanin1  = pFanout;
+        }
+    }
+    else // if ( Fraig_Regular(pPivot->p2) == pFanin )
+    {
+        assert( Fraig_Regular(pPivot->p2) == pFanin );
+        if ( Fraig_Regular(pFanout->p1) == pFanin )
+        {
+            pFanout->pFanFanin1 = pPivot->pFanFanin2;
+            pPivot->pFanFanin2  = pFanout;
+        }
+        else // if ( Fraig_Regular(pFanout->p2) == pFanin )
+        {
+            pFanout->pFanFanin2 = pPivot->pFanFanin2;
+            pPivot->pFanFanin2  = pFanout;
+        }
+    }
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Add the fanout to the node.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_NodeRemoveFaninFanout( Fraig_Node_t * pFanin, Fraig_Node_t * pFanoutToRemove )
+{
+    Fraig_Node_t * pFanout, * pFanout2, ** ppFanList;
+    // start the linked list of fanouts
+    ppFanList = &pFanin->pFanPivot; 
+    // go through the fanouts
+    Fraig_NodeForEachFanoutSafe( pFanin, pFanout, pFanout2 )
+    {
+        // skip the fanout-to-remove
+        if ( pFanout == pFanoutToRemove )
+            continue;
+        // add useful fanouts to the list
+        *ppFanList = pFanout;
+        ppFanList = Fraig_NodeReadNextFanoutPlace( pFanin, pFanout );
+    }
+    *ppFanList = NULL;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Transfers fanout to a different node.]
+
+  Description [Assumes that the other node currently has no fanouts.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_NodeTransferFanout( Fraig_Node_t * pNodeFrom, Fraig_Node_t * pNodeTo )
+{
+    Fraig_Node_t * pFanout;
+    assert( pNodeTo->pFanPivot == NULL );
+    assert( pNodeTo->pFanFanin1 == NULL );
+    assert( pNodeTo->pFanFanin2 == NULL );
+    // go through the fanouts and update their fanins
+    Fraig_NodeForEachFanout( pNodeFrom, pFanout )
+    {
+        if ( Fraig_Regular(pFanout->p1) == pNodeFrom )
+            pFanout->p1 = Fraig_NotCond( pNodeTo, Fraig_IsComplement(pFanout->p1) );
+        else if ( Fraig_Regular(pFanout->p2) == pNodeFrom )
+            pFanout->p2 = Fraig_NotCond( pNodeTo, Fraig_IsComplement(pFanout->p2) );            
+    }
+    // move the pointers
+    pNodeTo->pFanPivot  = pNodeFrom->pFanPivot;  
+    pNodeTo->pFanFanin1 = pNodeFrom->pFanFanin1; 
+    pNodeTo->pFanFanin2 = pNodeFrom->pFanFanin2;
+    pNodeFrom->pFanPivot  = NULL; 
+    pNodeFrom->pFanFanin1 = NULL; 
+    pNodeFrom->pFanFanin2 = NULL;  
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Returns the number of fanouts of a node.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_NodeGetFanoutNum( Fraig_Node_t * pNode )
+{
+    Fraig_Node_t * pFanout;
+    int Counter = 0;
+    Fraig_NodeForEachFanout( pNode, pFanout )
+        Counter++;
+    return Counter;
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+#endif
+
diff --git a/src/sat/fraig/fraigFeed.c b/src/sat/fraig/fraigFeed.c
new file mode 100644
index 00000000..8a3cc6c7
--- /dev/null
+++ b/src/sat/fraig/fraigFeed.c
@@ -0,0 +1,909 @@
+/**CFile****************************************************************
+
+  FileName    [fraigFeed.c]
+
+  PackageName [FRAIG: Functionally reduced AND-INV graphs.]
+
+  Synopsis    [Procedures to support the solver feedback.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 2.0. Started - October 1, 2004]
+
+  Revision    [$Id: fraigFeed.c,v 1.8 2005/07/08 01:01:31 alanmi Exp $]
+
+***********************************************************************/
+
+#include "fraigInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+static int   Fraig_FeedBackPrepare( Fraig_Man_t * p, int * pModel, Msat_IntVec_t * vVars );
+static int   Fraig_FeedBackInsert( Fraig_Man_t * p, int nVarsPi );
+static void  Fraig_FeedBackVerify( Fraig_Man_t * p, Fraig_Node_t * pOld, Fraig_Node_t * pNew );
+
+static void  Fraig_FeedBackCovering( Fraig_Man_t * p, Msat_IntVec_t * vPats );
+static       Fraig_NodeVec_t * Fraig_FeedBackCoveringStart( Fraig_Man_t * pMan );
+static int   Fraig_GetSmallestColumn( int * pHits, int nHits );
+static int   Fraig_GetHittingPattern( unsigned * pSims, int nWords );
+static void  Fraig_CancelCoveredColumns( Fraig_NodeVec_t * vColumns, int * pHits, int iPat );
+static void  Fraig_FeedBackCheckTable( Fraig_Man_t * p );
+static void  Fraig_FeedBackCheckTableF0( Fraig_Man_t * p );
+static void  Fraig_ReallocateSimulationInfo( Fraig_Man_t * p );
+
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Initializes the feedback information.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_FeedBackInit( Fraig_Man_t * p )
+{
+    p->vCones    = Fraig_NodeVecAlloc( 500 );
+    p->vPatsReal = Msat_IntVecAlloc( 1000 ); 
+    p->pSimsReal = (unsigned *)Fraig_MemFixedEntryFetch( p->mmSims );
+    memset( p->pSimsReal, 0, sizeof(unsigned) * p->nWordsDyna );
+    p->pSimsTemp = (unsigned *)Fraig_MemFixedEntryFetch( p->mmSims );
+    p->pSimsDiff = (unsigned *)Fraig_MemFixedEntryFetch( p->mmSims );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Processes the feedback from teh solver.]
+
+  Description [Array pModel gives the value of each variable in the SAT 
+  solver. Array vVars is the array of integer numbers of variables
+  involves in this conflict.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_FeedBack( Fraig_Man_t * p, int * pModel, Msat_IntVec_t * vVars, Fraig_Node_t * pOld, Fraig_Node_t * pNew )
+{
+    int nVarsPi, nWords;
+    int i, clk = clock();
+
+    // get the number of PI vars in the feedback (also sets the PI values)
+    nVarsPi = Fraig_FeedBackPrepare( p, pModel, vVars );
+
+    // set the PI values
+    nWords = Fraig_FeedBackInsert( p, nVarsPi );
+    assert( p->iWordStart + nWords <= p->nWordsDyna );
+
+    // resimulates the words from p->iWordStart to iWordStop
+    for ( i = 1; i < p->vNodes->nSize; i++ )
+        if ( Fraig_NodeIsAnd(p->vNodes->pArray[i]) )
+            Fraig_NodeSimulate( p->vNodes->pArray[i], p->iWordStart, p->iWordStart + nWords, 0 );
+
+    if ( p->fDoSparse )
+        Fraig_TableRehashF0( p, 0 );
+
+    if ( !p->fChoicing )
+    Fraig_FeedBackVerify( p, pOld, pNew );
+
+    // if there is no room left, compress the patterns
+    if ( p->iWordStart + nWords == p->nWordsDyna )
+        p->iWordStart = Fraig_FeedBackCompress( p );
+    else  // otherwise, update the starting word
+        p->iWordStart += nWords;
+
+p->timeFeed += clock() - clk;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Get the number and values of the PI variables.]
+
+  Description [Returns the number of PI variables involved in this feedback.
+  Fills in the internal presence and value data for the primary inputs.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_FeedBackPrepare( Fraig_Man_t * p, int * pModel, Msat_IntVec_t * vVars )
+{
+    Fraig_Node_t * pNode;
+    int i, nVars, nVarsPis, * pVars;
+
+    // clean the presence flag for all PIs
+    for ( i = 0; i < p->vInputs->nSize; i++ )
+    {
+        pNode = p->vInputs->pArray[i];
+        pNode->fFeedUse = 0;
+    }
+
+    // get the variables involved in the feedback
+    nVars = Msat_IntVecReadSize(vVars);
+    pVars = Msat_IntVecReadArray(vVars);
+
+    // set the values for the present variables
+    nVarsPis = 0;
+    for ( i = 0; i < nVars; i++ )
+    {
+        pNode = p->vNodes->pArray[ pVars[i] ];
+        if ( !Fraig_NodeIsVar(pNode) )
+            continue;
+        // set its value
+        pNode->fFeedUse = 1;
+        pNode->fFeedVal = !MSAT_LITSIGN(pModel[pVars[i]]);
+        nVarsPis++;
+    }
+    return nVarsPis;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Inserts the new simulation patterns.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_FeedBackInsert( Fraig_Man_t * p, int nVarsPi )
+{
+    Fraig_Node_t * pNode;
+    int nWords, iPatFlip, nPatFlipLimit, i, w;
+    int fUseNoPats = 0;
+    int fUse2Pats = 0;
+
+    // get the number of words 
+    if ( fUse2Pats )
+        nWords = FRAIG_NUM_WORDS( 2 * nVarsPi + 1 );
+    else if ( fUseNoPats )
+        nWords = 1;
+    else
+        nWords = FRAIG_NUM_WORDS( nVarsPi + 1 );
+    // update the number of words if they do not fit into the simulation info
+    if ( nWords > p->nWordsDyna - p->iWordStart )
+        nWords = p->nWordsDyna - p->iWordStart; 
+    // determine the bound on the flipping bit
+    nPatFlipLimit = nWords * 32 - 2;
+
+    // mark the real pattern
+    Msat_IntVecPush( p->vPatsReal, p->iWordStart * 32 ); 
+    // record the real pattern
+    Fraig_BitStringSetBit( p->pSimsReal, p->iWordStart * 32 );
+
+    // set the values at the PIs
+    iPatFlip = 1;
+    for ( i = 0; i < p->vInputs->nSize; i++ )
+    {
+        pNode = p->vInputs->pArray[i];
+        for ( w = p->iWordStart; w < p->iWordStart + nWords; w++ )
+            if ( !pNode->fFeedUse )
+                pNode->puSimD[w] = FRAIG_RANDOM_UNSIGNED;
+            else if ( pNode->fFeedVal )
+                pNode->puSimD[w] = FRAIG_FULL;
+            else // if ( !pNode->fFeedVal )
+                pNode->puSimD[w] = 0;
+
+        if ( fUse2Pats )
+        {
+            // flip two patterns
+            if ( pNode->fFeedUse && 2 * iPatFlip < nPatFlipLimit )
+            {
+                Fraig_BitStringXorBit( pNode->puSimD + p->iWordStart, 2 * iPatFlip - 1 );
+                Fraig_BitStringXorBit( pNode->puSimD + p->iWordStart, 2 * iPatFlip     );
+                Fraig_BitStringXorBit( pNode->puSimD + p->iWordStart, 2 * iPatFlip + 1 );
+                iPatFlip++;
+            }
+        }
+        else if ( fUseNoPats )
+        {
+        }
+        else
+        {
+            // flip the diagonal
+            if ( pNode->fFeedUse && iPatFlip < nPatFlipLimit )
+            {
+                Fraig_BitStringXorBit( pNode->puSimD + p->iWordStart, iPatFlip );
+                iPatFlip++;
+    //            Extra_PrintBinary( stdout, &pNode->puSimD, 45 ); printf( "\n" );
+            }
+        }
+        // clean the use mask
+        pNode->fFeedUse = 0;
+
+        // add the info to the D hash value of the PIs
+        for ( w = p->iWordStart; w < p->iWordStart + nWords; w++ )
+            pNode->uHashD ^= pNode->puSimD[w] * s_FraigPrimes[w];
+
+    }
+    return nWords;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Checks that the SAT solver pattern indeed distinquishes the nodes.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_FeedBackVerify( Fraig_Man_t * p, Fraig_Node_t * pOld, Fraig_Node_t * pNew )
+{
+    int fValue1, fValue2, iPat;
+    iPat   = Msat_IntVecReadEntry( p->vPatsReal, Msat_IntVecReadSize(p->vPatsReal)-1 );
+    fValue1 = (Fraig_BitStringHasBit( pOld->puSimD, iPat ));
+    fValue2 = (Fraig_BitStringHasBit( pNew->puSimD, iPat ));
+/*
+Fraig_PrintNode( p, pOld );
+printf( "\n" );
+Fraig_PrintNode( p, pNew );
+printf( "\n" );
+*/
+//    assert( fValue1 != fValue2 );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Compress the simulation patterns.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_FeedBackCompress( Fraig_Man_t * p )
+{
+    unsigned * pSims;
+    unsigned uHash;
+    int i, w, t, nPats, * pPats;
+    int fPerformChecks = (p->nBTLimit == -1);
+
+    // solve the covering problem
+    if ( fPerformChecks )
+    {
+        Fraig_FeedBackCheckTable( p );
+        if ( p->fDoSparse ) 
+            Fraig_FeedBackCheckTableF0( p );
+    }
+
+    // solve the covering problem
+    Fraig_FeedBackCovering( p, p->vPatsReal );
+
+
+    // get the number of additional patterns
+    nPats = Msat_IntVecReadSize( p->vPatsReal );
+    pPats = Msat_IntVecReadArray( p->vPatsReal );
+    // get the new starting word
+    p->iWordStart = FRAIG_NUM_WORDS( p->iPatsPerm + nPats );
+
+    // set the simulation info for the PIs
+    for ( i = 0; i < p->vInputs->nSize; i++ )
+    {
+        // get hold of the simulation info for this PI
+        pSims = p->vInputs->pArray[i]->puSimD;
+        // clean the storage for the new patterns
+        for ( w = p->iWordPerm; w < p->iWordStart; w++ )
+            p->pSimsTemp[w] = 0;
+        // set the patterns
+        for ( t = 0; t < nPats; t++ )
+            if ( Fraig_BitStringHasBit( pSims, pPats[t] ) )
+            {
+                // check if this pattern falls into temporary storage
+                if ( p->iPatsPerm + t < p->iWordPerm * 32 )
+                    Fraig_BitStringSetBit( pSims, p->iPatsPerm + t );
+                else
+                    Fraig_BitStringSetBit( p->pSimsTemp, p->iPatsPerm + t );
+            }
+        // copy the pattern 
+        for ( w = p->iWordPerm; w < p->iWordStart; w++ )
+            pSims[w] = p->pSimsTemp[w];
+        // recompute the hashing info
+        uHash = 0;
+        for ( w = 0; w < p->iWordStart; w++ )
+            uHash ^= pSims[w] * s_FraigPrimes[w];
+        p->vInputs->pArray[i]->uHashD = uHash;
+    }
+
+    // update info about the permanently stored patterns
+    p->iWordPerm = p->iWordStart;
+    p->iPatsPerm += nPats;
+    assert( p->iWordPerm == FRAIG_NUM_WORDS( p->iPatsPerm ) );
+
+    // resimulate and recompute the hash values
+    for ( i = 1; i < p->vNodes->nSize; i++ )
+        if ( Fraig_NodeIsAnd(p->vNodes->pArray[i]) )
+        {
+            p->vNodes->pArray[i]->uHashD = 0;
+            Fraig_NodeSimulate( p->vNodes->pArray[i], 0, p->iWordPerm, 0 );
+        }
+
+    // double-check that the nodes are still distinguished
+    if ( fPerformChecks )
+        Fraig_FeedBackCheckTable( p );
+
+    // rehash the values in the F0 table
+    if ( p->fDoSparse ) 
+    {
+        Fraig_TableRehashF0( p, 0 );
+        if ( fPerformChecks )
+            Fraig_FeedBackCheckTableF0( p );
+    }
+
+    // check if we need to resize the simulation info
+    // if less than FRAIG_WORDS_STORE words are left, reallocate simulation info
+    if ( p->iWordPerm + FRAIG_WORDS_STORE > p->nWordsDyna )
+        Fraig_ReallocateSimulationInfo( p );
+
+    // set the real patterns
+    Msat_IntVecClear( p->vPatsReal );
+    memset( p->pSimsReal, 0, sizeof(unsigned)*p->nWordsDyna );
+    for ( w = 0; w < p->iWordPerm; w++ )
+        p->pSimsReal[w] = FRAIG_FULL;
+    if ( p->iPatsPerm % 32 > 0 )
+        p->pSimsReal[p->iWordPerm-1] = FRAIG_MASK( p->iPatsPerm % 32 );
+//    printf( "The number of permanent words = %d.\n", p->iWordPerm );
+    return p->iWordStart;
+}
+
+
+
+
+/**Function*************************************************************
+
+  Synopsis    [Checks the correctness of the functional simulation table.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_FeedBackCovering( Fraig_Man_t * p, Msat_IntVec_t * vPats )
+{
+    Fraig_NodeVec_t * vColumns;
+    unsigned * pSims;
+    int * pHits, iPat, iCol, i;
+    int nOnesTotal, nSolStarting;
+    int fVeryVerbose = 0;
+
+    // collect the pairs to be distinguished
+    vColumns = Fraig_FeedBackCoveringStart( p );
+    // collect the number of 1s in each simulation vector
+    nOnesTotal = 0;
+    pHits = ALLOC( int, vColumns->nSize );
+    for ( i = 0; i < vColumns->nSize; i++ )
+    {
+        pSims = (unsigned *)vColumns->pArray[i];
+        pHits[i] = Fraig_BitStringCountOnes( pSims, p->iWordStart );
+        nOnesTotal += pHits[i];
+//        assert( pHits[i] > 0 );
+    }
+ 
+    // go through the patterns
+    nSolStarting = Msat_IntVecReadSize(vPats);
+    while ( (iCol = Fraig_GetSmallestColumn( pHits, vColumns->nSize )) != -1 )
+    {
+        // find the pattern, which hits this column
+        iPat = Fraig_GetHittingPattern( (unsigned *)vColumns->pArray[iCol], p->iWordStart );
+        // cancel the columns covered by this pattern
+        Fraig_CancelCoveredColumns( vColumns, pHits, iPat );
+        // save the pattern
+        Msat_IntVecPush( vPats, iPat );
+    }
+
+    // free the set of columns
+    for ( i = 0; i < vColumns->nSize; i++ )
+        Fraig_MemFixedEntryRecycle( p->mmSims, (char *)vColumns->pArray[i] );
+
+    // print stats related to the covering problem
+    if ( p->fVerbose && fVeryVerbose )
+    {
+        printf( "%3d\\%3d\\%3d   ",     p->nWordsRand, p->nWordsDyna, p->iWordPerm );
+        printf( "Col (pairs) = %5d.  ", vColumns->nSize );
+        printf( "Row (pats) = %5d.  ",  p->iWordStart * 32 );
+        printf( "Dns = %6.2f %%.  ",    vColumns->nSize==0? 0.0 : 100.0 * nOnesTotal / vColumns->nSize / p->iWordStart / 32 );
+        printf( "Sol = %3d (%3d).  ",   Msat_IntVecReadSize(vPats), nSolStarting );
+        printf( "\n" );
+    }
+    Fraig_NodeVecFree( vColumns );
+    free( pHits );
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Checks the correctness of the functional simulation table.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_NodeVec_t * Fraig_FeedBackCoveringStart( Fraig_Man_t * p )
+{
+    Fraig_NodeVec_t * vColumns;
+    Fraig_HashTable_t * pT = p->pTableF;
+    Fraig_Node_t * pEntF, * pEntD;
+    unsigned * pSims;
+    unsigned * pUnsigned1, * pUnsigned2;
+    int i, k, m, w;//, nOnes;
+
+    // start the set of columns
+    vColumns = Fraig_NodeVecAlloc( 100 );
+
+    // go through the pairs of nodes to be distinguished
+    for ( i = 0; i < pT->nBins; i++ )
+    Fraig_TableBinForEachEntryF( pT->pBins[i], pEntF )
+    {
+        p->vCones->nSize = 0;
+        Fraig_TableBinForEachEntryD( pEntF, pEntD )
+            Fraig_NodeVecPush( p->vCones, pEntD );
+        if ( p->vCones->nSize == 1 )
+            continue;
+        //////////////////////////////// bug fix by alanmi, September 14, 2006
+        if ( p->vCones->nSize > 20 ) 
+            continue;
+        ////////////////////////////////
+
+        for ( k = 0; k < p->vCones->nSize; k++ )
+            for ( m = k+1; m < p->vCones->nSize; m++ )
+            {
+                if ( !Fraig_CompareSimInfoUnderMask( p->vCones->pArray[k], p->vCones->pArray[m], p->iWordStart, 0, p->pSimsReal ) )
+                    continue;
+
+                // primary simulation patterns (counter-examples) cannot distinguish this pair
+                // get memory to store the feasible simulation patterns
+                pSims = (unsigned *)Fraig_MemFixedEntryFetch( p->mmSims );
+                // find the pattern that distinguish this column, exept the primary ones
+                pUnsigned1 = p->vCones->pArray[k]->puSimD;
+                pUnsigned2 = p->vCones->pArray[m]->puSimD;
+                for ( w = 0; w < p->iWordStart; w++ )
+                    pSims[w] = (pUnsigned1[w] ^ pUnsigned2[w]) & ~p->pSimsReal[w];
+                // store the pattern
+                Fraig_NodeVecPush( vColumns, (Fraig_Node_t *)pSims );
+//                nOnes = Fraig_BitStringCountOnes(pSims, p->iWordStart);
+//                assert( nOnes > 0 );
+            }      
+    }
+
+    // if the flag is not set, do not consider sparse nodes in p->pTableF0
+    if ( !p->fDoSparse )
+        return vColumns;
+
+    // recalculate their hash values based on p->pSimsReal
+    pT = p->pTableF0;
+    for ( i = 0; i < pT->nBins; i++ )
+    Fraig_TableBinForEachEntryF( pT->pBins[i], pEntF )
+    {
+        pSims = pEntF->puSimD;
+        pEntF->uHashD = 0;
+        for ( w = 0; w < p->iWordStart; w++ )
+            pEntF->uHashD ^= (pSims[w] & p->pSimsReal[w]) * s_FraigPrimes[w];
+    }
+
+    // rehash the table using these values
+    Fraig_TableRehashF0( p, 1 );
+
+    // collect the classes of equivalent node pairs
+    for ( i = 0; i < pT->nBins; i++ )
+    Fraig_TableBinForEachEntryF( pT->pBins[i], pEntF )
+    {
+        p->vCones->nSize = 0;
+        Fraig_TableBinForEachEntryD( pEntF, pEntD )
+            Fraig_NodeVecPush( p->vCones, pEntD );
+        if ( p->vCones->nSize == 1 )
+            continue;
+
+        // primary simulation patterns (counter-examples) cannot distinguish all these pairs
+        for ( k = 0; k < p->vCones->nSize; k++ )
+            for ( m = k+1; m < p->vCones->nSize; m++ )
+            {
+                // get memory to store the feasible simulation patterns
+                pSims = (unsigned *)Fraig_MemFixedEntryFetch( p->mmSims );
+                // find the patterns that are not distinquished
+                pUnsigned1 = p->vCones->pArray[k]->puSimD;
+                pUnsigned2 = p->vCones->pArray[m]->puSimD;
+                for ( w = 0; w < p->iWordStart; w++ )
+                    pSims[w] = (pUnsigned1[w] ^ pUnsigned2[w]) & ~p->pSimsReal[w];
+                // store the pattern
+                Fraig_NodeVecPush( vColumns, (Fraig_Node_t *)pSims );
+//                nOnes = Fraig_BitStringCountOnes(pSims, p->iWordStart);
+//                assert( nOnes > 0 );
+            }      
+    }
+    return vColumns;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Selects the column, which has the smallest number of hits.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_GetSmallestColumn( int * pHits, int nHits )
+{
+    int i, iColMin = -1, nHitsMin = 1000000;
+    for ( i = 0; i < nHits; i++ )
+    {
+        // skip covered columns
+        if ( pHits[i] == 0 )
+            continue;
+        // take the column if it can only be covered by one pattern
+        if ( pHits[i] == 1 )
+            return i;
+        // find the column, which requires the smallest number of patterns
+        if ( nHitsMin > pHits[i] )
+        {
+            nHitsMin = pHits[i];
+            iColMin = i;
+        }
+    }
+    return iColMin;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Select the pattern, which hits this column.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_GetHittingPattern( unsigned * pSims, int nWords )
+{
+    int i, b;
+    for ( i = 0; i < nWords; i++ )
+    {
+        if ( pSims[i] == 0 )
+            continue;
+        for ( b = 0; b < 32; b++ )
+            if ( pSims[i] & (1 << b) )
+                return i * 32 + b;
+    }
+    return -1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Cancel covered patterns.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_CancelCoveredColumns( Fraig_NodeVec_t * vColumns, int * pHits, int iPat )
+{
+    unsigned * pSims;
+    int i;
+    for ( i = 0; i < vColumns->nSize; i++ )
+    {
+        pSims = (unsigned *)vColumns->pArray[i];
+        if ( Fraig_BitStringHasBit( pSims, iPat ) )
+            pHits[i] = 0;
+    }
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Checks the correctness of the functional simulation table.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_FeedBackCheckTable( Fraig_Man_t * p )
+{
+    Fraig_HashTable_t * pT = p->pTableF;
+    Fraig_Node_t * pEntF, * pEntD;
+    int i, k, m, nPairs;
+    int clk = clock();
+
+    nPairs = 0;
+    for ( i = 0; i < pT->nBins; i++ )
+    Fraig_TableBinForEachEntryF( pT->pBins[i], pEntF )
+    {
+        p->vCones->nSize = 0;
+        Fraig_TableBinForEachEntryD( pEntF, pEntD )
+            Fraig_NodeVecPush( p->vCones, pEntD );
+        if ( p->vCones->nSize == 1 )
+            continue;
+        for ( k = 0; k < p->vCones->nSize; k++ )
+            for ( m = k+1; m < p->vCones->nSize; m++ )
+            {
+                if ( Fraig_CompareSimInfo( p->vCones->pArray[k], p->vCones->pArray[m], p->iWordStart, 0 ) )
+                    printf( "Nodes %d and %d have the same D simulation info.\n", 
+                        p->vCones->pArray[k]->Num, p->vCones->pArray[m]->Num );
+                nPairs++;
+            }   
+    }
+//    printf( "\nThe total of %d node pairs have been verified.\n", nPairs );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Checks the correctness of the functional simulation table.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_FeedBackCheckTableF0( Fraig_Man_t * p )
+{
+    Fraig_HashTable_t * pT = p->pTableF0;
+    Fraig_Node_t * pEntF;
+    int i, k, m, nPairs;
+
+    nPairs = 0;
+    for ( i = 0; i < pT->nBins; i++ )
+    {
+        p->vCones->nSize = 0;
+        Fraig_TableBinForEachEntryF( pT->pBins[i], pEntF )
+            Fraig_NodeVecPush( p->vCones, pEntF );
+        if ( p->vCones->nSize == 1 )
+            continue;
+        for ( k = 0; k < p->vCones->nSize; k++ )
+            for ( m = k+1; m < p->vCones->nSize; m++ )
+            {
+                if ( Fraig_CompareSimInfo( p->vCones->pArray[k], p->vCones->pArray[m], p->iWordStart, 0 ) )
+                    printf( "Nodes %d and %d have the same D simulation info.\n", 
+                        p->vCones->pArray[k]->Num, p->vCones->pArray[m]->Num );
+                nPairs++;
+            }   
+    }
+//    printf( "\nThe total of %d node pairs have been verified.\n", nPairs );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Doubles the size of simulation info.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_ReallocateSimulationInfo( Fraig_Man_t * p )
+{
+    Fraig_MemFixed_t * mmSimsNew;        // new memory manager for simulation info
+    Fraig_Node_t * pNode;
+    unsigned * pSimsNew;
+    unsigned uSignOld;
+    int i;
+
+    // allocate a new memory manager
+    p->nWordsDyna *= 2;
+    mmSimsNew = Fraig_MemFixedStart( sizeof(unsigned) * (p->nWordsRand + p->nWordsDyna) );
+
+    // set the new data for the constant node
+    pNode = p->pConst1;
+    pNode->puSimR = (unsigned *)Fraig_MemFixedEntryFetch( mmSimsNew );
+    pNode->puSimD = pNode->puSimR + p->nWordsRand;
+    memset( pNode->puSimR, 0, sizeof(unsigned) * p->nWordsRand );
+    memset( pNode->puSimD, 0, sizeof(unsigned) * p->nWordsDyna );
+
+    // copy the simulation info of the PIs
+    for ( i = 0; i < p->vInputs->nSize; i++ )
+    {
+        pNode = p->vInputs->pArray[i];
+        // copy the simulation info
+        pSimsNew = (unsigned *)Fraig_MemFixedEntryFetch( mmSimsNew );
+        memmove( pSimsNew, pNode->puSimR, sizeof(unsigned) * (p->nWordsRand + p->iWordStart) );
+        // attach the new info
+        pNode->puSimR = pSimsNew;
+        pNode->puSimD = pNode->puSimR + p->nWordsRand;
+        // signatures remain without changes
+    }
+
+    // replace the manager to free up some memory
+    Fraig_MemFixedStop( p->mmSims, 0 );
+    p->mmSims = mmSimsNew;
+
+    // resimulate the internal nodes (this should lead to the same signatures)
+    for ( i = 1; i < p->vNodes->nSize; i++ )
+    {
+        pNode = p->vNodes->pArray[i];
+        if ( !Fraig_NodeIsAnd(pNode) )
+            continue;
+        // allocate memory for the simulation info
+        pNode->puSimR = (unsigned *)Fraig_MemFixedEntryFetch( mmSimsNew );
+        pNode->puSimD = pNode->puSimR + p->nWordsRand;
+        // derive random simulation info
+        uSignOld = pNode->uHashR;
+        pNode->uHashR = 0;
+        Fraig_NodeSimulate( pNode, 0, p->nWordsRand, 1 );
+        assert( uSignOld == pNode->uHashR );
+        // derive dynamic simulation info
+        uSignOld = pNode->uHashD;
+        pNode->uHashD = 0;
+        Fraig_NodeSimulate( pNode, 0, p->iWordStart, 0 );
+        assert( uSignOld == pNode->uHashD );
+    }
+
+    // realloc temporary storage
+    p->pSimsReal = (unsigned *)Fraig_MemFixedEntryFetch( mmSimsNew );
+    memset( p->pSimsReal, 0, sizeof(unsigned) * p->nWordsDyna );
+    p->pSimsTemp = (unsigned *)Fraig_MemFixedEntryFetch( mmSimsNew );
+    p->pSimsDiff = (unsigned *)Fraig_MemFixedEntryFetch( mmSimsNew );
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Generated trivial counter example.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int * Fraig_ManAllocCounterExample( Fraig_Man_t * p )
+{
+    int * pModel;
+    pModel = ALLOC( int, p->vInputs->nSize );
+    memset( pModel, 0, sizeof(int) * p->vInputs->nSize );
+    return pModel;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Saves the counter example.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_ManSimulateBitNode_rec( Fraig_Man_t * p, Fraig_Node_t * pNode )
+{
+    int Value0, Value1;
+    if ( Fraig_NodeIsTravIdCurrent( p, pNode ) )
+        return pNode->fMark3;
+    Fraig_NodeSetTravIdCurrent( p, pNode );
+    Value0 = Fraig_ManSimulateBitNode_rec( p, Fraig_Regular(pNode->p1) );
+    Value1 = Fraig_ManSimulateBitNode_rec( p, Fraig_Regular(pNode->p2) );
+    Value0 ^= Fraig_IsComplement(pNode->p1);
+    Value1 ^= Fraig_IsComplement(pNode->p2);
+    pNode->fMark3 = Value0 & Value1;
+    return pNode->fMark3;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Simulates one bit.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_ManSimulateBitNode( Fraig_Man_t * p, Fraig_Node_t * pNode, int * pModel )
+{
+    int fCompl, RetValue, i;
+    // set the PI values
+    Fraig_ManIncrementTravId( p );
+    for ( i = 0; i < p->vInputs->nSize; i++ )
+    {
+        Fraig_NodeSetTravIdCurrent( p, p->vInputs->pArray[i] );
+        p->vInputs->pArray[i]->fMark3 = pModel[i];
+    }
+    // perform the traversal
+    fCompl = Fraig_IsComplement(pNode);
+    RetValue = Fraig_ManSimulateBitNode_rec( p, Fraig_Regular(pNode) );
+    return fCompl ^ RetValue;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Saves the counter example.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int * Fraig_ManSaveCounterExample( Fraig_Man_t * p, Fraig_Node_t * pNode )
+{
+    int * pModel;
+    int iPattern;
+    int i, fCompl;
+
+    // the node can be complemented
+    fCompl = Fraig_IsComplement(pNode);
+    // because we compare with constant 0, p->pConst1 should also be complemented
+    fCompl = !fCompl;
+
+    // derive the model
+    pModel = Fraig_ManAllocCounterExample( p );
+    iPattern = Fraig_FindFirstDiff( p->pConst1, Fraig_Regular(pNode), fCompl, p->nWordsRand, 1 );
+    if ( iPattern >= 0 )
+    {
+        for ( i = 0; i < p->vInputs->nSize; i++ )
+            if ( Fraig_BitStringHasBit( p->vInputs->pArray[i]->puSimR, iPattern ) )
+                pModel[i] = 1;
+/*
+printf( "SAT solver's pattern:\n" );
+for ( i = 0; i < p->vInputs->nSize; i++ )
+    printf( "%d", pModel[i] );
+printf( "\n" );
+*/
+        assert( Fraig_ManSimulateBitNode( p, pNode, pModel ) );
+        return pModel;
+    }
+    iPattern = Fraig_FindFirstDiff( p->pConst1, Fraig_Regular(pNode), fCompl, p->iWordStart, 0 );
+    if ( iPattern >= 0 )
+    {
+        for ( i = 0; i < p->vInputs->nSize; i++ )
+            if ( Fraig_BitStringHasBit( p->vInputs->pArray[i]->puSimD, iPattern ) )
+                pModel[i] = 1;
+/*
+printf( "SAT solver's pattern:\n" );
+for ( i = 0; i < p->vInputs->nSize; i++ )
+    printf( "%d", pModel[i] );
+printf( "\n" );
+*/
+        assert( Fraig_ManSimulateBitNode( p, pNode, pModel ) );
+        return pModel;
+    }
+    FREE( pModel );
+    return NULL;
+}
+
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/fraig/fraigInt.h b/src/sat/fraig/fraigInt.h
new file mode 100644
index 00000000..9c6e0d47
--- /dev/null
+++ b/src/sat/fraig/fraigInt.h
@@ -0,0 +1,451 @@
+/**CFile****************************************************************
+
+  FileName    [fraigInt.h]
+
+  PackageName [FRAIG: Functionally reduced AND-INV graphs.]
+
+  Synopsis    [Internal declarations of the FRAIG package.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 2.0. Started - October 1, 2004]
+
+  Revision    [$Id: fraigInt.h,v 1.15 2005/07/08 01:01:31 alanmi Exp $]
+
+***********************************************************************/
+
+#ifndef __FRAIG_INT_H__
+#define __FRAIG_INT_H__
+
+////////////////////////////////////////////////////////////////////////
+///                          INCLUDES                                ///
+////////////////////////////////////////////////////////////////////////
+
+//#include "leaks.h"       
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <time.h>
+
+#include "fraig.h"
+#include "msat.h"
+
+////////////////////////////////////////////////////////////////////////
+///                         PARAMETERS                               ///
+////////////////////////////////////////////////////////////////////////
+ 
+/*
+    The AIG node policy:
+    - Each node has its main number (pNode->Num)
+      This is the number of this node in the array of all nodes and its SAT variable number
+    - The PI nodes are stored along with other nodes
+      Additionally, PI nodes have a PI number, by which they are stored in the PI node array
+    - The constant node is has number 0 and is also stored in the array
+*/
+
+////////////////////////////////////////////////////////////////////////
+///                       MACRO DEFINITIONS                          ///
+////////////////////////////////////////////////////////////////////////
+ 
+// enable this macro to support the fanouts
+#define FRAIG_ENABLE_FANOUTS
+#define FRAIG_PATTERNS_RANDOM   2048   // should not be less than 128 and more than 32768 (2^15)
+#define FRAIG_PATTERNS_DYNAMIC  2048   // should not be less than 256 and more than 32768 (2^15)
+#define FRAIG_MAX_PRIMES        1024   // the maximum number of primes used for hashing
+
+// this parameter determines when simulation info is extended
+// it will be extended when the free storage in the dynamic simulation
+// info is less or equal to this number of words (FRAIG_WORDS_STORE)
+// this is done because if the free storage for dynamic simulation info 
+// is not sufficient, computation becomes inefficient 
+#define FRAIG_WORDS_STORE           5   
+
+// the bit masks
+#define FRAIG_MASK(n)             ((~((unsigned)0)) >> (32-(n)))
+#define FRAIG_FULL                 (~((unsigned)0))
+#define FRAIG_NUM_WORDS(n)         (((n)>>5) + (((n)&31) > 0))
+
+// maximum/minimum operators
+#define FRAIG_MIN(a,b)             (((a) < (b))? (a) : (b))
+#define FRAIG_MAX(a,b)             (((a) > (b))? (a) : (b))
+
+// generating random unsigned (#define RAND_MAX 0x7fff)
+#define FRAIG_RANDOM_UNSIGNED   ((((unsigned)rand()) << 24) ^ (((unsigned)rand()) << 12) ^ ((unsigned)rand()))
+
+// macros to get hold of the bits in a bit string
+#define Fraig_BitStringSetBit(p,i)  ((p)[(i)>>5] |= (1<<((i) & 31)))
+#define Fraig_BitStringXorBit(p,i)  ((p)[(i)>>5] ^= (1<<((i) & 31)))
+#define Fraig_BitStringHasBit(p,i) (((p)[(i)>>5]  & (1<<((i) & 31))) > 0)
+
+// macros to get hold of the bits in the support info
+//#define Fraig_NodeSetVarStr(p,i)      (Fraig_Regular(p)->pSuppStr[((i)%FRAIG_SUPP_SIGN)>>5] |= (1<<(((i)%FRAIG_SUPP_SIGN) & 31)))
+//#define Fraig_NodeHasVarStr(p,i)     ((Fraig_Regular(p)->pSuppStr[((i)%FRAIG_SUPP_SIGN)>>5]  & (1<<(((i)%FRAIG_SUPP_SIGN) & 31))) > 0)
+#define Fraig_NodeSetVarStr(p,i)     Fraig_BitStringSetBit(Fraig_Regular(p)->pSuppStr,i)
+#define Fraig_NodeHasVarStr(p,i)     Fraig_BitStringHasBit(Fraig_Regular(p)->pSuppStr,i)
+
+// copied from "util.h" for standaloneness
+#ifndef ALLOC
+#  define ALLOC(type, num)    \
+    ((type *) malloc(sizeof(type) * (num)))
+#endif 
+
+#ifndef REALLOC
+#  define REALLOC(type, obj, num)    \
+    (obj) ? ((type *) realloc((char *) obj, sizeof(type) * (num))) : \
+        ((type *) malloc(sizeof(type) * (num)))
+#endif 
+
+#ifndef FREE
+#  define FREE(obj)        \
+    ((obj) ? (free((char *) (obj)), (obj) = 0) : 0)
+#endif 
+
+// copied from "extra.h" for stand-aloneness
+#define Fraig_PrintTime(a,t)      printf( "%s = ", (a) ); printf( "%6.2f sec\n", (float)(t)/(float)(CLOCKS_PER_SEC) )
+
+#define Fraig_HashKey2(a,b,TSIZE) (((unsigned)(a) + (unsigned)(b) * 12582917) % TSIZE)
+//#define Fraig_HashKey2(a,b,TSIZE) (( ((unsigned)(a)->Num * 19) ^ ((unsigned)(b)->Num * 1999) ) % TSIZE)
+//#define Fraig_HashKey2(a,b,TSIZE) ( ((unsigned)((a)->Num + (b)->Num) * ((a)->Num + (b)->Num + 1) / 2) % TSIZE)
+// the other two hash functions give bad distribution of hash chain lengths (not clear why)
+
+#ifndef PRT
+#define PRT(a,t)        printf( "%s = ", (a) ); printf( "%6.2f sec\n", (float)(t)/(float)(CLOCKS_PER_SEC) )
+#endif 
+
+////////////////////////////////////////////////////////////////////////
+///                    STRUCTURE DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+typedef struct Fraig_MemFixed_t_    Fraig_MemFixed_t;    
+
+// the mapping manager
+struct Fraig_ManStruct_t_
+{
+    // the AIG nodes
+    Fraig_NodeVec_t *     vInputs;       // the array of primary inputs
+    Fraig_NodeVec_t *     vNodes;        // the array of all nodes, including primary inputs
+    Fraig_NodeVec_t *     vOutputs;      // the array of primary outputs (some internal nodes)
+    Fraig_Node_t *        pConst1;       // the pointer to the constant node (vNodes->pArray[0])
+
+    // info about the original circuit
+    char **               ppInputNames;  // the primary input names
+    char **               ppOutputNames; // the primary output names
+
+    // various hash-tables
+    Fraig_HashTable_t *   pTableS;       // hashing by structure
+    Fraig_HashTable_t *   pTableF;       // hashing by simulation info
+    Fraig_HashTable_t *   pTableF0;      // hashing by simulation info (sparse functions)
+
+    // parameters
+    int                   nWordsRand;    // the number of words of random simulation info
+    int                   nWordsDyna;    // the number of words of dynamic simulation info
+    int                   nBTLimit;      // the max number of backtracks to perform
+    int                   nSeconds;      // the runtime limit for the miter proof
+    int                   fFuncRed;      // performs only one level hashing
+    int                   fFeedBack;     // enables solver feedback
+    int                   fDist1Pats;    // enables solver feedback
+    int                   fDoSparse;     // performs equiv tests for sparse functions 
+    int                   fChoicing;     // enables recording structural choices
+    int                   fTryProve;     // tries to solve the final miter
+    int                   fVerbose;      // the verbosiness flag
+    int                   fVerboseP;     // the verbosiness flag
+    sint64                nInspLimit;    // the inspection limit
+
+    int                   nTravIds;      // the traversal counter
+    int                   nTravIds2;     // the traversal counter
+
+    // info related to the solver feedback
+    int                   iWordStart;    // the first word to use for simulation
+    int                   iWordPerm;     // the number of words stored permanently
+    int                   iPatsPerm;     // the number of patterns stored permanently
+    Fraig_NodeVec_t *     vCones;        // the temporary array of internal variables
+    Msat_IntVec_t *       vPatsReal;     // the array of real pattern numbers
+    unsigned *            pSimsReal;     // used for simulation patterns
+    unsigned *            pSimsDiff;     // used for simulation patterns
+    unsigned *            pSimsTemp;     // used for simulation patterns
+
+    // the support information
+    int                   nSuppWords;
+    unsigned **           pSuppS;
+    unsigned **           pSuppF;
+
+    // the memory managers
+    Fraig_MemFixed_t *    mmNodes;       // the memory manager for nodes
+    Fraig_MemFixed_t *    mmSims;        // the memory manager for simulation info
+
+    // solving the SAT problem
+    Msat_Solver_t *       pSat;          // the SAT solver
+    Msat_IntVec_t *       vProj;         // the temporary array of projection vars 
+    int                   nSatNums;      // the counter of SAT variables
+    int *                 pModel;        // the assignment, which satisfies the miter
+    // these arrays belong to the solver
+    Msat_IntVec_t *       vVarsInt;      // the temporary array of variables
+    Msat_ClauseVec_t *    vAdjacents;    // the temporary storage for connectivity
+    Msat_IntVec_t *       vVarsUsed;     // the array marking vars appearing in the cone
+
+    // various statistic variables
+    int                   nSatCalls;     // the number of times equivalence checking was called
+    int                   nSatProof;     // the number of times a proof was found
+    int                   nSatCounter;   // the number of times a counter example was found
+    int                   nSatFails;     // the number of times the SAT solver failed to complete due to resource limit or prediction
+    int                   nSatFailsReal; // the number of times the SAT solver failed to complete due to resource limit
+
+    int                   nSatCallsImp;  // the number of times equivalence checking was called
+    int                   nSatProofImp;  // the number of times a proof was found
+    int                   nSatCounterImp;// the number of times a counter example was found
+    int                   nSatFailsImp;  // the number of times the SAT solver failed to complete
+
+    int                   nSatZeros;     // the number of times the simulation vector is zero
+    int                   nSatSupps;     // the number of times the support info was useful
+    int                   nRefErrors;    // the number of ref counting errors
+    int                   nImplies;      // the number of implication cases
+    int                   nSatImpls;     // the number of implication SAT calls
+    int                   nVarsClauses;  // the number of variables with clauses
+    int                   nSimplifies0;
+    int                   nSimplifies1;
+    int                   nImplies0;
+    int                   nImplies1;
+
+    // runtime statistics
+    int                   timeToAig;     // time to transfer to the mapping structure
+    int                   timeSims;      // time to compute k-feasible cuts
+    int                   timeTrav;      // time to traverse the network
+    int                   timeFeed;      // time for solver feedback (recording and resimulating)
+    int                   timeImply;     // time to analyze implications
+    int                   timeSat;       // time to compute the truth table for each cut
+    int                   timeToNet;     // time to transfer back to the network
+    int                   timeTotal;     // the total mapping time
+    int                   time1;         // time to perform one task
+    int                   time2;         // time to perform another task
+    int                   time3;         // time to perform another task
+    int                   time4;         // time to perform another task
+};
+
+// the mapping node
+struct Fraig_NodeStruct_t_ 
+{
+    // various numbers associated with the node
+    int                   Num;           // the unique number (SAT var number) of this node 
+    int                   NumPi;         // if the node is a PI, this is its variable number
+    int                   Level;         // the level of the node
+    int                   nRefs;         // the number of references of the node
+    int                   TravId;        // the traversal ID (use to avoid cleaning marks)
+    int                   TravId2;       // the traversal ID (use to avoid cleaning marks)
+
+    // general information about the node
+    unsigned              fInv     :  1; // the mark to show that simulation info is complemented
+    unsigned              fNodePo  :  1; // the mark used for primary outputs
+    unsigned              fClauses :  1; // the clauses for this node are loaded
+    unsigned              fMark0   :  1; // the mark used for traversals
+    unsigned              fMark1   :  1; // the mark used for traversals
+    unsigned              fMark2   :  1; // the mark used for traversals
+    unsigned              fMark3   :  1; // the mark used for traversals
+    unsigned              fFeedUse :  1; // the presence of the variable in the feedback
+    unsigned              fFeedVal :  1; // the value of the variable in the feedback
+    unsigned              fFailTfo :  1; // the node is in the TFO of the failed SAT run
+    unsigned              nFanouts :  2; // the indicator of fanouts (none, one, or many)
+    unsigned              nOnes    : 20; // the number of 1's in the random sim info
+ 
+    // the children of the node
+    Fraig_Node_t *        p1;            // the first child
+    Fraig_Node_t *        p2;            // the second child
+    Fraig_NodeVec_t *     vFanins;       // the fanins of the supergate rooted at this node
+//    Fraig_NodeVec_t *     vFanouts;      // the fanouts of the supergate rooted at this node
+
+    // various linked lists
+    Fraig_Node_t *        pNextS;        // the next node in the structural hash table
+    Fraig_Node_t *        pNextF;        // the next node in the functional (simulation) hash table
+    Fraig_Node_t *        pNextD;        // the next node in the list of nodes based on dynamic simulation
+    Fraig_Node_t *        pNextE;        // the next structural choice (functionally-equivalent node)
+    Fraig_Node_t *        pRepr;         // the canonical functional representative of the node
+
+    // simulation data
+    unsigned              uHashR;        // the hash value for random information
+    unsigned              uHashD;        // the hash value for dynamic information 
+    unsigned *            puSimR;        // the simulation information (random)
+    unsigned *            puSimD;        // the simulation information (dynamic)
+
+    // misc information  
+    Fraig_Node_t *        pData0;        // temporary storage for the corresponding network node
+    Fraig_Node_t *        pData1;        // temporary storage for the corresponding network node
+
+#ifdef FRAIG_ENABLE_FANOUTS
+    // representation of node's fanouts
+    Fraig_Node_t *        pFanPivot;     // the first fanout of this node
+    Fraig_Node_t *        pFanFanin1;    // the next fanout of p1
+    Fraig_Node_t *        pFanFanin2;    // the next fanout of p2
+#endif
+}; 
+
+// the vector of nodes
+struct Fraig_NodeVecStruct_t_
+{
+    int                   nCap;          // the number of allocated entries
+    int                   nSize;         // the number of entries in the array
+    Fraig_Node_t **       pArray;        // the array of nodes
+};
+
+// the hash table 
+struct Fraig_HashTableStruct_t_
+{
+    Fraig_Node_t **       pBins;         // the table bins
+    int                   nBins;         // the size of the table
+    int                   nEntries;      // the total number of entries in the table
+};
+
+// getting hold of the next fanout of the node
+#define Fraig_NodeReadNextFanout( pNode, pFanout )                \
+    ( ( pFanout == NULL )? NULL :                                 \
+        ((Fraig_Regular((pFanout)->p1) == (pNode))?               \
+             (pFanout)->pFanFanin1 : (pFanout)->pFanFanin2) )
+// getting hold of the place where the next fanout will be attached
+#define Fraig_NodeReadNextFanoutPlace( pNode, pFanout )           \
+    ( (Fraig_Regular((pFanout)->p1) == (pNode))?                  \
+         &(pFanout)->pFanFanin1 : &(pFanout)->pFanFanin2 )
+// iterator through the fanouts of the node
+#define Fraig_NodeForEachFanout( pNode, pFanout )                 \
+    for ( pFanout = (pNode)->pFanPivot; pFanout;                  \
+          pFanout = Fraig_NodeReadNextFanout(pNode, pFanout) )
+// safe iterator through the fanouts of the node
+#define Fraig_NodeForEachFanoutSafe( pNode, pFanout, pFanout2 )   \
+    for ( pFanout  = (pNode)->pFanPivot,                          \
+          pFanout2 = Fraig_NodeReadNextFanout(pNode, pFanout);    \
+          pFanout;                                                \
+          pFanout  = pFanout2,                                    \
+          pFanout2 = Fraig_NodeReadNextFanout(pNode, pFanout) )
+
+// iterators through the entries in the linked lists of nodes
+// the list of nodes in the structural hash table
+#define Fraig_TableBinForEachEntryS( pBin, pEnt )                 \
+    for ( pEnt = pBin;                                            \
+          pEnt;                                                   \
+          pEnt = pEnt->pNextS )
+#define Fraig_TableBinForEachEntrySafeS( pBin, pEnt, pEnt2 )      \
+    for ( pEnt = pBin,                                            \
+          pEnt2 = pEnt? pEnt->pNextS: NULL;                       \
+          pEnt;                                                   \
+          pEnt = pEnt2,                                           \
+          pEnt2 = pEnt? pEnt->pNextS: NULL )
+// the list of nodes in the functional (simulation) hash table
+#define Fraig_TableBinForEachEntryF( pBin, pEnt )                 \
+    for ( pEnt = pBin;                                            \
+          pEnt;                                                   \
+          pEnt = pEnt->pNextF )
+#define Fraig_TableBinForEachEntrySafeF( pBin, pEnt, pEnt2 )      \
+    for ( pEnt = pBin,                                            \
+          pEnt2 = pEnt? pEnt->pNextF: NULL;                       \
+          pEnt;                                                   \
+          pEnt = pEnt2,                                           \
+          pEnt2 = pEnt? pEnt->pNextF: NULL )
+// the list of nodes with the same simulation and different functionality
+#define Fraig_TableBinForEachEntryD( pBin, pEnt )                 \
+    for ( pEnt = pBin;                                            \
+          pEnt;                                                   \
+          pEnt = pEnt->pNextD )
+#define Fraig_TableBinForEachEntrySafeD( pBin, pEnt, pEnt2 )      \
+    for ( pEnt = pBin,                                            \
+          pEnt2 = pEnt? pEnt->pNextD: NULL;                       \
+          pEnt;                                                   \
+          pEnt = pEnt2,                                           \
+          pEnt2 = pEnt? pEnt->pNextD: NULL )
+// the list of nodes with the same functionality 
+#define Fraig_TableBinForEachEntryE( pBin, pEnt )                 \
+    for ( pEnt = pBin;                                            \
+          pEnt;                                                   \
+          pEnt = pEnt->pNextE )
+#define Fraig_TableBinForEachEntrySafeE( pBin, pEnt, pEnt2 )      \
+    for ( pEnt = pBin,                                            \
+          pEnt2 = pEnt? pEnt->pNextE: NULL;                       \
+          pEnt;                                                   \
+          pEnt = pEnt2,                                           \
+          pEnt2 = pEnt? pEnt->pNextE: NULL )
+
+////////////////////////////////////////////////////////////////////////
+///                       GLOBAL VARIABLES                           ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/*=== fraigCanon.c =============================================================*/
+extern Fraig_Node_t *      Fraig_NodeAndCanon( Fraig_Man_t * pMan, Fraig_Node_t * p1, Fraig_Node_t * p2 );
+/*=== fraigFanout.c =============================================================*/
+extern void                Fraig_NodeAddFaninFanout( Fraig_Node_t * pFanin, Fraig_Node_t * pFanout );
+extern void                Fraig_NodeRemoveFaninFanout( Fraig_Node_t * pFanin, Fraig_Node_t * pFanoutToRemove );
+extern int                 Fraig_NodeGetFanoutNum( Fraig_Node_t * pNode );
+/*=== fraigFeed.c =============================================================*/
+extern void                Fraig_FeedBackInit( Fraig_Man_t * p );
+extern void                Fraig_FeedBack( Fraig_Man_t * p, int * pModel, Msat_IntVec_t * vVars, Fraig_Node_t * pOld, Fraig_Node_t * pNew );
+extern void                Fraig_FeedBackTest( Fraig_Man_t * p );
+extern int                 Fraig_FeedBackCompress( Fraig_Man_t * p );
+extern int *               Fraig_ManAllocCounterExample( Fraig_Man_t * p );
+extern int *               Fraig_ManSaveCounterExample( Fraig_Man_t * p, Fraig_Node_t * pNode );
+/*=== fraigMan.c =============================================================*/
+extern void                Fraig_ManCreateSolver( Fraig_Man_t * p );
+/*=== fraigMem.c =============================================================*/
+extern Fraig_MemFixed_t *  Fraig_MemFixedStart( int nEntrySize );
+extern void                Fraig_MemFixedStop( Fraig_MemFixed_t * p, int fVerbose );
+extern char *              Fraig_MemFixedEntryFetch( Fraig_MemFixed_t * p );
+extern void                Fraig_MemFixedEntryRecycle( Fraig_MemFixed_t * p, char * pEntry );
+extern void                Fraig_MemFixedRestart( Fraig_MemFixed_t * p );
+extern int                 Fraig_MemFixedReadMemUsage( Fraig_MemFixed_t * p );
+/*=== fraigNode.c =============================================================*/
+extern Fraig_Node_t *      Fraig_NodeCreateConst( Fraig_Man_t * p );
+extern Fraig_Node_t *      Fraig_NodeCreatePi( Fraig_Man_t * p );
+extern Fraig_Node_t *      Fraig_NodeCreate( Fraig_Man_t * p, Fraig_Node_t * p1, Fraig_Node_t * p2 );
+extern void                Fraig_NodeSimulate( Fraig_Node_t * pNode, int iWordStart, int iWordStop, int fUseRand );
+/*=== fraigPrime.c =============================================================*/
+extern int                 s_FraigPrimes[FRAIG_MAX_PRIMES];
+extern unsigned int        Cudd_PrimeFraig( unsigned int  p );
+/*=== fraigSat.c ===============================================================*/
+extern int                 Fraig_NodeIsImplication( Fraig_Man_t * p, Fraig_Node_t * pOld, Fraig_Node_t * pNew, int nBTLimit );
+/*=== fraigTable.c =============================================================*/
+extern Fraig_HashTable_t * Fraig_HashTableCreate( int nSize );
+extern void                Fraig_HashTableFree( Fraig_HashTable_t * p );
+extern int                 Fraig_HashTableLookupS( Fraig_Man_t * pMan, Fraig_Node_t * p1, Fraig_Node_t * p2, Fraig_Node_t ** ppNodeRes );
+extern Fraig_Node_t *      Fraig_HashTableLookupF( Fraig_Man_t * pMan, Fraig_Node_t * pNode );
+extern Fraig_Node_t *      Fraig_HashTableLookupF0( Fraig_Man_t * pMan, Fraig_Node_t * pNode );
+extern void                Fraig_HashTableInsertF0( Fraig_Man_t * pMan, Fraig_Node_t * pNode );
+extern int                 Fraig_CompareSimInfo( Fraig_Node_t * pNode1, Fraig_Node_t * pNode2, int iWordLast, int fUseRand );
+extern int                 Fraig_CompareSimInfoUnderMask( Fraig_Node_t * pNode1, Fraig_Node_t * pNode2, int iWordLast, int fUseRand, unsigned * puMask );
+extern int                 Fraig_FindFirstDiff( Fraig_Node_t * pNode1, Fraig_Node_t * pNode2, int fCompl, int iWordLast, int fUseRand );
+extern void                Fraig_CollectXors( Fraig_Node_t * pNode1, Fraig_Node_t * pNode2, int iWordLast, int fUseRand, unsigned * puMask );
+extern void                Fraig_TablePrintStatsS( Fraig_Man_t * pMan );
+extern void                Fraig_TablePrintStatsF( Fraig_Man_t * pMan );
+extern void                Fraig_TablePrintStatsF0( Fraig_Man_t * pMan );
+extern int                 Fraig_TableRehashF0( Fraig_Man_t * pMan, int fLinkEquiv );
+/*=== fraigUtil.c ===============================================================*/
+extern int                 Fraig_NodeCountPis( Msat_IntVec_t * vVars, int nVarsPi );
+extern int                 Fraig_NodeCountSuppVars( Fraig_Man_t * p, Fraig_Node_t * pNode, int fSuppStr );
+extern int                 Fraig_NodesCompareSupps( Fraig_Man_t * p, Fraig_Node_t * pOld, Fraig_Node_t * pNew );
+extern int                 Fraig_NodeAndSimpleCase_rec( Fraig_Node_t * pOld, Fraig_Node_t * pNew );
+extern int                 Fraig_NodeIsExorType( Fraig_Node_t * pNode );
+extern void                Fraig_ManSelectBestChoice( Fraig_Man_t * p );
+extern int                 Fraig_BitStringCountOnes( unsigned * pString, int nWords );
+extern void                Fraig_PrintBinary( FILE * pFile, unsigned * pSign, int nBits );
+extern int                 Fraig_NodeIsExorType( Fraig_Node_t * pNode );
+extern int                 Fraig_NodeIsExor( Fraig_Node_t * pNode );
+extern int                 Fraig_NodeIsMuxType( Fraig_Node_t * pNode );
+extern Fraig_Node_t *      Fraig_NodeRecognizeMux( Fraig_Node_t * pNode, Fraig_Node_t ** ppNodeT, Fraig_Node_t ** ppNodeE );
+extern int                 Fraig_ManCountExors( Fraig_Man_t * pMan );
+extern int                 Fraig_ManCountMuxes( Fraig_Man_t * pMan );
+extern int                 Fraig_NodeSimsContained( Fraig_Man_t * pMan, Fraig_Node_t * pNode1, Fraig_Node_t * pNode2 );
+extern int                 Fraig_NodeIsInSupergate( Fraig_Node_t * pOld, Fraig_Node_t * pNew );
+extern Fraig_NodeVec_t *   Fraig_CollectSupergate( Fraig_Node_t * pNode, int fStopAtMux );
+extern int                 Fraig_CountPis( Fraig_Man_t * p, Msat_IntVec_t * vVarNums );
+extern void                Fraig_ManIncrementTravId( Fraig_Man_t * pMan );
+extern void                Fraig_NodeSetTravIdCurrent( Fraig_Man_t * pMan, Fraig_Node_t * pNode );
+extern int                 Fraig_NodeIsTravIdCurrent( Fraig_Man_t * pMan, Fraig_Node_t * pNode );
+extern int                 Fraig_NodeIsTravIdPrevious( Fraig_Man_t * pMan, Fraig_Node_t * pNode );
+/*=== fraigVec.c ===============================================================*/
+extern void                Fraig_NodeVecSortByRefCount( Fraig_NodeVec_t * p );
+
+#endif
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
diff --git a/src/sat/fraig/fraigMan.c b/src/sat/fraig/fraigMan.c
new file mode 100644
index 00000000..7fd937d5
--- /dev/null
+++ b/src/sat/fraig/fraigMan.c
@@ -0,0 +1,540 @@
+/**CFile****************************************************************
+
+  FileName    [fraigMan.c]
+
+  PackageName [FRAIG: Functionally reduced AND-INV graphs.]
+
+  Synopsis    [Implementation of the FRAIG manager.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 2.0. Started - October 1, 2004]
+
+  Revision    [$Id: fraigMan.c,v 1.11 2005/07/08 01:01:31 alanmi Exp $]
+
+***********************************************************************/
+
+#include "fraigInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+int timeSelect;
+int timeAssign;
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Sets the default parameters of the package.]
+
+  Description [This set of parameters is tuned for equivalence checking.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Prove_ParamsSetDefault( Prove_Params_t * pParams )
+{
+    // clean the parameter structure
+    memset( pParams, 0, sizeof(Prove_Params_t) );
+    // general parameters
+    pParams->fUseFraiging         = 1;       // enables fraiging
+    pParams->fUseRewriting        = 1;       // enables rewriting
+    pParams->fUseBdds             = 0;       // enables BDD construction when other methods fail
+    pParams->fVerbose             = 0;       // prints verbose stats
+    // iterations
+    pParams->nItersMax            = 6;       // the number of iterations
+    // mitering 
+    pParams->nMiteringLimitStart  = 300;    // starting mitering limit
+    pParams->nMiteringLimitMulti  = 2.0;     // multiplicative coefficient to increase the limit in each iteration
+    // rewriting (currently not used)
+    pParams->nRewritingLimitStart = 3;       // the number of rewriting iterations
+    pParams->nRewritingLimitMulti = 1.0;     // multiplicative coefficient to increase the limit in each iteration
+    // fraiging 
+    pParams->nFraigingLimitStart  = 2;       // starting backtrack(conflict) limit
+    pParams->nFraigingLimitMulti  = 8.0;     // multiplicative coefficient to increase the limit in each iteration
+    // last-gasp BDD construction
+    pParams->nBddSizeLimit        = 1000000; // the number of BDD nodes when construction is aborted
+    pParams->fBddReorder          = 1;       // enables dynamic BDD variable reordering
+    // last-gasp mitering
+//    pParams->nMiteringLimitLast   = 1000000; // final mitering limit
+    pParams->nMiteringLimitLast   = 0;       // final mitering limit
+    // global SAT solver limits
+    pParams->nTotalBacktrackLimit = 0;       // global limit on the number of backtracks
+    pParams->nTotalInspectLimit   = 0;       // global limit on the number of clause inspects
+//    pParams->nTotalInspectLimit   = 100000000;  // global limit on the number of clause inspects
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Prints out the current values of CEC engine parameters.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Prove_ParamsPrint( Prove_Params_t * pParams )
+{
+    printf( "CEC enging parameters:\n" );
+    printf( "Fraiging enabled: %s\n", pParams->fUseFraiging? "yes":"no" );
+    printf( "Rewriting enabled: %s\n", pParams->fUseRewriting? "yes":"no" );
+    printf( "BDD construction enabled: %s\n", pParams->fUseBdds? "yes":"no" );
+    printf( "Verbose output enabled: %s\n", pParams->fVerbose? "yes":"no" );
+    printf( "Solver iterations: %d\n", pParams->nItersMax );
+    printf( "Starting mitering limit: %d\n", pParams->nMiteringLimitStart );
+    printf( "Multiplicative coeficient for mitering: %.2f\n", pParams->nMiteringLimitMulti );
+    printf( "Starting number of rewriting iterations: %d\n", pParams->nRewritingLimitStart );
+    printf( "Multiplicative coeficient for rewriting: %.2f\n", pParams->nRewritingLimitMulti );
+    printf( "Starting number of conflicts in fraiging: %d\n", pParams->nFraigingLimitMulti );
+    printf( "Multiplicative coeficient for fraiging: %.2f\n", pParams->nRewritingLimitMulti );
+    printf( "BDD size limit for bailing out: %.2f\n", pParams->nBddSizeLimit );
+    printf( "BDD reordering enabled: %s\n", pParams->fBddReorder? "yes":"no" );
+    printf( "Last-gasp mitering limit: %d\n", pParams->nMiteringLimitLast );
+    printf( "Total conflict limit: %d\n", pParams->nTotalBacktrackLimit );
+    printf( "Total inspection limit: %d\n", pParams->nTotalInspectLimit );
+    printf( "Parameter dump complete.\n" );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Sets the default parameters of the package.]
+
+  Description [This set of parameters is tuned for equivalence checking.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_ParamsSetDefault( Fraig_Params_t * pParams )
+{
+    memset( pParams, 0, sizeof(Fraig_Params_t) );
+    pParams->nPatsRand  = FRAIG_PATTERNS_RANDOM;  // the number of words of random simulation info
+    pParams->nPatsDyna  = FRAIG_PATTERNS_DYNAMIC; // the number of words of dynamic simulation info
+    pParams->nBTLimit   = 99;                     // the max number of backtracks to perform
+    pParams->nSeconds   = 20;                     // the max number of seconds to solve the miter
+    pParams->fFuncRed   =  1;                     // performs only one level hashing
+    pParams->fFeedBack  =  1;                     // enables solver feedback
+    pParams->fDist1Pats =  1;                     // enables distance-1 patterns
+    pParams->fDoSparse  =  0;                     // performs equiv tests for sparse functions 
+    pParams->fChoicing  =  0;                     // enables recording structural choices
+    pParams->fTryProve  =  1;                     // tries to solve the final miter
+    pParams->fVerbose   =  0;                     // the verbosiness flag
+    pParams->fVerboseP  =  0;                     // the verbose flag for reporting the proof
+    pParams->fInternal  =  0;                     // the flag indicates the internal run 
+    pParams->nConfLimit =  0;                     // the limit on the number of conflicts
+    pParams->nInspLimit =  0;                     // the limit on the number of inspections
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Sets the default parameters of the package.]
+
+  Description [This set of parameters is tuned for complete FRAIGing.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_ParamsSetDefaultFull( Fraig_Params_t * pParams )
+{
+    memset( pParams, 0, sizeof(Fraig_Params_t) );
+    pParams->nPatsRand  = FRAIG_PATTERNS_RANDOM;  // the number of words of random simulation info
+    pParams->nPatsDyna  = FRAIG_PATTERNS_DYNAMIC; // the number of words of dynamic simulation info
+    pParams->nBTLimit   = -1;                     // the max number of backtracks to perform
+    pParams->nSeconds   = 20;                     // the max number of seconds to solve the miter
+    pParams->fFuncRed   =  1;                     // performs only one level hashing
+    pParams->fFeedBack  =  1;                     // enables solver feedback
+    pParams->fDist1Pats =  1;                     // enables distance-1 patterns
+    pParams->fDoSparse  =  1;                     // performs equiv tests for sparse functions 
+    pParams->fChoicing  =  0;                     // enables recording structural choices
+    pParams->fTryProve  =  0;                     // tries to solve the final miter
+    pParams->fVerbose   =  0;                     // the verbosiness flag
+    pParams->fVerboseP  =  0;                     // the verbose flag for reporting the proof
+    pParams->fInternal  =  0;                     // the flag indicates the internal run 
+    pParams->nConfLimit =  0;                     // the limit on the number of conflicts
+    pParams->nInspLimit =  0;                     // the limit on the number of inspections
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Creates the new FRAIG manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_Man_t * Fraig_ManCreate( Fraig_Params_t * pParams )
+{
+    Fraig_Params_t Params;
+    Fraig_Man_t * p;
+
+    // set the random seed for simulation
+//    srand( 0xFEEDDEAF );
+    srand( 0xDEADCAFE );
+
+    // set parameters for equivalence checking
+    if ( pParams == NULL )
+        Fraig_ParamsSetDefault( pParams = &Params );
+    // adjust the amount of simulation info
+    if ( pParams->nPatsRand < 128 )
+        pParams->nPatsRand = 128;
+    if ( pParams->nPatsRand > 32768 )
+        pParams->nPatsRand = 32768;
+    if ( pParams->nPatsDyna < 128 )
+        pParams->nPatsDyna = 128;
+    if ( pParams->nPatsDyna > 32768 )
+        pParams->nPatsDyna = 32768;
+    // if reduction is not performed, allocate minimum simulation info
+    if ( !pParams->fFuncRed )
+        pParams->nPatsRand = pParams->nPatsDyna = 128;
+
+    // start the manager
+    p = ALLOC( Fraig_Man_t, 1 );
+    memset( p, 0, sizeof(Fraig_Man_t) );
+
+    // set the default parameters
+    p->nWordsRand = FRAIG_NUM_WORDS( pParams->nPatsRand );  // the number of words of random simulation info
+    p->nWordsDyna = FRAIG_NUM_WORDS( pParams->nPatsDyna );  // the number of patterns for dynamic simulation info
+    p->nBTLimit   = pParams->nBTLimit;    // -1 means infinite backtrack limit
+    p->nSeconds   = pParams->nSeconds;    // the timeout for the final miter
+    p->fFuncRed   = pParams->fFuncRed;    // enables functional reduction (otherwise, only one-level hashing is performed)
+    p->fFeedBack  = pParams->fFeedBack;   // enables solver feedback (the use of counter-examples in simulation)
+    p->fDist1Pats = pParams->fDist1Pats;  // enables solver feedback (the use of counter-examples in simulation)
+    p->fDoSparse  = pParams->fDoSparse;   // performs equivalence checking for sparse functions (whose sim-info is 0)
+    p->fChoicing  = pParams->fChoicing;   // disable accumulation of structural choices (keeps only the first choice)
+    p->fTryProve  = pParams->fTryProve;   // disable accumulation of structural choices (keeps only the first choice)
+    p->fVerbose   = pParams->fVerbose;    // disable verbose output
+    p->fVerboseP  = pParams->fVerboseP;   // disable verbose output
+    p->nInspLimit = pParams->nInspLimit;  // the limit on the number of inspections
+
+    // start memory managers
+    p->mmNodes    = Fraig_MemFixedStart( sizeof(Fraig_Node_t) );
+    p->mmSims     = Fraig_MemFixedStart( sizeof(unsigned) * (p->nWordsRand + p->nWordsDyna) );
+    // allocate node arrays
+    p->vInputs    = Fraig_NodeVecAlloc( 1000 );    // the array of primary inputs
+    p->vOutputs   = Fraig_NodeVecAlloc( 1000 );    // the array of primary outputs
+    p->vNodes     = Fraig_NodeVecAlloc( 1000 );    // the array of internal nodes
+    // start the tables
+    p->pTableS    = Fraig_HashTableCreate( 1000 ); // hashing by structure
+    p->pTableF    = Fraig_HashTableCreate( 1000 ); // hashing by function
+    p->pTableF0   = Fraig_HashTableCreate( 1000 ); // hashing by function (for sparse functions)
+    // create the constant node
+    p->pConst1    = Fraig_NodeCreateConst( p );
+    // initialize SAT solver feedback data structures
+    Fraig_FeedBackInit( p );
+    // initialize other variables
+    p->vProj      = Msat_IntVecAlloc( 10 ); 
+    p->nTravIds   = 1;
+    p->nTravIds2  = 1;
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Deallocates the mapping manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_ManFree( Fraig_Man_t * p )
+{
+    int i;
+    if ( p->fVerbose )   
+    {
+        if ( p->fChoicing ) Fraig_ManReportChoices( p );
+        Fraig_ManPrintStats( p );
+//        Fraig_TablePrintStatsS( p );
+//        Fraig_TablePrintStatsF( p );
+//        Fraig_TablePrintStatsF0( p );
+    }
+ 
+    for ( i = 0; i < p->vNodes->nSize; i++ )
+        if ( p->vNodes->pArray[i]->vFanins )
+        {
+            Fraig_NodeVecFree( p->vNodes->pArray[i]->vFanins );
+            p->vNodes->pArray[i]->vFanins = NULL;
+        }
+
+    if ( p->vInputs )    Fraig_NodeVecFree( p->vInputs );
+    if ( p->vNodes )     Fraig_NodeVecFree( p->vNodes );
+    if ( p->vOutputs )   Fraig_NodeVecFree( p->vOutputs );
+
+    if ( p->pTableS )    Fraig_HashTableFree( p->pTableS );
+    if ( p->pTableF )    Fraig_HashTableFree( p->pTableF );
+    if ( p->pTableF0 )   Fraig_HashTableFree( p->pTableF0 );
+
+    if ( p->pSat )       Msat_SolverFree( p->pSat );
+    if ( p->vProj )      Msat_IntVecFree( p->vProj );
+    if ( p->vCones )     Fraig_NodeVecFree( p->vCones );
+    if ( p->vPatsReal )  Msat_IntVecFree( p->vPatsReal );
+    if ( p->pModel )     free( p->pModel );
+
+    Fraig_MemFixedStop( p->mmNodes, 0 );
+    Fraig_MemFixedStop( p->mmSims, 0 );
+
+    if ( p->pSuppS )
+    {
+        FREE( p->pSuppS[0] );
+        FREE( p->pSuppS );
+    }
+    if ( p->pSuppF )
+    {
+        FREE( p->pSuppF[0] );
+        FREE( p->pSuppF );
+    }
+
+    FREE( p->ppOutputNames );
+    FREE( p->ppInputNames );
+    FREE( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Prepares the SAT solver to run on the two nodes.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_ManCreateSolver( Fraig_Man_t * p )
+{
+    extern int timeSelect;
+    extern int timeAssign;
+    assert( p->pSat == NULL );
+    // allocate data for SAT solving
+    p->pSat       = Msat_SolverAlloc( 500, 1, 1, 1, 1, 0 );
+    p->vVarsInt   = Msat_SolverReadConeVars( p->pSat );   
+    p->vAdjacents = Msat_SolverReadAdjacents( p->pSat );
+    p->vVarsUsed  = Msat_SolverReadVarsUsed( p->pSat );
+    timeSelect = 0;
+    timeAssign = 0;
+}
+
+ 
+/**Function*************************************************************
+
+  Synopsis    [Deallocates the mapping manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_ManPrintStats( Fraig_Man_t * p )
+{
+    double nMemory;
+    int clk = clock();
+    nMemory = ((double)(p->vInputs->nSize + p->vNodes->nSize) * 
+        (sizeof(Fraig_Node_t) + sizeof(unsigned)*(p->nWordsRand + p->nWordsDyna) /*+ p->nSuppWords*sizeof(unsigned)*/))/(1<<20);
+    printf( "Words: Random = %d. Dynamic = %d. Used = %d. Memory = %0.2f Mb.\n", 
+        p->nWordsRand, p->nWordsDyna, p->iWordPerm, nMemory );
+    printf( "Proof = %d. Counter-example = %d. Fail = %d. FailReal = %d. Zero = %d.\n", 
+        p->nSatProof, p->nSatCounter, p->nSatFails, p->nSatFailsReal, p->nSatZeros );
+    printf( "Nodes: Final = %d. Total = %d. Mux = %d. (Exor = %d.) ClaVars = %d.\n", 
+        Fraig_CountNodes(p,0), p->vNodes->nSize, Fraig_ManCountMuxes(p), Fraig_ManCountExors(p), p->nVarsClauses );
+    if ( p->pSat ) Msat_SolverPrintStats( p->pSat );
+    Fraig_PrintTime( "AIG simulation  ", p->timeSims  );
+    Fraig_PrintTime( "AIG traversal   ", p->timeTrav  );
+    Fraig_PrintTime( "Solver feedback ", p->timeFeed  );
+    Fraig_PrintTime( "SAT solving     ", p->timeSat   );
+    Fraig_PrintTime( "Network update  ", p->timeToNet );
+    Fraig_PrintTime( "TOTAL RUNTIME   ", p->timeTotal );
+    if ( p->time1 > 0 ) { Fraig_PrintTime( "time1", p->time1 ); }
+    if ( p->time2 > 0 ) { Fraig_PrintTime( "time2", p->time2 ); }
+    if ( p->time3 > 0 ) { Fraig_PrintTime( "time3", p->time3 ); }
+    if ( p->time4 > 0 ) { Fraig_PrintTime( "time4", p->time4 ); }
+//    PRT( "Selection ", timeSelect );
+//    PRT( "Assignment", timeAssign );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Allocates simulation information for all nodes.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_NodeVec_t * Fraig_UtilInfoAlloc( int nSize, int nWords, bool fClean )
+{
+    Fraig_NodeVec_t * vInfo;
+    unsigned * pUnsigned;
+    int i;
+    assert( nSize > 0 && nWords > 0 );
+    vInfo = Fraig_NodeVecAlloc( nSize );
+    pUnsigned = ALLOC( unsigned, nSize * nWords );
+    vInfo->pArray[0] = (Fraig_Node_t *)pUnsigned;
+    if ( fClean )
+        memset( pUnsigned, 0, sizeof(unsigned) * nSize * nWords );
+    for ( i = 1; i < nSize; i++ )
+        vInfo->pArray[i] = (Fraig_Node_t *)(((unsigned *)vInfo->pArray[i-1]) + nWords);
+    vInfo->nSize = nSize;
+    return vInfo;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Returns simulation info of all nodes.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_NodeVec_t * Fraig_ManGetSimInfo( Fraig_Man_t * p )
+{
+    Fraig_NodeVec_t * vInfo;
+    Fraig_Node_t * pNode;
+    unsigned * pUnsigned;
+    int nRandom, nDynamic;
+    int i, k, nWords;
+
+    nRandom  = Fraig_ManReadPatternNumRandom( p );
+    nDynamic = Fraig_ManReadPatternNumDynamic( p );
+    nWords = nRandom / 32 + nDynamic / 32;
+
+    vInfo = Fraig_UtilInfoAlloc( p->vNodes->nSize, nWords, 0 );
+    for ( i = 0; i < p->vNodes->nSize; i++ )
+    {
+        pNode = p->vNodes->pArray[i];
+        assert( i == pNode->Num );
+        pUnsigned = (unsigned *)vInfo->pArray[i];
+        for ( k = 0; k < nRandom / 32; k++ )
+            pUnsigned[k] = pNode->puSimR[k];
+        for ( k = 0; k < nDynamic / 32; k++ )
+            pUnsigned[nRandom / 32 + k] = pNode->puSimD[k];
+    }
+    return vInfo;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Returns 1 if A v B is always true based on the siminfo.]
+
+  Description [A v B is always true iff A' * B' is always false.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_ManCheckClauseUsingSimInfo( Fraig_Man_t * p, Fraig_Node_t * pNode1, Fraig_Node_t * pNode2 )
+{
+    int fCompl1, fCompl2, i;
+
+    fCompl1 = 1 ^ Fraig_IsComplement(pNode1) ^ Fraig_Regular(pNode1)->fInv;
+    fCompl2 = 1 ^ Fraig_IsComplement(pNode2) ^ Fraig_Regular(pNode2)->fInv;
+
+    pNode1 = Fraig_Regular(pNode1);
+    pNode2 = Fraig_Regular(pNode2);
+    assert( pNode1 != pNode2 );
+    
+    // check the simulation info
+    if ( fCompl1 && fCompl2 )
+    {
+        for ( i = 0; i < p->nWordsRand; i++ )
+            if ( ~pNode1->puSimR[i] & ~pNode2->puSimR[i] )
+                return 0;
+        for ( i = 0; i < p->iWordStart; i++ )
+            if ( ~pNode1->puSimD[i] & ~pNode2->puSimD[i] )
+                return 0;
+        return 1;
+    }
+    if ( !fCompl1 && fCompl2 )
+    {
+        for ( i = 0; i < p->nWordsRand; i++ )
+            if ( pNode1->puSimR[i] & ~pNode2->puSimR[i] )
+                return 0;
+        for ( i = 0; i < p->iWordStart; i++ )
+            if ( pNode1->puSimD[i] & ~pNode2->puSimD[i] )
+                return 0;
+        return 1;
+    }
+    if ( fCompl1 && !fCompl2 )
+    {
+        for ( i = 0; i < p->nWordsRand; i++ )
+            if ( ~pNode1->puSimR[i] & pNode2->puSimR[i] )
+                return 0;
+        for ( i = 0; i < p->iWordStart; i++ )
+            if ( ~pNode1->puSimD[i] & pNode2->puSimD[i] )
+                return 0;
+        return 1;
+    }
+//    if ( fCompl1 && fCompl2 )
+    {
+        for ( i = 0; i < p->nWordsRand; i++ )
+            if ( pNode1->puSimR[i] & pNode2->puSimR[i] )
+                return 0;
+        for ( i = 0; i < p->iWordStart; i++ )
+            if ( pNode1->puSimD[i] & pNode2->puSimD[i] )
+                return 0;
+        return 1;
+    }
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Adds clauses to the solver.]
+
+  Description [This procedure is used to add external clauses to the solver.
+  The clauses are given by sets of nodes. Each node stands for one literal.
+  If the node is complemented, the literal is negated.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_ManAddClause( Fraig_Man_t * p, Fraig_Node_t ** ppNodes, int nNodes )
+{
+    Fraig_Node_t * pNode;
+    int i, fComp, RetValue;
+    if ( p->pSat == NULL )
+        Fraig_ManCreateSolver( p );
+    // create four clauses
+    Msat_IntVecClear( p->vProj );
+    for ( i = 0; i < nNodes; i++ )
+    {
+        pNode = Fraig_Regular(ppNodes[i]);
+        fComp = Fraig_IsComplement(ppNodes[i]);
+        Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNode->Num, fComp) );
+//        printf( "%d(%d) ", pNode->Num, fComp );
+    }
+//    printf( "\n" );
+    RetValue = Msat_SolverAddClause( p->pSat, p->vProj );
+    assert( RetValue );
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
diff --git a/src/sat/fraig/fraigMem.c b/src/sat/fraig/fraigMem.c
new file mode 100644
index 00000000..500431c6
--- /dev/null
+++ b/src/sat/fraig/fraigMem.c
@@ -0,0 +1,246 @@
+/**CFile****************************************************************
+
+  FileName    [fraigMem.c]
+
+  PackageName [FRAIG: Functionally reduced AND-INV graphs.]
+
+  Synopsis    [Fixed-size-entry memory manager for the FRAIG package.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 2.0. Started - October 1, 2004]
+
+  Revision    [$Id: fraigMem.c,v 1.4 2005/07/08 01:01:31 alanmi Exp $]
+
+***********************************************************************/
+
+#include "fraigInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+struct Fraig_MemFixed_t_
+{
+    // information about individual entries
+    int           nEntrySize;    // the size of one entry
+    int           nEntriesAlloc; // the total number of entries allocated
+    int           nEntriesUsed;  // the number of entries in use
+    int           nEntriesMax;   // the max number of entries in use
+    char *        pEntriesFree;  // the linked list of free entries
+
+    // this is where the memory is stored
+    int           nChunkSize;    // the size of one chunk
+    int           nChunksAlloc;  // the maximum number of memory chunks 
+    int           nChunks;       // the current number of memory chunks 
+    char **       pChunks;       // the allocated memory
+
+    // statistics
+    int           nMemoryUsed;   // memory used in the allocated entries
+    int           nMemoryAlloc;  // memory allocated
+};
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Starts the internal memory manager.]
+
+  Description [Can only work with entry size at least 4 byte long.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_MemFixed_t * Fraig_MemFixedStart( int nEntrySize )
+{
+    Fraig_MemFixed_t * p;
+
+    p = ALLOC( Fraig_MemFixed_t, 1 );
+    memset( p, 0, sizeof(Fraig_MemFixed_t) );
+
+    p->nEntrySize    = nEntrySize;
+    p->nEntriesAlloc = 0;
+    p->nEntriesUsed  = 0;
+    p->pEntriesFree  = NULL;
+
+    if ( nEntrySize * (1 << 10) < (1<<16) )
+        p->nChunkSize = (1 << 10);
+    else
+        p->nChunkSize = (1<<16) / nEntrySize;
+    if ( p->nChunkSize < 8 )
+        p->nChunkSize = 8;
+
+    p->nChunksAlloc  = 64;
+    p->nChunks       = 0;
+    p->pChunks       = ALLOC( char *, p->nChunksAlloc );
+
+    p->nMemoryUsed   = 0;
+    p->nMemoryAlloc  = 0;
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Stops the internal memory manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_MemFixedStop( Fraig_MemFixed_t * p, int fVerbose )
+{
+    int i;
+    if ( p == NULL )
+        return;
+    if ( fVerbose )
+    {
+        printf( "Fixed memory manager: Entry = %5d. Chunk = %5d. Chunks used = %5d.\n",
+            p->nEntrySize, p->nChunkSize, p->nChunks );
+        printf( "   Entries used = %8d. Entries peak = %8d. Memory used = %8d. Memory alloc = %8d.\n",
+            p->nEntriesUsed, p->nEntriesMax, p->nEntrySize * p->nEntriesUsed, p->nMemoryAlloc );
+    }
+    for ( i = 0; i < p->nChunks; i++ )
+        free( p->pChunks[i] );
+    free( p->pChunks );
+    free( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Extracts one entry from the memory manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+char * Fraig_MemFixedEntryFetch( Fraig_MemFixed_t * p )
+{
+    char * pTemp;
+    int i;
+
+    // check if there are still free entries
+    if ( p->nEntriesUsed == p->nEntriesAlloc )
+    { // need to allocate more entries
+        assert( p->pEntriesFree == NULL );
+        if ( p->nChunks == p->nChunksAlloc )
+        {
+            p->nChunksAlloc *= 2;
+            p->pChunks = REALLOC( char *, p->pChunks, p->nChunksAlloc ); 
+        }
+        p->pEntriesFree = ALLOC( char, p->nEntrySize * p->nChunkSize );
+        p->nMemoryAlloc += p->nEntrySize * p->nChunkSize;
+        // transform these entries into a linked list
+        pTemp = p->pEntriesFree;
+        for ( i = 1; i < p->nChunkSize; i++ )
+        {
+            *((char **)pTemp) = pTemp + p->nEntrySize;
+            pTemp += p->nEntrySize;
+        }
+        // set the last link
+        *((char **)pTemp) = NULL;
+        // add the chunk to the chunk storage
+        p->pChunks[ p->nChunks++ ] = p->pEntriesFree;
+        // add to the number of entries allocated
+        p->nEntriesAlloc += p->nChunkSize;
+    }
+    // incrememt the counter of used entries
+    p->nEntriesUsed++;
+    if ( p->nEntriesMax < p->nEntriesUsed )
+        p->nEntriesMax = p->nEntriesUsed;
+    // return the first entry in the free entry list
+    pTemp = p->pEntriesFree;
+    p->pEntriesFree = *((char **)pTemp);
+    return pTemp;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Returns one entry into the memory manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_MemFixedEntryRecycle( Fraig_MemFixed_t * p, char * pEntry )
+{
+    // decrement the counter of used entries
+    p->nEntriesUsed--;
+    // add the entry to the linked list of free entries
+    *((char **)pEntry) = p->pEntriesFree;
+    p->pEntriesFree = pEntry;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Frees all associated memory and resets the manager.]
+
+  Description [Relocates all the memory except the first chunk.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_MemFixedRestart( Fraig_MemFixed_t * p )
+{
+    int i;
+    char * pTemp;
+
+    // deallocate all chunks except the first one
+    for ( i = 1; i < p->nChunks; i++ )
+        free( p->pChunks[i] );
+    p->nChunks = 1;
+    // transform these entries into a linked list
+    pTemp = p->pChunks[0];
+    for ( i = 1; i < p->nChunkSize; i++ )
+    {
+        *((char **)pTemp) = pTemp + p->nEntrySize;
+        pTemp += p->nEntrySize;
+    }
+    // set the last link
+    *((char **)pTemp) = NULL;
+    // set the free entry list
+    p->pEntriesFree  = p->pChunks[0];
+    // set the correct statistics
+    p->nMemoryAlloc  = p->nEntrySize * p->nChunkSize;
+    p->nMemoryUsed   = 0;
+    p->nEntriesAlloc = p->nChunkSize;
+    p->nEntriesUsed  = 0;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Reports the memory usage.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_MemFixedReadMemUsage( Fraig_MemFixed_t * p )
+{
+    return p->nMemoryAlloc;
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/fraig/fraigNode.c b/src/sat/fraig/fraigNode.c
new file mode 100644
index 00000000..6e3d3c7d
--- /dev/null
+++ b/src/sat/fraig/fraigNode.c
@@ -0,0 +1,313 @@
+/**CFile****************************************************************
+
+  FileName    [fraigNode.c]
+
+  PackageName [FRAIG: Functionally reduced AND-INV graphs.]
+
+  Synopsis    [Implementation of the FRAIG node.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 2.0. Started - October 1, 2004]
+
+  Revision    [$Id: fraigNode.c,v 1.3 2005/07/08 01:01:32 alanmi Exp $]
+
+***********************************************************************/
+
+#include "fraigInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+// returns the complemented attribute of the node
+#define Fraig_NodeIsSimComplement(p) (Fraig_IsComplement(p)? !(Fraig_Regular(p)->fInv) : (p)->fInv)
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Creates the constant 1 node.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_Node_t * Fraig_NodeCreateConst( Fraig_Man_t * p )
+{
+    Fraig_Node_t * pNode;
+
+    // create the node
+    pNode = (Fraig_Node_t *)Fraig_MemFixedEntryFetch( p->mmNodes );
+    memset( pNode, 0, sizeof(Fraig_Node_t) );
+
+    // assign the number and add to the array of nodes
+    pNode->Num   = p->vNodes->nSize;
+    Fraig_NodeVecPush( p->vNodes,  pNode );
+    pNode->NumPi = -1;  // this is not a PI, so its number is -1
+    pNode->Level =  0;  // just like a PI, it has 0 level
+    pNode->nRefs =  1;  // it is a persistent node, which comes referenced
+    pNode->fInv  =  1;  // the simulation info is complemented
+
+    // create the simulation info
+    pNode->puSimR = (unsigned *)Fraig_MemFixedEntryFetch( p->mmSims );
+    pNode->puSimD = pNode->puSimR + p->nWordsRand;
+    memset( pNode->puSimR, 0, sizeof(unsigned) * p->nWordsRand );
+    memset( pNode->puSimD, 0, sizeof(unsigned) * p->nWordsDyna );
+
+    // count the number of ones in the simulation vector
+    pNode->nOnes = p->nWordsRand * sizeof(unsigned) * 8;
+
+    // insert it into the hash table
+    Fraig_HashTableLookupF0( p, pNode );
+    return pNode;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Creates a primary input node.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_Node_t * Fraig_NodeCreatePi( Fraig_Man_t * p )
+{
+    Fraig_Node_t * pNode, * pNodeRes;
+    int i, clk;
+
+    // create the node
+    pNode = (Fraig_Node_t *)Fraig_MemFixedEntryFetch( p->mmNodes );
+    memset( pNode, 0, sizeof(Fraig_Node_t) );
+    pNode->puSimR = (unsigned *)Fraig_MemFixedEntryFetch( p->mmSims );
+    pNode->puSimD = pNode->puSimR + p->nWordsRand;
+    memset( pNode->puSimD, 0, sizeof(unsigned) * p->nWordsDyna );
+
+    // assign the number and add to the array of nodes
+    pNode->Num   = p->vNodes->nSize;
+    Fraig_NodeVecPush( p->vNodes,  pNode );
+
+    // assign the PI number and add to the array of primary inputs
+    pNode->NumPi = p->vInputs->nSize;   
+    Fraig_NodeVecPush( p->vInputs, pNode );
+
+    pNode->Level =  0;  // PI has 0 level
+    pNode->nRefs =  1;  // it is a persistent node, which comes referenced
+    pNode->fInv  =  0;  // the simulation info of the PI is not complemented
+
+    // derive the simulation info for the new node
+clk = clock();
+    // set the random simulation info for the primary input
+    pNode->uHashR = 0;
+    for ( i = 0; i < p->nWordsRand; i++ )
+    {
+        // generate the simulation info
+        pNode->puSimR[i] = FRAIG_RANDOM_UNSIGNED;
+        // for reasons that take very long to explain, it makes sense to have (0000000...) 
+        // pattern in the set (this helps if we need to return the counter-examples)
+        if ( i == 0 )
+            pNode->puSimR[i] <<= 1;
+        // compute the hash key
+        pNode->uHashR ^= pNode->puSimR[i] * s_FraigPrimes[i];
+    }
+    // count the number of ones in the simulation vector
+    pNode->nOnes = Fraig_BitStringCountOnes( pNode->puSimR, p->nWordsRand );
+
+    // set the systematic simulation info for the primary input
+    pNode->uHashD = 0;
+    for ( i = 0; i < p->iWordStart; i++ )
+    {
+        // generate the simulation info
+        pNode->puSimD[i] = FRAIG_RANDOM_UNSIGNED;
+        // compute the hash key
+        pNode->uHashD ^= pNode->puSimD[i] * s_FraigPrimes[i];
+    }
+p->timeSims += clock() - clk;
+
+    // insert it into the hash table
+    pNodeRes = Fraig_HashTableLookupF( p, pNode );
+    assert( pNodeRes == NULL );
+    // add to the runtime of simulation
+    return pNode;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Creates a new node.]
+
+  Description [This procedure should be called to create the constant
+  node and the PI nodes first.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_Node_t * Fraig_NodeCreate( Fraig_Man_t * p, Fraig_Node_t * p1, Fraig_Node_t * p2 )
+{
+    Fraig_Node_t * pNode;
+    int clk;
+
+    // create the node
+    pNode = (Fraig_Node_t *)Fraig_MemFixedEntryFetch( p->mmNodes );
+    memset( pNode, 0, sizeof(Fraig_Node_t) );
+
+    // assign the children
+    pNode->p1  = p1;  Fraig_Ref(p1);  Fraig_Regular(p1)->nRefs++;
+    pNode->p2  = p2;  Fraig_Ref(p2);  Fraig_Regular(p2)->nRefs++;
+
+    // assign the number and add to the array of nodes
+    pNode->Num = p->vNodes->nSize;
+    Fraig_NodeVecPush( p->vNodes,  pNode );
+
+    // assign the PI number
+    pNode->NumPi = -1;
+
+    // compute the level of this node
+    pNode->Level = 1 + FRAIG_MAX(Fraig_Regular(p1)->Level, Fraig_Regular(p2)->Level);
+    pNode->fInv  = Fraig_NodeIsSimComplement(p1) & Fraig_NodeIsSimComplement(p2);
+    pNode->fFailTfo = Fraig_Regular(p1)->fFailTfo | Fraig_Regular(p2)->fFailTfo;
+
+    // derive the simulation info 
+clk = clock();
+    // allocate memory for the simulation info
+    pNode->puSimR = (unsigned *)Fraig_MemFixedEntryFetch( p->mmSims );
+    pNode->puSimD = pNode->puSimR + p->nWordsRand;
+    // derive random simulation info
+    pNode->uHashR = 0;
+    Fraig_NodeSimulate( pNode, 0, p->nWordsRand, 1 );
+    // derive dynamic simulation info
+    pNode->uHashD = 0;
+    Fraig_NodeSimulate( pNode, 0, p->iWordStart, 0 );
+    // count the number of ones in the random simulation info
+    pNode->nOnes = Fraig_BitStringCountOnes( pNode->puSimR, p->nWordsRand );
+    if ( pNode->fInv )
+        pNode->nOnes = p->nWordsRand * 32 - pNode->nOnes;
+    // add to the runtime of simulation
+p->timeSims += clock() - clk;
+
+#ifdef FRAIG_ENABLE_FANOUTS
+    // create the fanout info
+    Fraig_NodeAddFaninFanout( Fraig_Regular(p1), pNode );
+    Fraig_NodeAddFaninFanout( Fraig_Regular(p2), pNode );
+#endif
+    return pNode;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Simulates the node.]
+
+  Description [Simulates the random or dynamic simulation info through 
+  the node. Uses phases of the children to determine their real simulation
+  info. Uses phase of the node to determine the way its simulation info 
+  is stored. The resulting info is guaranteed to be 0 for the first pattern.]
+  
+  SideEffects [This procedure modified the hash value of the simulation info.]
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_NodeSimulate( Fraig_Node_t * pNode, int iWordStart, int iWordStop, int fUseRand )
+{
+    unsigned * pSims, * pSims1, * pSims2;
+    unsigned uHash;
+    int fCompl, fCompl1, fCompl2, i;
+
+    assert( !Fraig_IsComplement(pNode) );
+
+    // get hold of the simulation information
+    pSims  = fUseRand? pNode->puSimR                    : pNode->puSimD;
+    pSims1 = fUseRand? Fraig_Regular(pNode->p1)->puSimR : Fraig_Regular(pNode->p1)->puSimD;
+    pSims2 = fUseRand? Fraig_Regular(pNode->p2)->puSimR : Fraig_Regular(pNode->p2)->puSimD;
+
+    // get complemented attributes of the children using their random info
+    fCompl  = pNode->fInv;
+    fCompl1 = Fraig_NodeIsSimComplement(pNode->p1);
+    fCompl2 = Fraig_NodeIsSimComplement(pNode->p2);
+
+    // simulate
+    uHash = 0;
+    if ( fCompl1 && fCompl2 )
+    {
+        if ( fCompl )
+            for ( i = iWordStart; i < iWordStop; i++ )
+            {
+                pSims[i] = (pSims1[i] | pSims2[i]);
+                uHash ^= pSims[i] * s_FraigPrimes[i];
+            }
+        else
+            for ( i = iWordStart; i < iWordStop; i++ )
+            {
+                pSims[i] = ~(pSims1[i] | pSims2[i]);
+                uHash ^= pSims[i] * s_FraigPrimes[i];
+            }
+    }
+    else if ( fCompl1 && !fCompl2 )
+    {
+        if ( fCompl )
+            for ( i = iWordStart; i < iWordStop; i++ )
+            {
+                pSims[i] = (pSims1[i] | ~pSims2[i]);
+                uHash ^= pSims[i] * s_FraigPrimes[i];
+            }
+        else
+            for ( i = iWordStart; i < iWordStop; i++ )
+            {
+                pSims[i] = (~pSims1[i] & pSims2[i]);
+                uHash ^= pSims[i] * s_FraigPrimes[i];
+            }
+    }
+    else if ( !fCompl1 && fCompl2 )
+    {
+        if ( fCompl )
+            for ( i = iWordStart; i < iWordStop; i++ )
+            {
+                pSims[i] = (~pSims1[i] | pSims2[i]);
+                uHash ^= pSims[i] * s_FraigPrimes[i];
+            }
+        else
+            for ( i = iWordStart; i < iWordStop; i++ )
+            {
+                pSims[i] = (pSims1[i] & ~pSims2[i]);
+                uHash ^= pSims[i] * s_FraigPrimes[i];
+            }
+    }
+    else // if ( !fCompl1 && !fCompl2 )
+    {
+        if ( fCompl )
+            for ( i = iWordStart; i < iWordStop; i++ )
+            {
+                pSims[i] = ~(pSims1[i] & pSims2[i]);
+                uHash ^= pSims[i] * s_FraigPrimes[i];
+            }
+        else
+            for ( i = iWordStart; i < iWordStop; i++ )
+            {
+                pSims[i] = (pSims1[i] & pSims2[i]);
+                uHash ^= pSims[i] * s_FraigPrimes[i];
+            }
+    }
+
+    if ( fUseRand )
+        pNode->uHashR ^= uHash;
+    else
+        pNode->uHashD ^= uHash;
+}
+
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
diff --git a/src/sat/fraig/fraigPrime.c b/src/sat/fraig/fraigPrime.c
new file mode 100644
index 00000000..127ad478
--- /dev/null
+++ b/src/sat/fraig/fraigPrime.c
@@ -0,0 +1,144 @@
+/**CFile****************************************************************
+
+  FileName    [fraigPrime.c]
+
+  PackageName [FRAIG: Functionally reduced AND-INV graphs.]
+
+  Synopsis    [The table of the first 1000 primes.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 2.0. Started - October 1, 2004]
+
+  Revision    [$Id: fraigPrime.c,v 1.4 2005/07/08 01:01:32 alanmi Exp $]
+
+***********************************************************************/
+
+#include "fraigInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+// The 1,024 smallest prime numbers used to compute the hash value
+// http://www.math.utah.edu/~alfeld/math/primelist.html
+int s_FraigPrimes[FRAIG_MAX_PRIMES] = { 2, 3, 5, 
+7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 
+101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 
+193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 
+293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 
+409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 
+521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619, 631, 
+641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 
+757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 
+881, 883, 887, 907, 911, 919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997, 
+1009, 1013, 1019, 1021, 1031, 1033, 1039, 1049, 1051, 1061, 1063, 1069, 1087, 1091, 
+1093, 1097, 1103, 1109, 1117, 1123, 1129, 1151, 1153, 1163, 1171, 1181, 1187, 1193, 
+1201, 1213, 1217, 1223, 1229, 1231, 1237, 1249, 1259, 1277, 1279, 1283, 1289, 1291, 
+1297, 1301, 1303, 1307, 1319, 1321, 1327, 1361, 1367, 1373, 1381, 1399, 1409, 1423, 
+1427, 1429, 1433, 1439, 1447, 1451, 1453, 1459, 1471, 1481, 1483, 1487, 1489, 1493, 
+1499, 1511, 1523, 1531, 1543, 1549, 1553, 1559, 1567, 1571, 1579, 1583, 1597, 1601, 
+1607, 1609, 1613, 1619, 1621, 1627, 1637, 1657, 1663, 1667, 1669, 1693, 1697, 1699, 
+1709, 1721, 1723, 1733, 1741, 1747, 1753, 1759, 1777, 1783, 1787, 1789, 1801, 1811, 
+1823, 1831, 1847, 1861, 1867, 1871, 1873, 1877, 1879, 1889, 1901, 1907, 1913, 1931, 
+1933, 1949, 1951, 1973, 1979, 1987, 1993, 1997, 1999, 2003, 2011, 2017, 2027, 2029, 
+2039, 2053, 2063, 2069, 2081, 2083, 2087, 2089, 2099, 2111, 2113, 2129, 2131, 2137, 
+2141, 2143, 2153, 2161, 2179, 2203, 2207, 2213, 2221, 2237, 2239, 2243, 2251, 2267, 
+2269, 2273, 2281, 2287, 2293, 2297, 2309, 2311, 2333, 2339, 2341, 2347, 2351, 2357, 
+2371, 2377, 2381, 2383, 2389, 2393, 2399, 2411, 2417, 2423, 2437, 2441, 2447, 2459, 
+2467, 2473, 2477, 2503, 2521, 2531, 2539, 2543, 2549, 2551, 2557, 2579, 2591, 2593, 
+2609, 2617, 2621, 2633, 2647, 2657, 2659, 2663, 2671, 2677, 2683, 2687, 2689, 2693, 
+2699, 2707, 2711, 2713, 2719, 2729, 2731, 2741, 2749, 2753, 2767, 2777, 2789, 2791, 
+2797, 2801, 2803, 2819, 2833, 2837, 2843, 2851, 2857, 2861, 2879, 2887, 2897, 2903, 
+2909, 2917, 2927, 2939, 2953, 2957, 2963, 2969, 2971, 2999, 3001, 3011, 3019, 3023, 
+3037, 3041, 3049, 3061, 3067, 3079, 3083, 3089, 3109, 3119, 3121, 3137, 3163, 3167, 
+3169, 3181, 3187, 3191, 3203, 3209, 3217, 3221, 3229, 3251, 3253, 3257, 3259, 3271, 
+3299, 3301, 3307, 3313, 3319, 3323, 3329, 3331, 3343, 3347, 3359, 3361, 3371, 3373, 
+3389, 3391, 3407, 3413, 3433, 3449, 3457, 3461, 3463, 3467, 3469, 3491, 3499, 3511, 
+3517, 3527, 3529, 3533, 3539, 3541, 3547, 3557, 3559, 3571, 3581, 3583, 3593, 3607, 
+3613, 3617, 3623, 3631, 3637, 3643, 3659, 3671, 3673, 3677, 3691, 3697, 3701, 3709, 
+3719, 3727, 3733, 3739, 3761, 3767, 3769, 3779, 3793, 3797, 3803, 3821, 3823, 3833, 
+3847, 3851, 3853, 3863, 3877, 3881, 3889, 3907, 3911, 3917, 3919, 3923, 3929, 3931, 
+3943, 3947, 3967, 3989, 4001, 4003, 4007, 4013, 4019, 4021, 4027, 4049, 4051, 4057, 
+4073, 4079, 4091, 4093, 4099, 4111, 4127, 4129, 4133, 4139, 4153, 4157, 4159, 4177, 
+4201, 4211, 4217, 4219, 4229, 4231, 4241, 4243, 4253, 4259, 4261, 4271, 4273, 4283, 
+4289, 4297, 4327, 4337, 4339, 4349, 4357, 4363, 4373, 4391, 4397, 4409, 4421, 4423, 
+4441, 4447, 4451, 4457, 4463, 4481, 4483, 4493, 4507, 4513, 4517, 4519, 4523, 4547, 
+4549, 4561, 4567, 4583, 4591, 4597, 4603, 4621, 4637, 4639, 4643, 4649, 4651, 4657, 
+4663, 4673, 4679, 4691, 4703, 4721, 4723, 4729, 4733, 4751, 4759, 4783, 4787, 4789, 
+4793, 4799, 4801, 4813, 4817, 4831, 4861, 4871, 4877, 4889, 4903, 4909, 4919, 4931, 
+4933, 4937, 4943, 4951, 4957, 4967, 4969, 4973, 4987, 4993, 4999, 5003, 5009, 5011, 
+5021, 5023, 5039, 5051, 5059, 5077, 5081, 5087, 5099, 5101, 5107, 5113, 5119, 5147, 
+5153, 5167, 5171, 5179, 5189, 5197, 5209, 5227, 5231, 5233, 5237, 5261, 5273, 5279, 
+5281, 5297, 5303, 5309, 5323, 5333, 5347, 5351, 5381, 5387, 5393, 5399, 5407, 5413, 
+5417, 5419, 5431, 5437, 5441, 5443, 5449, 5471, 5477, 5479, 5483, 5501, 5503, 5507, 
+5519, 5521, 5527, 5531, 5557, 5563, 5569, 5573, 5581, 5591, 5623, 5639, 5641, 5647, 
+5651, 5653, 5657, 5659, 5669, 5683, 5689, 5693, 5701, 5711, 5717, 5737, 5741, 5743, 
+5749, 5779, 5783, 5791, 5801, 5807, 5813, 5821, 5827, 5839, 5843, 5849, 5851, 5857, 
+5861, 5867, 5869, 5879, 5881, 5897, 5903, 5923, 5927, 5939, 5953, 5981, 5987, 6007, 
+6011, 6029, 6037, 6043, 6047, 6053, 6067, 6073, 6079, 6089, 6091, 6101, 6113, 6121, 
+6131, 6133, 6143, 6151, 6163, 6173, 6197, 6199, 6203, 6211, 6217, 6221, 6229, 6247, 
+6257, 6263, 6269, 6271, 6277, 6287, 6299, 6301, 6311, 6317, 6323, 6329, 6337, 6343, 
+6353, 6359, 6361, 6367, 6373, 6379, 6389, 6397, 6421, 6427, 6449, 6451, 6469, 6473, 
+6481, 6491, 6521, 6529, 6547, 6551, 6553, 6563, 6569, 6571, 6577, 6581, 6599, 6607, 
+6619, 6637, 6653, 6659, 6661, 6673, 6679, 6689, 6691, 6701, 6703, 6709, 6719, 6733, 
+6737, 6761, 6763, 6779, 6781, 6791, 6793, 6803, 6823, 6827, 6829, 6833, 6841, 6857, 
+6863, 6869, 6871, 6883, 6899, 6907, 6911, 6917, 6947, 6949, 6959, 6961, 6967, 6971, 
+6977, 6983, 6991, 6997, 7001, 7013, 7019, 7027, 7039, 7043, 7057, 7069, 7079, 7103, 
+7109, 7121, 7127, 7129, 7151, 7159, 7177, 7187, 7193, 7207, 7211, 7213, 7219, 7229, 
+7237, 7243, 7247, 7253, 7283, 7297, 7307, 7309, 7321, 7331, 7333, 7349, 7351, 7369, 
+7393, 7411, 7417, 7433, 7451, 7457, 7459, 7477, 7481, 7487, 7489, 7499, 7507, 7517, 
+7523, 7529, 7537, 7541, 7547, 7549, 7559, 7561, 7573, 7577, 7583, 7589, 7591, 7603, 
+7607, 7621, 7639, 7643, 7649, 7669, 7673, 7681, 7687, 7691, 7699, 7703, 7717, 7723, 
+7727, 7741, 7753, 7757, 7759, 7789, 7793, 7817, 7823, 7829, 7841, 7853, 7867, 7873, 
+7877, 7879, 7883, 7901, 7907, 7919, 7927, 7933, 7937, 7949, 7951, 7963, 7993, 8009, 
+8011, 8017, 8039, 8053, 8059, 8069, 8081, 8087, 8089, 8093, 8101, 8111, 8117, 8123, 
+8147, 8161 };
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function********************************************************************
+
+  Synopsis    [Returns the next prime &gt;= p.]
+
+  Description [Copied from CUDD, for stand-aloneness.]
+
+  SideEffects [None]
+
+  SeeAlso     []
+
+******************************************************************************/
+unsigned int Cudd_PrimeFraig( unsigned int  p)
+{
+    int i,pn;
+
+    p--;
+    do {
+        p++;
+        if (p&1) {
+        pn = 1;
+        i = 3;
+        while ((unsigned) (i * i) <= p) {
+        if (p % i == 0) {
+            pn = 0;
+            break;
+        }
+        i += 2;
+        }
+    } else {
+        pn = 0;
+    }
+    } while (!pn);
+    return(p);
+
+} /* end of Cudd_Prime */
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/fraig/fraigSat.c b/src/sat/fraig/fraigSat.c
new file mode 100644
index 00000000..53057fc3
--- /dev/null
+++ b/src/sat/fraig/fraigSat.c
@@ -0,0 +1,1455 @@
+/**CFile****************************************************************
+
+  FileName    [fraigSat.c]
+
+  PackageName [FRAIG: Functionally reduced AND-INV graphs.]
+
+  Synopsis    [Proving functional equivalence using SAT.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 2.0. Started - October 1, 2004]
+
+  Revision    [$Id: fraigSat.c,v 1.10 2005/07/08 01:01:32 alanmi Exp $]
+
+***********************************************************************/
+
+#include "fraigInt.h"
+#include "math.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+static void Fraig_OrderVariables( Fraig_Man_t * pMan, Fraig_Node_t * pOld, Fraig_Node_t * pNew );
+static void Fraig_SetupAdjacent( Fraig_Man_t * pMan, Msat_IntVec_t * vConeVars );
+static void Fraig_SetupAdjacentMark( Fraig_Man_t * pMan, Msat_IntVec_t * vConeVars );
+static void Fraig_PrepareCones( Fraig_Man_t * pMan, Fraig_Node_t * pOld, Fraig_Node_t * pNew );
+static void Fraig_PrepareCones_rec( Fraig_Man_t * pMan, Fraig_Node_t * pNode );
+
+static void Fraig_SupergateAddClauses( Fraig_Man_t * pMan, Fraig_Node_t * pNode, Fraig_NodeVec_t * vSuper );
+static void Fraig_SupergateAddClausesExor( Fraig_Man_t * pMan, Fraig_Node_t * pNode );
+static void Fraig_SupergateAddClausesMux( Fraig_Man_t * pMan, Fraig_Node_t * pNode );
+//static void Fraig_DetectFanoutFreeCone( Fraig_Man_t * pMan, Fraig_Node_t * pNode );
+static void Fraig_DetectFanoutFreeConeMux( Fraig_Man_t * pMan, Fraig_Node_t * pNode );
+static void Fraig_SetActivity( Fraig_Man_t * pMan, Fraig_Node_t * pOld, Fraig_Node_t * pNew );
+
+extern void * Msat_ClauseVecReadEntry( void * p, int i );
+
+// The lesson learned seems to be that variable should be in reverse topological order
+// from the output of the miter. The ordering of adjacency lists is very important.
+// The best way seems to be fanins followed by fanouts. Slight changes to this order
+// leads to big degradation in quality.
+
+static int nMuxes;
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Checks equivalence of two nodes.]
+
+  Description [Returns 1 iff the nodes are equivalent.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_NodesAreEqual( Fraig_Man_t * p, Fraig_Node_t * pNode1, Fraig_Node_t * pNode2, int nBTLimit, int nTimeLimit )
+{
+    if ( pNode1 == pNode2 )
+        return 1;
+    if ( pNode1 == Fraig_Not(pNode2) )
+        return 0;
+    return Fraig_NodeIsEquivalent( p, Fraig_Regular(pNode1), Fraig_Regular(pNode2), nBTLimit, nTimeLimit );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Tries to prove the final miter.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_ManProveMiter( Fraig_Man_t * p )
+{
+    Fraig_Node_t * pNode;
+    int i, clk;
+
+    if ( !p->fTryProve )
+        return;
+ 
+    clk = clock();
+    // consider all outputs of the multi-output miter
+    for ( i = 0; i < p->vOutputs->nSize; i++ )
+    {
+        pNode = Fraig_Regular(p->vOutputs->pArray[i]);
+        // skip already constant nodes
+        if ( pNode == p->pConst1 )
+            continue;
+        // skip nodes that are different according to simulation
+        if ( !Fraig_CompareSimInfo( pNode, p->pConst1, p->nWordsRand, 1 ) )
+            continue;
+        if ( Fraig_NodeIsEquivalent( p, p->pConst1, pNode, -1, p->nSeconds ) )
+        {
+            if ( Fraig_IsComplement(p->vOutputs->pArray[i]) ^ Fraig_NodeComparePhase(p->pConst1, pNode) )
+                p->vOutputs->pArray[i] = Fraig_Not(p->pConst1);
+            else
+                p->vOutputs->pArray[i] = p->pConst1;
+        }
+    }
+    if ( p->fVerboseP ) 
+    {
+//        PRT( "Final miter proof time", clock() - clk );
+    }
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Returns 1 if the miter is unsat; 0 if sat; -1 if undecided.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_ManCheckMiter( Fraig_Man_t * p )
+{
+    Fraig_Node_t * pNode;
+    int i;
+    FREE( p->pModel );
+    for ( i = 0; i < p->vOutputs->nSize; i++ )
+    {
+        // get the output node (it can be complemented!)
+        pNode = p->vOutputs->pArray[i];
+        // if the miter is constant 0, the problem is UNSAT
+        if ( pNode == Fraig_Not(p->pConst1) )
+            continue;
+        // consider the special case when the miter is constant 1
+        if ( pNode == p->pConst1 )
+        {
+            // in this case, any counter example will do to distinquish it from constant 0
+            // here we pick the counter example composed of all zeros
+            p->pModel = Fraig_ManAllocCounterExample( p );
+            return 0;
+        }
+        // save the counter example
+        p->pModel = Fraig_ManSaveCounterExample( p, pNode );
+        // if the model is not found, return undecided
+        if ( p->pModel == NULL )
+            return -1;
+        else
+            return 0;
+    }
+    return 1;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Returns 1 if pOld is in the TFI of pNew.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_MarkTfi_rec( Fraig_Man_t * pMan, Fraig_Node_t * pNode )
+{
+    // skip the visited node
+    if ( pNode->TravId == pMan->nTravIds )
+        return 0;
+    pNode->TravId = pMan->nTravIds;
+    // skip the PI node
+    if ( pNode->NumPi >= 0 )
+        return 1;
+    // check the children
+    return Fraig_MarkTfi_rec( pMan, Fraig_Regular(pNode->p1) ) +
+           Fraig_MarkTfi_rec( pMan, Fraig_Regular(pNode->p2) );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Returns 1 if pOld is in the TFI of pNew.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_MarkTfi2_rec( Fraig_Man_t * pMan, Fraig_Node_t * pNode )
+{
+    // skip the visited node
+    if ( pNode->TravId == pMan->nTravIds )
+        return 0;
+    // skip the boundary node
+    if ( pNode->TravId == pMan->nTravIds-1 )
+    {
+        pNode->TravId = pMan->nTravIds;
+        return 1;
+    }
+    pNode->TravId = pMan->nTravIds;
+    // skip the PI node
+    if ( pNode->NumPi >= 0 )
+        return 1;
+    // check the children
+    return Fraig_MarkTfi2_rec( pMan, Fraig_Regular(pNode->p1) ) +
+           Fraig_MarkTfi2_rec( pMan, Fraig_Regular(pNode->p2) );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Returns 1 if pOld is in the TFI of pNew.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_MarkTfi3_rec( Fraig_Man_t * pMan, Fraig_Node_t * pNode )
+{
+    // skip the visited node
+    if ( pNode->TravId == pMan->nTravIds )
+        return 1;
+    // skip the boundary node
+    if ( pNode->TravId == pMan->nTravIds-1 )
+    {
+        pNode->TravId = pMan->nTravIds;
+        return 1;
+    }
+    pNode->TravId = pMan->nTravIds;
+    // skip the PI node
+    if ( pNode->NumPi >= 0 )
+        return 0;
+    // check the children
+    return Fraig_MarkTfi3_rec( pMan, Fraig_Regular(pNode->p1) ) *
+           Fraig_MarkTfi3_rec( pMan, Fraig_Regular(pNode->p2) );
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_VarsStudy( Fraig_Man_t * p, Fraig_Node_t * pOld, Fraig_Node_t * pNew )
+{
+    int NumPis, NumCut, fContain;
+
+    // mark the TFI of pNew
+    p->nTravIds++;
+    NumPis = Fraig_MarkTfi_rec( p, pNew );
+    printf( "(%d)(%d,%d):", NumPis, pOld->Level, pNew->Level );
+
+    // check if the old is in the TFI
+    if ( pOld->TravId == p->nTravIds )
+    {
+        printf( "* " );
+        return;
+    }
+
+    // count the boundary of nodes in pOld
+    p->nTravIds++;
+    NumCut = Fraig_MarkTfi2_rec( p, pOld );
+    printf( "%d", NumCut );
+
+    // check if the new is contained in the old's support
+    p->nTravIds++;
+    fContain = Fraig_MarkTfi3_rec( p, pNew );
+    printf( "%c ", fContain? '+':'-' );
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Checks whether two nodes are functinally equivalent.]
+
+  Description [The flag (fComp) tells whether the nodes to be checked
+  are in the opposite polarity. The second flag (fSkipZeros) tells whether
+  the checking should be performed if the simulation vectors are zeros.
+  Returns 1 if the nodes are equivalent; 0 othewise.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_NodeIsEquivalent( Fraig_Man_t * p, Fraig_Node_t * pOld, Fraig_Node_t * pNew, int nBTLimit, int nTimeLimit )
+{
+    int RetValue, RetValue1, i, fComp, clk;
+    int fVerbose = 0;
+    int fSwitch = 0;
+
+    // make sure the nodes are not complemented
+    assert( !Fraig_IsComplement(pNew) );
+    assert( !Fraig_IsComplement(pOld) );
+    assert( pNew != pOld );
+
+    // if at least one of the nodes is a failed node, perform adjustments:
+    // if the backtrack limit is small, simply skip this node
+    // if the backtrack limit is > 10, take the quare root of the limit
+    if ( nBTLimit > 0 && (pOld->fFailTfo || pNew->fFailTfo) )
+    {
+        p->nSatFails++;
+//            return 0;
+//        if ( nBTLimit > 10 )
+//            nBTLimit /= 10;
+        if ( nBTLimit <= 10 )
+            return 0;
+        nBTLimit = (int)sqrt(nBTLimit);
+//        fSwitch = 1;
+    }
+
+    p->nSatCalls++;
+
+    // make sure the solver is allocated and has enough variables
+    if ( p->pSat == NULL )
+        Fraig_ManCreateSolver( p );
+    // make sure the SAT solver has enough variables
+    for ( i = Msat_SolverReadVarNum(p->pSat); i < p->vNodes->nSize; i++ )
+        Msat_SolverAddVar( p->pSat, p->vNodes->pArray[i]->Level );
+
+
+ 
+/*
+    {
+        Fraig_Node_t * ppNodes[2] = { pOld, pNew };
+        extern void Fraig_MappingShowNodes( Fraig_Man_t * pMan, Fraig_Node_t ** ppRoots, int nRoots, char * pFileName );
+        Fraig_MappingShowNodes( p, ppNodes, 2, "temp_aig" );
+    }
+*/
+
+    nMuxes = 0;
+
+
+    // get the logic cone
+clk = clock();
+//    Fraig_VarsStudy( p, pOld, pNew );
+    Fraig_OrderVariables( p, pOld, pNew );
+//    Fraig_PrepareCones( p, pOld, pNew );
+p->timeTrav += clock() - clk;
+
+//    printf( "The number of MUXes detected = %d (%5.2f %% of logic).  ", nMuxes, 300.0*nMuxes/(p->vNodes->nSize - p->vInputs->nSize) );
+//    PRT( "Time", clock() - clk );
+
+if ( fVerbose )
+    printf( "%d(%d) - ", Fraig_CountPis(p,p->vVarsInt), Msat_IntVecReadSize(p->vVarsInt) );
+
+
+    // prepare variable activity
+    Fraig_SetActivity( p, pOld, pNew );
+
+    // get the complemented attribute
+    fComp = Fraig_NodeComparePhase( pOld, pNew );
+//Msat_SolverPrintClauses( p->pSat );
+
+    ////////////////////////////////////////////
+    // prepare the solver to run incrementally on these variables
+//clk = clock();
+    Msat_SolverPrepare( p->pSat, p->vVarsInt );
+//p->time3 += clock() - clk;
+
+
+    // solve under assumptions
+    // A = 1; B = 0     OR     A = 1; B = 1 
+    Msat_IntVecClear( p->vProj );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pOld->Num, 0) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNew->Num, !fComp) );
+
+//Msat_SolverWriteDimacs( p->pSat, "temp_fraig.cnf" );
+
+    // run the solver
+clk = clock();
+    RetValue1 = Msat_SolverSolve( p->pSat, p->vProj, nBTLimit, nTimeLimit );
+p->timeSat += clock() - clk;
+
+    if ( RetValue1 == MSAT_FALSE )
+    {
+//p->time1 += clock() - clk;
+
+if ( fVerbose )
+{
+    printf( "unsat  %d  ", Msat_SolverReadBackTracks(p->pSat) );
+PRT( "time", clock() - clk );
+}
+
+        // add the clause
+        Msat_IntVecClear( p->vProj );
+        Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pOld->Num, 1) );
+        Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNew->Num, fComp) );
+        RetValue = Msat_SolverAddClause( p->pSat, p->vProj );
+        assert( RetValue );
+        // continue solving the other implication
+    }
+    else if ( RetValue1 == MSAT_TRUE )
+    {
+//p->time2 += clock() - clk;
+
+if ( fVerbose )
+{
+    printf( "sat  %d  ", Msat_SolverReadBackTracks(p->pSat) );
+PRT( "time", clock() - clk );
+}
+
+        // record the counter example
+        Fraig_FeedBack( p, Msat_SolverReadModelArray(p->pSat), p->vVarsInt, pOld, pNew );
+
+//        if ( pOld->fFailTfo || pNew->fFailTfo )
+//            printf( "*" );
+//        printf( "s(%d)", pNew->Level );
+        if ( fSwitch )
+             printf( "s(%d)", pNew->Level );
+        p->nSatCounter++;
+        return 0;
+    }
+    else // if ( RetValue1 == MSAT_UNKNOWN )
+    {
+p->time3 += clock() - clk;
+
+//        if ( pOld->fFailTfo || pNew->fFailTfo )
+//            printf( "*" );
+//        printf( "T(%d)", pNew->Level );
+
+        // mark the node as the failed node
+        if ( pOld != p->pConst1 ) 
+            pOld->fFailTfo = 1;
+        pNew->fFailTfo = 1;
+//        p->nSatFails++;
+        if ( fSwitch )
+             printf( "T(%d)", pNew->Level );
+        p->nSatFailsReal++;
+        return 0;
+    }
+
+    // if the old node was constant 0, we already know the answer
+    if ( pOld == p->pConst1 )
+        return 1;
+
+    ////////////////////////////////////////////
+    // prepare the solver to run incrementally 
+//clk = clock();
+    Msat_SolverPrepare( p->pSat, p->vVarsInt );
+//p->time3 += clock() - clk;
+    // solve under assumptions
+    // A = 0; B = 1     OR     A = 0; B = 0 
+    Msat_IntVecClear( p->vProj );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pOld->Num, 1) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNew->Num, fComp) );
+    // run the solver
+clk = clock();
+    RetValue1 = Msat_SolverSolve( p->pSat, p->vProj, nBTLimit, nTimeLimit );
+p->timeSat += clock() - clk;
+
+    if ( RetValue1 == MSAT_FALSE )
+    {
+//p->time1 += clock() - clk;
+
+if ( fVerbose )
+{
+    printf( "unsat  %d  ", Msat_SolverReadBackTracks(p->pSat) );
+PRT( "time", clock() - clk );
+}
+
+        // add the clause
+        Msat_IntVecClear( p->vProj );
+        Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pOld->Num, 0) );
+        Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNew->Num, !fComp) );
+        RetValue = Msat_SolverAddClause( p->pSat, p->vProj );
+        assert( RetValue );
+        // continue solving the other implication
+    }
+    else if ( RetValue1 == MSAT_TRUE )
+    {
+//p->time2 += clock() - clk;
+
+if ( fVerbose )
+{
+    printf( "sat  %d  ", Msat_SolverReadBackTracks(p->pSat) );
+PRT( "time", clock() - clk );
+}
+
+        // record the counter example
+        Fraig_FeedBack( p, Msat_SolverReadModelArray(p->pSat), p->vVarsInt, pOld, pNew );
+        p->nSatCounter++;
+
+//        if ( pOld->fFailTfo || pNew->fFailTfo )
+//            printf( "*" );
+//        printf( "s(%d)", pNew->Level );
+        if ( fSwitch )
+             printf( "s(%d)", pNew->Level );
+        return 0;
+    }
+    else // if ( RetValue1 == MSAT_UNKNOWN )
+    {
+p->time3 += clock() - clk;
+
+//        if ( pOld->fFailTfo || pNew->fFailTfo )
+//            printf( "*" );
+//        printf( "T(%d)", pNew->Level );
+        if ( fSwitch )
+             printf( "T(%d)", pNew->Level );
+
+        // mark the node as the failed node
+        pOld->fFailTfo = 1;
+        pNew->fFailTfo = 1;
+//        p->nSatFails++;
+        p->nSatFailsReal++;
+        return 0;
+    }
+
+    // return SAT proof
+    p->nSatProof++;
+
+//    if ( pOld->fFailTfo || pNew->fFailTfo )
+//        printf( "*" );
+//    printf( "u(%d)", pNew->Level );
+
+    if ( fSwitch )
+         printf( "u(%d)", pNew->Level );
+
+    return 1;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Checks whether pOld => pNew.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_NodeIsImplication( Fraig_Man_t * p, Fraig_Node_t * pOld, Fraig_Node_t * pNew, int nBTLimit )
+{
+    int RetValue, RetValue1, i, fComp, clk;
+    int fVerbose = 0;
+
+    // make sure the nodes are not complemented
+    assert( !Fraig_IsComplement(pNew) );
+    assert( !Fraig_IsComplement(pOld) );
+    assert( pNew != pOld );
+
+    p->nSatCallsImp++;
+
+    // make sure the solver is allocated and has enough variables
+    if ( p->pSat == NULL )
+        Fraig_ManCreateSolver( p );
+    // make sure the SAT solver has enough variables
+    for ( i = Msat_SolverReadVarNum(p->pSat); i < p->vNodes->nSize; i++ )
+        Msat_SolverAddVar( p->pSat, p->vNodes->pArray[i]->Level );
+
+   // get the logic cone
+clk = clock();
+    Fraig_OrderVariables( p, pOld, pNew );
+//    Fraig_PrepareCones( p, pOld, pNew );
+p->timeTrav += clock() - clk;
+
+if ( fVerbose )
+    printf( "%d(%d) - ", Fraig_CountPis(p,p->vVarsInt), Msat_IntVecReadSize(p->vVarsInt) );
+
+
+    // get the complemented attribute
+    fComp = Fraig_NodeComparePhase( pOld, pNew );
+//Msat_SolverPrintClauses( p->pSat );
+
+    ////////////////////////////////////////////
+    // prepare the solver to run incrementally on these variables
+//clk = clock();
+    Msat_SolverPrepare( p->pSat, p->vVarsInt );
+//p->time3 += clock() - clk;
+
+    // solve under assumptions
+    // A = 1; B = 0     OR     A = 1; B = 1 
+    Msat_IntVecClear( p->vProj );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pOld->Num, 0) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNew->Num, !fComp) );
+    // run the solver
+clk = clock();
+    RetValue1 = Msat_SolverSolve( p->pSat, p->vProj, nBTLimit, 1000000 );
+p->timeSat += clock() - clk;
+
+    if ( RetValue1 == MSAT_FALSE )
+    {
+//p->time1 += clock() - clk;
+
+if ( fVerbose )
+{
+    printf( "unsat  %d  ", Msat_SolverReadBackTracks(p->pSat) );
+PRT( "time", clock() - clk );
+}
+
+        // add the clause
+        Msat_IntVecClear( p->vProj );
+        Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pOld->Num, 1) );
+        Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNew->Num, fComp) );
+        RetValue = Msat_SolverAddClause( p->pSat, p->vProj );
+        assert( RetValue );
+//        p->nSatProofImp++;
+        return 1;
+    }
+    else if ( RetValue1 == MSAT_TRUE )
+    {
+//p->time2 += clock() - clk;
+
+if ( fVerbose )
+{
+    printf( "sat  %d  ", Msat_SolverReadBackTracks(p->pSat) );
+PRT( "time", clock() - clk );
+}
+        // record the counter example
+        Fraig_FeedBack( p, Msat_SolverReadModelArray(p->pSat), p->vVarsInt, pOld, pNew );
+        p->nSatCounterImp++;
+        return 0;
+    }
+    else // if ( RetValue1 == MSAT_UNKNOWN )
+    {
+p->time3 += clock() - clk;
+        p->nSatFailsImp++;
+        return 0;
+    }
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Prepares the SAT solver to run on the two nodes.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_ManCheckClauseUsingSat( Fraig_Man_t * p, Fraig_Node_t * pNode1, Fraig_Node_t * pNode2, int nBTLimit )
+{
+    Fraig_Node_t * pNode1R, * pNode2R;
+    int RetValue, RetValue1, i, clk;
+    int fVerbose = 0;
+
+    pNode1R = Fraig_Regular(pNode1);
+    pNode2R = Fraig_Regular(pNode2);
+    assert( pNode1R != pNode2R );
+
+    // make sure the solver is allocated and has enough variables
+    if ( p->pSat == NULL )
+        Fraig_ManCreateSolver( p );
+    // make sure the SAT solver has enough variables
+    for ( i = Msat_SolverReadVarNum(p->pSat); i < p->vNodes->nSize; i++ )
+        Msat_SolverAddVar( p->pSat, p->vNodes->pArray[i]->Level );
+
+   // get the logic cone
+clk = clock();
+    Fraig_OrderVariables( p, pNode1R, pNode2R );
+//    Fraig_PrepareCones( p, pNode1R, pNode2R );
+p->timeTrav += clock() - clk;
+
+    ////////////////////////////////////////////
+    // prepare the solver to run incrementally on these variables
+//clk = clock();
+    Msat_SolverPrepare( p->pSat, p->vVarsInt );
+//p->time3 += clock() - clk;
+
+    // solve under assumptions
+    // A = 1; B = 0     OR     A = 1; B = 1 
+    Msat_IntVecClear( p->vProj );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNode1R->Num, !Fraig_IsComplement(pNode1)) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNode2R->Num, !Fraig_IsComplement(pNode2)) );
+    // run the solver
+clk = clock();
+    RetValue1 = Msat_SolverSolve( p->pSat, p->vProj, nBTLimit, 1000000 );
+p->timeSat += clock() - clk;
+
+    if ( RetValue1 == MSAT_FALSE )
+    {
+//p->time1 += clock() - clk;
+
+if ( fVerbose )
+{
+    printf( "unsat  %d  ", Msat_SolverReadBackTracks(p->pSat) );
+PRT( "time", clock() - clk );
+}
+
+        // add the clause
+        Msat_IntVecClear( p->vProj );
+        Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNode1R->Num, Fraig_IsComplement(pNode1)) );
+        Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNode2R->Num, Fraig_IsComplement(pNode2)) );
+        RetValue = Msat_SolverAddClause( p->pSat, p->vProj );
+        assert( RetValue );
+//        p->nSatProofImp++;
+        return 1;
+    }
+    else if ( RetValue1 == MSAT_TRUE )
+    {
+//p->time2 += clock() - clk;
+
+if ( fVerbose )
+{
+    printf( "sat  %d  ", Msat_SolverReadBackTracks(p->pSat) );
+PRT( "time", clock() - clk );
+}
+        // record the counter example
+//        Fraig_FeedBack( p, Msat_SolverReadModelArray(p->pSat), p->vVarsInt, pNode1R, pNode2R );
+        p->nSatCounterImp++;
+        return 0;
+    }
+    else // if ( RetValue1 == MSAT_UNKNOWN )
+    {
+p->time3 += clock() - clk;
+        p->nSatFailsImp++;
+        return 0;
+    }
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Prepares the SAT solver to run on the two nodes.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_PrepareCones( Fraig_Man_t * pMan, Fraig_Node_t * pOld, Fraig_Node_t * pNew )
+{
+//    Msat_IntVec_t * vAdjs;
+//    int * pVars, nVars, i, k;
+    int nVarsAlloc;
+
+    assert( pOld != pNew );
+    assert( !Fraig_IsComplement(pOld) );
+    assert( !Fraig_IsComplement(pNew) );
+    // clean the variables
+    nVarsAlloc = Msat_IntVecReadSize(pMan->vVarsUsed);
+    Msat_IntVecFill( pMan->vVarsUsed, nVarsAlloc, 0 );
+    Msat_IntVecClear( pMan->vVarsInt );
+
+    pMan->nTravIds++;
+    Fraig_PrepareCones_rec( pMan, pNew );
+    Fraig_PrepareCones_rec( pMan, pOld );
+
+
+/*
+    nVars = Msat_IntVecReadSize( pMan->vVarsInt );
+    pVars = Msat_IntVecReadArray( pMan->vVarsInt );
+    for ( i = 0; i < nVars; i++ )
+    {
+        // process its connections
+        vAdjs = (Msat_IntVec_t *)Msat_ClauseVecReadEntry( pMan->vAdjacents, pVars[i] );
+        printf( "%d=%d { ", pVars[i], Msat_IntVecReadSize(vAdjs) );
+        for ( k = 0; k < Msat_IntVecReadSize(vAdjs); k++ )
+            printf( "%d ", Msat_IntVecReadEntry(vAdjs,k) );
+        printf( "}\n" );
+
+    }
+    i = 0;
+*/
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Traverses the cone, collects the numbers and adds the clauses.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_PrepareCones_rec( Fraig_Man_t * pMan, Fraig_Node_t * pNode )
+{
+    Fraig_Node_t * pFanin;
+    Msat_IntVec_t * vAdjs;
+    int fUseMuxes = 1, i;
+    int fItIsTime;
+
+    // skip if the node is aleady visited
+    assert( !Fraig_IsComplement(pNode) );
+    if ( pNode->TravId == pMan->nTravIds )
+        return;
+    pNode->TravId = pMan->nTravIds;
+
+    // collect the node's number (closer to reverse topological order)
+    Msat_IntVecPush( pMan->vVarsInt, pNode->Num );
+    Msat_IntVecWriteEntry( pMan->vVarsUsed, pNode->Num, 1 );
+    if ( !Fraig_NodeIsAnd( pNode ) )
+        return;
+
+    // if the node does not have fanins, create them
+    fItIsTime = 0;
+    if ( pNode->vFanins == NULL )
+    {
+        fItIsTime = 1;
+        // create the fanins of the supergate
+        assert( pNode->fClauses == 0 );
+        if ( fUseMuxes && Fraig_NodeIsMuxType(pNode) )
+        {
+            pNode->vFanins = Fraig_NodeVecAlloc( 4 );
+            Fraig_NodeVecPushUnique( pNode->vFanins, Fraig_Regular(Fraig_Regular(pNode->p1)->p1) );
+            Fraig_NodeVecPushUnique( pNode->vFanins, Fraig_Regular(Fraig_Regular(pNode->p1)->p2) );
+            Fraig_NodeVecPushUnique( pNode->vFanins, Fraig_Regular(Fraig_Regular(pNode->p2)->p1) );
+            Fraig_NodeVecPushUnique( pNode->vFanins, Fraig_Regular(Fraig_Regular(pNode->p2)->p2) );
+            Fraig_SupergateAddClausesMux( pMan, pNode );
+        }
+        else
+        {
+            pNode->vFanins = Fraig_CollectSupergate( pNode, fUseMuxes );
+            Fraig_SupergateAddClauses( pMan, pNode, pNode->vFanins );
+        }
+        assert( pNode->vFanins->nSize > 1 );
+        pNode->fClauses = 1;
+        pMan->nVarsClauses++;
+
+        // add fanins
+        vAdjs = (Msat_IntVec_t *)Msat_ClauseVecReadEntry( pMan->vAdjacents, pNode->Num );
+        assert( Msat_IntVecReadSize( vAdjs ) == 0 );
+        for ( i = 0; i < pNode->vFanins->nSize; i++ )
+        {
+            pFanin = Fraig_Regular(pNode->vFanins->pArray[i]);
+            Msat_IntVecPush( vAdjs, pFanin->Num );
+        }
+    }
+
+    // recursively visit the fanins
+    for ( i = 0; i < pNode->vFanins->nSize; i++ )
+        Fraig_PrepareCones_rec( pMan, Fraig_Regular(pNode->vFanins->pArray[i]) );
+
+    if ( fItIsTime )
+    {
+        // recursively visit the fanins
+        for ( i = 0; i < pNode->vFanins->nSize; i++ )
+        {
+            pFanin = Fraig_Regular(pNode->vFanins->pArray[i]);
+            vAdjs = (Msat_IntVec_t *)Msat_ClauseVecReadEntry( pMan->vAdjacents, pFanin->Num );
+            Msat_IntVecPush( vAdjs, pNode->Num );
+        }
+    }
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Collect variables using their proximity from the nodes.]
+
+  Description [This procedure creates a variable order based on collecting
+  first the nodes that are the closest to the given two target nodes.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_OrderVariables( Fraig_Man_t * pMan, Fraig_Node_t * pOld, Fraig_Node_t * pNew )
+{
+    Fraig_Node_t * pNode, * pFanin;
+    int i, k, Number, fUseMuxes = 1;
+    int nVarsAlloc;
+
+    assert( pOld != pNew );
+    assert( !Fraig_IsComplement(pOld) );
+    assert( !Fraig_IsComplement(pNew) );
+
+    pMan->nTravIds++;
+
+    // clean the variables
+    nVarsAlloc = Msat_IntVecReadSize(pMan->vVarsUsed);
+    Msat_IntVecFill( pMan->vVarsUsed, nVarsAlloc, 0 );
+    Msat_IntVecClear( pMan->vVarsInt );
+
+    // add the first node
+    Msat_IntVecPush( pMan->vVarsInt, pOld->Num );
+    Msat_IntVecWriteEntry( pMan->vVarsUsed, pOld->Num, 1 );
+    pOld->TravId = pMan->nTravIds;
+
+    // add the second node
+    Msat_IntVecPush( pMan->vVarsInt, pNew->Num );
+    Msat_IntVecWriteEntry( pMan->vVarsUsed, pNew->Num, 1 );
+    pNew->TravId = pMan->nTravIds;
+
+    // create the variable order
+    for ( i = 0; i < Msat_IntVecReadSize(pMan->vVarsInt); i++ )
+    {
+        // get the new node on the frontier
+        Number = Msat_IntVecReadEntry(pMan->vVarsInt, i);
+        pNode = pMan->vNodes->pArray[Number];
+        if ( !Fraig_NodeIsAnd(pNode) )
+            continue;
+
+        // if the node does not have fanins, create them
+        if ( pNode->vFanins == NULL )
+        {
+            // create the fanins of the supergate
+            assert( pNode->fClauses == 0 );
+            // detecting a fanout-free cone (experiment only)
+//            Fraig_DetectFanoutFreeCone( pMan, pNode );
+
+            if ( fUseMuxes && Fraig_NodeIsMuxType(pNode) )
+            {
+                pNode->vFanins = Fraig_NodeVecAlloc( 4 );
+                Fraig_NodeVecPushUnique( pNode->vFanins, Fraig_Regular(Fraig_Regular(pNode->p1)->p1) );
+                Fraig_NodeVecPushUnique( pNode->vFanins, Fraig_Regular(Fraig_Regular(pNode->p1)->p2) );
+                Fraig_NodeVecPushUnique( pNode->vFanins, Fraig_Regular(Fraig_Regular(pNode->p2)->p1) );
+                Fraig_NodeVecPushUnique( pNode->vFanins, Fraig_Regular(Fraig_Regular(pNode->p2)->p2) );
+                Fraig_SupergateAddClausesMux( pMan, pNode );
+//                Fraig_DetectFanoutFreeConeMux( pMan, pNode );
+
+                nMuxes++;
+            }
+            else
+            {
+                pNode->vFanins = Fraig_CollectSupergate( pNode, fUseMuxes );
+                Fraig_SupergateAddClauses( pMan, pNode, pNode->vFanins );
+            }
+            assert( pNode->vFanins->nSize > 1 );
+            pNode->fClauses = 1;
+            pMan->nVarsClauses++;
+
+            pNode->fMark2 = 1; // goes together with Fraig_SetupAdjacentMark()
+        }
+
+        // explore the implication fanins of pNode
+        for ( k = 0; k < pNode->vFanins->nSize; k++ )
+        {
+            pFanin = Fraig_Regular(pNode->vFanins->pArray[k]);
+            if ( pFanin->TravId == pMan->nTravIds ) // already collected
+                continue;
+            // collect and mark
+            Msat_IntVecPush( pMan->vVarsInt, pFanin->Num );
+            Msat_IntVecWriteEntry( pMan->vVarsUsed, pFanin->Num, 1 );
+            pFanin->TravId = pMan->nTravIds;
+        }
+    }
+
+    // set up the adjacent variable information
+//    Fraig_SetupAdjacent( pMan, pMan->vVarsInt );
+    Fraig_SetupAdjacentMark( pMan, pMan->vVarsInt );
+}
+
+
+
+/**Function*************************************************************
+
+  Synopsis    [Set up the adjacent variable information.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_SetupAdjacent( Fraig_Man_t * pMan, Msat_IntVec_t * vConeVars )
+{
+    Fraig_Node_t * pNode, * pFanin;
+    Msat_IntVec_t * vAdjs;
+    int * pVars, nVars, i, k;
+
+    // clean the adjacents for the variables
+    nVars = Msat_IntVecReadSize( vConeVars );
+    pVars = Msat_IntVecReadArray( vConeVars );
+    for ( i = 0; i < nVars; i++ )
+    {
+        // process its connections
+        vAdjs = (Msat_IntVec_t *)Msat_ClauseVecReadEntry( pMan->vAdjacents, pVars[i] );
+        Msat_IntVecClear( vAdjs );
+
+        pNode = pMan->vNodes->pArray[pVars[i]];
+        if ( !Fraig_NodeIsAnd(pNode) )
+            continue;
+
+        // add fanins
+        vAdjs = (Msat_IntVec_t *)Msat_ClauseVecReadEntry( pMan->vAdjacents, pVars[i] );
+        for ( k = 0; k < pNode->vFanins->nSize; k++ )
+//        for ( k = pNode->vFanins->nSize - 1; k >= 0; k-- )
+        {
+            pFanin = Fraig_Regular(pNode->vFanins->pArray[k]);
+            Msat_IntVecPush( vAdjs, pFanin->Num );
+//            Msat_IntVecPushUniqueOrder( vAdjs, pFanin->Num );
+        }
+    }
+    // add the fanouts
+    for ( i = 0; i < nVars; i++ )
+    {
+        pNode = pMan->vNodes->pArray[pVars[i]];
+        if ( !Fraig_NodeIsAnd(pNode) )
+            continue;
+
+        // add the edges
+        for ( k = 0; k < pNode->vFanins->nSize; k++ )
+//        for ( k = pNode->vFanins->nSize - 1; k >= 0; k-- )
+        {
+            pFanin = Fraig_Regular(pNode->vFanins->pArray[k]);
+            vAdjs = (Msat_IntVec_t *)Msat_ClauseVecReadEntry( pMan->vAdjacents, pFanin->Num );
+            Msat_IntVecPush( vAdjs, pNode->Num );
+//            Msat_IntVecPushUniqueOrder( vAdjs, pFanin->Num );
+        }
+    }
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Set up the adjacent variable information.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_SetupAdjacentMark( Fraig_Man_t * pMan, Msat_IntVec_t * vConeVars )
+{
+    Fraig_Node_t * pNode, * pFanin;
+    Msat_IntVec_t * vAdjs;
+    int * pVars, nVars, i, k;
+
+    // clean the adjacents for the variables
+    nVars = Msat_IntVecReadSize( vConeVars );
+    pVars = Msat_IntVecReadArray( vConeVars );
+    for ( i = 0; i < nVars; i++ )
+    {
+        pNode = pMan->vNodes->pArray[pVars[i]];
+        if ( pNode->fMark2 == 0 )
+            continue;
+//        pNode->fMark2 = 0;
+
+        // process its connections
+//        vAdjs = (Msat_IntVec_t *)Msat_ClauseVecReadEntry( pMan->vAdjacents, pVars[i] );
+//        Msat_IntVecClear( vAdjs );
+
+        if ( !Fraig_NodeIsAnd(pNode) )
+            continue;
+
+        // add fanins
+        vAdjs = (Msat_IntVec_t *)Msat_ClauseVecReadEntry( pMan->vAdjacents, pVars[i] );
+        for ( k = 0; k < pNode->vFanins->nSize; k++ )
+//        for ( k = pNode->vFanins->nSize - 1; k >= 0; k-- )
+        {
+            pFanin = Fraig_Regular(pNode->vFanins->pArray[k]);
+            Msat_IntVecPush( vAdjs, pFanin->Num );
+//            Msat_IntVecPushUniqueOrder( vAdjs, pFanin->Num );
+        }
+    }
+    // add the fanouts
+    for ( i = 0; i < nVars; i++ )
+    {
+        pNode = pMan->vNodes->pArray[pVars[i]];
+        if ( pNode->fMark2 == 0 )
+            continue;
+        pNode->fMark2 = 0;
+
+        if ( !Fraig_NodeIsAnd(pNode) )
+            continue;
+
+        // add the edges
+        for ( k = 0; k < pNode->vFanins->nSize; k++ )
+//        for ( k = pNode->vFanins->nSize - 1; k >= 0; k-- )
+        {
+            pFanin = Fraig_Regular(pNode->vFanins->pArray[k]);
+            vAdjs = (Msat_IntVec_t *)Msat_ClauseVecReadEntry( pMan->vAdjacents, pFanin->Num );
+            Msat_IntVecPush( vAdjs, pNode->Num );
+//            Msat_IntVecPushUniqueOrder( vAdjs, pFanin->Num );
+        }
+    }
+}
+
+
+
+
+/**Function*************************************************************
+
+  Synopsis    [Adds clauses to the solver.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_SupergateAddClauses( Fraig_Man_t * p, Fraig_Node_t * pNode, Fraig_NodeVec_t * vSuper )
+{
+    int fComp1, RetValue, nVars, Var, Var1, i;
+
+    assert( Fraig_NodeIsAnd( pNode ) );
+    nVars = Msat_SolverReadVarNum(p->pSat);
+
+    Var = pNode->Num;
+    assert( Var  < nVars ); 
+    for ( i = 0; i < vSuper->nSize; i++ )
+    {
+        // get the predecessor nodes
+        // get the complemented attributes of the nodes
+        fComp1 = Fraig_IsComplement(vSuper->pArray[i]);
+        // determine the variable numbers
+        Var1 = Fraig_Regular(vSuper->pArray[i])->Num;
+        // check that the variables are in the SAT manager
+        assert( Var1 < nVars );
+
+        // suppose the AND-gate is A * B = C
+        // add !A => !C   or   A + !C
+    //  fprintf( pFile, "%d %d 0%c", Var1, -Var, 10 );
+        Msat_IntVecClear( p->vProj );
+        Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(Var1, fComp1) );
+        Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(Var,  1) );
+        RetValue = Msat_SolverAddClause( p->pSat, p->vProj );
+        assert( RetValue );
+    }
+
+    // add A & B => C   or   !A + !B + C
+//  fprintf( pFile, "%d %d %d 0%c", -Var1, -Var2, Var, 10 );
+    Msat_IntVecClear( p->vProj );
+    for ( i = 0; i < vSuper->nSize; i++ )
+    {
+        // get the predecessor nodes
+        // get the complemented attributes of the nodes
+        fComp1 = Fraig_IsComplement(vSuper->pArray[i]);
+        // determine the variable numbers
+        Var1 = Fraig_Regular(vSuper->pArray[i])->Num;
+
+        // add this variable to the array
+        Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(Var1, !fComp1) );
+    }
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(Var, 0) );
+    RetValue = Msat_SolverAddClause( p->pSat, p->vProj );
+    assert( RetValue );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Adds clauses to the solver.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_SupergateAddClausesExor( Fraig_Man_t * p, Fraig_Node_t * pNode )
+{
+    Fraig_Node_t * pNode1, * pNode2;
+    int fComp, RetValue;
+
+    assert( !Fraig_IsComplement( pNode ) );
+    assert( Fraig_NodeIsExorType( pNode ) );
+    // get nodes
+    pNode1 = Fraig_Regular(Fraig_Regular(pNode->p1)->p1);
+    pNode2 = Fraig_Regular(Fraig_Regular(pNode->p1)->p2);
+    // get the complemented attribute of the EXOR/NEXOR gate
+    fComp = Fraig_NodeIsExor( pNode ); // 1 if EXOR, 0 if NEXOR
+
+    // create four clauses
+    Msat_IntVecClear( p->vProj );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNode->Num,   fComp) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNode1->Num,  fComp) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNode2->Num,  fComp) );
+    RetValue = Msat_SolverAddClause( p->pSat, p->vProj );
+    assert( RetValue );
+    Msat_IntVecClear( p->vProj );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNode->Num,   fComp) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNode1->Num, !fComp) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNode2->Num, !fComp) );
+    RetValue = Msat_SolverAddClause( p->pSat, p->vProj );
+    assert( RetValue );
+    Msat_IntVecClear( p->vProj );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNode->Num,  !fComp) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNode1->Num,  fComp) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNode2->Num, !fComp) );
+    RetValue = Msat_SolverAddClause( p->pSat, p->vProj );
+    assert( RetValue );
+    Msat_IntVecClear( p->vProj );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNode->Num,  !fComp) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNode1->Num, !fComp) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(pNode2->Num,  fComp) );
+    RetValue = Msat_SolverAddClause( p->pSat, p->vProj );
+    assert( RetValue );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Adds clauses to the solver.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_SupergateAddClausesMux( Fraig_Man_t * p, Fraig_Node_t * pNode )
+{
+    Fraig_Node_t * pNodeI, * pNodeT, * pNodeE;
+    int RetValue, VarF, VarI, VarT, VarE, fCompT, fCompE;
+
+    assert( !Fraig_IsComplement( pNode ) );
+    assert( Fraig_NodeIsMuxType( pNode ) );
+    // get nodes (I = if, T = then, E = else)
+    pNodeI = Fraig_NodeRecognizeMux( pNode, &pNodeT, &pNodeE );
+    // get the variable numbers
+    VarF = pNode->Num;
+    VarI = pNodeI->Num;
+    VarT = Fraig_Regular(pNodeT)->Num;
+    VarE = Fraig_Regular(pNodeE)->Num;
+    // get the complementation flags
+    fCompT = Fraig_IsComplement(pNodeT);
+    fCompE = Fraig_IsComplement(pNodeE);
+
+    // f = ITE(i, t, e)
+
+    // i' + t' + f
+    // i' + t  + f'
+    // i  + e' + f
+    // i  + e  + f'
+
+    // create four clauses
+    Msat_IntVecClear( p->vProj );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(VarI,  1) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(VarT,  1^fCompT) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(VarF,  0) );
+    RetValue = Msat_SolverAddClause( p->pSat, p->vProj );
+    assert( RetValue );
+    Msat_IntVecClear( p->vProj );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(VarI,  1) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(VarT,  0^fCompT) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(VarF,  1) );
+    RetValue = Msat_SolverAddClause( p->pSat, p->vProj );
+    assert( RetValue );
+    Msat_IntVecClear( p->vProj );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(VarI,  0) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(VarE,  1^fCompE) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(VarF,  0) );
+    RetValue = Msat_SolverAddClause( p->pSat, p->vProj );
+    assert( RetValue );
+    Msat_IntVecClear( p->vProj );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(VarI,  0) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(VarE,  0^fCompE) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(VarF,  1) );
+    RetValue = Msat_SolverAddClause( p->pSat, p->vProj );
+    assert( RetValue );
+
+    // two additional clauses
+    // t' & e' -> f'
+    // t  & e  -> f 
+
+    // t  + e   + f'
+    // t' + e'  + f 
+
+    if ( VarT == VarE )
+    {
+//        assert( fCompT == !fCompE );
+        return;
+    }
+
+    Msat_IntVecClear( p->vProj );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(VarT,  0^fCompT) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(VarE,  0^fCompE) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(VarF,  1) );
+    RetValue = Msat_SolverAddClause( p->pSat, p->vProj );
+    assert( RetValue );
+    Msat_IntVecClear( p->vProj );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(VarT,  1^fCompT) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(VarE,  1^fCompE) );
+    Msat_IntVecPush( p->vProj, MSAT_VAR2LIT(VarF,  0) );
+    RetValue = Msat_SolverAddClause( p->pSat, p->vProj );
+    assert( RetValue );
+
+}
+
+
+
+
+
+/**Function*************************************************************
+
+  Synopsis    [Returns the array of nodes to be combined into one multi-input AND-gate.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_DetectFanoutFreeCone_rec( Fraig_Node_t * pNode, Fraig_NodeVec_t * vSuper, Fraig_NodeVec_t * vInside, int fFirst )
+{
+    // make the pointer regular
+    pNode = Fraig_Regular(pNode);
+    // if the new node is complemented or a PI, another gate begins
+    if ( (!fFirst && pNode->nRefs > 1) || Fraig_NodeIsVar(pNode) )
+    {
+        Fraig_NodeVecPushUnique( vSuper, pNode );
+        return;
+    }
+    // go through the branches
+    Fraig_DetectFanoutFreeCone_rec( pNode->p1, vSuper, vInside, 0 );
+    Fraig_DetectFanoutFreeCone_rec( pNode->p2, vSuper, vInside, 0 );
+    // add the node
+    Fraig_NodeVecPushUnique( vInside, pNode );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Returns the array of nodes to be combined into one multi-input AND-gate.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+/*
+void Fraig_DetectFanoutFreeCone( Fraig_Man_t * pMan, Fraig_Node_t * pNode )
+{
+    Fraig_NodeVec_t * vFanins;
+    Fraig_NodeVec_t * vInside;
+    int nCubes;
+    extern int Fraig_CutSopCountCubes( Fraig_Man_t * pMan, Fraig_NodeVec_t * vFanins, Fraig_NodeVec_t * vInside );
+
+    vFanins = Fraig_NodeVecAlloc( 8 );
+    vInside = Fraig_NodeVecAlloc( 8 );
+
+    Fraig_DetectFanoutFreeCone_rec( pNode, vFanins, vInside, 1 );
+    assert( vInside->pArray[vInside->nSize-1] == pNode );
+
+    nCubes = Fraig_CutSopCountCubes( pMan, vFanins, vInside );
+
+printf( "%d(%d)", vFanins->nSize, nCubes );
+    Fraig_NodeVecFree( vFanins );
+    Fraig_NodeVecFree( vInside );
+}
+*/
+
+
+
+/**Function*************************************************************
+
+  Synopsis    [Returns the array of nodes to be combined into one multi-input AND-gate.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_DetectFanoutFreeConeMux_rec( Fraig_Node_t * pNode, Fraig_NodeVec_t * vSuper, Fraig_NodeVec_t * vInside, int fFirst )
+{
+    // make the pointer regular
+    pNode = Fraig_Regular(pNode);
+    // if the new node is complemented or a PI, another gate begins
+    if ( (!fFirst && pNode->nRefs > 1) || Fraig_NodeIsVar(pNode) || !Fraig_NodeIsMuxType(pNode) )
+    {
+        Fraig_NodeVecPushUnique( vSuper, pNode );
+        return;
+    }
+    // go through the branches
+    Fraig_DetectFanoutFreeConeMux_rec( Fraig_Regular(pNode->p1)->p1, vSuper, vInside, 0 );
+    Fraig_DetectFanoutFreeConeMux_rec( Fraig_Regular(pNode->p1)->p2, vSuper, vInside, 0 );
+    Fraig_DetectFanoutFreeConeMux_rec( Fraig_Regular(pNode->p2)->p1, vSuper, vInside, 0 );
+    Fraig_DetectFanoutFreeConeMux_rec( Fraig_Regular(pNode->p2)->p2, vSuper, vInside, 0 );
+    // add the node
+    Fraig_NodeVecPushUnique( vInside, pNode );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Returns the array of nodes to be combined into one multi-input AND-gate.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_DetectFanoutFreeConeMux( Fraig_Man_t * pMan, Fraig_Node_t * pNode )
+{
+    Fraig_NodeVec_t * vFanins;
+    Fraig_NodeVec_t * vInside;
+    int nCubes;
+    extern int Fraig_CutSopCountCubes( Fraig_Man_t * pMan, Fraig_NodeVec_t * vFanins, Fraig_NodeVec_t * vInside );
+
+    vFanins = Fraig_NodeVecAlloc( 8 );
+    vInside = Fraig_NodeVecAlloc( 8 );
+
+    Fraig_DetectFanoutFreeConeMux_rec( pNode, vFanins, vInside, 1 );
+    assert( vInside->pArray[vInside->nSize-1] == pNode );
+
+//    nCubes = Fraig_CutSopCountCubes( pMan, vFanins, vInside );
+    nCubes = 0;
+
+printf( "%d(%d)", vFanins->nSize, nCubes );
+    Fraig_NodeVecFree( vFanins );
+    Fraig_NodeVecFree( vInside );
+}
+
+
+
+/**Function*************************************************************
+
+  Synopsis    [Collect variables using their proximity from the nodes.]
+
+  Description [This procedure creates a variable order based on collecting
+  first the nodes that are the closest to the given two target nodes.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_SetActivity( Fraig_Man_t * pMan, Fraig_Node_t * pOld, Fraig_Node_t * pNew )
+{
+    Fraig_Node_t * pNode;
+    int i, Number, MaxLevel;
+    float * pFactors = Msat_SolverReadFactors(pMan->pSat);
+    if ( pFactors == NULL )
+        return;
+    MaxLevel = FRAIG_MAX( pOld->Level, pNew->Level );
+    // create the variable order
+    for ( i = 0; i < Msat_IntVecReadSize(pMan->vVarsInt); i++ )
+    {
+        // get the new node on the frontier
+        Number = Msat_IntVecReadEntry(pMan->vVarsInt, i);
+        pNode = pMan->vNodes->pArray[Number];
+        pFactors[pNode->Num] = (float)pow( 0.97, MaxLevel - pNode->Level );
+//        if ( pNode->Num % 50 == 0 )
+//        printf( "(%d) %.2f  ", MaxLevel - pNode->Level, pFactors[pNode->Num] );
+    }
+//    printf( "\n" );
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/fraig/fraigTable.c b/src/sat/fraig/fraigTable.c
new file mode 100644
index 00000000..b68bbe0e
--- /dev/null
+++ b/src/sat/fraig/fraigTable.c
@@ -0,0 +1,657 @@
+/**CFile****************************************************************
+
+  FileName    [fraigTable.c]
+
+  PackageName [FRAIG: Functionally reduced AND-INV graphs.]
+
+  Synopsis    [Structural and functional hash tables.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 2.0. Started - October 1, 2004]
+
+  Revision    [$Id: fraigTable.c,v 1.7 2005/07/08 01:01:34 alanmi Exp $]
+
+***********************************************************************/
+
+#include "fraigInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+static void Fraig_TableResizeS( Fraig_HashTable_t * p );
+static void Fraig_TableResizeF( Fraig_HashTable_t * p, int fUseSimR );
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Allocates the hash table.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_HashTable_t * Fraig_HashTableCreate( int nSize )
+{
+    Fraig_HashTable_t * p;
+    // allocate the table
+    p = ALLOC( Fraig_HashTable_t, 1 );
+    memset( p, 0, sizeof(Fraig_HashTable_t) );
+    // allocate and clean the bins
+    p->nBins = Cudd_PrimeFraig(nSize);
+    p->pBins = ALLOC( Fraig_Node_t *, p->nBins );
+    memset( p->pBins, 0, sizeof(Fraig_Node_t *) * p->nBins );
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Deallocates the supergate hash table.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_HashTableFree( Fraig_HashTable_t * p )
+{
+    FREE( p->pBins );
+    FREE( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Looks up an entry in the structural hash table.]
+
+  Description [If the entry with the same children does not exists, 
+  creates it, inserts it into the table, and returns 0. If the entry 
+  with the same children exists, finds it, and return 1. In both cases, 
+  the new/old entry is returned in ppNodeRes.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_HashTableLookupS( Fraig_Man_t * pMan, Fraig_Node_t * p1, Fraig_Node_t * p2, Fraig_Node_t ** ppNodeRes )
+{
+    Fraig_HashTable_t * p = pMan->pTableS;
+    Fraig_Node_t * pEnt;
+    unsigned Key;
+
+    // order the arguments
+    if ( Fraig_Regular(p1)->Num > Fraig_Regular(p2)->Num )
+        pEnt = p1, p1 = p2, p2 = pEnt;
+
+    Key = Fraig_HashKey2( p1, p2, p->nBins );
+    Fraig_TableBinForEachEntryS( p->pBins[Key], pEnt )
+        if ( pEnt->p1 == p1 && pEnt->p2 == p2 )
+        {
+            *ppNodeRes = pEnt;
+            return 1;
+        }
+    // check if it is a good time for table resizing
+    if ( p->nEntries >= 2 * p->nBins )
+    {
+        Fraig_TableResizeS( p );
+        Key = Fraig_HashKey2( p1, p2, p->nBins );
+    }
+    // create the new node
+    pEnt = Fraig_NodeCreate( pMan, p1, p2 );
+    // add the node to the corresponding linked list in the table
+    pEnt->pNextS = p->pBins[Key];
+    p->pBins[Key] = pEnt;
+    *ppNodeRes = pEnt;
+    p->nEntries++;
+    return 0;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Insert the entry in the functional hash table.]
+
+  Description [If the entry with the same key exists, return it right away.  
+  If the entry with the same key does not exists, inserts it and returns NULL. ]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_Node_t * Fraig_HashTableLookupF( Fraig_Man_t * pMan, Fraig_Node_t * pNode )
+{
+    Fraig_HashTable_t * p = pMan->pTableF;
+    Fraig_Node_t * pEnt, * pEntD;
+    unsigned Key;
+
+    // go through the hash table entries
+    Key = pNode->uHashR % p->nBins;
+    Fraig_TableBinForEachEntryF( p->pBins[Key], pEnt )
+    {
+        // if their simulation info differs, skip
+        if ( !Fraig_CompareSimInfo( pNode, pEnt, pMan->nWordsRand, 1 ) )
+            continue;
+        // equivalent up to the complement
+        Fraig_TableBinForEachEntryD( pEnt, pEntD )
+        {
+            // if their simulation info differs, skip
+            if ( !Fraig_CompareSimInfo( pNode, pEntD, pMan->iWordStart, 0 ) )
+                continue;
+            // found a simulation-equivalent node
+            return pEntD; 
+        }
+        // did not find a simulation equivalent node
+        // add the node to the corresponding linked list
+        pNode->pNextD = pEnt->pNextD;
+        pEnt->pNextD  = pNode;
+        // return NULL, because there is no functional equivalence in this case
+        return NULL;
+    }
+
+    // check if it is a good time for table resizing
+    if ( p->nEntries >= 2 * p->nBins )
+    {
+        Fraig_TableResizeF( p, 1 );
+        Key = pNode->uHashR % p->nBins;
+    }
+
+    // add the node to the corresponding linked list in the table
+    pNode->pNextF = p->pBins[Key];
+    p->pBins[Key] = pNode;
+    p->nEntries++;
+    // return NULL, because there is no functional equivalence in this case
+    return NULL;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Insert the entry in the functional hash table.]
+
+  Description [If the entry with the same key exists, return it right away.  
+  If the entry with the same key does not exists, inserts it and returns NULL. ]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_Node_t * Fraig_HashTableLookupF0( Fraig_Man_t * pMan, Fraig_Node_t * pNode )
+{
+    Fraig_HashTable_t * p = pMan->pTableF0;
+    Fraig_Node_t * pEnt;
+    unsigned Key;
+
+    // go through the hash table entries
+    Key = pNode->uHashD % p->nBins;
+    Fraig_TableBinForEachEntryF( p->pBins[Key], pEnt )
+    {
+        // if their simulation info differs, skip
+        if ( !Fraig_CompareSimInfo( pNode, pEnt, pMan->iWordStart, 0 ) )
+            continue;
+        // found a simulation-equivalent node
+        return pEnt; 
+    }
+
+    // check if it is a good time for table resizing
+    if ( p->nEntries >= 2 * p->nBins )
+    {
+        Fraig_TableResizeF( p, 0 );
+        Key = pNode->uHashD % p->nBins;
+    }
+
+    // add the node to the corresponding linked list in the table
+    pNode->pNextF = p->pBins[Key];
+    p->pBins[Key] = pNode;
+    p->nEntries++;
+    // return NULL, because there is no functional equivalence in this case
+    return NULL;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Insert the entry in the functional hash table.]
+
+  Description [Unconditionally add the node to the corresponding 
+  linked list in the table.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_HashTableInsertF0( Fraig_Man_t * pMan, Fraig_Node_t * pNode )
+{
+    Fraig_HashTable_t * p = pMan->pTableF0;
+    unsigned Key = pNode->uHashD % p->nBins;
+
+    pNode->pNextF = p->pBins[Key];
+    p->pBins[Key] = pNode;
+    p->nEntries++;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Resizes the table.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_TableResizeS( Fraig_HashTable_t * p )
+{
+    Fraig_Node_t ** pBinsNew;
+    Fraig_Node_t * pEnt, * pEnt2;
+    int nBinsNew, Counter, i, clk;
+    unsigned Key;
+
+clk = clock();
+    // get the new table size
+    nBinsNew = Cudd_PrimeFraig(2 * p->nBins); 
+    // allocate a new array
+    pBinsNew = ALLOC( Fraig_Node_t *, nBinsNew );
+    memset( pBinsNew, 0, sizeof(Fraig_Node_t *) * nBinsNew );
+    // rehash the entries from the old table
+    Counter = 0;
+    for ( i = 0; i < p->nBins; i++ )
+        Fraig_TableBinForEachEntrySafeS( p->pBins[i], pEnt, pEnt2 )
+        {
+            Key = Fraig_HashKey2( pEnt->p1, pEnt->p2, nBinsNew );
+            pEnt->pNextS = pBinsNew[Key];
+            pBinsNew[Key] = pEnt;
+            Counter++;
+        }
+    assert( Counter == p->nEntries );
+//    printf( "Increasing the structural table size from %6d to %6d. ", p->nBins, nBinsNew );
+//    PRT( "Time", clock() - clk );
+    // replace the table and the parameters
+    free( p->pBins );
+    p->pBins = pBinsNew;
+    p->nBins = nBinsNew;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Resizes the table.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_TableResizeF( Fraig_HashTable_t * p, int fUseSimR )
+{
+    Fraig_Node_t ** pBinsNew;
+    Fraig_Node_t * pEnt, * pEnt2;
+    int nBinsNew, Counter, i, clk;
+    unsigned Key;
+
+clk = clock();
+    // get the new table size
+    nBinsNew = Cudd_PrimeFraig(2 * p->nBins); 
+    // allocate a new array
+    pBinsNew = ALLOC( Fraig_Node_t *, nBinsNew );
+    memset( pBinsNew, 0, sizeof(Fraig_Node_t *) * nBinsNew );
+    // rehash the entries from the old table
+    Counter = 0;
+    for ( i = 0; i < p->nBins; i++ )
+        Fraig_TableBinForEachEntrySafeF( p->pBins[i], pEnt, pEnt2 )
+        {
+            if ( fUseSimR )
+                Key = pEnt->uHashR % nBinsNew;
+            else
+                Key = pEnt->uHashD % nBinsNew;
+            pEnt->pNextF = pBinsNew[Key];
+            pBinsNew[Key] = pEnt;
+            Counter++;
+        }
+    assert( Counter == p->nEntries );
+//    printf( "Increasing the functional table size from %6d to %6d. ", p->nBins, nBinsNew );
+//    PRT( "Time", clock() - clk );
+    // replace the table and the parameters
+    free( p->pBins );
+    p->pBins = pBinsNew;
+    p->nBins = nBinsNew;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Compares two pieces of simulation info.]
+
+  Description [Returns 1 if they are equal.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_CompareSimInfo( Fraig_Node_t * pNode1, Fraig_Node_t * pNode2, int iWordLast, int fUseRand )
+{
+    int i;
+    assert( !Fraig_IsComplement(pNode1) );
+    assert( !Fraig_IsComplement(pNode2) );
+    if ( fUseRand )
+    {
+        // if their signatures differ, skip
+        if ( pNode1->uHashR != pNode2->uHashR )
+            return 0;
+        // check the simulation info
+        for ( i = 0; i < iWordLast; i++ )
+            if ( pNode1->puSimR[i] != pNode2->puSimR[i] )
+                return 0;
+    }
+    else
+    {
+        // if their signatures differ, skip
+        if ( pNode1->uHashD != pNode2->uHashD )
+            return 0;
+        // check the simulation info
+        for ( i = 0; i < iWordLast; i++ )
+            if ( pNode1->puSimD[i] != pNode2->puSimD[i] )
+                return 0;
+    }
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Find the number of the different pattern.]
+
+  Description [Returns -1 if there is no such pattern]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_FindFirstDiff( Fraig_Node_t * pNode1, Fraig_Node_t * pNode2, int fCompl, int iWordLast, int fUseRand )
+{
+    int i, v;
+    assert( !Fraig_IsComplement(pNode1) );
+    assert( !Fraig_IsComplement(pNode2) );
+    // take into account possible internal complementation
+    fCompl ^= pNode1->fInv;
+    fCompl ^= pNode2->fInv;
+    // find the pattern
+    if ( fCompl )
+    {
+        if ( fUseRand )
+        {
+            for ( i = 0; i < iWordLast; i++ )
+                if ( pNode1->puSimR[i] != ~pNode2->puSimR[i] )
+                    for ( v = 0; v < 32; v++ )
+                        if ( (pNode1->puSimR[i] ^ ~pNode2->puSimR[i]) & (1 << v) )
+                            return i * 32 + v;
+        }
+        else
+        {
+            for ( i = 0; i < iWordLast; i++ )
+                if ( pNode1->puSimD[i] !=  ~pNode2->puSimD[i] )
+                    for ( v = 0; v < 32; v++ )
+                        if ( (pNode1->puSimD[i] ^ ~pNode2->puSimD[i]) & (1 << v) )
+                            return i * 32 + v;
+        }
+    }
+    else
+    {
+        if ( fUseRand )
+        {
+            for ( i = 0; i < iWordLast; i++ )
+                if ( pNode1->puSimR[i] != pNode2->puSimR[i] )
+                    for ( v = 0; v < 32; v++ )
+                        if ( (pNode1->puSimR[i] ^ pNode2->puSimR[i]) & (1 << v) )
+                            return i * 32 + v;
+        }
+        else
+        {
+            for ( i = 0; i < iWordLast; i++ )
+                if ( pNode1->puSimD[i] !=  pNode2->puSimD[i] )
+                    for ( v = 0; v < 32; v++ )
+                        if ( (pNode1->puSimD[i] ^ pNode2->puSimD[i]) & (1 << v) )
+                            return i * 32 + v;
+        }
+    }
+    return -1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Compares two pieces of simulation info.]
+
+  Description [Returns 1 if they are equal.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_CompareSimInfoUnderMask( Fraig_Node_t * pNode1, Fraig_Node_t * pNode2, int iWordLast, int fUseRand, unsigned * puMask )
+{
+    unsigned * pSims1, * pSims2;
+    int i;
+    assert( !Fraig_IsComplement(pNode1) );
+    assert( !Fraig_IsComplement(pNode2) );
+    // get hold of simulation info
+    pSims1 = fUseRand? pNode1->puSimR : pNode1->puSimD;
+    pSims2 = fUseRand? pNode2->puSimR : pNode2->puSimD;    
+    // check the simulation info
+    for ( i = 0; i < iWordLast; i++ )
+        if ( (pSims1[i] & puMask[i]) != (pSims2[i] & puMask[i]) )
+            return 0;
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Compares two pieces of simulation info.]
+
+  Description [Returns 1 if they are equal.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_CollectXors( Fraig_Node_t * pNode1, Fraig_Node_t * pNode2, int iWordLast, int fUseRand, unsigned * puMask )
+{
+    unsigned * pSims1, * pSims2;
+    int i;
+    assert( !Fraig_IsComplement(pNode1) );
+    assert( !Fraig_IsComplement(pNode2) );
+    // get hold of simulation info
+    pSims1 = fUseRand? pNode1->puSimR : pNode1->puSimD;
+    pSims2 = fUseRand? pNode2->puSimR : pNode2->puSimD;    
+    // check the simulation info
+    for ( i = 0; i < iWordLast; i++ )
+        puMask[i] = ( pSims1[i] ^ pSims2[i] );
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Prints stats of the structural table.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_TablePrintStatsS( Fraig_Man_t * pMan )
+{
+    Fraig_HashTable_t * pT = pMan->pTableS;
+    Fraig_Node_t * pNode;
+    int i, Counter;
+
+    printf( "Structural table. Table size = %d. Number of entries = %d.\n", pT->nBins, pT->nEntries );
+    for ( i = 0; i < pT->nBins; i++ )
+    {
+        Counter = 0;
+        Fraig_TableBinForEachEntryS( pT->pBins[i], pNode )
+            Counter++;
+        if ( Counter > 1 )
+        {
+            printf( "%d ", Counter );
+            if ( Counter > 50 )
+                printf( "{%d} ", i );
+        }
+    }
+    printf( "\n" );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Prints stats of the structural table.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_TablePrintStatsF( Fraig_Man_t * pMan )
+{
+    Fraig_HashTable_t * pT = pMan->pTableF;
+    Fraig_Node_t * pNode;
+    int i, Counter;
+
+    printf( "Functional table. Table size = %d. Number of entries = %d.\n", pT->nBins, pT->nEntries );
+    for ( i = 0; i < pT->nBins; i++ )
+    {
+        Counter = 0;
+        Fraig_TableBinForEachEntryF( pT->pBins[i], pNode )
+            Counter++;
+        if ( Counter > 1 )
+            printf( "{%d} ", Counter );
+    }
+    printf( "\n" );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Prints stats of the structural table.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_TablePrintStatsF0( Fraig_Man_t * pMan )
+{
+    Fraig_HashTable_t * pT = pMan->pTableF0;
+    Fraig_Node_t * pNode;
+    int i, Counter;
+
+    printf( "Zero-node table. Table size = %d. Number of entries = %d.\n", pT->nBins, pT->nEntries );
+    for ( i = 0; i < pT->nBins; i++ )
+    {
+        Counter = 0;
+        Fraig_TableBinForEachEntryF( pT->pBins[i], pNode )
+            Counter++;
+        if ( Counter == 0 )
+            continue;
+/*
+        printf( "\nBin = %4d :  Number of entries = %4d\n", i, Counter );
+        Fraig_TableBinForEachEntryF( pT->pBins[i], pNode )
+            printf( "Node %5d. Hash = %10d.\n", pNode->Num, pNode->uHashD );
+*/
+    }
+    printf( "\n" );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Rehashes the table after the simulation info has changed.]
+
+  Description [Assumes that the hash values have been updated after performing
+  additional simulation. Rehashes the table using the new hash values. 
+  Uses pNextF to link the entries in the bins. Uses pNextD to link the entries 
+  with identical hash values. Returns 1 if the identical entries have been found.
+  Note that identical hash values may mean that the simulation data is different.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_TableRehashF0( Fraig_Man_t * pMan, int fLinkEquiv )
+{
+    Fraig_HashTable_t * pT = pMan->pTableF0;
+    Fraig_Node_t ** pBinsNew;
+    Fraig_Node_t * pEntF, * pEntF2, * pEnt, * pEntD2, * pEntN;
+    int ReturnValue, Counter, i;
+    unsigned Key;
+
+    // allocate a new array of bins
+    pBinsNew = ALLOC( Fraig_Node_t *, pT->nBins );
+    memset( pBinsNew, 0, sizeof(Fraig_Node_t *) * pT->nBins );
+
+    // rehash the entries in the table
+    // go through all the nodes in the F-lists (and possible in D-lists, if used)
+    Counter = 0;
+    ReturnValue = 0;
+    for ( i = 0; i < pT->nBins; i++ )
+        Fraig_TableBinForEachEntrySafeF( pT->pBins[i], pEntF, pEntF2 )
+        Fraig_TableBinForEachEntrySafeD( pEntF, pEnt, pEntD2 )
+        {
+            // decide where to put entry pEnt
+            Key = pEnt->uHashD % pT->nBins;
+            if ( fLinkEquiv )
+            {
+                // go through the entries in the new bin
+                Fraig_TableBinForEachEntryF( pBinsNew[Key], pEntN )
+                {
+                    // if they have different values skip
+                    if ( pEnt->uHashD != pEntN->uHashD )
+                        continue;
+                    // they have the same hash value, add pEnt to the D-list pEnt3
+                    pEnt->pNextD  = pEntN->pNextD;
+                    pEntN->pNextD = pEnt;
+                    ReturnValue = 1;
+                    Counter++;
+                    break;
+                }
+                if ( pEntN != NULL ) // already linked
+                    continue;
+                // we did not find equal entry
+            }
+            // link the new entry
+            pEnt->pNextF  = pBinsNew[Key];
+            pBinsNew[Key] = pEnt;
+            pEnt->pNextD  = NULL;
+            Counter++;
+        }
+    assert( Counter == pT->nEntries );
+    // replace the table and the parameters
+    free( pT->pBins );
+    pT->pBins = pBinsNew;
+    return ReturnValue;
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/fraig/fraigUtil.c b/src/sat/fraig/fraigUtil.c
new file mode 100644
index 00000000..342a7111
--- /dev/null
+++ b/src/sat/fraig/fraigUtil.c
@@ -0,0 +1,1034 @@
+/**CFile****************************************************************
+
+  FileName    [fraigUtil.c]
+
+  PackageName [FRAIG: Functionally reduced AND-INV graphs.]
+
+  Synopsis    [Various utilities.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 2.0. Started - October 1, 2004]
+
+  Revision    [$Id: fraigUtil.c,v 1.15 2005/07/08 01:01:34 alanmi Exp $]
+
+***********************************************************************/
+
+#include "fraigInt.h"
+#include <limits.h>
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+static int bit_count[256] = {
+  0,1,1,2,1,2,2,3,1,2,2,3,2,3,3,4,1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,
+  1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,
+  1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,
+  2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,
+  1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,
+  2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,
+  2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,
+  3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,4,5,5,6,5,6,6,7,5,6,6,7,6,7,7,8
+};
+
+static void Fraig_Dfs_rec( Fraig_Man_t * pMan, Fraig_Node_t * pNode, Fraig_NodeVec_t * vNodes, int fEquiv );
+static int  Fraig_CheckTfi_rec( Fraig_Man_t * pMan, Fraig_Node_t * pNode, Fraig_Node_t * pOld );
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Computes the DFS ordering of the nodes.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_NodeVec_t * Fraig_Dfs( Fraig_Man_t * pMan, int fEquiv )
+{
+    Fraig_NodeVec_t * vNodes;
+    int i;
+    pMan->nTravIds++;
+    vNodes = Fraig_NodeVecAlloc( 100 );
+    for ( i = 0; i < pMan->vOutputs->nSize; i++ )
+        Fraig_Dfs_rec( pMan, Fraig_Regular(pMan->vOutputs->pArray[i]), vNodes, fEquiv );
+    return vNodes;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Computes the DFS ordering of the nodes.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_NodeVec_t * Fraig_DfsOne( Fraig_Man_t * pMan, Fraig_Node_t * pNode, int fEquiv )
+{
+    Fraig_NodeVec_t * vNodes;
+    pMan->nTravIds++;
+    vNodes = Fraig_NodeVecAlloc( 100 );
+    Fraig_Dfs_rec( pMan, Fraig_Regular(pNode), vNodes, fEquiv );
+    return vNodes;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Computes the DFS ordering of the nodes.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_NodeVec_t * Fraig_DfsNodes( Fraig_Man_t * pMan, Fraig_Node_t ** ppNodes, int nNodes, int fEquiv )
+{
+    Fraig_NodeVec_t * vNodes;
+    int i;
+    pMan->nTravIds++;
+    vNodes = Fraig_NodeVecAlloc( 100 );
+    for ( i = 0; i < nNodes; i++ )
+        Fraig_Dfs_rec( pMan, Fraig_Regular(ppNodes[i]), vNodes, fEquiv );
+    return vNodes;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Recursively computes the DFS ordering of the nodes.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_Dfs_rec( Fraig_Man_t * pMan, Fraig_Node_t * pNode, Fraig_NodeVec_t * vNodes, int fEquiv )
+{
+    assert( !Fraig_IsComplement(pNode) );
+    // skip the visited node
+    if ( pNode->TravId == pMan->nTravIds )
+        return;
+    pNode->TravId = pMan->nTravIds;
+    // visit the transitive fanin
+    if ( Fraig_NodeIsAnd(pNode) )
+    {
+        Fraig_Dfs_rec( pMan, Fraig_Regular(pNode->p1), vNodes, fEquiv );
+        Fraig_Dfs_rec( pMan, Fraig_Regular(pNode->p2), vNodes, fEquiv );
+    }
+    if ( fEquiv && pNode->pNextE )
+        Fraig_Dfs_rec( pMan, pNode->pNextE, vNodes, fEquiv );
+    // save the node
+    Fraig_NodeVecPush( vNodes, pNode );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Computes the DFS ordering of the nodes.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_CountNodes( Fraig_Man_t * pMan, int fEquiv )
+{
+    Fraig_NodeVec_t * vNodes;
+    int RetValue;
+    vNodes = Fraig_Dfs( pMan, fEquiv );
+    RetValue = vNodes->nSize;
+    Fraig_NodeVecFree( vNodes );
+    return RetValue;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Returns 1 if pOld is in the TFI of pNew.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_CheckTfi( Fraig_Man_t * pMan, Fraig_Node_t * pOld, Fraig_Node_t * pNew )
+{
+    assert( !Fraig_IsComplement(pOld) );
+    assert( !Fraig_IsComplement(pNew) );
+    pMan->nTravIds++;
+    return Fraig_CheckTfi_rec( pMan, pNew, pOld );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Returns 1 if pOld is in the TFI of pNew.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_CheckTfi_rec( Fraig_Man_t * pMan, Fraig_Node_t * pNode, Fraig_Node_t * pOld )
+{
+    // check the trivial cases
+    if ( pNode == NULL )
+        return 0;
+    if ( pNode->Num < pOld->Num && !pMan->fChoicing )
+        return 0;
+    if ( pNode == pOld )
+        return 1;
+    // skip the visited node
+    if ( pNode->TravId == pMan->nTravIds )
+        return 0;
+    pNode->TravId = pMan->nTravIds;
+    // check the children
+    if ( Fraig_CheckTfi_rec( pMan, Fraig_Regular(pNode->p1), pOld ) )
+        return 1;
+    if ( Fraig_CheckTfi_rec( pMan, Fraig_Regular(pNode->p2), pOld ) )
+        return 1;
+    // check equivalent nodes
+    return Fraig_CheckTfi_rec( pMan, pNode->pNextE, pOld );
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Returns 1 if pOld is in the TFI of pNew.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_CheckTfi2( Fraig_Man_t * pMan, Fraig_Node_t * pOld, Fraig_Node_t * pNew )
+{
+    Fraig_NodeVec_t * vNodes;
+    int RetValue;
+    vNodes = Fraig_DfsOne( pMan, pNew, 1 );
+    RetValue = (pOld->TravId == pMan->nTravIds);
+    Fraig_NodeVecFree( vNodes );
+    return RetValue;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Sets the number of fanouts (none, one, or many).]
+
+  Description [This procedure collects the nodes reachable from
+  the POs of the AIG and sets the type of fanout counter (none, one,
+  or many) for each node. This procedure is useful to determine
+  fanout-free cones of AND-nodes, which is helpful for rebalancing
+  the AIG (see procedure Fraig_ManRebalance, or something like that).]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_ManMarkRealFanouts( Fraig_Man_t * p )
+{
+    Fraig_NodeVec_t * vNodes;
+    Fraig_Node_t * pNodeR;
+    int i;
+    // collect the nodes reachable
+    vNodes = Fraig_Dfs( p, 0 );
+    // clean the fanouts field
+    for ( i = 0; i < vNodes->nSize; i++ )
+    {
+        vNodes->pArray[i]->nFanouts = 0;
+        vNodes->pArray[i]->pData0 = NULL;
+    }
+    // mark reachable nodes by setting the two-bit counter pNode->nFans
+    for ( i = 0; i < vNodes->nSize; i++ )
+    {
+        pNodeR = Fraig_Regular(vNodes->pArray[i]->p1);
+        if ( pNodeR && ++pNodeR->nFanouts == 3 )
+            pNodeR->nFanouts = 2;
+        pNodeR = Fraig_Regular(vNodes->pArray[i]->p2);
+        if ( pNodeR && ++pNodeR->nFanouts == 3 )
+            pNodeR->nFanouts = 2;
+    }
+    Fraig_NodeVecFree( vNodes );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Creates the constant 1 node.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_BitStringCountOnes( unsigned * pString, int nWords )
+{
+    unsigned char * pSuppBytes = (unsigned char *)pString;
+    int i, nOnes, nBytes = sizeof(unsigned) * nWords;
+    // count the number of ones in the simulation vector
+    for ( i = nOnes = 0; i < nBytes; i++ )
+        nOnes += bit_count[pSuppBytes[i]];
+    return nOnes;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Verify one useful property.]
+
+  Description [This procedure verifies one useful property. After 
+  the FRAIG construction with choice nodes is over, each primary node 
+  should have fanins that are primary nodes. The primary nodes is the 
+  one that does not have pNode->pRepr set to point to another node.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_ManCheckConsistency( Fraig_Man_t * p )
+{
+    Fraig_Node_t * pNode;
+    Fraig_NodeVec_t * pVec;
+    int i;
+    pVec = Fraig_Dfs( p, 0 );
+    for ( i = 0; i < pVec->nSize; i++ )
+    {
+        pNode = pVec->pArray[i];
+        if ( Fraig_NodeIsVar(pNode) )
+        {
+            if ( pNode->pRepr )
+                printf( "Primary input %d is a secondary node.\n", pNode->Num );
+        }
+        else if ( Fraig_NodeIsConst(pNode) )
+        {
+            if ( pNode->pRepr )
+                printf( "Constant 1 %d is a secondary node.\n", pNode->Num );
+        }
+        else
+        {
+            if ( pNode->pRepr )
+                printf( "Internal node %d is a secondary node.\n", pNode->Num );
+            if ( Fraig_Regular(pNode->p1)->pRepr )
+                printf( "Internal node %d has first fanin %d that is a secondary node.\n", 
+                    pNode->Num, Fraig_Regular(pNode->p1)->Num );
+            if ( Fraig_Regular(pNode->p2)->pRepr )
+                printf( "Internal node %d has second fanin %d that is a secondary node.\n", 
+                    pNode->Num, Fraig_Regular(pNode->p2)->Num );
+        }
+    }
+    Fraig_NodeVecFree( pVec );
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Prints the node.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_PrintNode( Fraig_Man_t * p, Fraig_Node_t * pNode )
+{
+    Fraig_NodeVec_t * vNodes;
+    Fraig_Node_t * pTemp;
+    int fCompl1, fCompl2, i;
+
+    vNodes = Fraig_DfsOne( p, pNode, 0 );
+    for ( i = 0; i < vNodes->nSize; i++ )
+    {
+        pTemp = vNodes->pArray[i];
+        if ( Fraig_NodeIsVar(pTemp) )
+        {
+            printf( "%3d : PI          ", pTemp->Num );
+            Fraig_PrintBinary( stdout, (unsigned *)&pTemp->puSimR, 20 );
+            printf( "   " );
+            Fraig_PrintBinary( stdout, (unsigned *)&pTemp->puSimD, 20 );
+            printf( "  %d\n", pTemp->fInv );
+            continue;
+        }
+
+        fCompl1 = Fraig_IsComplement(pTemp->p1);
+        fCompl2 = Fraig_IsComplement(pTemp->p2);
+        printf( "%3d : %c%3d %c%3d   ", pTemp->Num,
+            (fCompl1? '-':'+'), Fraig_Regular(pTemp->p1)->Num,
+            (fCompl2? '-':'+'), Fraig_Regular(pTemp->p2)->Num );
+        Fraig_PrintBinary( stdout, (unsigned *)&pTemp->puSimR, 20 );
+        printf( "   " );
+        Fraig_PrintBinary( stdout, (unsigned *)&pTemp->puSimD, 20 );
+        printf( "  %d\n", pTemp->fInv );
+    }
+    Fraig_NodeVecFree( vNodes );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Prints the bit string.]
+
+  Description []
+
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_PrintBinary( FILE * pFile, unsigned * pSign, int nBits )
+{
+    int Remainder, nWords;
+    int w, i;
+
+    Remainder = (nBits%(sizeof(unsigned)*8));
+    nWords    = (nBits/(sizeof(unsigned)*8)) + (Remainder>0);
+
+    for ( w = nWords-1; w >= 0; w-- )
+        for ( i = ((w == nWords-1 && Remainder)? Remainder-1: 31); i >= 0; i-- )
+            fprintf( pFile, "%c", '0' + (int)((pSign[w] & (1<<i)) > 0) );
+
+//  fprintf( pFile, "\n" );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Sets up the mask.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_GetMaxLevel( Fraig_Man_t * pMan )
+{
+    int nLevelMax, i;
+    nLevelMax = 0;
+    for ( i = 0; i < pMan->vOutputs->nSize; i++ )
+        nLevelMax = nLevelMax > Fraig_Regular(pMan->vOutputs->pArray[i])->Level? 
+                nLevelMax : Fraig_Regular(pMan->vOutputs->pArray[i])->Level;
+    return nLevelMax;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Analyses choice nodes.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_MappingUpdateLevel_rec( Fraig_Man_t * pMan, Fraig_Node_t * pNode, int fMaximum )
+{
+    Fraig_Node_t * pTemp;
+    int Level1, Level2, LevelE;
+    assert( !Fraig_IsComplement(pNode) );
+    if ( !Fraig_NodeIsAnd(pNode) )
+        return pNode->Level;
+    // skip the visited node
+    if ( pNode->TravId == pMan->nTravIds )
+        return pNode->Level;
+    pNode->TravId = pMan->nTravIds;
+    // compute levels of the children nodes
+    Level1 = Fraig_MappingUpdateLevel_rec( pMan, Fraig_Regular(pNode->p1), fMaximum );
+    Level2 = Fraig_MappingUpdateLevel_rec( pMan, Fraig_Regular(pNode->p2), fMaximum );
+    pNode->Level = 1 + FRAIG_MAX( Level1, Level2 );
+    if ( pNode->pNextE )
+    {
+        LevelE = Fraig_MappingUpdateLevel_rec( pMan, pNode->pNextE, fMaximum );
+        if ( fMaximum )
+        {
+            if ( pNode->Level < LevelE )
+                pNode->Level = LevelE;
+        }
+        else
+        {
+            if ( pNode->Level > LevelE )
+                pNode->Level = LevelE;
+        }
+        // set the level of all equivalent nodes to be the same minimum
+        if ( pNode->pRepr == NULL ) // the primary node
+            for ( pTemp = pNode->pNextE; pTemp; pTemp = pTemp->pNextE )
+                pTemp->Level = pNode->Level;
+    }
+    return pNode->Level;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Resets the levels of the nodes in the choice graph.]
+
+  Description [Makes the level of the choice nodes to be equal to the
+  maximum of the level of the nodes in the equivalence class. This way
+  sorting by level leads to the reverse topological order, which is
+  needed for the required time computation.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_MappingSetChoiceLevels( Fraig_Man_t * pMan, int fMaximum )
+{
+    int i;
+    pMan->nTravIds++;
+    for ( i = 0; i < pMan->vOutputs->nSize; i++ )
+        Fraig_MappingUpdateLevel_rec( pMan, Fraig_Regular(pMan->vOutputs->pArray[i]), fMaximum );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Reports statistics on choice nodes.]
+
+  Description [The number of choice nodes is the number of primary nodes,
+  which has pNextE set to a pointer. The number of choices is the number
+  of entries in the equivalent-node lists of the primary nodes.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_ManReportChoices( Fraig_Man_t * pMan )
+{
+    Fraig_Node_t * pNode, * pTemp;
+    int nChoiceNodes, nChoices;
+    int i, LevelMax1, LevelMax2;
+
+    // report the number of levels
+    LevelMax1 = Fraig_GetMaxLevel( pMan );
+    Fraig_MappingSetChoiceLevels( pMan, 0 );
+    LevelMax2 = Fraig_GetMaxLevel( pMan );
+
+    // report statistics about choices
+    nChoiceNodes = nChoices = 0;
+    for ( i = 0; i < pMan->vNodes->nSize; i++ )
+    {
+        pNode = pMan->vNodes->pArray[i];
+        if ( pNode->pRepr == NULL && pNode->pNextE != NULL )
+        { // this is a choice node = the primary node that has equivalent nodes
+            nChoiceNodes++;
+            for ( pTemp = pNode; pTemp; pTemp = pTemp->pNextE )
+                nChoices++;
+        }
+    }
+    printf( "Maximum level: Original = %d. Reduced due to choices = %d.\n", LevelMax1, LevelMax2 );
+    printf( "Choice stats:  Choice nodes = %d. Total choices = %d.\n", nChoiceNodes, nChoices );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Returns 1 if the node is the root of EXOR/NEXOR gate.]
+
+  Description [The node can be complemented.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_NodeIsExorType( Fraig_Node_t * pNode )
+{
+    Fraig_Node_t * pNode1, * pNode2;
+    // make the node regular (it does not matter for EXOR/NEXOR)
+    pNode = Fraig_Regular(pNode);
+    // if the node or its children are not ANDs or not compl, this cannot be EXOR type
+    if ( !Fraig_NodeIsAnd(pNode) )
+        return 0;
+    if ( !Fraig_NodeIsAnd(pNode->p1) || !Fraig_IsComplement(pNode->p1) )
+        return 0;
+    if ( !Fraig_NodeIsAnd(pNode->p2) || !Fraig_IsComplement(pNode->p2) )
+        return 0;
+
+    // get children
+    pNode1 = Fraig_Regular(pNode->p1);
+    pNode2 = Fraig_Regular(pNode->p2);
+    assert( pNode1->Num < pNode2->Num );
+
+    // compare grandchildren
+    return pNode1->p1 == Fraig_Not(pNode2->p1) && pNode1->p2 == Fraig_Not(pNode2->p2);
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Returns 1 if the node is the root of MUX or EXOR/NEXOR.]
+
+  Description [The node can be complemented.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_NodeIsMuxType( Fraig_Node_t * pNode )
+{
+    Fraig_Node_t * pNode1, * pNode2;
+
+    // make the node regular (it does not matter for EXOR/NEXOR)
+    pNode = Fraig_Regular(pNode);
+    // if the node or its children are not ANDs or not compl, this cannot be EXOR type
+    if ( !Fraig_NodeIsAnd(pNode) )
+        return 0;
+    if ( !Fraig_NodeIsAnd(pNode->p1) || !Fraig_IsComplement(pNode->p1) )
+        return 0;
+    if ( !Fraig_NodeIsAnd(pNode->p2) || !Fraig_IsComplement(pNode->p2) )
+        return 0;
+
+    // get children
+    pNode1 = Fraig_Regular(pNode->p1);
+    pNode2 = Fraig_Regular(pNode->p2);
+    assert( pNode1->Num < pNode2->Num );
+
+    // compare grandchildren
+    // node is an EXOR/NEXOR
+    if ( pNode1->p1 == Fraig_Not(pNode2->p1) && pNode1->p2 == Fraig_Not(pNode2->p2) )
+        return 1; 
+
+    // otherwise the node is MUX iff it has a pair of equal grandchildren
+    return pNode1->p1 == Fraig_Not(pNode2->p1) || 
+           pNode1->p1 == Fraig_Not(pNode2->p2) ||
+           pNode1->p2 == Fraig_Not(pNode2->p1) ||
+           pNode1->p2 == Fraig_Not(pNode2->p2);
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Returns 1 if the node is EXOR, 0 if it is NEXOR.]
+
+  Description [The node should be EXOR type and not complemented.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_NodeIsExor( Fraig_Node_t * pNode )
+{
+    Fraig_Node_t * pNode1;
+    assert( !Fraig_IsComplement(pNode) );
+    assert( Fraig_NodeIsExorType(pNode) );
+    assert( Fraig_IsComplement(pNode->p1) );
+    // get children
+    pNode1 = Fraig_Regular(pNode->p1);
+    return Fraig_IsComplement(pNode1->p1) == Fraig_IsComplement(pNode1->p2);
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Recognizes what nodes are control and data inputs of a MUX.]
+
+  Description [If the node is a MUX, returns the control variable C.
+  Assigns nodes T and E to be the then and else variables of the MUX. 
+  Node C is never complemented. Nodes T and E can be complemented.
+  This function also recognizes EXOR/NEXOR gates as MUXes.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_Node_t * Fraig_NodeRecognizeMux( Fraig_Node_t * pNode, Fraig_Node_t ** ppNodeT, Fraig_Node_t ** ppNodeE )
+{
+    Fraig_Node_t * pNode1, * pNode2;
+    assert( !Fraig_IsComplement(pNode) );
+    assert( Fraig_NodeIsMuxType(pNode) );
+    // get children
+    pNode1 = Fraig_Regular(pNode->p1);
+    pNode2 = Fraig_Regular(pNode->p2);
+    // find the control variable
+    if ( pNode1->p1 == Fraig_Not(pNode2->p1) )
+    {
+        if ( Fraig_IsComplement(pNode1->p1) )
+        { // pNode2->p1 is positive phase of C
+            *ppNodeT = Fraig_Not(pNode2->p2);
+            *ppNodeE = Fraig_Not(pNode1->p2);
+            return pNode2->p1;
+        }
+        else
+        { // pNode1->p1 is positive phase of C
+            *ppNodeT = Fraig_Not(pNode1->p2);
+            *ppNodeE = Fraig_Not(pNode2->p2);
+            return pNode1->p1;
+        }
+    }
+    else if ( pNode1->p1 == Fraig_Not(pNode2->p2) )
+    {
+        if ( Fraig_IsComplement(pNode1->p1) )
+        { // pNode2->p2 is positive phase of C
+            *ppNodeT = Fraig_Not(pNode2->p1);
+            *ppNodeE = Fraig_Not(pNode1->p2);
+            return pNode2->p2;
+        }
+        else
+        { // pNode1->p1 is positive phase of C
+            *ppNodeT = Fraig_Not(pNode1->p2);
+            *ppNodeE = Fraig_Not(pNode2->p1);
+            return pNode1->p1;
+        }
+    }
+    else if ( pNode1->p2 == Fraig_Not(pNode2->p1) )
+    {
+        if ( Fraig_IsComplement(pNode1->p2) )
+        { // pNode2->p1 is positive phase of C
+            *ppNodeT = Fraig_Not(pNode2->p2);
+            *ppNodeE = Fraig_Not(pNode1->p1);
+            return pNode2->p1;
+        }
+        else
+        { // pNode1->p2 is positive phase of C
+            *ppNodeT = Fraig_Not(pNode1->p1);
+            *ppNodeE = Fraig_Not(pNode2->p2);
+            return pNode1->p2;
+        }
+    }
+    else if ( pNode1->p2 == Fraig_Not(pNode2->p2) )
+    {
+        if ( Fraig_IsComplement(pNode1->p2) )
+        { // pNode2->p2 is positive phase of C
+            *ppNodeT = Fraig_Not(pNode2->p1);
+            *ppNodeE = Fraig_Not(pNode1->p1);
+            return pNode2->p2;
+        }
+        else
+        { // pNode1->p2 is positive phase of C
+            *ppNodeT = Fraig_Not(pNode1->p1);
+            *ppNodeE = Fraig_Not(pNode2->p1);
+            return pNode1->p2;
+        }
+    }
+    assert( 0 ); // this is not MUX
+    return NULL;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Counts the number of EXOR type nodes.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_ManCountExors( Fraig_Man_t * pMan )
+{
+    int i, nExors;
+    nExors = 0;
+    for ( i = 0; i < pMan->vNodes->nSize; i++ )
+        nExors += Fraig_NodeIsExorType( pMan->vNodes->pArray[i] );
+    return nExors;
+
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Counts the number of EXOR type nodes.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_ManCountMuxes( Fraig_Man_t * pMan )
+{
+    int i, nMuxes;
+    nMuxes = 0;
+    for ( i = 0; i < pMan->vNodes->nSize; i++ )
+        nMuxes += Fraig_NodeIsMuxType( pMan->vNodes->pArray[i] );
+    return nMuxes;
+
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Returns 1 if siminfo of Node1 is contained in siminfo of Node2.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_NodeSimsContained( Fraig_Man_t * pMan, Fraig_Node_t * pNode1, Fraig_Node_t * pNode2 )
+{
+    unsigned * pUnsigned1, * pUnsigned2;
+    int i;
+
+    // compare random siminfo
+    pUnsigned1 = pNode1->puSimR;
+    pUnsigned2 = pNode2->puSimR;
+    for ( i = 0; i < pMan->nWordsRand; i++ )
+        if ( pUnsigned1[i] & ~pUnsigned2[i] )
+            return 0;
+
+    // compare systematic siminfo
+    pUnsigned1 = pNode1->puSimD;
+    pUnsigned2 = pNode2->puSimD;
+    for ( i = 0; i < pMan->iWordStart; i++ )
+        if ( pUnsigned1[i] & ~pUnsigned2[i] )
+            return 0;
+
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Count the number of PI variables.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_CountPis( Fraig_Man_t * p, Msat_IntVec_t * vVarNums )
+{
+    int * pVars, nVars, i, Counter;
+
+    nVars = Msat_IntVecReadSize(vVarNums);
+    pVars = Msat_IntVecReadArray(vVarNums);
+    Counter = 0;
+    for ( i = 0; i < nVars; i++ )
+        Counter += Fraig_NodeIsVar( p->vNodes->pArray[pVars[i]] );
+    return Counter;
+}
+
+
+
+/**Function*************************************************************
+
+  Synopsis    [Counts the number of EXOR type nodes.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_ManPrintRefs( Fraig_Man_t * pMan )
+{
+    Fraig_NodeVec_t * vPivots;
+    Fraig_Node_t * pNode, * pNode2;
+    int i, k, Counter, nProved;
+    int clk;
+
+    vPivots = Fraig_NodeVecAlloc( 1000 );
+    for ( i = 0; i < pMan->vNodes->nSize; i++ )
+    {
+        pNode = pMan->vNodes->pArray[i];
+
+        if ( pNode->nOnes == 0 || pNode->nOnes == (unsigned)pMan->nWordsRand * 32 )
+            continue;
+
+        if ( pNode->nRefs > 5 )
+        {
+            Fraig_NodeVecPush( vPivots, pNode );
+//            printf( "Node %6d : nRefs = %2d   Level = %3d.\n", pNode->Num, pNode->nRefs, pNode->Level );
+        }
+    }
+    printf( "Total nodes = %d. Referenced nodes = %d.\n", pMan->vNodes->nSize, vPivots->nSize );
+
+clk = clock();
+    // count implications
+    Counter = nProved = 0;
+    for ( i = 0; i < vPivots->nSize; i++ )
+        for ( k = i+1; k < vPivots->nSize; k++ )
+        {
+            pNode  = vPivots->pArray[i];
+            pNode2 = vPivots->pArray[k];
+            if ( Fraig_NodeSimsContained( pMan, pNode, pNode2 ) )
+            {
+                if ( Fraig_NodeIsImplication( pMan, pNode, pNode2, -1 ) )
+                    nProved++;
+                Counter++;
+            }
+            else if ( Fraig_NodeSimsContained( pMan, pNode2, pNode ) )
+            {
+                if ( Fraig_NodeIsImplication( pMan, pNode2, pNode, -1 ) )
+                    nProved++;
+                Counter++;
+            }
+        }
+    printf( "Number of candidate pairs = %d.  Proved = %d.\n", Counter, nProved );
+PRT( "Time", clock() - clk );
+    return 0;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Checks if pNew exists among the implication fanins of pOld.]
+
+  Description [If pNew is an implication fanin of pOld, returns 1. 
+  If Fraig_Not(pNew) is an implication fanin of pOld, return -1.
+  Otherwise returns 0.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_NodeIsInSupergate( Fraig_Node_t * pOld, Fraig_Node_t * pNew )
+{
+    int RetValue1, RetValue2;
+    if ( Fraig_Regular(pOld) == Fraig_Regular(pNew) )
+        return (pOld == pNew)? 1 : -1;
+    if ( Fraig_IsComplement(pOld) || Fraig_NodeIsVar(pOld) )
+        return 0;
+    RetValue1 = Fraig_NodeIsInSupergate( pOld->p1, pNew );
+    RetValue2 = Fraig_NodeIsInSupergate( pOld->p2, pNew );
+    if ( RetValue1 == -1 || RetValue2 == -1 )
+        return -1;
+    if ( RetValue1 ==  1 || RetValue2 ==  1 )
+        return 1;
+    return 0;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Returns the array of nodes to be combined into one multi-input AND-gate.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_CollectSupergate_rec( Fraig_Node_t * pNode, Fraig_NodeVec_t * vSuper, int fFirst, int fStopAtMux )
+{
+    // if the new node is complemented or a PI, another gate begins
+//    if ( Fraig_IsComplement(pNode) || Fraig_NodeIsVar(pNode) || Fraig_NodeIsMuxType(pNode) )
+    if ( (!fFirst && Fraig_Regular(pNode)->nRefs > 1) || 
+          Fraig_IsComplement(pNode) || Fraig_NodeIsVar(pNode) || 
+          (fStopAtMux && Fraig_NodeIsMuxType(pNode)) )
+    {
+        Fraig_NodeVecPushUnique( vSuper, pNode );
+        return;
+    }
+    // go through the branches
+    Fraig_CollectSupergate_rec( pNode->p1, vSuper, 0, fStopAtMux );
+    Fraig_CollectSupergate_rec( pNode->p2, vSuper, 0, fStopAtMux );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Returns the array of nodes to be combined into one multi-input AND-gate.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_NodeVec_t * Fraig_CollectSupergate( Fraig_Node_t * pNode, int fStopAtMux )
+{
+    Fraig_NodeVec_t * vSuper;
+    vSuper = Fraig_NodeVecAlloc( 8 );
+    Fraig_CollectSupergate_rec( pNode, vSuper, 1, fStopAtMux );
+    return vSuper;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_ManIncrementTravId( Fraig_Man_t * pMan )
+{
+    pMan->nTravIds2++;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_NodeSetTravIdCurrent( Fraig_Man_t * pMan, Fraig_Node_t * pNode )
+{
+    pNode->TravId2 = pMan->nTravIds2;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_NodeIsTravIdCurrent( Fraig_Man_t * pMan, Fraig_Node_t * pNode )
+{
+    return pNode->TravId2 == pMan->nTravIds2;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_NodeIsTravIdPrevious( Fraig_Man_t * pMan, Fraig_Node_t * pNode )
+{
+    return pNode->TravId2 == pMan->nTravIds2 - 1;
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/fraig/fraigVec.c b/src/sat/fraig/fraigVec.c
new file mode 100644
index 00000000..ba3feecd
--- /dev/null
+++ b/src/sat/fraig/fraigVec.c
@@ -0,0 +1,545 @@
+/**CFile****************************************************************
+
+  FileName    [fraigVec.c]
+
+  PackageName [FRAIG: Functionally reduced AND-INV graphs.]
+
+  Synopsis    [Vector of FRAIG nodes.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 2.0. Started - October 1, 2004]
+
+  Revision    [$Id: fraigVec.c,v 1.7 2005/07/08 01:01:34 alanmi Exp $]
+
+***********************************************************************/
+
+#include "fraigInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Allocates a vector with the given capacity.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_NodeVec_t * Fraig_NodeVecAlloc( int nCap )
+{
+    Fraig_NodeVec_t * p;
+    p = ALLOC( Fraig_NodeVec_t, 1 );
+    if ( nCap > 0 && nCap < 8 )
+        nCap = 8;
+    p->nSize  = 0;
+    p->nCap   = nCap;
+    p->pArray = p->nCap? ALLOC( Fraig_Node_t *, p->nCap ) : NULL;
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_NodeVecFree( Fraig_NodeVec_t * p )
+{
+    FREE( p->pArray );
+    FREE( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Duplicates the integer array.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_NodeVec_t * Fraig_NodeVecDup( Fraig_NodeVec_t * pVec )
+{
+    Fraig_NodeVec_t * p;
+    p = ALLOC( Fraig_NodeVec_t, 1 );
+    p->nSize  = pVec->nSize;
+    p->nCap   = pVec->nCap;
+    p->pArray = p->nCap? ALLOC( Fraig_Node_t *, p->nCap ) : NULL;
+    memcpy( p->pArray, pVec->pArray, sizeof(Fraig_Node_t *) * pVec->nSize );
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_Node_t ** Fraig_NodeVecReadArray( Fraig_NodeVec_t * p )
+{
+    return p->pArray;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_NodeVecReadSize( Fraig_NodeVec_t * p )
+{
+    return p->nSize;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Resizes the vector to the given capacity.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_NodeVecGrow( Fraig_NodeVec_t * p, int nCapMin )
+{
+    if ( p->nCap >= nCapMin )
+        return;
+    p->pArray = REALLOC( Fraig_Node_t *, p->pArray, nCapMin ); 
+    p->nCap   = nCapMin;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_NodeVecShrink( Fraig_NodeVec_t * p, int nSizeNew )
+{
+    assert( p->nSize >= nSizeNew );
+    p->nSize = nSizeNew;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_NodeVecClear( Fraig_NodeVec_t * p )
+{
+    p->nSize = 0;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_NodeVecPush( Fraig_NodeVec_t * p, Fraig_Node_t * Entry )
+{
+    if ( p->nSize == p->nCap )
+    {
+        if ( p->nCap < 16 )
+            Fraig_NodeVecGrow( p, 16 );
+        else
+            Fraig_NodeVecGrow( p, 2 * p->nCap );
+    }
+    p->pArray[p->nSize++] = Entry;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Add the element while ensuring uniqueness.]
+
+  Description [Returns 1 if the element was found, and 0 if it was new. ]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_NodeVecPushUnique( Fraig_NodeVec_t * p, Fraig_Node_t * Entry )
+{
+    int i;
+    for ( i = 0; i < p->nSize; i++ )
+        if ( p->pArray[i] == Entry )
+            return 1;
+    Fraig_NodeVecPush( p, Entry );
+    return 0;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Inserts a new node in the order by arrival times.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_NodeVecPushOrder( Fraig_NodeVec_t * p, Fraig_Node_t * pNode )
+{
+    Fraig_Node_t * pNode1, * pNode2;
+    int i;
+    Fraig_NodeVecPush( p, pNode );
+    // find the p of the node
+    for ( i = p->nSize-1; i > 0; i-- )
+    {
+        pNode1 = p->pArray[i  ];
+        pNode2 = p->pArray[i-1];
+        if ( pNode1 >= pNode2 )
+            break;
+        p->pArray[i  ] = pNode2;
+        p->pArray[i-1] = pNode1;
+    }
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Add the element while ensuring uniqueness in the order.]
+
+  Description [Returns 1 if the element was found, and 0 if it was new. ]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_NodeVecPushUniqueOrder( Fraig_NodeVec_t * p, Fraig_Node_t * pNode )
+{
+    int i;
+    for ( i = 0; i < p->nSize; i++ )
+        if ( p->pArray[i] == pNode )
+            return 1;
+    Fraig_NodeVecPushOrder( p, pNode );
+    return 0;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Inserts a new node in the order by arrival times.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_NodeVecPushOrderByLevel( Fraig_NodeVec_t * p, Fraig_Node_t * pNode )
+{
+    Fraig_Node_t * pNode1, * pNode2;
+    int i;
+    Fraig_NodeVecPush( p, pNode );
+    // find the p of the node
+    for ( i = p->nSize-1; i > 0; i-- )
+    {
+        pNode1 = p->pArray[i  ];
+        pNode2 = p->pArray[i-1];
+        if ( Fraig_Regular(pNode1)->Level <= Fraig_Regular(pNode2)->Level )
+            break;
+        p->pArray[i  ] = pNode2;
+        p->pArray[i-1] = pNode1;
+    }
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Add the element while ensuring uniqueness in the order.]
+
+  Description [Returns 1 if the element was found, and 0 if it was new. ]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_NodeVecPushUniqueOrderByLevel( Fraig_NodeVec_t * p, Fraig_Node_t * pNode )
+{
+    int i;
+    for ( i = 0; i < p->nSize; i++ )
+        if ( p->pArray[i] == pNode )
+            return 1;
+    Fraig_NodeVecPushOrderByLevel( p, pNode );
+    return 0;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_Node_t * Fraig_NodeVecPop( Fraig_NodeVec_t * p )
+{
+    return p->pArray[--p->nSize];
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_NodeVecRemove( Fraig_NodeVec_t * p, Fraig_Node_t * Entry )
+{
+    int i;
+    for ( i = 0; i < p->nSize; i++ )
+        if ( p->pArray[i] == Entry )
+            break;
+    assert( i < p->nSize );
+    for ( i++; i < p->nSize; i++ )
+        p->pArray[i-1] = p->pArray[i];
+    p->nSize--;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_NodeVecWriteEntry( Fraig_NodeVec_t * p, int i, Fraig_Node_t * Entry )
+{
+    assert( i >= 0 && i < p->nSize );
+    p->pArray[i] = Entry;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Fraig_Node_t * Fraig_NodeVecReadEntry( Fraig_NodeVec_t * p, int i )
+{
+    assert( i >= 0 && i < p->nSize );
+    return p->pArray[i];
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Comparison procedure for two clauses.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_NodeVecCompareLevelsIncreasing( Fraig_Node_t ** pp1, Fraig_Node_t ** pp2 )
+{
+    int Level1 = Fraig_Regular(*pp1)->Level;
+    int Level2 = Fraig_Regular(*pp2)->Level;
+    if ( Level1 < Level2 )
+        return -1;
+    if ( Level1 > Level2 )
+        return 1;
+    return 0; 
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Comparison procedure for two clauses.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_NodeVecCompareLevelsDecreasing( Fraig_Node_t ** pp1, Fraig_Node_t ** pp2 )
+{
+    int Level1 = Fraig_Regular(*pp1)->Level;
+    int Level2 = Fraig_Regular(*pp2)->Level;
+    if ( Level1 > Level2 )
+        return -1;
+    if ( Level1 < Level2 )
+        return 1;
+    return 0; 
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Comparison procedure for two clauses.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_NodeVecCompareNumbers( Fraig_Node_t ** pp1, Fraig_Node_t ** pp2 )
+{
+    int Num1 = Fraig_Regular(*pp1)->Num;
+    int Num2 = Fraig_Regular(*pp2)->Num;
+    if ( Num1 < Num2 )
+        return -1;
+    if ( Num1 > Num2 )
+        return 1;
+    return 0; 
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Comparison procedure for two clauses.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Fraig_NodeVecCompareRefCounts( Fraig_Node_t ** pp1, Fraig_Node_t ** pp2 )
+{
+    int nRefs1 = Fraig_Regular(*pp1)->nRefs;
+    int nRefs2 = Fraig_Regular(*pp2)->nRefs;
+
+    if ( nRefs1 < nRefs2 )
+        return -1;
+    if ( nRefs1 > nRefs2 )
+        return 1;
+
+    nRefs1 = Fraig_Regular(*pp1)->Level;
+    nRefs2 = Fraig_Regular(*pp2)->Level;
+
+    if ( nRefs1 < nRefs2 )
+        return -1;
+    if ( nRefs1 > nRefs2 )
+        return 1;
+    return 0; 
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Sorting the entries by their integer value.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_NodeVecSortByLevel( Fraig_NodeVec_t * p, int fIncreasing )
+{
+    if ( fIncreasing )
+        qsort( (void *)p->pArray, p->nSize, sizeof(Fraig_Node_t *), 
+                (int (*)(const void *, const void *)) Fraig_NodeVecCompareLevelsIncreasing );
+    else 
+        qsort( (void *)p->pArray, p->nSize, sizeof(Fraig_Node_t *), 
+                (int (*)(const void *, const void *)) Fraig_NodeVecCompareLevelsDecreasing );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Sorting the entries by their integer value.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_NodeVecSortByNumber( Fraig_NodeVec_t * p )
+{
+    qsort( (void *)p->pArray, p->nSize, sizeof(Fraig_Node_t *), 
+            (int (*)(const void *, const void *)) Fraig_NodeVecCompareNumbers );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Sorting the entries by their integer value.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Fraig_NodeVecSortByRefCount( Fraig_NodeVec_t * p )
+{
+    qsort( (void *)p->pArray, p->nSize, sizeof(Fraig_Node_t *), 
+            (int (*)(const void *, const void *)) Fraig_NodeVecCompareRefCounts );
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
diff --git a/src/sat/fraig/module.make b/src/sat/fraig/module.make
new file mode 100644
index 00000000..cc6eb9d3
--- /dev/null
+++ b/src/sat/fraig/module.make
@@ -0,0 +1,12 @@
+SRC +=  src/sat/fraig/fraigApi.c \
+    src/sat/fraig/fraigCanon.c \
+    src/sat/fraig/fraigFanout.c \
+    src/sat/fraig/fraigFeed.c \
+    src/sat/fraig/fraigMan.c \
+    src/sat/fraig/fraigMem.c \
+    src/sat/fraig/fraigNode.c \
+    src/sat/fraig/fraigPrime.c \
+    src/sat/fraig/fraigSat.c \
+    src/sat/fraig/fraigTable.c \
+    src/sat/fraig/fraigUtil.c \
+    src/sat/fraig/fraigVec.c
diff --git a/src/sat/msat/module.make b/src/sat/msat/module.make
new file mode 100644
index 00000000..0dadfbe1
--- /dev/null
+++ b/src/sat/msat/module.make
@@ -0,0 +1,13 @@
+SRC +=  src/sat/msat/msatActivity.c \
+    src/sat/msat/msatClause.c \
+    src/sat/msat/msatClauseVec.c \
+    src/sat/msat/msatMem.c \
+    src/sat/msat/msatOrderJ.c \
+    src/sat/msat/msatQueue.c \
+    src/sat/msat/msatRead.c \
+    src/sat/msat/msatSolverApi.c \
+    src/sat/msat/msatSolverCore.c \
+    src/sat/msat/msatSolverIo.c \
+    src/sat/msat/msatSolverSearch.c \
+    src/sat/msat/msatSort.c \
+    src/sat/msat/msatVec.c
diff --git a/src/sat/msat/msat.h b/src/sat/msat/msat.h
new file mode 100644
index 00000000..53353ba6
--- /dev/null
+++ b/src/sat/msat/msat.h
@@ -0,0 +1,172 @@
+/**CFile****************************************************************
+
+  FileName    [msat.h]
+
+  PackageName [A C version of SAT solver MINISAT, originally developed 
+  in C++ by Niklas Een and Niklas Sorensson, Chalmers University of 
+  Technology, Sweden: http://www.cs.chalmers.se/~een/Satzoo.]
+
+  Synopsis    [External definitions of the solver.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - January 1, 2004.]
+
+  Revision    [$Id: msat.h,v 1.6 2004/05/12 06:30:20 satrajit Exp $]
+
+***********************************************************************/
+
+#ifndef __MSAT_H__
+#define __MSAT_H__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+////////////////////////////////////////////////////////////////////////
+///                          INCLUDES                                ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                         PARAMETERS                               ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                    STRUCTURE DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+#ifdef bool
+#undef bool
+#endif
+
+#ifndef __MVTYPES_H__
+typedef int  bool;
+#endif
+
+typedef struct Msat_Solver_t_      Msat_Solver_t;
+
+// the vector of intergers and of clauses
+typedef struct Msat_IntVec_t_      Msat_IntVec_t;
+typedef struct Msat_ClauseVec_t_   Msat_ClauseVec_t;
+typedef struct Msat_VarHeap_t_     Msat_VarHeap_t;
+
+// the return value of the solver
+typedef enum { MSAT_FALSE = -1, MSAT_UNKNOWN = 0, MSAT_TRUE = 1 } Msat_Type_t;
+
+// representation of variables and literals
+// the literal (l) is the variable (v) and the sign (s)
+// s = 0 the variable is positive
+// s = 1 the variable is negative
+#define MSAT_VAR2LIT(v,s) (2*(v)+(s)) 
+#define MSAT_LITNOT(l)    ((l)^1)
+#define MSAT_LITSIGN(l)   ((l)&1)     
+#define MSAT_LIT2VAR(l)   ((l)>>1)
+
+////////////////////////////////////////////////////////////////////////
+///                       GLOBAL VARIABLES                           ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                       MACRO DEFINITIONS                          ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DECLARATIONS                        ///
+////////////////////////////////////////////////////////////////////////
+
+/*=== satRead.c ============================================================*/
+extern bool             Msat_SolverParseDimacs( FILE * pFile, Msat_Solver_t ** p, int fVerbose );
+/*=== satSolver.c ===========================================================*/
+// adding vars, clauses, simplifying the database, and solving
+extern bool             Msat_SolverAddVar( Msat_Solver_t * p, int Level );
+extern bool             Msat_SolverAddClause( Msat_Solver_t * p, Msat_IntVec_t * pLits );
+extern bool             Msat_SolverSimplifyDB( Msat_Solver_t * p );
+extern bool             Msat_SolverSolve( Msat_Solver_t * p, Msat_IntVec_t * pVecAssumps, int nBackTrackLimit, int nTimeLimit );
+// printing stats, assignments, and clauses
+extern void             Msat_SolverPrintStats( Msat_Solver_t * p );
+extern void             Msat_SolverPrintAssignment( Msat_Solver_t * p );
+extern void             Msat_SolverPrintClauses( Msat_Solver_t * p );
+extern void             Msat_SolverWriteDimacs( Msat_Solver_t * p, char * pFileName );
+// access to the solver internal data
+extern int              Msat_SolverReadVarNum( Msat_Solver_t * p );
+extern int              Msat_SolverReadClauseNum( Msat_Solver_t * p );
+extern int              Msat_SolverReadVarAllocNum( Msat_Solver_t * p );
+extern int *            Msat_SolverReadAssignsArray( Msat_Solver_t * p );
+extern int *            Msat_SolverReadModelArray( Msat_Solver_t * p );
+extern unsigned         Msat_SolverReadTruth( Msat_Solver_t * p );
+extern int              Msat_SolverReadBackTracks( Msat_Solver_t * p );
+extern int              Msat_SolverReadInspects( Msat_Solver_t * p );
+extern void             Msat_SolverSetVerbosity( Msat_Solver_t * p, int fVerbose );
+extern void             Msat_SolverSetProofWriting( Msat_Solver_t * p, int fProof );
+extern void             Msat_SolverSetVarTypeA( Msat_Solver_t * p, int Var );
+extern void             Msat_SolverSetVarMap( Msat_Solver_t * p, Msat_IntVec_t * vVarMap );
+extern void             Msat_SolverMarkLastClauseTypeA( Msat_Solver_t * p );
+extern void             Msat_SolverMarkClausesStart( Msat_Solver_t * p );
+extern float *          Msat_SolverReadFactors( Msat_Solver_t * p );
+// returns the solution after incremental solving
+extern int              Msat_SolverReadSolutions( Msat_Solver_t * p );
+extern int *            Msat_SolverReadSolutionsArray( Msat_Solver_t * p );
+extern Msat_ClauseVec_t *  Msat_SolverReadAdjacents( Msat_Solver_t * p );
+extern Msat_IntVec_t *  Msat_SolverReadConeVars( Msat_Solver_t * p );
+extern Msat_IntVec_t *  Msat_SolverReadVarsUsed( Msat_Solver_t * p );
+/*=== satSolverSearch.c ===========================================================*/
+extern void             Msat_SolverRemoveLearned( Msat_Solver_t * p );
+extern void             Msat_SolverRemoveMarked( Msat_Solver_t * p );
+/*=== satSolverApi.c ===========================================================*/
+// allocation, cleaning, and freeing the solver
+extern Msat_Solver_t *  Msat_SolverAlloc( int nVars, double dClaInc, double dClaDecay, double dVarInc, double dVarDecay, bool fVerbose );
+extern void             Msat_SolverResize( Msat_Solver_t * pMan, int nVarsAlloc );
+extern void             Msat_SolverClean( Msat_Solver_t * p, int nVars );
+extern void             Msat_SolverPrepare( Msat_Solver_t * pSat, Msat_IntVec_t * vVars );
+extern void             Msat_SolverFree( Msat_Solver_t * p );
+/*=== satVec.c ===========================================================*/
+extern Msat_IntVec_t *  Msat_IntVecAlloc( int nCap );
+extern Msat_IntVec_t *  Msat_IntVecAllocArray( int * pArray, int nSize );
+extern Msat_IntVec_t *  Msat_IntVecAllocArrayCopy( int * pArray, int nSize );
+extern Msat_IntVec_t *  Msat_IntVecDup( Msat_IntVec_t * pVec );
+extern Msat_IntVec_t *  Msat_IntVecDupArray( Msat_IntVec_t * pVec );
+extern void             Msat_IntVecFree( Msat_IntVec_t * p );
+extern void             Msat_IntVecFill( Msat_IntVec_t * p, int nSize, int Entry );
+extern int *            Msat_IntVecReleaseArray( Msat_IntVec_t * p );
+extern int *            Msat_IntVecReadArray( Msat_IntVec_t * p );
+extern int              Msat_IntVecReadSize( Msat_IntVec_t * p );
+extern int              Msat_IntVecReadEntry( Msat_IntVec_t * p, int i );
+extern int              Msat_IntVecReadEntryLast( Msat_IntVec_t * p );
+extern void             Msat_IntVecWriteEntry( Msat_IntVec_t * p, int i, int Entry );
+extern void             Msat_IntVecGrow( Msat_IntVec_t * p, int nCapMin );
+extern void             Msat_IntVecShrink( Msat_IntVec_t * p, int nSizeNew );
+extern void             Msat_IntVecClear( Msat_IntVec_t * p );
+extern void             Msat_IntVecPush( Msat_IntVec_t * p, int Entry );
+extern int              Msat_IntVecPushUnique( Msat_IntVec_t * p, int Entry );
+extern void             Msat_IntVecPushUniqueOrder( Msat_IntVec_t * p, int Entry, int fIncrease );
+extern int              Msat_IntVecPop( Msat_IntVec_t * p );
+extern void             Msat_IntVecSort( Msat_IntVec_t * p, int fReverse );
+/*=== satHeap.c ===========================================================*/
+extern Msat_VarHeap_t * Msat_VarHeapAlloc();
+extern void             Msat_VarHeapSetActivity( Msat_VarHeap_t * p, double * pActivity );
+extern void             Msat_VarHeapStart( Msat_VarHeap_t * p, int * pVars, int nVars, int nVarsAlloc );
+extern void             Msat_VarHeapGrow( Msat_VarHeap_t * p, int nSize );
+extern void             Msat_VarHeapStop( Msat_VarHeap_t * p );
+extern void             Msat_VarHeapPrint( FILE * pFile, Msat_VarHeap_t * p );
+extern void             Msat_VarHeapCheck( Msat_VarHeap_t * p );
+extern void             Msat_VarHeapCheckOne( Msat_VarHeap_t * p, int iVar );
+extern int              Msat_VarHeapContainsVar( Msat_VarHeap_t * p, int iVar );
+extern void             Msat_VarHeapInsert( Msat_VarHeap_t * p, int iVar );  
+extern void             Msat_VarHeapUpdate( Msat_VarHeap_t * p, int iVar );  
+extern void             Msat_VarHeapDelete( Msat_VarHeap_t * p, int iVar );  
+extern double           Msat_VarHeapReadMaxWeight( Msat_VarHeap_t * p );
+extern int              Msat_VarHeapCountNodes( Msat_VarHeap_t * p, double WeightLimit );  
+extern int              Msat_VarHeapReadMax( Msat_VarHeap_t * p );  
+extern int              Msat_VarHeapGetMax( Msat_VarHeap_t * p );  
+ 
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
diff --git a/src/sat/msat/msatActivity.c b/src/sat/msat/msatActivity.c
new file mode 100644
index 00000000..1cd795bd
--- /dev/null
+++ b/src/sat/msat/msatActivity.c
@@ -0,0 +1,160 @@
+/**CFile****************************************************************
+
+  FileName    [msatActivity.c]
+
+  PackageName [A C version of SAT solver MINISAT, originally developed 
+  in C++ by Niklas Een and Niklas Sorensson, Chalmers University of 
+  Technology, Sweden: http://www.cs.chalmers.se/~een/Satzoo.]
+
+  Synopsis    [Procedures controlling activity of variables and clauses.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - January 1, 2004.]
+
+  Revision    [$Id: msatActivity.c,v 1.0 2004/01/01 1:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include "msatInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverVarBumpActivity( Msat_Solver_t * p, Msat_Lit_t Lit )
+{
+    Msat_Var_t Var;
+    if ( p->dVarDecay < 0 ) // (negative decay means static variable order -- don't bump)
+        return;
+    Var = MSAT_LIT2VAR(Lit);
+    p->pdActivity[Var] += p->dVarInc;
+//    p->pdActivity[Var] += p->dVarInc * p->pFactors[Var];
+    if ( p->pdActivity[Var] > 1e100 )
+        Msat_SolverVarRescaleActivity( p );
+    Msat_OrderUpdate( p->pOrder, Var );
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverVarDecayActivity( Msat_Solver_t * p )
+{
+    if ( p->dVarDecay >= 0 )
+        p->dVarInc *= p->dVarDecay;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Divide all variable activities by 1e100.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverVarRescaleActivity( Msat_Solver_t * p )
+{
+    int i;
+    for ( i = 0; i < p->nVars; i++ )
+        p->pdActivity[i] *= 1e-100;
+    p->dVarInc *= 1e-100;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverClaBumpActivity( Msat_Solver_t * p, Msat_Clause_t * pC )
+{
+    float Activ;
+    Activ = Msat_ClauseReadActivity(pC);
+    if ( Activ + p->dClaInc > 1e20 )
+    {
+        Msat_SolverClaRescaleActivity( p );
+        Activ = Msat_ClauseReadActivity( pC );
+    }
+    Msat_ClauseWriteActivity( pC, Activ + (float)p->dClaInc );
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverClaDecayActivity( Msat_Solver_t * p )
+{
+    p->dClaInc *= p->dClaDecay;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Divide all constraint activities by 1e20.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverClaRescaleActivity( Msat_Solver_t * p )
+{
+    Msat_Clause_t ** pLearned;
+    int nLearned, i;
+    float Activ;
+    nLearned = Msat_ClauseVecReadSize( p->vLearned );
+    pLearned = Msat_ClauseVecReadArray( p->vLearned );
+    for ( i = 0; i < nLearned; i++ )
+    {
+        Activ = Msat_ClauseReadActivity( pLearned[i] );
+        Msat_ClauseWriteActivity( pLearned[i], Activ * (float)1e-20 );
+    }
+    p->dClaInc *= 1e-20;
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/msat/msatClause.c b/src/sat/msat/msatClause.c
new file mode 100644
index 00000000..2ba8cd32
--- /dev/null
+++ b/src/sat/msat/msatClause.c
@@ -0,0 +1,529 @@
+/**CFile****************************************************************
+
+  FileName    [msatClause.c]
+
+  PackageName [A C version of SAT solver MINISAT, originally developed 
+  in C++ by Niklas Een and Niklas Sorensson, Chalmers University of 
+  Technology, Sweden: http://www.cs.chalmers.se/~een/Satzoo.]
+
+  Synopsis    [Procedures working with SAT clauses.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - January 1, 2004.]
+
+  Revision    [$Id: msatClause.c,v 1.0 2004/01/01 1:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include "msatInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+struct Msat_Clause_t_
+{
+    int           Num;              // unique number of the clause
+    unsigned      fLearned   :  1;  // 1 if the clause is learned
+    unsigned      fMark      :  1;  // used to mark visited clauses during proof recording
+    unsigned      fTypeA     :  1;  // used to mark clauses belonging to A for interpolant computation
+    unsigned      nSize      : 14;  // the number of literals in the clause
+    unsigned      nSizeAlloc : 15;  // the number of bytes allocated for the clause
+    Msat_Lit_t     pData[0];
+};
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Creates a new clause.]
+
+  Description [Returns FALSE if top-level conflict detected (must be handled); 
+  TRUE otherwise. 'pClause_out' may be set to NULL if clause is already 
+  satisfied by the top-level assignment.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+bool Msat_ClauseCreate( Msat_Solver_t * p, Msat_IntVec_t * vLits, bool fLearned, Msat_Clause_t ** pClause_out )
+{
+    int * pAssigns = Msat_SolverReadAssignsArray(p);
+    Msat_ClauseVec_t ** pvWatched;
+    Msat_Clause_t * pC;
+    int * pLits;
+    int nLits, i, j;
+    int nBytes;
+    Msat_Var_t Var;
+    bool Sign;
+
+    *pClause_out = NULL;
+
+    nLits = Msat_IntVecReadSize(vLits);
+    pLits = Msat_IntVecReadArray(vLits);
+
+    if ( !fLearned ) 
+    {
+        int * pSeen = Msat_SolverReadSeenArray( p );
+        int nSeenId;
+        assert( Msat_SolverReadDecisionLevel(p) == 0 );
+        // sorting literals makes the code trace-equivalent 
+        // with to the original C++ solver
+        Msat_IntVecSort( vLits, 0 );
+        // increment the counter of seen twice
+        nSeenId = Msat_SolverIncrementSeenId( p );
+        nSeenId = Msat_SolverIncrementSeenId( p );
+        // nSeenId - 1 stands for negative
+        // nSeenId     stands for positive
+        // Remove false literals
+
+        // there is a bug here!!!!
+        // when the same var in opposite polarities is given, it drops one polarity!!!
+
+        for ( i = j = 0; i < nLits; i++ ) {
+            // get the corresponding variable
+            Var  = MSAT_LIT2VAR(pLits[i]);
+            Sign = MSAT_LITSIGN(pLits[i]); // Sign=0 for positive
+            // check if we already saw this variable in the this clause
+            if ( pSeen[Var] >= nSeenId - 1 )
+            {
+                if ( (pSeen[Var] != nSeenId) == Sign ) // the same lit
+                    continue;
+                return 1; // two opposite polarity lits -- don't add the clause
+            }
+            // mark the variable as seen
+            pSeen[Var] = nSeenId - !Sign;
+
+            // analize the value of this literal
+            if ( pAssigns[Var] != MSAT_VAR_UNASSIGNED )
+            {
+                if ( pAssigns[Var] == pLits[i] )
+                    return 1;  // the clause is always true -- don't add anything
+                // the literal has no impact - skip it
+                continue;
+            }
+            // otherwise, add this literal to the clause
+            pLits[j++] = pLits[i];
+        }
+        Msat_IntVecShrink( vLits, j );
+        nLits = j;
+/*
+        // the problem with this code is that performance is very
+        // sensitive to the ordering of adjacency lits
+        // the best ordering requires fanins first, next fanouts
+        // this ordering is more convenient to make from FRAIG
+
+        // create the adjacency information
+        if ( nLits > 2 )
+        {
+            Msat_Var_t VarI, VarJ;
+            Msat_IntVec_t * pAdjI, * pAdjJ;
+
+            for ( i = 0; i < nLits; i++ )
+            {
+                VarI = MSAT_LIT2VAR(pLits[i]);
+                pAdjI = (Msat_IntVec_t *)p->vAdjacents->pArray[VarI];
+
+                for ( j = i+1; j < nLits; j++ )
+                {
+                    VarJ = MSAT_LIT2VAR(pLits[j]);
+                    pAdjJ = (Msat_IntVec_t *)p->vAdjacents->pArray[VarJ];
+
+                    Msat_IntVecPushUniqueOrder( pAdjI, VarJ, 1 );
+                    Msat_IntVecPushUniqueOrder( pAdjJ, VarI, 1 );
+                }
+            }
+        }
+*/
+    }
+    // 'vLits' is now the (possibly) reduced vector of literals.
+    if ( nLits == 0 )
+        return 0;
+    if ( nLits == 1 )
+        return Msat_SolverEnqueue( p, pLits[0], NULL );
+
+    // Allocate clause:
+//    nBytes = sizeof(unsigned)*(nLits + 1 + (int)fLearned);
+    nBytes = sizeof(unsigned)*(nLits + 2 + (int)fLearned);
+#ifdef USE_SYSTEM_MEMORY_MANAGEMENT
+    pC = (Msat_Clause_t *)ALLOC( char, nBytes );
+#else
+    pC = (Msat_Clause_t *)Msat_MmStepEntryFetch( Msat_SolverReadMem(p), nBytes );
+#endif
+    pC->Num        = p->nClauses++;
+    pC->fTypeA     = 0;
+    pC->fMark      = 0;
+    pC->fLearned   = fLearned;
+    pC->nSize      = nLits;
+    pC->nSizeAlloc = nBytes;
+    memcpy( pC->pData, pLits, sizeof(int)*nLits );
+
+    // For learnt clauses only:
+    if ( fLearned )
+    {
+        int * pLevel = Msat_SolverReadDecisionLevelArray( p );
+        int iLevelMax, iLevelCur, iLitMax;
+
+        // Put the second watch on the literal with highest decision level:
+        iLitMax = 1;
+        iLevelMax = pLevel[ MSAT_LIT2VAR(pLits[1]) ];
+        for ( i = 2; i < nLits; i++ )
+        {
+            iLevelCur = pLevel[ MSAT_LIT2VAR(pLits[i]) ];
+            assert( iLevelCur != -1 );
+            if ( iLevelMax < iLevelCur )
+            // this is very strange - shouldn't it be???
+            // if ( iLevelMax > iLevelCur )
+                iLevelMax = iLevelCur, iLitMax = i;
+        }
+        pC->pData[1]       = pLits[iLitMax];
+        pC->pData[iLitMax] = pLits[1];
+
+        // Bumping:
+        // (newly learnt clauses should be considered active)
+        Msat_ClauseWriteActivity( pC, 0.0 );
+        Msat_SolverClaBumpActivity( p, pC ); 
+//        if ( nLits < 20 )
+        for ( i = 0; i < nLits; i++ )
+        {
+            Msat_SolverVarBumpActivity( p, pLits[i] );
+//            Msat_SolverVarBumpActivity( p, pLits[i] );
+//            p->pFreq[ MSAT_LIT2VAR(pLits[i]) ]++;
+        }
+    }
+
+    // Store clause:
+    pvWatched = Msat_SolverReadWatchedArray( p );
+    Msat_ClauseVecPush( pvWatched[ MSAT_LITNOT(pC->pData[0]) ], pC );
+    Msat_ClauseVecPush( pvWatched[ MSAT_LITNOT(pC->pData[1]) ], pC );
+    *pClause_out = pC;
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Deallocates the clause.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_ClauseFree( Msat_Solver_t * p, Msat_Clause_t * pC, bool fRemoveWatched )
+{
+    if ( fRemoveWatched )
+    {
+        Msat_Lit_t Lit;
+        Msat_ClauseVec_t ** pvWatched;
+        pvWatched = Msat_SolverReadWatchedArray( p );
+        Lit = MSAT_LITNOT( pC->pData[0] );
+        Msat_ClauseRemoveWatch( pvWatched[Lit], pC );
+        Lit = MSAT_LITNOT( pC->pData[1] );
+        Msat_ClauseRemoveWatch( pvWatched[Lit], pC ); 
+    }
+
+#ifdef USE_SYSTEM_MEMORY_MANAGEMENT
+    free( pC );
+#else
+    Msat_MmStepEntryRecycle( Msat_SolverReadMem(p), (char *)pC, pC->nSizeAlloc );
+#endif
+
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Access the data field of the clause.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+bool  Msat_ClauseReadLearned( Msat_Clause_t * pC )  {  return pC->fLearned; }
+int   Msat_ClauseReadSize( Msat_Clause_t * pC )     {  return pC->nSize;    }
+int * Msat_ClauseReadLits( Msat_Clause_t * pC )     {  return pC->pData;    }
+bool  Msat_ClauseReadMark( Msat_Clause_t * pC )     {  return pC->fMark;    }
+int   Msat_ClauseReadNum( Msat_Clause_t * pC )      {  return pC->Num;      }
+bool  Msat_ClauseReadTypeA( Msat_Clause_t * pC )    {  return pC->fTypeA;    }
+
+void  Msat_ClauseSetMark( Msat_Clause_t * pC, bool fMark )   {  pC->fMark = fMark;   }
+void  Msat_ClauseSetNum( Msat_Clause_t * pC, int Num )       {  pC->Num = Num;       }
+void  Msat_ClauseSetTypeA( Msat_Clause_t * pC, bool fTypeA ) {  pC->fTypeA = fTypeA; }
+
+/**Function*************************************************************
+
+  Synopsis    [Checks whether the learned clause is locked.]
+
+  Description [The clause may be locked if it is the reason of a
+  recent conflict. Such clause cannot be removed from the database.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+bool Msat_ClauseIsLocked( Msat_Solver_t * p, Msat_Clause_t * pC )
+{
+    Msat_Clause_t ** pReasons = Msat_SolverReadReasonArray( p );
+    return (bool)(pReasons[MSAT_LIT2VAR(pC->pData[0])] == pC);
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Reads the activity of the given clause.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+float Msat_ClauseReadActivity( Msat_Clause_t * pC )
+{
+    return *((float *)(pC->pData + pC->nSize));
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Sets the activity of the clause.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_ClauseWriteActivity( Msat_Clause_t * pC, float Num )
+{
+    *((float *)(pC->pData + pC->nSize)) = Num;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Propages the assignment.]
+
+  Description [The literal that has become true (Lit) is given to this 
+  procedure. The array of current variable assignments is given for
+  efficiency. The output literal (pLit_out) can be the second watched
+  literal (if TRUE is returned) or the conflict literal (if FALSE is 
+  returned). This messy interface is used to improve performance.
+  This procedure accounts for ~50% of the runtime of the solver.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+bool Msat_ClausePropagate( Msat_Clause_t * pC, Msat_Lit_t Lit, int * pAssigns, Msat_Lit_t * pLit_out )
+{
+    // make sure the false literal is pC->pData[1]
+    Msat_Lit_t LitF = MSAT_LITNOT(Lit);
+    if ( pC->pData[0] == LitF )
+         pC->pData[0] = pC->pData[1], pC->pData[1] = LitF;
+    assert( pC->pData[1] == LitF );
+    // if the 0-th watch is true, clause is already satisfied
+    if ( pAssigns[MSAT_LIT2VAR(pC->pData[0])] == pC->pData[0] )
+        return 1; 
+    // look for a new watch
+    if ( pC->nSize > 2 )
+    {
+        int i;
+        for ( i = 2; i < (int)pC->nSize; i++ )
+            if ( pAssigns[MSAT_LIT2VAR(pC->pData[i])] != MSAT_LITNOT(pC->pData[i]) )
+            {
+                pC->pData[1] = pC->pData[i], pC->pData[i] = LitF;
+                *pLit_out = MSAT_LITNOT(pC->pData[1]);
+                return 1; 
+            }
+    }
+    // clause is unit under assignment
+    *pLit_out = pC->pData[0];
+    return 0;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Simplifies the clause.]
+
+  Description [Assumes everything has been propagated! (esp. watches 
+  in clauses are NOT unsatisfied)]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+bool Msat_ClauseSimplify( Msat_Clause_t * pC, int * pAssigns )
+{
+    Msat_Var_t Var;
+    int i, j;
+    for ( i = j = 0; i < (int)pC->nSize; i++ )
+    {
+        Var = MSAT_LIT2VAR(pC->pData[i]);
+        if ( pAssigns[Var] == MSAT_VAR_UNASSIGNED )
+        {
+            pC->pData[j++] = pC->pData[i];
+            continue;
+        }
+        if ( pAssigns[Var] == pC->pData[i] )
+            return 1;
+        // otherwise, the value of the literal is false
+        // make sure, this literal is not watched
+        assert( i >= 2 );
+    }
+    // if the size has changed, update it and move activity
+    if ( j < (int)pC->nSize )
+    {
+        float Activ = Msat_ClauseReadActivity(pC);
+        pC->nSize = j;
+        Msat_ClauseWriteActivity(pC, Activ);
+    }
+    return 0;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Computes reason of conflict in the given clause.]
+
+  Description [If the literal is unassigned, finds the reason by 
+  complementing literals in the given cluase (pC). If the literal is
+  assigned, makes sure that this literal is the first one in the clause
+  and computes the complement of all other literals in the clause.
+  Returns the reason in the given array (vLits_out). If the clause is
+  learned, bumps its activity.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_ClauseCalcReason( Msat_Solver_t * p, Msat_Clause_t * pC, Msat_Lit_t Lit, Msat_IntVec_t * vLits_out )
+{
+    int i;
+    // clear the reason
+    Msat_IntVecClear( vLits_out );
+    assert( Lit == MSAT_LIT_UNASSIGNED || Lit == pC->pData[0] );
+    for ( i = (Lit != MSAT_LIT_UNASSIGNED); i < (int)pC->nSize; i++ )
+    {
+        assert( Msat_SolverReadAssignsArray(p)[MSAT_LIT2VAR(pC->pData[i])] == MSAT_LITNOT(pC->pData[i]) );
+        Msat_IntVecPush( vLits_out, MSAT_LITNOT(pC->pData[i]) );
+    }
+    if ( pC->fLearned ) 
+        Msat_SolverClaBumpActivity( p, pC );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Removes the given clause from the watched list.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_ClauseRemoveWatch( Msat_ClauseVec_t * vClauses, Msat_Clause_t * pC )
+{
+    Msat_Clause_t ** pClauses;
+    int nClauses, i;
+    nClauses = Msat_ClauseVecReadSize( vClauses );
+    pClauses = Msat_ClauseVecReadArray( vClauses );
+    for ( i = 0; pClauses[i] != pC; i++ )
+        assert( i < nClauses );
+    for (      ; i < nClauses - 1; i++ )
+        pClauses[i] = pClauses[i+1];
+    Msat_ClauseVecPop( vClauses );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Prints the given clause.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_ClausePrint( Msat_Clause_t * pC )
+{
+    int i;
+    if ( pC == NULL )
+        printf( "NULL pointer" );
+    else 
+    {
+        if ( pC->fLearned )
+            printf( "Act = %.4f  ", Msat_ClauseReadActivity(pC) );
+        for ( i = 0; i < (int)pC->nSize; i++ )
+            printf( " %s%d", ((pC->pData[i]&1)? "-": ""),  pC->pData[i]/2 + 1 );
+    }
+    printf( "\n" );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Writes the given clause in a file in DIMACS format.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_ClauseWriteDimacs( FILE * pFile, Msat_Clause_t * pC, bool fIncrement )
+{
+    int i;
+    for ( i = 0; i < (int)pC->nSize; i++ )
+        fprintf( pFile, "%s%d ", ((pC->pData[i]&1)? "-": ""),  pC->pData[i]/2 + (int)(fIncrement>0) );
+    if ( fIncrement )
+        fprintf( pFile, "0" );
+    fprintf( pFile, "\n" );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Prints the given clause.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_ClausePrintSymbols( Msat_Clause_t * pC )
+{
+    int i;
+    if ( pC == NULL )
+        printf( "NULL pointer" );
+    else 
+    {
+//        if ( pC->fLearned )
+//            printf( "Act = %.4f  ", Msat_ClauseReadActivity(pC) );
+        for ( i = 0; i < (int)pC->nSize; i++ )
+            printf(" "L_LIT, L_lit(pC->pData[i]));
+    }
+    printf( "\n" );
+}
+
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/msat/msatClauseVec.c b/src/sat/msat/msatClauseVec.c
new file mode 100644
index 00000000..04691cf2
--- /dev/null
+++ b/src/sat/msat/msatClauseVec.c
@@ -0,0 +1,232 @@
+/**CFile****************************************************************
+
+  FileName    [msatClauseVec.c]
+
+  PackageName [A C version of SAT solver MINISAT, originally developed 
+  in C++ by Niklas Een and Niklas Sorensson, Chalmers University of 
+  Technology, Sweden: http://www.cs.chalmers.se/~een/Satzoo.]
+
+  Synopsis    [Procedures working with arrays of SAT clauses.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - January 1, 2004.]
+
+  Revision    [$Id: msatClauseVec.c,v 1.0 2004/01/01 1:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include "msatInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Allocates a vector with the given capacity.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_ClauseVec_t * Msat_ClauseVecAlloc( int nCap )
+{
+    Msat_ClauseVec_t * p;
+    p = ALLOC( Msat_ClauseVec_t, 1 );
+    if ( nCap > 0 && nCap < 16 )
+        nCap = 16;
+    p->nSize  = 0;
+    p->nCap   = nCap;
+    p->pArray = p->nCap? ALLOC( Msat_Clause_t *, p->nCap ) : NULL;
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_ClauseVecFree( Msat_ClauseVec_t * p )
+{
+    FREE( p->pArray );
+    FREE( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_Clause_t ** Msat_ClauseVecReadArray( Msat_ClauseVec_t * p )
+{
+    return p->pArray;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Msat_ClauseVecReadSize( Msat_ClauseVec_t * p )
+{
+    return p->nSize;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Resizes the vector to the given capacity.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_ClauseVecGrow( Msat_ClauseVec_t * p, int nCapMin )
+{
+    if ( p->nCap >= nCapMin )
+        return;
+    p->pArray = REALLOC( Msat_Clause_t *, p->pArray, nCapMin ); 
+    p->nCap   = nCapMin;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_ClauseVecShrink( Msat_ClauseVec_t * p, int nSizeNew )
+{
+    assert( p->nSize >= nSizeNew );
+    p->nSize = nSizeNew;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_ClauseVecClear( Msat_ClauseVec_t * p )
+{
+    p->nSize = 0;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_ClauseVecPush( Msat_ClauseVec_t * p, Msat_Clause_t * Entry )
+{
+    if ( p->nSize == p->nCap )
+    {
+        if ( p->nCap < 16 )
+            Msat_ClauseVecGrow( p, 16 );
+        else
+            Msat_ClauseVecGrow( p, 2 * p->nCap );
+    }
+    p->pArray[p->nSize++] = Entry;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_Clause_t * Msat_ClauseVecPop( Msat_ClauseVec_t * p )
+{
+    return p->pArray[--p->nSize];
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_ClauseVecWriteEntry( Msat_ClauseVec_t * p, int i, Msat_Clause_t * Entry )
+{
+    assert( i >= 0 && i < p->nSize );
+    p->pArray[i] = Entry;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_Clause_t * Msat_ClauseVecReadEntry( Msat_ClauseVec_t * p, int i )
+{
+    assert( i >= 0 && i < p->nSize );
+    return p->pArray[i];
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/msat/msatInt.h b/src/sat/msat/msatInt.h
new file mode 100644
index 00000000..03903abe
--- /dev/null
+++ b/src/sat/msat/msatInt.h
@@ -0,0 +1,306 @@
+/**CFile****************************************************************
+
+  FileName    [msatInt.c]
+
+  PackageName [A C version of SAT solver MINISAT, originally developed 
+  in C++ by Niklas Een and Niklas Sorensson, Chalmers University of 
+  Technology, Sweden: http://www.cs.chalmers.se/~een/Satzoo.]
+
+  Synopsis    [Internal definitions of the solver.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - January 1, 2004.]
+
+  Revision    [$Id: msatInt.c,v 1.0 2004/01/01 1:00:00 alanmi Exp $]
+
+***********************************************************************/
+ 
+#ifndef __MSAT_INT_H__
+#define __MSAT_INT_H__
+
+////////////////////////////////////////////////////////////////////////
+///                          INCLUDES                                ///
+////////////////////////////////////////////////////////////////////////
+
+//#include "leaks.h"       
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <time.h>
+#include <math.h>
+#include "msat.h"
+
+////////////////////////////////////////////////////////////////////////
+///                         PARAMETERS                               ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                    STRUCTURE DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+#ifdef _MSC_VER
+typedef __int64     int64;
+#else
+typedef long long   int64;
+#endif
+
+// outputs the runtime in seconds
+#define PRT(a,t) \
+    printf( "%s = ", (a) ); printf( "%6.2f sec\n", (float)(t)/(float)(CLOCKS_PER_SEC) )
+
+// memory management macros
+#define ALLOC(type, num)    \
+    ((type *) malloc(sizeof(type) * (num)))
+#define REALLOC(type, obj, num)    \
+    ((obj) ? ((type *) realloc((char *)(obj), sizeof(type) * (num))) : \
+        ((type *) malloc(sizeof(type) * (num))))
+#define FREE(obj)        \
+    ((obj) ? (free((char *)(obj)), (obj) = 0) : 0)
+
+// By default, custom memory management is used
+// which guarantees constant time allocation/deallocation 
+// for SAT clauses and other frequently modified objects.
+// For debugging, it is possible use system memory management
+// directly. In which case, uncomment the macro below.
+//#define USE_SYSTEM_MEMORY_MANAGEMENT 
+
+// internal data structures
+typedef struct Msat_Clause_t_      Msat_Clause_t;
+typedef struct Msat_Queue_t_       Msat_Queue_t;
+typedef struct Msat_Order_t_       Msat_Order_t;
+// memory managers (duplicated from Extra for stand-aloneness)
+typedef struct Msat_MmFixed_t_     Msat_MmFixed_t;    
+typedef struct Msat_MmFlex_t_      Msat_MmFlex_t;     
+typedef struct Msat_MmStep_t_      Msat_MmStep_t;     
+// variables and literals
+typedef int                       Msat_Lit_t;  
+typedef int                       Msat_Var_t;  
+// the type of return value
+#define MSAT_VAR_UNASSIGNED (-1)
+#define MSAT_LIT_UNASSIGNED (-2)
+#define MSAT_ORDER_UNKNOWN  (-3)
+
+// printing the search tree
+#define L_IND      "%-*d"
+#define L_ind      Msat_SolverReadDecisionLevel(p)*3+3,Msat_SolverReadDecisionLevel(p)
+#define L_LIT      "%s%d"
+#define L_lit(Lit) MSAT_LITSIGN(Lit)?"-":"", MSAT_LIT2VAR(Lit)+1
+
+typedef struct Msat_SolverStats_t_ Msat_SolverStats_t;
+struct Msat_SolverStats_t_
+{
+    int64   nStarts;        // the number of restarts
+    int64   nDecisions;     // the number of decisions
+    int64   nPropagations;  // the number of implications
+    int64   nInspects;      // the number of times clauses are vising while watching them
+    int64   nConflicts;     // the number of conflicts
+    int64   nSuccesses;     // the number of sat assignments found
+};
+
+typedef struct Msat_SearchParams_t_ Msat_SearchParams_t;
+struct Msat_SearchParams_t_
+{
+    double  dVarDecay;
+    double  dClaDecay;
+};
+
+// sat solver data structure visible through all the internal files
+struct Msat_Solver_t_
+{
+    int                 nClauses;    // the total number of clauses
+    int                 nClausesStart; // the number of clauses before adding
+    Msat_ClauseVec_t *  vClauses;    // problem clauses
+    Msat_ClauseVec_t *  vLearned;    // learned clauses
+    double              dClaInc;     // Amount to bump next clause with.
+    double              dClaDecay;   // INVERSE decay factor for clause activity: stores 1/decay.
+
+    double *            pdActivity;  // A heuristic measurement of the activity of a variable.
+    float *             pFactors;    // the multiplicative factors of variable activity
+    double              dVarInc;     // Amount to bump next variable with.
+    double              dVarDecay;   // INVERSE decay factor for variable activity: stores 1/decay. Use negative value for static variable order.
+    Msat_Order_t *      pOrder;      // Keeps track of the decision variable order.
+
+    Msat_ClauseVec_t ** pvWatched;   // 'pvWatched[lit]' is a list of constraints watching 'lit' (will go there if literal becomes true).
+    Msat_Queue_t *      pQueue;      // Propagation queue.
+
+    int                 nVars;       // the current number of variables
+    int                 nVarsAlloc;  // the maximum allowed number of variables
+    int *               pAssigns;    // The current assignments (literals or MSAT_VAR_UNKOWN)
+    int *               pModel;      // The satisfying assignment
+    Msat_IntVec_t *     vTrail;      // List of assignments made. 
+    Msat_IntVec_t *     vTrailLim;   // Separator indices for different decision levels in 'trail'.
+    Msat_Clause_t **    pReasons;    // 'reason[var]' is the clause that implied the variables current value, or 'NULL' if none.
+    int *               pLevel;      // 'level[var]' is the decision level at which assignment was made. 
+    int                 nLevelRoot;  // Level of first proper decision.
+
+    double              dRandSeed;   // For the internal random number generator (makes solver deterministic over different platforms). 
+
+    bool                fVerbose;    // the verbosity flag
+    double              dProgress;   // Set by 'search()'.
+
+    // the variable cone and variable connectivity
+    Msat_IntVec_t *     vConeVars;
+    Msat_IntVec_t *     vVarsUsed;
+    Msat_ClauseVec_t *  vAdjacents;
+
+    // internal data used during conflict analysis
+    int *               pSeen;       // time when a lit was seen for the last time
+    int                 nSeenId;     // the id of current seeing
+    Msat_IntVec_t *     vReason;     // the temporary array of literals
+    Msat_IntVec_t *     vTemp;       // the temporary array of literals
+    int *               pFreq;       // the number of times each var participated in conflicts
+
+    // the memory manager
+    Msat_MmStep_t *     pMem;
+
+    // statistics
+    Msat_SolverStats_t  Stats;
+    int                 nTwoLits;
+    int                 nTwoLitsL;
+    int                 nClausesInit;
+    int                 nClausesAlloc;
+    int                 nClausesAllocL;
+    int                 nBackTracks;
+};
+
+struct Msat_ClauseVec_t_
+{
+    Msat_Clause_t **    pArray;
+    int                 nSize;
+    int                 nCap;
+};
+
+struct Msat_IntVec_t_
+{
+    int *               pArray;
+    int                 nSize;
+    int                 nCap;
+};
+
+////////////////////////////////////////////////////////////////////////
+///                       GLOBAL VARIABLES                           ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                       MACRO DEFINITIONS                          ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DECLARATIONS                        ///
+////////////////////////////////////////////////////////////////////////
+
+/*=== satActivity.c ===========================================================*/
+extern void                Msat_SolverVarDecayActivity( Msat_Solver_t * p );
+extern void                Msat_SolverVarRescaleActivity( Msat_Solver_t * p );
+extern void                Msat_SolverClaDecayActivity( Msat_Solver_t * p );
+extern void                Msat_SolverClaRescaleActivity( Msat_Solver_t * p );
+/*=== satSolverApi.c ===========================================================*/
+extern Msat_Clause_t *     Msat_SolverReadClause( Msat_Solver_t * p, int Num );
+/*=== satSolver.c ===========================================================*/
+extern int                 Msat_SolverReadDecisionLevel( Msat_Solver_t * p );
+extern int *               Msat_SolverReadDecisionLevelArray( Msat_Solver_t * p );
+extern Msat_Clause_t **    Msat_SolverReadReasonArray( Msat_Solver_t * p );
+extern Msat_Type_t         Msat_SolverReadVarValue( Msat_Solver_t * p, Msat_Var_t Var );
+extern Msat_ClauseVec_t *  Msat_SolverReadLearned( Msat_Solver_t * p );
+extern Msat_ClauseVec_t ** Msat_SolverReadWatchedArray( Msat_Solver_t * p );
+extern int *               Msat_SolverReadSeenArray( Msat_Solver_t * p );
+extern int                 Msat_SolverIncrementSeenId( Msat_Solver_t * p );
+extern Msat_MmStep_t *     Msat_SolverReadMem( Msat_Solver_t * p );
+extern void                Msat_SolverClausesIncrement( Msat_Solver_t * p );
+extern void                Msat_SolverClausesDecrement( Msat_Solver_t * p );
+extern void                Msat_SolverClausesIncrementL( Msat_Solver_t * p );
+extern void                Msat_SolverClausesDecrementL( Msat_Solver_t * p );
+extern void                Msat_SolverVarBumpActivity( Msat_Solver_t * p, Msat_Lit_t Lit );
+extern void                Msat_SolverClaBumpActivity( Msat_Solver_t * p, Msat_Clause_t * pC );
+extern bool                Msat_SolverEnqueue( Msat_Solver_t * p, Msat_Lit_t Lit, Msat_Clause_t * pC );
+extern double              Msat_SolverProgressEstimate( Msat_Solver_t * p );
+/*=== satSolverSearch.c ===========================================================*/
+extern bool                Msat_SolverAssume( Msat_Solver_t * p, Msat_Lit_t Lit );
+extern Msat_Clause_t *     Msat_SolverPropagate( Msat_Solver_t * p );
+extern void                Msat_SolverCancelUntil( Msat_Solver_t * p, int Level );
+extern Msat_Type_t         Msat_SolverSearch( Msat_Solver_t * p, int nConfLimit, int nLearnedLimit, int nBackTrackLimit, Msat_SearchParams_t * pPars );
+/*=== satQueue.c ===========================================================*/
+extern Msat_Queue_t *      Msat_QueueAlloc( int nVars );
+extern void                Msat_QueueFree( Msat_Queue_t * p );
+extern int                 Msat_QueueReadSize( Msat_Queue_t * p );
+extern void                Msat_QueueInsert( Msat_Queue_t * p, int Lit );
+extern int                 Msat_QueueExtract( Msat_Queue_t * p );
+extern void                Msat_QueueClear( Msat_Queue_t * p );
+/*=== satOrder.c ===========================================================*/
+extern Msat_Order_t *      Msat_OrderAlloc( Msat_Solver_t * pSat );
+extern void                Msat_OrderSetBounds( Msat_Order_t * p, int nVarsMax );
+extern void                Msat_OrderClean( Msat_Order_t * p, Msat_IntVec_t * vCone );
+extern int                 Msat_OrderCheck( Msat_Order_t * p );
+extern void                Msat_OrderFree( Msat_Order_t * p );
+extern int                 Msat_OrderVarSelect( Msat_Order_t * p );
+extern void                Msat_OrderVarAssigned( Msat_Order_t * p, int Var );
+extern void                Msat_OrderVarUnassigned( Msat_Order_t * p, int Var );
+extern void                Msat_OrderUpdate( Msat_Order_t * p, int Var );
+/*=== satClause.c ===========================================================*/
+extern bool                Msat_ClauseCreate( Msat_Solver_t * p, Msat_IntVec_t * vLits, bool fLearnt, Msat_Clause_t ** pClause_out );
+extern Msat_Clause_t *     Msat_ClauseCreateFake( Msat_Solver_t * p, Msat_IntVec_t * vLits );
+extern Msat_Clause_t *     Msat_ClauseCreateFakeLit( Msat_Solver_t * p, Msat_Lit_t Lit );
+extern bool                Msat_ClauseReadLearned( Msat_Clause_t * pC );
+extern int                 Msat_ClauseReadSize( Msat_Clause_t * pC );
+extern int *               Msat_ClauseReadLits( Msat_Clause_t * pC );
+extern bool                Msat_ClauseReadMark( Msat_Clause_t * pC );
+extern void                Msat_ClauseSetMark( Msat_Clause_t * pC, bool fMark );
+extern int                 Msat_ClauseReadNum( Msat_Clause_t * pC );
+extern void                Msat_ClauseSetNum( Msat_Clause_t * pC, int Num );
+extern bool                Msat_ClauseReadTypeA( Msat_Clause_t * pC );
+extern void                Msat_ClauseSetTypeA( Msat_Clause_t * pC, bool fTypeA );
+extern bool                Msat_ClauseIsLocked( Msat_Solver_t * p, Msat_Clause_t * pC );
+extern float               Msat_ClauseReadActivity( Msat_Clause_t * pC );
+extern void                Msat_ClauseWriteActivity( Msat_Clause_t * pC, float Num );
+extern void                Msat_ClauseFree( Msat_Solver_t * p, Msat_Clause_t * pC, bool fRemoveWatched );
+extern bool                Msat_ClausePropagate( Msat_Clause_t * pC, Msat_Lit_t Lit, int * pAssigns, Msat_Lit_t * pLit_out );
+extern bool                Msat_ClauseSimplify( Msat_Clause_t * pC, int * pAssigns );
+extern void                Msat_ClauseCalcReason( Msat_Solver_t * p, Msat_Clause_t * pC, Msat_Lit_t Lit, Msat_IntVec_t * vLits_out );
+extern void                Msat_ClauseRemoveWatch( Msat_ClauseVec_t * vClauses, Msat_Clause_t * pC );
+extern void                Msat_ClausePrint( Msat_Clause_t * pC );
+extern void                Msat_ClausePrintSymbols( Msat_Clause_t * pC );
+extern void                Msat_ClauseWriteDimacs( FILE * pFile, Msat_Clause_t * pC, bool fIncrement );
+extern unsigned            Msat_ClauseComputeTruth( Msat_Solver_t * p, Msat_Clause_t * pC );
+/*=== satSort.c ===========================================================*/
+extern void                Msat_SolverSortDB( Msat_Solver_t * p );
+/*=== satClauseVec.c ===========================================================*/
+extern Msat_ClauseVec_t *  Msat_ClauseVecAlloc( int nCap );
+extern void                Msat_ClauseVecFree( Msat_ClauseVec_t * p );
+extern Msat_Clause_t **    Msat_ClauseVecReadArray( Msat_ClauseVec_t * p );
+extern int                 Msat_ClauseVecReadSize( Msat_ClauseVec_t * p );
+extern void                Msat_ClauseVecGrow( Msat_ClauseVec_t * p, int nCapMin );
+extern void                Msat_ClauseVecShrink( Msat_ClauseVec_t * p, int nSizeNew );
+extern void                Msat_ClauseVecClear( Msat_ClauseVec_t * p );
+extern void                Msat_ClauseVecPush( Msat_ClauseVec_t * p, Msat_Clause_t * Entry );
+extern Msat_Clause_t *     Msat_ClauseVecPop( Msat_ClauseVec_t * p );
+extern void                Msat_ClauseVecWriteEntry( Msat_ClauseVec_t * p, int i, Msat_Clause_t * Entry );
+extern Msat_Clause_t *     Msat_ClauseVecReadEntry( Msat_ClauseVec_t * p, int i );
+
+/*=== satMem.c ===========================================================*/
+// fixed-size-block memory manager
+extern Msat_MmFixed_t *    Msat_MmFixedStart( int nEntrySize );
+extern void                Msat_MmFixedStop( Msat_MmFixed_t * p, int fVerbose );
+extern char *              Msat_MmFixedEntryFetch( Msat_MmFixed_t * p );
+extern void                Msat_MmFixedEntryRecycle( Msat_MmFixed_t * p, char * pEntry );
+extern void                Msat_MmFixedRestart( Msat_MmFixed_t * p );
+extern int                 Msat_MmFixedReadMemUsage( Msat_MmFixed_t * p );
+// flexible-size-block memory manager
+extern Msat_MmFlex_t *     Msat_MmFlexStart();
+extern void                Msat_MmFlexStop( Msat_MmFlex_t * p, int fVerbose );
+extern char *              Msat_MmFlexEntryFetch( Msat_MmFlex_t * p, int nBytes );
+extern int                 Msat_MmFlexReadMemUsage( Msat_MmFlex_t * p );
+// hierarchical memory manager
+extern Msat_MmStep_t *     Msat_MmStepStart( int nSteps );
+extern void                Msat_MmStepStop( Msat_MmStep_t * p, int fVerbose );
+extern char *              Msat_MmStepEntryFetch( Msat_MmStep_t * p, int nBytes );
+extern void                Msat_MmStepEntryRecycle( Msat_MmStep_t * p, char * pEntry, int nBytes );
+extern int                 Msat_MmStepReadMemUsage( Msat_MmStep_t * p );
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+#endif
diff --git a/src/sat/msat/msatMem.c b/src/sat/msat/msatMem.c
new file mode 100644
index 00000000..30bf4a96
--- /dev/null
+++ b/src/sat/msat/msatMem.c
@@ -0,0 +1,529 @@
+/**CFile****************************************************************
+
+  FileName    [msatMem.c]
+
+  PackageName [A C version of SAT solver MINISAT, originally developed 
+  in C++ by Niklas Een and Niklas Sorensson, Chalmers University of 
+  Technology, Sweden: http://www.cs.chalmers.se/~een/Satzoo.]
+
+  Synopsis    [Memory managers borrowed from Extra.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - January 1, 2004.]
+
+  Revision    [$Id: msatMem.c,v 1.0 2004/01/01 1:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include "msatInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+struct Msat_MmFixed_t_
+{
+    // information about individual entries
+    int           nEntrySize;    // the size of one entry
+    int           nEntriesAlloc; // the total number of entries allocated
+    int           nEntriesUsed;  // the number of entries in use
+    int           nEntriesMax;   // the max number of entries in use
+    char *        pEntriesFree;  // the linked list of free entries
+
+    // this is where the memory is stored
+    int           nChunkSize;    // the size of one chunk
+    int           nChunksAlloc;  // the maximum number of memory chunks 
+    int           nChunks;       // the current number of memory chunks 
+    char **       pChunks;       // the allocated memory
+
+    // statistics
+    int           nMemoryUsed;   // memory used in the allocated entries
+    int           nMemoryAlloc;  // memory allocated
+};
+
+struct Msat_MmFlex_t_
+{
+    // information about individual entries
+    int           nEntriesUsed;  // the number of entries allocated
+    char *        pCurrent;      // the current pointer to free memory
+    char *        pEnd;          // the first entry outside the free memory
+
+    // this is where the memory is stored
+    int           nChunkSize;    // the size of one chunk
+    int           nChunksAlloc;  // the maximum number of memory chunks 
+    int           nChunks;       // the current number of memory chunks 
+    char **       pChunks;       // the allocated memory
+
+    // statistics
+    int           nMemoryUsed;   // memory used in the allocated entries
+    int           nMemoryAlloc;  // memory allocated
+};
+
+
+struct Msat_MmStep_t_
+{
+    int                nMems;    // the number of fixed memory managers employed
+    Msat_MmFixed_t **   pMems;    // memory managers: 2^1 words, 2^2 words, etc
+    int                nMapSize; // the size of the memory array
+    Msat_MmFixed_t **   pMap;     // maps the number of bytes into its memory manager
+};
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Allocates memory pieces of fixed size.]
+
+  Description [The size of the chunk is computed as the minimum of
+  1024 entries and 64K. Can only work with entry size at least 4 byte long.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_MmFixed_t * Msat_MmFixedStart( int nEntrySize )
+{
+    Msat_MmFixed_t * p;
+
+    p = ALLOC( Msat_MmFixed_t, 1 );
+    memset( p, 0, sizeof(Msat_MmFixed_t) );
+
+    p->nEntrySize    = nEntrySize;
+    p->nEntriesAlloc = 0;
+    p->nEntriesUsed  = 0;
+    p->pEntriesFree  = NULL;
+
+    if ( nEntrySize * (1 << 10) < (1<<16) )
+        p->nChunkSize = (1 << 10);
+    else
+        p->nChunkSize = (1<<16) / nEntrySize;
+    if ( p->nChunkSize < 8 )
+        p->nChunkSize = 8;
+
+    p->nChunksAlloc  = 64;
+    p->nChunks       = 0;
+    p->pChunks       = ALLOC( char *, p->nChunksAlloc );
+
+    p->nMemoryUsed   = 0;
+    p->nMemoryAlloc  = 0;
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_MmFixedStop( Msat_MmFixed_t * p, int fVerbose )
+{
+    int i;
+    if ( p == NULL )
+        return;
+    if ( fVerbose )
+    {
+        printf( "Fixed memory manager: Entry = %5d. Chunk = %5d. Chunks used = %5d.\n",
+            p->nEntrySize, p->nChunkSize, p->nChunks );
+        printf( "   Entries used = %8d. Entries peak = %8d. Memory used = %8d. Memory alloc = %8d.\n",
+            p->nEntriesUsed, p->nEntriesMax, p->nEntrySize * p->nEntriesUsed, p->nMemoryAlloc );
+    }
+    for ( i = 0; i < p->nChunks; i++ )
+        free( p->pChunks[i] );
+    free( p->pChunks );
+    free( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+char * Msat_MmFixedEntryFetch( Msat_MmFixed_t * p )
+{
+    char * pTemp;
+    int i;
+
+    // check if there are still free entries
+    if ( p->nEntriesUsed == p->nEntriesAlloc )
+    { // need to allocate more entries
+        assert( p->pEntriesFree == NULL );
+        if ( p->nChunks == p->nChunksAlloc )
+        {
+            p->nChunksAlloc *= 2;
+            p->pChunks = REALLOC( char *, p->pChunks, p->nChunksAlloc ); 
+        }
+        p->pEntriesFree = ALLOC( char, p->nEntrySize * p->nChunkSize );
+        p->nMemoryAlloc += p->nEntrySize * p->nChunkSize;
+        // transform these entries into a linked list
+        pTemp = p->pEntriesFree;
+        for ( i = 1; i < p->nChunkSize; i++ )
+        {
+            *((char **)pTemp) = pTemp + p->nEntrySize;
+            pTemp += p->nEntrySize;
+        }
+        // set the last link
+        *((char **)pTemp) = NULL;
+        // add the chunk to the chunk storage
+        p->pChunks[ p->nChunks++ ] = p->pEntriesFree;
+        // add to the number of entries allocated
+        p->nEntriesAlloc += p->nChunkSize;
+    }
+    // incrememt the counter of used entries
+    p->nEntriesUsed++;
+    if ( p->nEntriesMax < p->nEntriesUsed )
+        p->nEntriesMax = p->nEntriesUsed;
+    // return the first entry in the free entry list
+    pTemp = p->pEntriesFree;
+    p->pEntriesFree = *((char **)pTemp);
+    return pTemp;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_MmFixedEntryRecycle( Msat_MmFixed_t * p, char * pEntry )
+{
+    // decrement the counter of used entries
+    p->nEntriesUsed--;
+    // add the entry to the linked list of free entries
+    *((char **)pEntry) = p->pEntriesFree;
+    p->pEntriesFree = pEntry;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description [Relocates all the memory except the first chunk.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_MmFixedRestart( Msat_MmFixed_t * p )
+{
+    int i;
+    char * pTemp;
+
+    // deallocate all chunks except the first one
+    for ( i = 1; i < p->nChunks; i++ )
+        free( p->pChunks[i] );
+    p->nChunks = 1;
+    // transform these entries into a linked list
+    pTemp = p->pChunks[0];
+    for ( i = 1; i < p->nChunkSize; i++ )
+    {
+        *((char **)pTemp) = pTemp + p->nEntrySize;
+        pTemp += p->nEntrySize;
+    }
+    // set the last link
+    *((char **)pTemp) = NULL;
+    // set the free entry list
+    p->pEntriesFree  = p->pChunks[0];
+    // set the correct statistics
+    p->nMemoryAlloc  = p->nEntrySize * p->nChunkSize;
+    p->nMemoryUsed   = 0;
+    p->nEntriesAlloc = p->nChunkSize;
+    p->nEntriesUsed  = 0;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Msat_MmFixedReadMemUsage( Msat_MmFixed_t * p )
+{
+    return p->nMemoryAlloc;
+}
+
+
+
+/**Function*************************************************************
+
+  Synopsis    [Allocates entries of flexible size.]
+
+  Description [Can only work with entry size at least 4 byte long.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_MmFlex_t * Msat_MmFlexStart()
+{
+    Msat_MmFlex_t * p;
+
+    p = ALLOC( Msat_MmFlex_t, 1 );
+    memset( p, 0, sizeof(Msat_MmFlex_t) );
+
+    p->nEntriesUsed  = 0;
+    p->pCurrent      = NULL;
+    p->pEnd          = NULL;
+
+    p->nChunkSize    = (1 << 12);
+    p->nChunksAlloc  = 64;
+    p->nChunks       = 0;
+    p->pChunks       = ALLOC( char *, p->nChunksAlloc );
+
+    p->nMemoryUsed   = 0;
+    p->nMemoryAlloc  = 0;
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_MmFlexStop( Msat_MmFlex_t * p, int fVerbose )
+{
+    int i;
+    if ( p == NULL )
+        return;
+    if ( fVerbose )
+    {
+        printf( "Flexible memory manager: Chunk size = %d. Chunks used = %d.\n",
+            p->nChunkSize, p->nChunks );
+        printf( "   Entries used = %d. Memory used = %d. Memory alloc = %d.\n",
+            p->nEntriesUsed, p->nMemoryUsed, p->nMemoryAlloc );
+    }
+    for ( i = 0; i < p->nChunks; i++ )
+        free( p->pChunks[i] );
+    free( p->pChunks );
+    free( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+char * Msat_MmFlexEntryFetch( Msat_MmFlex_t * p, int nBytes )
+{
+    char * pTemp;
+    // check if there are still free entries
+    if ( p->pCurrent == NULL || p->pCurrent + nBytes > p->pEnd )
+    { // need to allocate more entries
+        if ( p->nChunks == p->nChunksAlloc )
+        {
+            p->nChunksAlloc *= 2;
+            p->pChunks = REALLOC( char *, p->pChunks, p->nChunksAlloc ); 
+        }
+        if ( nBytes > p->nChunkSize )
+        {
+            // resize the chunk size if more memory is requested than it can give
+            // (ideally, this should never happen)
+            p->nChunkSize = 2 * nBytes;
+        }
+        p->pCurrent = ALLOC( char, p->nChunkSize );
+        p->pEnd     = p->pCurrent + p->nChunkSize;
+        p->nMemoryAlloc += p->nChunkSize;
+        // add the chunk to the chunk storage
+        p->pChunks[ p->nChunks++ ] = p->pCurrent;
+    }
+    assert( p->pCurrent + nBytes <= p->pEnd );
+    // increment the counter of used entries
+    p->nEntriesUsed++;
+    // keep track of the memory used
+    p->nMemoryUsed += nBytes;
+    // return the next entry
+    pTemp = p->pCurrent;
+    p->pCurrent += nBytes;
+    return pTemp;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Msat_MmFlexReadMemUsage( Msat_MmFlex_t * p )
+{
+    return p->nMemoryAlloc;
+}
+
+
+
+
+
+/**Function*************************************************************
+
+  Synopsis    [Starts the hierarchical memory manager.]
+
+  Description [This manager can allocate entries of any size.
+  Iternally they are mapped into the entries with the number of bytes
+  equal to the power of 2. The smallest entry size is 8 bytes. The
+  next one is 16 bytes etc. So, if the user requests 6 bytes, he gets 
+  8 byte entry. If we asks for 25 bytes, he gets 32 byte entry etc.
+  The input parameters "nSteps" says how many fixed memory managers
+  are employed internally. Calling this procedure with nSteps equal
+  to 10 results in 10 hierarchically arranged internal memory managers, 
+  which can allocate up to 4096 (1Kb) entries. Requests for larger 
+  entries are handed over to malloc() and then free()ed.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_MmStep_t * Msat_MmStepStart( int nSteps )
+{
+    Msat_MmStep_t * p;
+    int i, k;
+    p = ALLOC( Msat_MmStep_t, 1 );
+    p->nMems = nSteps;
+    // start the fixed memory managers
+    p->pMems = ALLOC( Msat_MmFixed_t *, p->nMems );
+    for ( i = 0; i < p->nMems; i++ )
+        p->pMems[i] = Msat_MmFixedStart( (8<<i) );
+    // set up the mapping of the required memory size into the corresponding manager
+    p->nMapSize = (4<<p->nMems);
+    p->pMap = ALLOC( Msat_MmFixed_t *, p->nMapSize+1 );
+    p->pMap[0] = NULL;
+    for ( k = 1; k <= 4; k++ )
+        p->pMap[k] = p->pMems[0];
+    for ( i = 0; i < p->nMems; i++ )
+        for ( k = (4<<i)+1; k <= (8<<i); k++ )
+            p->pMap[k] = p->pMems[i];
+//for ( i = 1; i < 100; i ++ )
+//printf( "%10d: size = %10d\n", i, p->pMap[i]->nEntrySize );
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Stops the memory manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_MmStepStop( Msat_MmStep_t * p, int fVerbose )
+{
+    int i;
+    for ( i = 0; i < p->nMems; i++ )
+        Msat_MmFixedStop( p->pMems[i], fVerbose );
+    free( p->pMems );
+    free( p->pMap );
+    free( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Creates the entry.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+char * Msat_MmStepEntryFetch( Msat_MmStep_t * p, int nBytes )
+{
+    if ( nBytes == 0 )
+        return NULL;
+    if ( nBytes > p->nMapSize )
+    {
+//        printf( "Allocating %d bytes.\n", nBytes );
+        return ALLOC( char, nBytes );
+    }
+    return Msat_MmFixedEntryFetch( p->pMap[nBytes] );
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Recycles the entry.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_MmStepEntryRecycle( Msat_MmStep_t * p, char * pEntry, int nBytes )
+{
+    if ( nBytes == 0 )
+        return;
+    if ( nBytes > p->nMapSize )
+    {
+        free( pEntry );
+        return;
+    }
+    Msat_MmFixedEntryRecycle( p->pMap[nBytes], pEntry );
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Msat_MmStepReadMemUsage( Msat_MmStep_t * p )
+{
+    int i, nMemTotal = 0;
+    for ( i = 0; i < p->nMems; i++ )
+        nMemTotal += p->pMems[i]->nMemoryAlloc;
+    return nMemTotal;
+}
diff --git a/src/sat/msat/msatOrderH.c b/src/sat/msat/msatOrderH.c
new file mode 100644
index 00000000..956e7fc6
--- /dev/null
+++ b/src/sat/msat/msatOrderH.c
@@ -0,0 +1,405 @@
+/**CFile****************************************************************
+
+  FileName    [msatOrder.c]
+
+  PackageName [A C version of SAT solver MINISAT, originally developed 
+  in C++ by Niklas Een and Niklas Sorensson, Chalmers University of 
+  Technology, Sweden: http://www.cs.chalmers.se/~een/Satzoo.]
+
+  Synopsis    [The manager of variable assignment.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - January 1, 2004.]
+
+  Revision    [$Id: msatOrder.c,v 1.0 2005/05/30 1:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include "msatInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+// the variable package data structure
+struct Msat_Order_t_
+{
+    Msat_Solver_t *      pSat;         // the SAT solver 
+    Msat_IntVec_t *      vIndex;       // the heap
+    Msat_IntVec_t *      vHeap;        // the mapping of var num into its heap num
+};
+
+//The solver can communicate to the variable order the following parts:
+//- the array of current assignments (pSat->pAssigns)
+//- the array of variable activities (pSat->pdActivity)
+//- the array of variables currently in the cone (pSat->vConeVars)
+//- the array of arrays of variables adjucent to each(pSat->vAdjacents)
+
+#define HLEFT(i)               ((i)<<1)
+#define HRIGHT(i)             (((i)<<1)+1)
+#define HPARENT(i)             ((i)>>1)
+#define HCOMPARE(p, i, j)      ((p)->pSat->pdActivity[i] > (p)->pSat->pdActivity[j])
+#define HHEAP(p, i)            ((p)->vHeap->pArray[i])
+#define HSIZE(p)               ((p)->vHeap->nSize)
+#define HOKAY(p, i)            ((i) >= 0 && (i) < (p)->vIndex->nSize)
+#define HINHEAP(p, i)          (HOKAY(p, i) && (p)->vIndex->pArray[i] != 0)
+#define HEMPTY(p)              (HSIZE(p) == 1)
+
+static int Msat_HeapCheck_rec( Msat_Order_t * p, int i );
+static int Msat_HeapGetTop( Msat_Order_t * p );
+static void Msat_HeapInsert( Msat_Order_t * p, int n );
+static void Msat_HeapIncrease( Msat_Order_t * p, int n );
+static void Msat_HeapPercolateUp( Msat_Order_t * p, int i );
+static void Msat_HeapPercolateDown( Msat_Order_t * p, int i );
+
+extern int timeSelect;
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Allocates the ordering structure.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_Order_t * Msat_OrderAlloc( Msat_Solver_t * pSat )
+{
+    Msat_Order_t * p;
+    p = ALLOC( Msat_Order_t, 1 );
+    memset( p, 0, sizeof(Msat_Order_t) );
+    p->pSat   = pSat;
+    p->vIndex = Msat_IntVecAlloc( 0 );
+    p->vHeap  = Msat_IntVecAlloc( 0 );
+    Msat_OrderSetBounds( p, pSat->nVarsAlloc );
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Sets the bound of the ordering structure.]
+
+  Description [Should be called whenever the SAT solver is resized.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_OrderSetBounds( Msat_Order_t * p, int nVarsMax )
+{
+    Msat_IntVecGrow( p->vIndex, nVarsMax );
+    Msat_IntVecGrow( p->vHeap, nVarsMax + 1 );
+    p->vIndex->nSize = nVarsMax;
+    p->vHeap->nSize = 0;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Cleans the ordering structure.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_OrderClean( Msat_Order_t * p, Msat_IntVec_t * vCone )
+{
+    int i;
+    for ( i = 0; i < p->vIndex->nSize; i++ )
+        p->vIndex->pArray[i] = 0;
+    for ( i = 0; i < vCone->nSize; i++ )
+    {
+        assert( i+1 < p->vHeap->nCap );
+        p->vHeap->pArray[i+1] = vCone->pArray[i];
+
+        assert( vCone->pArray[i] < p->vIndex->nSize );
+        p->vIndex->pArray[vCone->pArray[i]] = i+1;
+    }
+    p->vHeap->nSize = vCone->nSize + 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Checks that the J-boundary is okay.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Msat_OrderCheck( Msat_Order_t * p )
+{
+    return Msat_HeapCheck_rec( p, 1 );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Frees the ordering structure.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_OrderFree( Msat_Order_t * p )
+{
+    Msat_IntVecFree( p->vHeap );
+    Msat_IntVecFree( p->vIndex );
+    free( p );
+}
+
+
+
+/**Function*************************************************************
+
+  Synopsis    [Selects the next variable to assign.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Msat_OrderVarSelect( Msat_Order_t * p )
+{
+    // Activity based decision:
+//    while (!heap.empty()){
+//        Var next = heap.getmin();
+//        if (toLbool(assigns[next]) == l_Undef)
+//            return next;
+//    }
+//    return var_Undef;
+
+    int Var;
+    int clk = clock();
+
+    while ( !HEMPTY(p) )
+    {
+        Var = Msat_HeapGetTop(p);
+        if ( (p)->pSat->pAssigns[Var] == MSAT_VAR_UNASSIGNED )
+        {
+//assert( Msat_OrderCheck(p) );
+timeSelect += clock() - clk;
+            return Var;
+        }
+    }
+    return MSAT_ORDER_UNKNOWN;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Updates J-boundary when the variable is assigned.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_OrderVarAssigned( Msat_Order_t * p, int Var )
+{
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Updates the order after a variable is unassigned.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_OrderVarUnassigned( Msat_Order_t * p, int Var )
+{
+//    if (!heap.inHeap(x))
+//        heap.insert(x);
+
+    int clk = clock();
+    if ( !HINHEAP(p,Var) )
+        Msat_HeapInsert( p, Var );
+timeSelect += clock() - clk;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Updates the order after a variable changed weight.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_OrderUpdate( Msat_Order_t * p, int Var )
+{
+//    if (heap.inHeap(x))
+//        heap.increase(x);
+
+    int clk = clock();
+    if ( HINHEAP(p,Var) )
+        Msat_HeapIncrease( p, Var );
+timeSelect += clock() - clk;
+}
+
+
+
+
+/**Function*************************************************************
+
+  Synopsis    [Checks the heap property recursively.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Msat_HeapCheck_rec( Msat_Order_t * p, int i )
+{
+    return i >= HSIZE(p) ||
+        ( HPARENT(i) == 0 || !HCOMPARE(p, HHEAP(p, i), HHEAP(p, HPARENT(i))) ) &&
+        Msat_HeapCheck_rec( p, HLEFT(i) ) && Msat_HeapCheck_rec( p, HRIGHT(i) );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Retrieves the minimum element.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Msat_HeapGetTop( Msat_Order_t * p )
+{
+    int Result, NewTop;
+    Result                    = HHEAP(p, 1);
+    NewTop                    = Msat_IntVecPop( p->vHeap );
+    p->vHeap->pArray[1]       = NewTop;
+    p->vIndex->pArray[NewTop] = 1;
+    p->vIndex->pArray[Result] = 0;
+    if ( p->vHeap->nSize > 1 )
+        Msat_HeapPercolateDown( p, 1 );
+    return Result;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Inserts the new element.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_HeapInsert( Msat_Order_t * p, int n )
+{
+    assert( HOKAY(p, n) );
+    p->vIndex->pArray[n] = HSIZE(p);
+    Msat_IntVecPush( p->vHeap, n );
+    Msat_HeapPercolateUp( p, p->vIndex->pArray[n] );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Inserts the new element.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_HeapIncrease( Msat_Order_t * p, int n )
+{
+    Msat_HeapPercolateUp( p, p->vIndex->pArray[n] );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Moves the entry up.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_HeapPercolateUp( Msat_Order_t * p, int i )
+{
+    int x = HHEAP(p, i);
+    while ( HPARENT(i) != 0 && HCOMPARE(p, x, HHEAP(p, HPARENT(i))) )
+    {
+        p->vHeap->pArray[i]            = HHEAP(p, HPARENT(i));
+        p->vIndex->pArray[HHEAP(p, i)] = i;
+        i                              = HPARENT(i);
+    }
+    p->vHeap->pArray[i]  = x;
+    p->vIndex->pArray[x] = i;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Moves the entry down.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_HeapPercolateDown( Msat_Order_t * p, int i )
+{
+    int x = HHEAP(p, i);
+    int Child;
+    while ( HLEFT(i) < HSIZE(p) )
+    {
+        if ( HRIGHT(i) < HSIZE(p) && HCOMPARE(p, HHEAP(p, HRIGHT(i)), HHEAP(p, HLEFT(i))) )
+            Child = HRIGHT(i);
+        else
+            Child = HLEFT(i);
+        if ( !HCOMPARE(p, HHEAP(p, Child), x) )
+            break;
+        p->vHeap->pArray[i]            = HHEAP(p, Child);
+        p->vIndex->pArray[HHEAP(p, i)] = i;
+        i                              = Child;
+    }
+    p->vHeap->pArray[i]  = x;
+    p->vIndex->pArray[x] = i;
+}
+
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/msat/msatOrderJ.c b/src/sat/msat/msatOrderJ.c
new file mode 100644
index 00000000..4db7ff7b
--- /dev/null
+++ b/src/sat/msat/msatOrderJ.c
@@ -0,0 +1,472 @@
+/**CFile****************************************************************
+
+  FileName    [msatOrder.c]
+
+  PackageName [A C version of SAT solver MINISAT, originally developed 
+  in C++ by Niklas Een and Niklas Sorensson, Chalmers University of 
+  Technology, Sweden: http://www.cs.chalmers.se/~een/Satzoo.]
+
+  Synopsis    [The manager of variable assignment.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - January 1, 2004.]
+
+  Revision    [$Id: msatOrder.c,v 1.0 2005/05/30 1:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include "msatInt.h"
+
+/* 
+The J-boundary (justification boundary) is defined as a set of unassigned 
+variables belonging to the cone of interest, such that for each of them,
+there exist an adjacent assigned variable in the cone of interest.
+*/
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+typedef struct Msat_OrderVar_t_  Msat_OrderVar_t;
+typedef struct Msat_OrderRing_t_ Msat_OrderRing_t;
+
+// the variable data structure
+struct Msat_OrderVar_t_
+{
+    Msat_OrderVar_t    * pNext;
+    Msat_OrderVar_t    * pPrev;
+    int                  Num;
+};
+
+// the ring of variables data structure (J-boundary)
+struct Msat_OrderRing_t_
+{
+    Msat_OrderVar_t    * pRoot; 
+    int                 nItems;
+};
+
+// the variable package data structure
+struct Msat_Order_t_
+{
+    Msat_Solver_t *      pSat;         // the SAT solver 
+    Msat_OrderVar_t *    pVars;        // the storage for variables
+    int                 nVarsAlloc;   // the number of variables allocated
+    Msat_OrderRing_t     rVars;        // the J-boundary as a ring of variables
+};
+
+//The solver can communicate to the variable order the following parts:
+//- the array of current assignments (pSat->pAssigns)
+//- the array of variable activities (pSat->pdActivity)
+//- the array of variables currently in the cone (pSat->vConeVars)
+//- the array of arrays of variables adjucent to each(pSat->vAdjacents)
+
+#define Msat_OrderVarIsInBoundary( p, i )   ((p)->pVars[i].pNext)
+#define Msat_OrderVarIsAssigned( p, i )     ((p)->pSat->pAssigns[i] != MSAT_VAR_UNASSIGNED)
+#define Msat_OrderVarIsUsedInCone( p, i )   ((p)->pSat->vVarsUsed->pArray[i])
+
+// iterator through the entries in J-boundary
+#define Msat_OrderRingForEachEntry( pRing, pVar, pNext )         \
+    for ( pVar = pRing,                                         \
+          pNext = pVar? pVar->pNext : NULL;                     \
+          pVar;                                                 \
+          pVar = (pNext != pRing)? pNext : NULL,                \
+          pNext = pVar? pVar->pNext : NULL )
+
+static void Msat_OrderRingAddLast( Msat_OrderRing_t * pRing, Msat_OrderVar_t * pVar );
+static void Msat_OrderRingRemove( Msat_OrderRing_t * pRing, Msat_OrderVar_t * pVar );
+
+extern int timeSelect;
+extern int timeAssign;
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Allocates the ordering structure.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_Order_t * Msat_OrderAlloc( Msat_Solver_t * pSat )
+{
+    Msat_Order_t * p;
+    p = ALLOC( Msat_Order_t, 1 );
+    memset( p, 0, sizeof(Msat_Order_t) );
+    p->pSat = pSat;
+    Msat_OrderSetBounds( p, pSat->nVarsAlloc );
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Sets the bound of the ordering structure.]
+
+  Description [Should be called whenever the SAT solver is resized.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_OrderSetBounds( Msat_Order_t * p, int nVarsMax )
+{
+    int i;
+    // add variables if they are missing
+    if ( p->nVarsAlloc < nVarsMax )
+    {
+        p->pVars = REALLOC( Msat_OrderVar_t, p->pVars, nVarsMax );
+        for ( i = p->nVarsAlloc; i < nVarsMax; i++ )
+        {
+            p->pVars[i].pNext = p->pVars[i].pPrev = NULL;
+            p->pVars[i].Num = i;
+        }
+        p->nVarsAlloc = nVarsMax;
+    }
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Cleans the ordering structure.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_OrderClean( Msat_Order_t * p, Msat_IntVec_t * vCone )
+{
+    Msat_OrderVar_t * pVar, * pNext;
+    // quickly undo the ring
+    Msat_OrderRingForEachEntry( p->rVars.pRoot, pVar, pNext )
+        pVar->pNext = pVar->pPrev = NULL;
+    p->rVars.pRoot  = NULL;
+    p->rVars.nItems = 0;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Checks that the J-boundary is okay.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Msat_OrderCheck( Msat_Order_t * p )
+{
+    Msat_OrderVar_t * pVar, * pNext;
+    Msat_IntVec_t * vRound;
+    int * pRound, nRound;
+    int * pVars, nVars, i, k;
+    int Counter = 0;
+
+    // go through all the variables in the boundary
+    Msat_OrderRingForEachEntry( p->rVars.pRoot, pVar, pNext )
+    {
+        assert( !Msat_OrderVarIsAssigned(p, pVar->Num) );
+        // go though all the variables in the neighborhood
+        // and check that it is true that there is least one assigned
+        vRound = (Msat_IntVec_t *)Msat_ClauseVecReadEntry( p->pSat->vAdjacents, pVar->Num );
+        nRound = Msat_IntVecReadSize( vRound );
+        pRound = Msat_IntVecReadArray( vRound );
+        for ( i = 0; i < nRound; i++ )
+        {
+            if ( !Msat_OrderVarIsUsedInCone(p, pRound[i]) )
+                continue;
+            if ( Msat_OrderVarIsAssigned(p, pRound[i]) )
+                break;
+        }
+//        assert( i != nRound );
+//        if ( i == nRound )
+//            return 0;
+        if ( i == nRound )
+            Counter++;
+    }
+    if ( Counter > 0 )
+        printf( "%d(%d) ", Counter, p->rVars.nItems );
+
+    // we may also check other unassigned variables in the cone
+    // to make sure that if they are not in J-boundary, 
+    // then they do not have an assigned neighbor
+    nVars = Msat_IntVecReadSize( p->pSat->vConeVars );
+    pVars = Msat_IntVecReadArray( p->pSat->vConeVars );
+    for ( i = 0; i < nVars; i++ )
+    {
+        assert( Msat_OrderVarIsUsedInCone(p, pVars[i]) );
+        // skip assigned vars, vars in the boundary, and vars not used in the cone
+        if ( Msat_OrderVarIsAssigned(p, pVars[i]) || 
+             Msat_OrderVarIsInBoundary(p, pVars[i]) )
+            continue;
+        // make sure, it does not have assigned neighbors
+        vRound = (Msat_IntVec_t *)Msat_ClauseVecReadEntry( p->pSat->vAdjacents, pVars[i] );
+        nRound = Msat_IntVecReadSize( vRound );
+        pRound = Msat_IntVecReadArray( vRound );
+        for ( k = 0; k < nRound; k++ )
+        {
+            if ( !Msat_OrderVarIsUsedInCone(p, pRound[k]) )
+                continue;
+            if ( Msat_OrderVarIsAssigned(p, pRound[k]) )
+                break;
+        }
+//        assert( k == nRound );
+//        if ( k != nRound )
+//            return 0;
+    }
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Frees the ordering structure.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_OrderFree( Msat_Order_t * p )
+{
+    free( p->pVars );
+    free( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Selects the next variable to assign.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Msat_OrderVarSelect( Msat_Order_t * p )
+{
+    Msat_OrderVar_t * pVar, * pNext, * pVarBest;
+    double * pdActs = p->pSat->pdActivity;
+    double dfActBest;
+//    int clk = clock();
+
+    pVarBest = NULL;
+    dfActBest = -1.0;
+    Msat_OrderRingForEachEntry( p->rVars.pRoot, pVar, pNext )
+    {
+        if ( dfActBest < pdActs[pVar->Num] )
+        {
+            dfActBest = pdActs[pVar->Num];
+            pVarBest  = pVar;
+        }
+    }
+//timeSelect += clock() - clk;
+//timeAssign += clock() - clk;
+
+//if ( pVarBest && pVarBest->Num % 1000 == 0 )
+//printf( "%d ", p->rVars.nItems );
+
+//    Msat_OrderCheck( p );
+    if ( pVarBest )
+    {
+        assert( Msat_OrderVarIsUsedInCone(p, pVarBest->Num) );
+        return pVarBest->Num;
+    }
+    return MSAT_ORDER_UNKNOWN;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Updates J-boundary when the variable is assigned.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_OrderVarAssigned( Msat_Order_t * p, int Var )
+{
+    Msat_IntVec_t * vRound;
+    int i;//, clk = clock();
+
+    // make sure the variable is in the boundary
+    assert( Var < p->nVarsAlloc );
+    // if it is not in the boundary (initial decision, random decision), do not remove
+    if ( Msat_OrderVarIsInBoundary( p, Var ) )
+        Msat_OrderRingRemove( &p->rVars, &p->pVars[Var] );
+    // add to the boundary those neighbors that are (1) unassigned, (2) not in boundary
+    // because for them we know that there is a variable (Var) which is assigned
+    vRound = (Msat_IntVec_t *)p->pSat->vAdjacents->pArray[Var];
+    for ( i = 0; i < vRound->nSize; i++ )
+    {
+        if ( !Msat_OrderVarIsUsedInCone(p, vRound->pArray[i]) )
+            continue;
+        if ( Msat_OrderVarIsAssigned(p, vRound->pArray[i]) )
+            continue;
+        if ( Msat_OrderVarIsInBoundary(p, vRound->pArray[i]) )
+            continue;
+        Msat_OrderRingAddLast( &p->rVars, &p->pVars[vRound->pArray[i]] );
+    }
+//timeSelect += clock() - clk;
+//    Msat_OrderCheck( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Updates the order after a variable is unassigned.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_OrderVarUnassigned( Msat_Order_t * p, int Var )
+{
+    Msat_IntVec_t * vRound, * vRound2;
+    int i, k;//, clk = clock();
+
+    // make sure the variable is not in the boundary
+    assert( Var < p->nVarsAlloc );
+    assert( !Msat_OrderVarIsInBoundary( p, Var ) );
+    // go through its neigbors - if one of them is assigned add this var
+    // add to the boundary those neighbors that are not there already
+    // this will also get rid of variable outside of the current cone
+    // because they are unassigned in Msat_SolverPrepare()
+    vRound = (Msat_IntVec_t *)p->pSat->vAdjacents->pArray[Var];
+    for ( i = 0; i < vRound->nSize; i++ )
+        if ( Msat_OrderVarIsAssigned(p, vRound->pArray[i]) ) 
+            break;
+    if ( i != vRound->nSize )
+        Msat_OrderRingAddLast( &p->rVars, &p->pVars[Var] );
+
+    // unassigning a variable may lead to its adjacents dropping from the boundary
+    for ( i = 0; i < vRound->nSize; i++ )
+        if ( Msat_OrderVarIsInBoundary(p, vRound->pArray[i]) )
+        { // the neighbor is in the J-boundary (and unassigned)
+            assert( !Msat_OrderVarIsAssigned(p, vRound->pArray[i]) );
+            vRound2 = (Msat_IntVec_t *)p->pSat->vAdjacents->pArray[vRound->pArray[i]];
+            // go through its neighbors and determine if there is at least one assigned
+            for ( k = 0; k < vRound2->nSize; k++ )
+                if ( Msat_OrderVarIsAssigned(p, vRound2->pArray[k]) ) 
+                    break;
+            if ( k == vRound2->nSize ) // there is no assigned vars, delete this one
+                Msat_OrderRingRemove( &p->rVars, &p->pVars[vRound->pArray[i]] );
+        }
+//timeSelect += clock() - clk;
+//    Msat_OrderCheck( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Updates the order after a variable changed weight.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_OrderUpdate( Msat_Order_t * p, int Var )
+{
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Adds node to the end of the ring.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_OrderRingAddLast( Msat_OrderRing_t * pRing, Msat_OrderVar_t * pVar )
+{
+//printf( "adding %d\n", pVar->Num );
+    // check that the node is not in a ring
+    assert( pVar->pPrev == NULL );
+    assert( pVar->pNext == NULL );
+    // if the ring is empty, make the node point to itself
+    pRing->nItems++;
+    if ( pRing->pRoot == NULL )
+    {
+        pRing->pRoot  = pVar;
+        pVar->pPrev  = pVar;
+        pVar->pNext  = pVar;
+        return;
+    }
+    // if the ring is not empty, add it as the last entry
+    pVar->pPrev = pRing->pRoot->pPrev;
+    pVar->pNext = pRing->pRoot;
+    pVar->pPrev->pNext = pVar;
+    pVar->pNext->pPrev = pVar;
+
+    // move the root so that it points to the new entry
+//    pRing->pRoot = pRing->pRoot->pPrev;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Removes the node from the ring.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_OrderRingRemove( Msat_OrderRing_t * pRing, Msat_OrderVar_t * pVar )
+{
+//printf( "removing %d\n", pVar->Num );
+    // check that the var is in a ring
+    assert( pVar->pPrev );
+    assert( pVar->pNext );
+    pRing->nItems--;
+    if ( pRing->nItems == 0 )
+    {
+        assert( pRing->pRoot == pVar );
+        pVar->pPrev = NULL;
+        pVar->pNext = NULL;
+        pRing->pRoot = NULL;
+        return;
+    }
+    // move the root if needed
+    if ( pRing->pRoot == pVar )
+        pRing->pRoot = pVar->pNext;
+    // move the root to the next entry after pVar
+    // this way all the additions to the list will be traversed first
+//    pRing->pRoot = pVar->pPrev;
+    // delete the node
+    pVar->pPrev->pNext = pVar->pNext;
+    pVar->pNext->pPrev = pVar->pPrev;
+    pVar->pPrev = NULL;
+    pVar->pNext = NULL;
+}
+
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/msat/msatQueue.c b/src/sat/msat/msatQueue.c
new file mode 100644
index 00000000..5938e042
--- /dev/null
+++ b/src/sat/msat/msatQueue.c
@@ -0,0 +1,157 @@
+/**CFile****************************************************************
+
+  FileName    [msatQueue.c]
+
+  PackageName [A C version of SAT solver MINISAT, originally developed 
+  in C++ by Niklas Een and Niklas Sorensson, Chalmers University of 
+  Technology, Sweden: http://www.cs.chalmers.se/~een/Satzoo.]
+
+  Synopsis    [The manager of the assignment propagation queue.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - January 1, 2004.]
+
+  Revision    [$Id: msatQueue.c,v 1.0 2004/01/01 1:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include "msatInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+struct Msat_Queue_t_ 
+{
+    int         nVars;
+    int *       pVars;
+    int         iFirst;
+    int         iLast;
+};
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Allocates the variable propagation queue.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_Queue_t * Msat_QueueAlloc( int nVars )
+{
+    Msat_Queue_t * p;
+    p = ALLOC( Msat_Queue_t, 1 );
+    memset( p, 0, sizeof(Msat_Queue_t) );
+    p->nVars  = nVars;
+    p->pVars  = ALLOC( int, nVars );
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Deallocate the variable propagation queue.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_QueueFree( Msat_Queue_t * p )
+{
+    free( p->pVars );
+    free( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Reads the queue size.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Msat_QueueReadSize( Msat_Queue_t * p )
+{
+    return p->iLast - p->iFirst;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Insert an entry into the queue.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_QueueInsert( Msat_Queue_t * p, int Lit )
+{
+    if ( p->iLast == p->nVars )
+    {
+        int i;
+        assert( 0 );
+        for ( i = 0; i < p->iLast; i++ )
+            printf( "entry = %2d  lit = %2d  var = %2d \n", i, p->pVars[i], p->pVars[i]/2 );
+    }
+    assert( p->iLast < p->nVars );
+    p->pVars[p->iLast++] = Lit;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Extracts an entry from the queue.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Msat_QueueExtract( Msat_Queue_t * p )
+{
+    if ( p->iFirst == p->iLast )
+        return -1;
+    return p->pVars[p->iFirst++];
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Resets the queue.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_QueueClear( Msat_Queue_t * p )
+{
+    p->iFirst = 0;
+    p->iLast  = 0;
+}
+
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/msat/msatRead.c b/src/sat/msat/msatRead.c
new file mode 100644
index 00000000..738562ef
--- /dev/null
+++ b/src/sat/msat/msatRead.c
@@ -0,0 +1,268 @@
+/**CFile****************************************************************
+
+  FileName    [msatRead.c]
+
+  PackageName [A C version of SAT solver MINISAT, originally developed 
+  in C++ by Niklas Een and Niklas Sorensson, Chalmers University of 
+  Technology, Sweden: http://www.cs.chalmers.se/~een/Satzoo.]
+
+  Synopsis    [The reader of the CNF formula in DIMACS format.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - January 1, 2004.]
+
+  Revision    [$Id: msatRead.c,v 1.0 2004/01/01 1:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include "msatInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+static char * Msat_FileRead( FILE * pFile );
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Read the file into the internal buffer.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+char * Msat_FileRead( FILE * pFile )
+{
+    int nFileSize;
+    char * pBuffer;
+    // get the file size, in bytes
+    fseek( pFile, 0, SEEK_END );  
+    nFileSize = ftell( pFile );  
+    // move the file current reading position to the beginning
+    rewind( pFile ); 
+    // load the contents of the file into memory
+    pBuffer = ALLOC( char, nFileSize + 3 );
+    fread( pBuffer, nFileSize, 1, pFile );
+    // terminate the string with '\0'
+    pBuffer[ nFileSize + 0] = '\n';
+    pBuffer[ nFileSize + 1] = '\0';
+    return pBuffer;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+static void Msat_ReadWhitespace( char ** pIn ) 
+{
+    while ((**pIn >= 9 && **pIn <= 13) || **pIn == 32)
+        (*pIn)++; 
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+static void Msat_ReadNotWhitespace( char ** pIn ) 
+{
+    while ( !((**pIn >= 9 && **pIn <= 13) || **pIn == 32) )
+        (*pIn)++; 
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+static void skipLine( char ** pIn ) 
+{
+    while ( 1 )
+    {
+        if (**pIn == 0) 
+            return;
+        if (**pIn == '\n') 
+        { 
+            (*pIn)++; 
+            return; 
+        }
+        (*pIn)++; 
+    } 
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+static int Msat_ReadInt( char ** pIn ) 
+{
+    int     val = 0;
+    bool    neg = 0;
+
+    Msat_ReadWhitespace( pIn );
+    if ( **pIn == '-' ) 
+        neg = 1, 
+        (*pIn)++;
+    else if ( **pIn == '+' ) 
+        (*pIn)++;
+    if ( **pIn < '0' || **pIn > '9' ) 
+        fprintf(stderr, "PARSE ERROR! Unexpected char: %c\n", **pIn), 
+        exit(1);
+    while ( **pIn >= '0' && **pIn <= '9' )
+        val = val*10 + (**pIn - '0'),
+        (*pIn)++;
+    return neg ? -val : val; 
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+static void Msat_ReadClause( char ** pIn, Msat_Solver_t * p, Msat_IntVec_t * pLits ) 
+{
+    int nVars = Msat_SolverReadVarNum( p );
+    int parsed_lit, var, sign;
+
+    Msat_IntVecClear( pLits );
+    while ( 1 )
+    {
+        parsed_lit = Msat_ReadInt(pIn);
+        if ( parsed_lit == 0 ) 
+            break;
+        var = abs(parsed_lit) - 1;
+        sign = (parsed_lit > 0);
+        if ( var >= nVars )
+        {
+            printf( "Variable %d is larger than the number of allocated variables (%d).\n", var+1, nVars );
+            exit(1);
+        }
+        Msat_IntVecPush( pLits, MSAT_VAR2LIT(var, !sign) );
+    }
+}
+ 
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+static bool Msat_ReadDimacs( char * pText, Msat_Solver_t ** pS, bool fVerbose ) 
+{
+    Msat_Solver_t * p;
+    Msat_IntVec_t * pLits;
+    char * pIn = pText;
+    int nVars, nClas;
+    while ( 1 )
+    {
+        Msat_ReadWhitespace( &pIn );
+        if ( *pIn == 0 )
+            break;
+        else if ( *pIn == 'c' )
+            skipLine( &pIn );
+        else if ( *pIn == 'p' )
+        {
+            pIn++;
+            Msat_ReadWhitespace( &pIn );
+            Msat_ReadNotWhitespace( &pIn );
+
+            nVars = Msat_ReadInt( &pIn );
+            nClas = Msat_ReadInt( &pIn );
+            skipLine( &pIn );
+            // start the solver
+            p = Msat_SolverAlloc( nVars, 1, 1, 1, 1, 0 ); 
+            Msat_SolverClean( p, nVars );
+            Msat_SolverSetVerbosity( p, fVerbose );
+            // allocate the vector
+            pLits = Msat_IntVecAlloc( nVars );
+        }
+        else
+        {
+            if ( p == NULL )
+            {
+                printf( "There is no parameter line.\n" );
+                exit(1);
+            }
+            Msat_ReadClause( &pIn, p, pLits );
+            if ( !Msat_SolverAddClause( p, pLits ) )
+                return 0;
+        }
+    }
+    Msat_IntVecFree( pLits );
+    *pS = p;
+    return Msat_SolverSimplifyDB( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Starts the solver and reads the DIMAC file.]
+
+  Description [Returns FALSE upon immediate conflict.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+bool Msat_SolverParseDimacs( FILE * pFile, Msat_Solver_t ** p, int fVerbose )
+{
+    char * pText;
+    bool Value;
+    pText = Msat_FileRead( pFile );
+    Value = Msat_ReadDimacs( pText, p, fVerbose );
+    free( pText );
+    return Value;
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/msat/msatSolverApi.c b/src/sat/msat/msatSolverApi.c
new file mode 100644
index 00000000..ee3507a6
--- /dev/null
+++ b/src/sat/msat/msatSolverApi.c
@@ -0,0 +1,500 @@
+/**CFile****************************************************************
+
+  FileName    [msatSolverApi.c]
+
+  PackageName [A C version of SAT solver MINISAT, originally developed 
+  in C++ by Niklas Een and Niklas Sorensson, Chalmers University of 
+  Technology, Sweden: http://www.cs.chalmers.se/~een/Satzoo.]
+
+  Synopsis    [APIs of the SAT solver.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - January 1, 2004.]
+
+  Revision    [$Id: msatSolverApi.c,v 1.0 2004/01/01 1:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include "msatInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+static void Msat_SolverSetupTruthTables( unsigned uTruths[][2] );
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Simple SAT solver APIs.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int                Msat_SolverReadVarNum( Msat_Solver_t * p )                  { return p->nVars;      }
+int                Msat_SolverReadClauseNum( Msat_Solver_t * p )               { return p->nClauses;   }
+int                Msat_SolverReadVarAllocNum( Msat_Solver_t * p )             { return p->nVarsAlloc; }
+int                Msat_SolverReadDecisionLevel( Msat_Solver_t * p )           { return Msat_IntVecReadSize(p->vTrailLim); }
+int *              Msat_SolverReadDecisionLevelArray( Msat_Solver_t * p )      { return p->pLevel;     }
+Msat_Clause_t **    Msat_SolverReadReasonArray( Msat_Solver_t * p )            { return p->pReasons;   }
+Msat_Lit_t          Msat_SolverReadVarValue( Msat_Solver_t * p, Msat_Var_t Var ) { return p->pAssigns[Var]; }
+Msat_ClauseVec_t *  Msat_SolverReadLearned( Msat_Solver_t * p )                { return p->vLearned;   }
+Msat_ClauseVec_t ** Msat_SolverReadWatchedArray( Msat_Solver_t * p )           { return p->pvWatched;  }
+int *              Msat_SolverReadAssignsArray( Msat_Solver_t * p )            { return p->pAssigns;   }
+int *              Msat_SolverReadModelArray( Msat_Solver_t * p )              { return p->pModel;     }
+int                Msat_SolverReadBackTracks( Msat_Solver_t * p )              { return (int)p->Stats.nConflicts; }
+int                Msat_SolverReadInspects( Msat_Solver_t * p )                { return (int)p->Stats.nInspects;  }
+Msat_MmStep_t *     Msat_SolverReadMem( Msat_Solver_t * p )                    { return p->pMem;       }
+int *              Msat_SolverReadSeenArray( Msat_Solver_t * p )               { return p->pSeen;      }
+int                Msat_SolverIncrementSeenId( Msat_Solver_t * p )             { return ++p->nSeenId;  }
+void               Msat_SolverSetVerbosity( Msat_Solver_t * p, int fVerbose )  { p->fVerbose = fVerbose; }
+void               Msat_SolverClausesIncrement( Msat_Solver_t * p )            { p->nClausesAlloc++;   }
+void               Msat_SolverClausesDecrement( Msat_Solver_t * p )            { p->nClausesAlloc--;   }
+void               Msat_SolverClausesIncrementL( Msat_Solver_t * p )           { p->nClausesAllocL++;  }
+void               Msat_SolverClausesDecrementL( Msat_Solver_t * p )           { p->nClausesAllocL--;  }
+void               Msat_SolverMarkLastClauseTypeA( Msat_Solver_t * p )         { Msat_ClauseSetTypeA( Msat_ClauseVecReadEntry( p->vClauses, Msat_ClauseVecReadSize(p->vClauses)-1 ), 1 ); }
+void               Msat_SolverMarkClausesStart( Msat_Solver_t * p )            { p->nClausesStart = Msat_ClauseVecReadSize(p->vClauses); }
+float *            Msat_SolverReadFactors( Msat_Solver_t * p )                 { return p->pFactors;   }
+
+/**Function*************************************************************
+
+  Synopsis    [Reads the clause with the given number.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_Clause_t * Msat_SolverReadClause( Msat_Solver_t * p, int Num )
+{
+    int nClausesP;
+    assert( Num < p->nClauses );
+    nClausesP = Msat_ClauseVecReadSize( p->vClauses );
+    if ( Num < nClausesP )
+        return Msat_ClauseVecReadEntry( p->vClauses, Num );
+    return Msat_ClauseVecReadEntry( p->vLearned, Num - nClausesP );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Reads the clause with the given number.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_ClauseVec_t *  Msat_SolverReadAdjacents( Msat_Solver_t * p )
+{
+    return p->vAdjacents;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Reads the clause with the given number.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_IntVec_t *  Msat_SolverReadConeVars( Msat_Solver_t * p )
+{
+    return p->vConeVars;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Reads the clause with the given number.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_IntVec_t *  Msat_SolverReadVarsUsed( Msat_Solver_t * p )
+{
+    return p->vVarsUsed;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Allocates the solver.]
+
+  Description [After the solver is allocated, the procedure
+  Msat_SolverClean() should be called to set the number of variables.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_Solver_t * Msat_SolverAlloc( int nVarsAlloc,
+    double dClaInc, double dClaDecay, 
+    double dVarInc, double dVarDecay, 
+    bool fVerbose )
+{
+    Msat_Solver_t * p;
+    int i;
+
+    assert(sizeof(Msat_Lit_t) == sizeof(unsigned));
+    assert(sizeof(float)     == sizeof(unsigned));
+
+    p = ALLOC( Msat_Solver_t, 1 );
+    memset( p, 0, sizeof(Msat_Solver_t) );
+
+    p->nVarsAlloc = nVarsAlloc;
+    p->nVars     = 0;
+
+    p->nClauses  = 0;
+    p->vClauses  = Msat_ClauseVecAlloc( 512 );
+    p->vLearned  = Msat_ClauseVecAlloc( 512 );
+
+    p->dClaInc   = dClaInc;
+    p->dClaDecay = dClaDecay;
+    p->dVarInc   = dVarInc;
+    p->dVarDecay = dVarDecay;
+
+    p->pdActivity = ALLOC( double, p->nVarsAlloc );
+    p->pFactors   = ALLOC( float, p->nVarsAlloc );
+    for ( i = 0; i < p->nVarsAlloc; i++ )
+    {
+        p->pdActivity[i] = 0.0;
+        p->pFactors[i]   = 1.0;
+    }
+
+    p->pAssigns  = ALLOC( int, p->nVarsAlloc ); 
+    p->pModel    = ALLOC( int, p->nVarsAlloc ); 
+    for ( i = 0; i < p->nVarsAlloc; i++ )
+        p->pAssigns[i] = MSAT_VAR_UNASSIGNED;
+//    p->pOrder    = Msat_OrderAlloc( p->pAssigns, p->pdActivity, p->nVarsAlloc );
+    p->pOrder    = Msat_OrderAlloc( p );
+
+    p->pvWatched = ALLOC( Msat_ClauseVec_t *, 2 * p->nVarsAlloc );
+    for ( i = 0; i < 2 * p->nVarsAlloc; i++ )
+        p->pvWatched[i] = Msat_ClauseVecAlloc( 16 );
+    p->pQueue    = Msat_QueueAlloc( p->nVarsAlloc );
+
+    p->vTrail    = Msat_IntVecAlloc( p->nVarsAlloc );
+    p->vTrailLim = Msat_IntVecAlloc( p->nVarsAlloc );
+    p->pReasons  = ALLOC( Msat_Clause_t *, p->nVarsAlloc );
+    memset( p->pReasons, 0, sizeof(Msat_Clause_t *) * p->nVarsAlloc );
+    p->pLevel = ALLOC( int, p->nVarsAlloc );
+    for ( i = 0; i < p->nVarsAlloc; i++ )
+        p->pLevel[i] = -1;
+    p->dRandSeed = 91648253;
+    p->fVerbose  = fVerbose;
+    p->dProgress = 0.0;
+//    p->pModel = Msat_IntVecAlloc( p->nVarsAlloc );
+    p->pMem = Msat_MmStepStart( 10 );
+
+    p->vConeVars   = Msat_IntVecAlloc( p->nVarsAlloc ); 
+    p->vAdjacents  = Msat_ClauseVecAlloc( p->nVarsAlloc );
+    for ( i = 0; i < p->nVarsAlloc; i++ )
+        Msat_ClauseVecPush( p->vAdjacents, (Msat_Clause_t *)Msat_IntVecAlloc(5) );
+    p->vVarsUsed   = Msat_IntVecAlloc( p->nVarsAlloc ); 
+    Msat_IntVecFill( p->vVarsUsed, p->nVarsAlloc, 1 );
+
+
+    p->pSeen     = ALLOC( int, p->nVarsAlloc );
+    memset( p->pSeen, 0, sizeof(int) * p->nVarsAlloc );
+    p->nSeenId   = 1;
+    p->vReason   = Msat_IntVecAlloc( p->nVarsAlloc );
+    p->vTemp     = Msat_IntVecAlloc( p->nVarsAlloc );
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Resizes the solver.]
+
+  Description [Assumes that the solver contains some clauses, and that 
+  it is currently between the calls. Resizes the solver to accomodate 
+  more variables.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverResize( Msat_Solver_t * p, int nVarsAlloc )
+{
+    int nVarsAllocOld, i;
+
+    nVarsAllocOld = p->nVarsAlloc;
+    p->nVarsAlloc = nVarsAlloc;
+
+    p->pdActivity = REALLOC( double, p->pdActivity, p->nVarsAlloc );
+    p->pFactors   = REALLOC( float, p->pFactors, p->nVarsAlloc );
+    for ( i = nVarsAllocOld; i < p->nVarsAlloc; i++ )
+    {
+        p->pdActivity[i] = 0.0;
+        p->pFactors[i]   = 1.0;
+    }
+
+    p->pAssigns  = REALLOC( int, p->pAssigns, p->nVarsAlloc );
+    p->pModel    = REALLOC( int, p->pModel, p->nVarsAlloc );
+    for ( i = nVarsAllocOld; i < p->nVarsAlloc; i++ )
+        p->pAssigns[i] = MSAT_VAR_UNASSIGNED;
+
+//    Msat_OrderRealloc( p->pOrder, p->pAssigns, p->pdActivity, p->nVarsAlloc );
+    Msat_OrderSetBounds( p->pOrder, p->nVarsAlloc );
+
+    p->pvWatched = REALLOC( Msat_ClauseVec_t *, p->pvWatched, 2 * p->nVarsAlloc );
+    for ( i = 2 * nVarsAllocOld; i < 2 * p->nVarsAlloc; i++ )
+        p->pvWatched[i] = Msat_ClauseVecAlloc( 16 );
+
+    Msat_QueueFree( p->pQueue );
+    p->pQueue    = Msat_QueueAlloc( p->nVarsAlloc );
+
+    p->pReasons  = REALLOC( Msat_Clause_t *, p->pReasons, p->nVarsAlloc );
+    p->pLevel    = REALLOC( int, p->pLevel, p->nVarsAlloc );
+    for ( i = nVarsAllocOld; i < p->nVarsAlloc; i++ )
+    {
+        p->pReasons[i] = NULL;
+        p->pLevel[i] = -1;
+    }
+
+    p->pSeen     = REALLOC( int, p->pSeen, p->nVarsAlloc );
+    for ( i = nVarsAllocOld; i < p->nVarsAlloc; i++ )
+        p->pSeen[i] = 0;
+
+    Msat_IntVecGrow( p->vTrail, p->nVarsAlloc );
+    Msat_IntVecGrow( p->vTrailLim, p->nVarsAlloc );
+
+    // make sure the array of adjucents has room to store the variable numbers
+    for ( i = Msat_ClauseVecReadSize(p->vAdjacents); i < p->nVarsAlloc; i++ )
+        Msat_ClauseVecPush( p->vAdjacents, (Msat_Clause_t *)Msat_IntVecAlloc(5) );
+    Msat_IntVecFill( p->vVarsUsed, p->nVarsAlloc, 1 );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Prepares the solver.]
+
+  Description [Cleans the solver assuming that the problem will involve 
+  the given number of variables (nVars). This procedure is useful 
+  for many small (incremental) SAT problems, to prevent the solver
+  from being reallocated each time.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverClean( Msat_Solver_t * p, int nVars )
+{
+    int i;
+    // free the clauses
+    int nClauses;
+    Msat_Clause_t ** pClauses;
+
+    assert( p->nVarsAlloc >= nVars );
+    p->nVars    = nVars;
+    p->nClauses = 0;
+
+    nClauses = Msat_ClauseVecReadSize( p->vClauses );
+    pClauses = Msat_ClauseVecReadArray( p->vClauses );
+    for ( i = 0; i < nClauses; i++ )
+        Msat_ClauseFree( p, pClauses[i], 0 );
+//    Msat_ClauseVecFree( p->vClauses );
+    Msat_ClauseVecClear( p->vClauses );
+
+    nClauses = Msat_ClauseVecReadSize( p->vLearned );
+    pClauses = Msat_ClauseVecReadArray( p->vLearned );
+    for ( i = 0; i < nClauses; i++ )
+        Msat_ClauseFree( p, pClauses[i], 0 );
+//    Msat_ClauseVecFree( p->vLearned );
+    Msat_ClauseVecClear( p->vLearned );
+
+//    FREE( p->pdActivity );
+    for ( i = 0; i < p->nVars; i++ )
+        p->pdActivity[i] = 0;
+
+//    Msat_OrderFree( p->pOrder );
+//    Msat_OrderClean( p->pOrder, p->nVars, NULL );
+    Msat_OrderSetBounds( p->pOrder, p->nVars );
+
+    for ( i = 0; i < 2 * p->nVars; i++ )
+//        Msat_ClauseVecFree( p->pvWatched[i] );
+        Msat_ClauseVecClear( p->pvWatched[i] );
+//    FREE( p->pvWatched );
+//    Msat_QueueFree( p->pQueue );
+    Msat_QueueClear( p->pQueue );
+
+//    FREE( p->pAssigns );
+    for ( i = 0; i < p->nVars; i++ )
+        p->pAssigns[i] = MSAT_VAR_UNASSIGNED;
+//    Msat_IntVecFree( p->vTrail );
+    Msat_IntVecClear( p->vTrail );
+//    Msat_IntVecFree( p->vTrailLim );
+    Msat_IntVecClear( p->vTrailLim );
+//    FREE( p->pReasons );
+    memset( p->pReasons, 0, sizeof(Msat_Clause_t *) * p->nVars );
+//    FREE( p->pLevel );
+    for ( i = 0; i < p->nVars; i++ )
+        p->pLevel[i] = -1;
+//    Msat_IntVecFree( p->pModel );
+//    Msat_MmStepStop( p->pMem, 0 );
+    p->dRandSeed = 91648253;
+    p->dProgress = 0.0;
+
+//    FREE( p->pSeen );
+    memset( p->pSeen, 0, sizeof(int) * p->nVars );
+    p->nSeenId = 1;
+//    Msat_IntVecFree( p->vReason );
+    Msat_IntVecClear( p->vReason );
+//    Msat_IntVecFree( p->vTemp );
+    Msat_IntVecClear( p->vTemp );
+//    printf(" The number of clauses remaining = %d (%d).\n", p->nClausesAlloc, p->nClausesAllocL );
+//    FREE( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Frees the solver.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverFree( Msat_Solver_t * p )
+{
+    int i;
+
+    // free the clauses
+    int nClauses;
+    Msat_Clause_t ** pClauses;
+//printf( "clauses = %d. learned = %d.\n", Msat_ClauseVecReadSize( p->vClauses ), 
+//                                         Msat_ClauseVecReadSize( p->vLearned ) );
+
+    nClauses = Msat_ClauseVecReadSize( p->vClauses );
+    pClauses = Msat_ClauseVecReadArray( p->vClauses );
+    for ( i = 0; i < nClauses; i++ )
+        Msat_ClauseFree( p, pClauses[i], 0 );
+    Msat_ClauseVecFree( p->vClauses );
+
+    nClauses = Msat_ClauseVecReadSize( p->vLearned );
+    pClauses = Msat_ClauseVecReadArray( p->vLearned );
+    for ( i = 0; i < nClauses; i++ )
+        Msat_ClauseFree( p, pClauses[i], 0 );
+    Msat_ClauseVecFree( p->vLearned );
+
+    FREE( p->pdActivity );
+    FREE( p->pFactors );
+    Msat_OrderFree( p->pOrder );
+
+    for ( i = 0; i < 2 * p->nVarsAlloc; i++ )
+        Msat_ClauseVecFree( p->pvWatched[i] );
+    FREE( p->pvWatched );
+    Msat_QueueFree( p->pQueue );
+
+    FREE( p->pAssigns );
+    FREE( p->pModel );
+    Msat_IntVecFree( p->vTrail );
+    Msat_IntVecFree( p->vTrailLim );
+    FREE( p->pReasons );
+    FREE( p->pLevel );
+
+    Msat_MmStepStop( p->pMem, 0 );
+
+    nClauses = Msat_ClauseVecReadSize( p->vAdjacents );
+    pClauses = Msat_ClauseVecReadArray( p->vAdjacents );
+    for ( i = 0; i < nClauses; i++ )
+        Msat_IntVecFree( (Msat_IntVec_t *)pClauses[i] );
+    Msat_ClauseVecFree( p->vAdjacents );
+    Msat_IntVecFree( p->vConeVars );
+    Msat_IntVecFree( p->vVarsUsed );
+
+    FREE( p->pSeen );
+    Msat_IntVecFree( p->vReason );
+    Msat_IntVecFree( p->vTemp );
+    FREE( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Prepares the solver to run on a subset of variables.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverPrepare( Msat_Solver_t * p, Msat_IntVec_t * vVars )
+{
+
+    int i;
+    // undo the previous data
+    for ( i = 0; i < p->nVarsAlloc; i++ )
+    {
+        p->pAssigns[i]   = MSAT_VAR_UNASSIGNED;
+        p->pReasons[i]   = NULL;
+        p->pLevel[i]     = -1;
+        p->pdActivity[i] = 0.0;
+    }
+
+    // set the new variable order
+    Msat_OrderClean( p->pOrder, vVars );
+
+    Msat_QueueClear( p->pQueue );
+    Msat_IntVecClear( p->vTrail );
+    Msat_IntVecClear( p->vTrailLim );
+    p->dProgress = 0.0;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Sets up the truth tables.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverSetupTruthTables( unsigned uTruths[][2] )
+{
+    int m, v;
+    // set up the truth tables
+    for ( m = 0; m < 32; m++ )
+        for ( v = 0; v < 5; v++ )
+            if ( m & (1 << v) )
+                uTruths[v][0] |= (1 << m);
+    // make adjustments for the case of 6 variables
+    for ( v = 0; v < 5; v++ )
+        uTruths[v][1] = uTruths[v][0];
+    uTruths[5][0] = 0;
+    uTruths[5][1] = ~((unsigned)0);
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/msat/msatSolverCore.c b/src/sat/msat/msatSolverCore.c
new file mode 100644
index 00000000..f9fee73c
--- /dev/null
+++ b/src/sat/msat/msatSolverCore.c
@@ -0,0 +1,212 @@
+/**CFile****************************************************************
+
+  FileName    [msatSolverCore.c]
+
+  PackageName [A C version of SAT solver MINISAT, originally developed 
+  in C++ by Niklas Een and Niklas Sorensson, Chalmers University of 
+  Technology, Sweden: http://www.cs.chalmers.se/~een/Satzoo.]
+
+  Synopsis    [The SAT solver core procedures.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - January 1, 2004.]
+
+  Revision    [$Id: msatSolverCore.c,v 1.2 2004/05/12 03:37:40 satrajit Exp $]
+
+***********************************************************************/
+
+#include "msatInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Adds one variable to the solver.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+bool Msat_SolverAddVar( Msat_Solver_t * p, int Level )
+{
+    if ( p->nVars == p->nVarsAlloc )
+        Msat_SolverResize( p, 2 * p->nVarsAlloc );
+    p->pLevel[p->nVars] = Level;
+    p->nVars++;
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Adds one clause to the solver's clause database.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+bool Msat_SolverAddClause( Msat_Solver_t * p, Msat_IntVec_t * vLits )
+{
+    Msat_Clause_t * pC; 
+    bool Value;
+    Value = Msat_ClauseCreate( p, vLits, 0, &pC );
+    if ( pC != NULL )
+        Msat_ClauseVecPush( p->vClauses, pC );
+//    else if ( p->fProof )
+//        Msat_ClauseCreateFake( p, vLits );
+    return Value;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Returns search-space coverage. Not extremely reliable.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+double Msat_SolverProgressEstimate( Msat_Solver_t * p )
+{
+    double dProgress = 0.0;
+    double dF = 1.0 / p->nVars;
+    int i;
+    for ( i = 0; i < p->nVars; i++ )
+        if ( p->pAssigns[i] != MSAT_VAR_UNASSIGNED )
+            dProgress += pow( dF, p->pLevel[i] );
+    return dProgress / p->nVars;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Prints statistics about the solver.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverPrintStats( Msat_Solver_t * p )
+{
+    printf("C solver (%d vars; %d clauses; %d learned):\n", 
+        p->nVars, Msat_ClauseVecReadSize(p->vClauses), Msat_ClauseVecReadSize(p->vLearned) );
+    printf("starts        : %lld\n", p->Stats.nStarts);
+    printf("conflicts     : %lld\n", p->Stats.nConflicts);
+    printf("decisions     : %lld\n", p->Stats.nDecisions);
+    printf("propagations  : %lld\n", p->Stats.nPropagations);
+    printf("inspects      : %lld\n", p->Stats.nInspects);
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Top-level solve.]
+
+  Description [If using assumptions (non-empty 'assumps' vector), you must 
+  call 'simplifyDB()' first to see that no top-level conflict is present 
+  (which would put the solver in an undefined state. If the last argument
+  is given (vProj), the solver enumerates through the satisfying solutions,
+  which are projected on the variables listed in this array. Note that the
+  variables in the array may be complemented, in which case the derived
+  assignment for the variable is complemented.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+bool Msat_SolverSolve( Msat_Solver_t * p, Msat_IntVec_t * vAssumps, int nBackTrackLimit, int nTimeLimit )
+{
+    Msat_SearchParams_t Params = { 0.95, 0.999 };
+    double nConflictsLimit, nLearnedLimit;
+    Msat_Type_t Status;
+    int timeStart = clock();
+    int64 nConflictsOld = p->Stats.nConflicts;
+    int64 nDecisionsOld = p->Stats.nDecisions;
+
+//    p->pFreq = ALLOC( int, p->nVarsAlloc );
+//    memset( p->pFreq, 0, sizeof(int) * p->nVarsAlloc );
+ 
+    if ( vAssumps )
+    {
+        int * pAssumps, nAssumps, i;
+
+        assert( Msat_IntVecReadSize(p->vTrailLim) == 0 );
+
+        nAssumps = Msat_IntVecReadSize( vAssumps );
+        pAssumps = Msat_IntVecReadArray( vAssumps );
+        for ( i = 0; i < nAssumps; i++ )
+        {
+            if ( !Msat_SolverAssume(p, pAssumps[i]) || Msat_SolverPropagate(p) )
+            {
+                Msat_QueueClear( p->pQueue );
+                Msat_SolverCancelUntil( p, 0 );
+                return MSAT_FALSE;
+            }
+        }
+    }
+    p->nLevelRoot   = Msat_SolverReadDecisionLevel(p);
+    p->nClausesInit = Msat_ClauseVecReadSize( p->vClauses );    
+    nConflictsLimit = 100;
+    nLearnedLimit   = Msat_ClauseVecReadSize(p->vClauses) / 3;
+    Status = MSAT_UNKNOWN;
+    p->nBackTracks = (int)p->Stats.nConflicts;
+    while ( Status == MSAT_UNKNOWN )
+    {
+        if ( p->fVerbose )
+            printf("Solving -- conflicts=%d   learnts=%d   progress=%.4f %%\n", 
+                (int)nConflictsLimit, (int)nLearnedLimit, p->dProgress*100);
+        Status = Msat_SolverSearch( p, (int)nConflictsLimit, (int)nLearnedLimit, nBackTrackLimit, &Params );
+        nConflictsLimit *= 1.5;
+        nLearnedLimit   *= 1.1;
+        // if the limit on the number of backtracks is given, quit the restart loop
+        if ( nBackTrackLimit > 0 && (int)p->Stats.nConflicts - p->nBackTracks > nBackTrackLimit )
+            break;
+        // if the runtime limit is exceeded, quit the restart loop
+        if ( nTimeLimit > 0 && clock() - timeStart >= nTimeLimit * CLOCKS_PER_SEC )
+            break;
+    }
+    Msat_SolverCancelUntil( p, 0 );
+    p->nBackTracks = (int)p->Stats.nConflicts - p->nBackTracks;
+/*
+    PRT( "True solver runtime", clock() - timeStart );
+    // print the statistics
+    {
+        int i, Counter = 0;
+        for ( i = 0; i < p->nVars; i++ )
+            if ( p->pFreq[i] > 0 )
+            {
+                printf( "%d ", p->pFreq[i] );
+                Counter++;
+            }
+        if ( Counter )
+            printf( "\n" );
+        printf( "Total = %d. Used = %d.  Decisions = %d. Imps = %d. Conflicts = %d. ", p->nVars, Counter, (int)p->Stats.nDecisions, (int)p->Stats.nPropagations, (int)p->Stats.nConflicts );
+        PRT( "Time", clock() - timeStart );
+    }
+*/
+    return Status;
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/msat/msatSolverIo.c b/src/sat/msat/msatSolverIo.c
new file mode 100644
index 00000000..05b7f6a9
--- /dev/null
+++ b/src/sat/msat/msatSolverIo.c
@@ -0,0 +1,177 @@
+/**CFile****************************************************************
+
+  FileName    [msatSolverIo.c]
+
+  PackageName [A C version of SAT solver MINISAT, originally developed 
+  in C++ by Niklas Een and Niklas Sorensson, Chalmers University of 
+  Technology, Sweden: http://www.cs.chalmers.se/~een/Satzoo.]
+
+  Synopsis    [Input/output of CNFs.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - January 1, 2004.]
+
+  Revision    [$Id: msatSolverIo.c,v 1.0 2004/01/01 1:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include "msatInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+static char * Msat_TimeStamp();
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverPrintAssignment( Msat_Solver_t * p )
+{
+    int i;
+    printf( "Current assignments are: \n" );
+    for ( i = 0; i < p->nVars; i++ )
+        printf( "%d", i % 10 );
+    printf( "\n" );
+    for ( i = 0; i < p->nVars; i++ )
+        if ( p->pAssigns[i] == MSAT_VAR_UNASSIGNED )
+            printf( "." );
+        else
+        {
+            assert( i == MSAT_LIT2VAR(p->pAssigns[i]) );
+            if ( MSAT_LITSIGN(p->pAssigns[i]) )
+                printf( "0" );
+            else 
+                printf( "1" );
+        }
+    printf( "\n" );
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverPrintClauses( Msat_Solver_t * p )
+{
+    Msat_Clause_t ** pClauses;
+    int nClauses, i;
+
+    printf( "Original clauses: \n" );
+    nClauses = Msat_ClauseVecReadSize( p->vClauses );
+    pClauses = Msat_ClauseVecReadArray( p->vClauses );
+    for ( i = 0; i < nClauses; i++ )
+    {
+        printf( "%3d: ", i );
+        Msat_ClausePrint( pClauses[i] );
+    }
+
+    printf( "Learned clauses: \n" );
+    nClauses = Msat_ClauseVecReadSize( p->vLearned );
+    pClauses = Msat_ClauseVecReadArray( p->vLearned );
+    for ( i = 0; i < nClauses; i++ )
+    {
+        printf( "%3d: ", i );
+        Msat_ClausePrint( pClauses[i] );
+    }
+
+    printf( "Variable activity: \n" );
+    for ( i = 0; i < p->nVars; i++ )
+        printf( "%3d : %.4f\n", i, p->pdActivity[i] );
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverWriteDimacs( Msat_Solver_t * p, char * pFileName )
+{
+    FILE * pFile;
+    Msat_Clause_t ** pClauses;
+    int nClauses, i;
+
+    nClauses = Msat_ClauseVecReadSize(p->vClauses) + Msat_ClauseVecReadSize(p->vLearned);
+    for ( i = 0; i < p->nVars; i++ )
+        nClauses += ( p->pLevel[i] == 0 );
+
+    pFile = fopen( pFileName, "wb" );
+    fprintf( pFile, "c Produced by Msat_SolverWriteDimacs() on %s\n", Msat_TimeStamp() );
+    fprintf( pFile, "p cnf %d %d\n", p->nVars, nClauses );
+
+    nClauses = Msat_ClauseVecReadSize( p->vClauses );
+    pClauses = Msat_ClauseVecReadArray( p->vClauses );
+    for ( i = 0; i < nClauses; i++ )
+        Msat_ClauseWriteDimacs( pFile, pClauses[i], 1 );
+
+    nClauses = Msat_ClauseVecReadSize( p->vLearned );
+    pClauses = Msat_ClauseVecReadArray( p->vLearned );
+    for ( i = 0; i < nClauses; i++ )
+        Msat_ClauseWriteDimacs( pFile, pClauses[i], 1 );
+
+    // write zero-level assertions
+    for ( i = 0; i < p->nVars; i++ )
+        if ( p->pLevel[i] == 0 )
+            fprintf( pFile, "%s%d 0\n", ((p->pAssigns[i]&1)? "-": ""), i + 1 );
+
+    fprintf( pFile, "\n" );
+    fclose( pFile );
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Returns the time stamp.]
+
+  Description []
+
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+char * Msat_TimeStamp()
+{
+    static char Buffer[100];
+    time_t ltime;
+    char * TimeStamp;
+    // get the current time
+    time( &ltime );
+    TimeStamp = asctime( localtime( &ltime ) );
+    TimeStamp[ strlen(TimeStamp) - 1 ] = 0;
+    strcpy( Buffer, TimeStamp );
+    return Buffer;
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/msat/msatSolverSearch.c b/src/sat/msat/msatSolverSearch.c
new file mode 100644
index 00000000..11a6540c
--- /dev/null
+++ b/src/sat/msat/msatSolverSearch.c
@@ -0,0 +1,629 @@
+/**CFile****************************************************************
+
+  FileName    [msatSolverSearch.c]
+
+  PackageName [A C version of SAT solver MINISAT, originally developed 
+  in C++ by Niklas Een and Niklas Sorensson, Chalmers University of 
+  Technology, Sweden: http://www.cs.chalmers.se/~een/Satzoo.]
+
+  Synopsis    [The search part of the solver.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - January 1, 2004.]
+
+  Revision    [$Id: msatSolverSearch.c,v 1.0 2004/01/01 1:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include "msatInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+static void            Msat_SolverUndoOne( Msat_Solver_t * p );
+static void            Msat_SolverCancel( Msat_Solver_t * p );
+static Msat_Clause_t * Msat_SolverRecord( Msat_Solver_t * p, Msat_IntVec_t * vLits );
+static void            Msat_SolverAnalyze( Msat_Solver_t * p, Msat_Clause_t * pC, Msat_IntVec_t * vLits_out, int * pLevel_out );
+static void            Msat_SolverReduceDB( Msat_Solver_t * p );
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Makes the next assumption (Lit).]
+
+  Description [Returns FALSE if immediate conflict.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+bool Msat_SolverAssume( Msat_Solver_t * p, Msat_Lit_t Lit )
+{
+    assert( Msat_QueueReadSize(p->pQueue) == 0 );
+    if ( p->fVerbose )
+        printf(L_IND"assume("L_LIT")\n", L_ind, L_lit(Lit));
+    Msat_IntVecPush( p->vTrailLim, Msat_IntVecReadSize(p->vTrail) );
+//    assert( Msat_IntVecReadSize(p->vTrailLim) <= Msat_IntVecReadSize(p->vTrail) + 1 );
+//    assert( Msat_IntVecReadSize( p->vTrailLim ) < p->nVars );
+    return Msat_SolverEnqueue( p, Lit, NULL );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Reverts one variable binding on the trail.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverUndoOne( Msat_Solver_t * p )
+{
+    Msat_Lit_t Lit;
+    Msat_Var_t Var;
+    Lit = Msat_IntVecPop( p->vTrail ); 
+    Var = MSAT_LIT2VAR(Lit);
+    p->pAssigns[Var] = MSAT_VAR_UNASSIGNED;
+    p->pReasons[Var] = NULL;
+    p->pLevel[Var]   = -1;
+//    Msat_OrderUndo( p->pOrder, Var );
+    Msat_OrderVarUnassigned( p->pOrder, Var );
+
+    if ( p->fVerbose )
+        printf(L_IND"unbind("L_LIT")\n", L_ind, L_lit(Lit)); 
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Reverts to the state before last Msat_SolverAssume().]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverCancel( Msat_Solver_t * p )
+{
+    int c;
+    assert( Msat_QueueReadSize(p->pQueue) == 0 );
+    if ( p->fVerbose )
+    {
+        if ( Msat_IntVecReadSize(p->vTrail) != Msat_IntVecReadEntryLast(p->vTrailLim) )
+        {
+            Msat_Lit_t Lit;
+            Lit = Msat_IntVecReadEntry( p->vTrail, Msat_IntVecReadEntryLast(p->vTrailLim) ); 
+            printf(L_IND"cancel("L_LIT")\n", L_ind, L_lit(Lit));
+        }
+    }
+    for ( c = Msat_IntVecReadSize(p->vTrail) - Msat_IntVecPop( p->vTrailLim ); c != 0; c-- )
+        Msat_SolverUndoOne( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Reverts to the state at given level.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverCancelUntil( Msat_Solver_t * p, int Level )
+{
+    while ( Msat_IntVecReadSize(p->vTrailLim) > Level )
+        Msat_SolverCancel(p);
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Record a clause and drive backtracking.]
+
+  Description [vLits[0] must contain the asserting literal.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_Clause_t * Msat_SolverRecord( Msat_Solver_t * p, Msat_IntVec_t * vLits )
+{
+    Msat_Clause_t * pC;
+    int Value;
+    assert( Msat_IntVecReadSize(vLits) != 0 );
+    Value = Msat_ClauseCreate( p, vLits, 1, &pC );
+    assert( Value );
+    Value = Msat_SolverEnqueue( p, Msat_IntVecReadEntry(vLits,0), pC );
+    assert( Value );
+    if ( pC )
+        Msat_ClauseVecPush( p->vLearned, pC );
+    return pC;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Enqueues one variable assignment.]
+
+  Description [Puts a new fact on the propagation queue and immediately 
+  updates the variable value. Should a conflict arise, FALSE is returned.
+  Otherwise returns TRUE.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+bool Msat_SolverEnqueue( Msat_Solver_t * p, Msat_Lit_t Lit, Msat_Clause_t * pC )
+{
+    Msat_Var_t Var = MSAT_LIT2VAR(Lit);
+
+    // skip literals that are not in the current cone
+    if ( !Msat_IntVecReadEntry( p->vVarsUsed, Var ) )
+        return 1;
+
+//    assert( Msat_QueueReadSize(p->pQueue) == Msat_IntVecReadSize(p->vTrail) );
+    // if the literal is assigned
+    // return 1 if the assignment is consistent
+    // return 0 if the assignment is inconsistent (conflict)
+    if ( p->pAssigns[Var] != MSAT_VAR_UNASSIGNED )
+        return p->pAssigns[Var] == Lit;
+    // new fact - store it
+    if ( p->fVerbose )
+    {
+//        printf(L_IND"bind("L_LIT")\n", L_ind, L_lit(Lit));
+        printf(L_IND"bind("L_LIT")  ", L_ind, L_lit(Lit));
+        Msat_ClausePrintSymbols( pC );
+    }
+    p->pAssigns[Var] = Lit;
+    p->pLevel[Var]   = Msat_IntVecReadSize(p->vTrailLim);
+//    p->pReasons[Var] = p->pLevel[Var]? pC: NULL;
+    p->pReasons[Var] = pC;
+    Msat_IntVecPush( p->vTrail, Lit );
+    Msat_QueueInsert( p->pQueue, Lit );
+
+    Msat_OrderVarAssigned( p->pOrder, Var );
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Propagates the assignments in the queue.]
+
+  Description [Propagates all enqueued facts. If a conflict arises, 
+  the conflicting clause is returned, otherwise NULL.]
+               
+  SideEffects [The propagation queue is empty, even if there was a conflict.]
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_Clause_t * Msat_SolverPropagate( Msat_Solver_t * p )
+{
+    Msat_ClauseVec_t ** pvWatched = p->pvWatched;
+    Msat_Clause_t ** pClauses;
+    Msat_Clause_t * pConflict;
+    Msat_Lit_t Lit, Lit_out;
+    int i, j, nClauses;
+
+    // propagate all the literals in the queue
+    while ( (Lit = Msat_QueueExtract( p->pQueue )) >= 0 )
+    {
+        p->Stats.nPropagations++;
+        // get the clauses watched by this literal
+        nClauses = Msat_ClauseVecReadSize( pvWatched[Lit] );
+        pClauses = Msat_ClauseVecReadArray( pvWatched[Lit] );
+        // go through the watched clauses and decide what to do with them
+        for ( i = j = 0; i < nClauses; i++ )
+        {
+            p->Stats.nInspects++;
+            // clear the returned literal
+            Lit_out = -1;
+            // propagate the clause
+            if ( !Msat_ClausePropagate( pClauses[i], Lit, p->pAssigns, &Lit_out ) )
+            {   // the clause is unit
+                // "Lit_out" contains the new assignment to be enqueued
+                if ( Msat_SolverEnqueue( p, Lit_out, pClauses[i] ) ) 
+                { // consistent assignment 
+                    // no changes to the implication queue; the watch is the same too
+                    pClauses[j++] = pClauses[i];
+                    continue;
+                }
+                // remember the reason of conflict (will be returned)
+                pConflict = pClauses[i];
+                // leave the remaning clauses in the same watched list
+                for ( ; i < nClauses; i++ )
+                    pClauses[j++] = pClauses[i];
+                Msat_ClauseVecShrink( pvWatched[Lit], j );
+                // clear the propagation queue
+                Msat_QueueClear( p->pQueue );
+                return pConflict;
+            }
+            // the clause is not unit
+            // in this case "Lit_out" contains the new watch if it has changed
+            if ( Lit_out >= 0 )
+                Msat_ClauseVecPush( pvWatched[Lit_out], pClauses[i] );
+            else // the watch did not change
+                pClauses[j++] = pClauses[i];
+        }
+        Msat_ClauseVecShrink( pvWatched[Lit], j );
+    }
+    return NULL;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Simplifies the data base.]
+
+  Description [Simplify all constraints according to the current top-level 
+  assigment (redundant constraints may be removed altogether).]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+bool Msat_SolverSimplifyDB( Msat_Solver_t * p )
+{
+    Msat_ClauseVec_t * vClauses;
+    Msat_Clause_t ** pClauses;
+    int nClauses, Type, i, j;
+    int * pAssigns;
+    int Counter;
+
+    assert( Msat_SolverReadDecisionLevel(p) == 0 );
+    if ( Msat_SolverPropagate(p) != NULL )
+        return 0;
+//Msat_SolverPrintClauses( p );
+//Msat_SolverPrintAssignment( p );
+//printf( "Simplification\n" );
+
+    // simplify and reassign clause numbers
+    Counter = 0;
+    pAssigns = Msat_SolverReadAssignsArray( p );
+    for ( Type = 0; Type < 2; Type++ )
+    {
+        vClauses = Type? p->vLearned : p->vClauses;
+        nClauses = Msat_ClauseVecReadSize( vClauses );
+        pClauses = Msat_ClauseVecReadArray( vClauses );
+        for ( i = j = 0; i < nClauses; i++ )
+            if ( Msat_ClauseSimplify( pClauses[i], pAssigns ) )
+                Msat_ClauseFree( p, pClauses[i], 1 );
+            else
+            {
+                pClauses[j++] = pClauses[i];
+                Msat_ClauseSetNum( pClauses[i], Counter++ );
+            }
+        Msat_ClauseVecShrink( vClauses, j );
+    }
+    p->nClauses = Counter;
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Cleans the clause databased from the useless learnt clauses.]
+
+  Description [Removes half of the learnt clauses, minus the clauses locked 
+  by the current assignment. Locked clauses are clauses that are reason 
+  to a some assignment.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverReduceDB( Msat_Solver_t * p )
+{
+    Msat_Clause_t ** pLearned;
+    int nLearned, i, j;
+    double dExtraLim = p->dClaInc / Msat_ClauseVecReadSize(p->vLearned); 
+    // Remove any clause below this activity
+
+    // sort the learned clauses in the increasing order of activity
+    Msat_SolverSortDB( p );
+
+    // discard the first half the clauses (the less active ones)
+    nLearned = Msat_ClauseVecReadSize( p->vLearned );
+    pLearned = Msat_ClauseVecReadArray( p->vLearned );
+    for ( i = j = 0; i < nLearned / 2; i++ )
+        if ( !Msat_ClauseIsLocked( p, pLearned[i]) )
+            Msat_ClauseFree( p, pLearned[i], 1 );
+        else
+            pLearned[j++] = pLearned[i];
+    // filter the more active clauses and leave those above the limit
+    for (  ; i < nLearned; i++ )
+        if ( !Msat_ClauseIsLocked( p, pLearned[i] ) && 
+            Msat_ClauseReadActivity(pLearned[i]) < dExtraLim )
+            Msat_ClauseFree( p, pLearned[i], 1 );
+        else
+            pLearned[j++] = pLearned[i];
+    Msat_ClauseVecShrink( p->vLearned, j );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Removes the learned clauses.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverRemoveLearned( Msat_Solver_t * p )
+{
+    Msat_Clause_t ** pLearned;
+    int nLearned, i;
+
+    // discard the learned clauses
+    nLearned = Msat_ClauseVecReadSize( p->vLearned );
+    pLearned = Msat_ClauseVecReadArray( p->vLearned );
+    for ( i = 0; i < nLearned; i++ )
+    {
+        assert( !Msat_ClauseIsLocked( p, pLearned[i]) );
+        
+        Msat_ClauseFree( p, pLearned[i], 1 );
+    }
+    Msat_ClauseVecShrink( p->vLearned, 0 );
+    p->nClauses = Msat_ClauseVecReadSize(p->vClauses);
+
+    for ( i = 0; i < p->nVarsAlloc; i++ )
+        p->pReasons[i] = NULL;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Removes the recently added clauses.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverRemoveMarked( Msat_Solver_t * p )
+{
+    Msat_Clause_t ** pLearned, ** pClauses;
+    int nLearned, nClauses, i;
+
+    // discard the learned clauses
+    nClauses = Msat_ClauseVecReadSize( p->vClauses );
+    pClauses = Msat_ClauseVecReadArray( p->vClauses );
+    for ( i = p->nClausesStart; i < nClauses; i++ )
+    {
+//        assert( !Msat_ClauseIsLocked( p, pClauses[i]) );
+        Msat_ClauseFree( p, pClauses[i], 1 );
+    }
+    Msat_ClauseVecShrink( p->vClauses, p->nClausesStart );
+
+    // discard the learned clauses
+    nLearned = Msat_ClauseVecReadSize( p->vLearned );
+    pLearned = Msat_ClauseVecReadArray( p->vLearned );
+    for ( i = 0; i < nLearned; i++ )
+    {
+//        assert( !Msat_ClauseIsLocked( p, pLearned[i]) );
+        Msat_ClauseFree( p, pLearned[i], 1 );
+    }
+    Msat_ClauseVecShrink( p->vLearned, 0 );
+    p->nClauses = Msat_ClauseVecReadSize(p->vClauses);
+/*
+    // undo the previous data
+    for ( i = 0; i < p->nVarsAlloc; i++ )
+    {
+        p->pAssigns[i]   = MSAT_VAR_UNASSIGNED;
+        p->pReasons[i]   = NULL;
+        p->pLevel[i]     = -1;
+        p->pdActivity[i] = 0.0;
+    }
+    Msat_OrderClean( p->pOrder, p->nVars, NULL );
+    Msat_QueueClear( p->pQueue );
+*/
+}
+
+
+
+/**Function*************************************************************
+
+  Synopsis    [Analyze conflict and produce a reason clause.]
+
+  Description [Current decision level must be greater than root level.]
+               
+  SideEffects [vLits_out[0] is the asserting literal at level pLevel_out.]
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverAnalyze( Msat_Solver_t * p, Msat_Clause_t * pC, Msat_IntVec_t * vLits_out, int * pLevel_out )
+{
+    Msat_Lit_t LitQ, Lit = MSAT_LIT_UNASSIGNED;
+    Msat_Var_t VarQ, Var;
+    int * pReasonArray, nReasonSize;
+    int j, pathC = 0, nLevelCur = Msat_IntVecReadSize(p->vTrailLim);
+    int iStep = Msat_IntVecReadSize(p->vTrail) - 1;
+
+    // increment the seen counter
+    p->nSeenId++;
+    // empty the vector array
+    Msat_IntVecClear( vLits_out );
+    Msat_IntVecPush( vLits_out, -1 ); // (leave room for the asserting literal)
+    *pLevel_out = 0;
+    do {
+        assert( pC != NULL );  // (otherwise should be UIP)
+        // get the reason of conflict
+        Msat_ClauseCalcReason( p, pC, Lit, p->vReason );
+        nReasonSize  = Msat_IntVecReadSize( p->vReason );
+        pReasonArray = Msat_IntVecReadArray( p->vReason );
+        for ( j = 0; j < nReasonSize; j++ ) {
+            LitQ = pReasonArray[j];
+            VarQ = MSAT_LIT2VAR(LitQ);
+            if ( p->pSeen[VarQ] != p->nSeenId ) {
+                p->pSeen[VarQ] = p->nSeenId;
+
+                // added to better fine-tune the search
+                Msat_SolverVarBumpActivity( p, LitQ );
+
+                // skip all the literals on this decision level
+                if ( p->pLevel[VarQ] == nLevelCur )
+                    pathC++;
+                else if ( p->pLevel[VarQ] > 0 ) { 
+                    // add the literals on other decision levels but
+                    // exclude variables from decision level 0
+                    Msat_IntVecPush( vLits_out, MSAT_LITNOT(LitQ) );
+                    if ( *pLevel_out < p->pLevel[VarQ] )
+                        *pLevel_out = p->pLevel[VarQ];
+                }
+            }
+        }
+        // Select next clause to look at:
+        do {
+//            Lit = Msat_IntVecReadEntryLast(p->vTrail);
+            Lit = Msat_IntVecReadEntry( p->vTrail, iStep-- );
+            Var = MSAT_LIT2VAR(Lit);
+            pC = p->pReasons[Var];
+//            Msat_SolverUndoOne( p );
+        } while ( p->pSeen[Var] != p->nSeenId );
+        pathC--;
+    } while ( pathC > 0 );
+    // we do not unbind the variables above
+    // this will be done after conflict analysis
+
+    Msat_IntVecWriteEntry( vLits_out, 0, MSAT_LITNOT(Lit) );
+    if ( p->fVerbose )
+    {
+        printf( L_IND"Learnt {", L_ind );
+        nReasonSize  = Msat_IntVecReadSize( vLits_out );
+        pReasonArray = Msat_IntVecReadArray( vLits_out );
+        for ( j = 0; j < nReasonSize; j++ ) 
+            printf(" "L_LIT, L_lit(pReasonArray[j]));
+        printf(" } at level %d\n", *pLevel_out); 
+    }
+}
+
+/**Function*************************************************************
+
+  Synopsis    [The search procedure called between the restarts.]
+
+  Description [Search for a satisfying solution as long as the number of 
+  conflicts does not exceed the limit (nConfLimit) while keeping the number 
+  of learnt clauses below the provided limit (nLearnedLimit). NOTE! Use 
+  negative value for nConfLimit or nLearnedLimit to indicate infinity.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_Type_t Msat_SolverSearch( Msat_Solver_t * p, int nConfLimit, int nLearnedLimit, int nBackTrackLimit, Msat_SearchParams_t * pPars )
+{
+    Msat_Clause_t * pConf;
+    Msat_Var_t Var;
+    int nLevelBack, nConfs, nAssigns, Value;
+    int i;
+
+    assert( Msat_SolverReadDecisionLevel(p) == p->nLevelRoot );
+    p->Stats.nStarts++;
+    p->dVarDecay = 1 / pPars->dVarDecay;
+    p->dClaDecay = 1 / pPars->dClaDecay;
+
+    // reset the activities
+    for ( i = 0; i < p->nVars; i++ )
+       p->pdActivity[i] = (double)p->pFactors[i];
+//       p->pdActivity[i] = 0.0;
+
+    nConfs = 0;
+    while ( 1 )
+    {
+        pConf = Msat_SolverPropagate( p );
+        if ( pConf != NULL ){
+            // CONFLICT
+            if ( p->fVerbose )
+            {
+//                printf(L_IND"**CONFLICT**\n", L_ind);
+                printf(L_IND"**CONFLICT**  ", L_ind);
+                Msat_ClausePrintSymbols( pConf );
+            }
+            // count conflicts
+            p->Stats.nConflicts++;
+            nConfs++;
+
+            // if top level, return UNSAT
+            if ( Msat_SolverReadDecisionLevel(p) == p->nLevelRoot )
+                return MSAT_FALSE;
+
+            // perform conflict analysis
+            Msat_SolverAnalyze( p, pConf, p->vTemp, &nLevelBack );
+            Msat_SolverCancelUntil( p, (p->nLevelRoot > nLevelBack)? p->nLevelRoot : nLevelBack );
+            Msat_SolverRecord( p, p->vTemp );
+
+            // it is important that recording is done after cancelling
+            // because canceling cleans the queue while recording adds to it
+            Msat_SolverVarDecayActivity( p );
+            Msat_SolverClaDecayActivity( p );
+
+        }
+        else{
+            // NO CONFLICT
+            if ( Msat_IntVecReadSize(p->vTrailLim) == 0 ) {
+                // Simplify the set of problem clauses:
+//                Value = Msat_SolverSimplifyDB(p);
+//                assert( Value );
+            }
+            nAssigns = Msat_IntVecReadSize( p->vTrail );
+            if ( nLearnedLimit >= 0 && Msat_ClauseVecReadSize(p->vLearned) >= nLearnedLimit + nAssigns ) {
+                // Reduce the set of learnt clauses:
+                Msat_SolverReduceDB(p);
+            }
+
+            Var = Msat_OrderVarSelect( p->pOrder );
+            if ( Var == MSAT_ORDER_UNKNOWN ) {
+                // Model found and stored in p->pAssigns
+                memcpy( p->pModel, p->pAssigns, sizeof(int) * p->nVars );
+                Msat_QueueClear( p->pQueue );
+                Msat_SolverCancelUntil( p, p->nLevelRoot );
+                return MSAT_TRUE;
+            }
+            if ( nConfLimit > 0 && nConfs > nConfLimit ) {
+                // Reached bound on number of conflicts:
+                p->dProgress = Msat_SolverProgressEstimate( p );
+                Msat_QueueClear( p->pQueue );
+                Msat_SolverCancelUntil( p, p->nLevelRoot );
+                return MSAT_UNKNOWN; 
+            }
+            else if ( nBackTrackLimit > 0 && (int)p->Stats.nConflicts - p->nBackTracks > nBackTrackLimit ) {
+                // Reached bound on number of conflicts:
+                Msat_QueueClear( p->pQueue );
+                Msat_SolverCancelUntil( p, p->nLevelRoot );
+                return MSAT_UNKNOWN; 
+            }
+            else{
+                // New variable decision:
+                p->Stats.nDecisions++;
+                assert( Var != MSAT_ORDER_UNKNOWN && Var >= 0 && Var < p->nVars );
+                Value = Msat_SolverAssume(p, MSAT_VAR2LIT(Var,0) );
+                assert( Value );
+            }
+        }
+    }
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/msat/msatSort.c b/src/sat/msat/msatSort.c
new file mode 100644
index 00000000..3b89d102
--- /dev/null
+++ b/src/sat/msat/msatSort.c
@@ -0,0 +1,173 @@
+/**CFile****************************************************************
+
+  FileName    [msatSort.c]
+
+  PackageName [A C version of SAT solver MINISAT, originally developed 
+  in C++ by Niklas Een and Niklas Sorensson, Chalmers University of 
+  Technology, Sweden: http://www.cs.chalmers.se/~een/Satzoo.]
+
+  Synopsis    [Sorting clauses.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - January 1, 2004.]
+
+  Revision    [$Id: msatSort.c,v 1.0 2004/01/01 1:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include "msatInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+static int Msat_SolverSortCompare( Msat_Clause_t ** ppC1, Msat_Clause_t ** ppC2 );
+
+// Returns a random float 0 <= x < 1. Seed must never be 0.
+static double drand(double seed) {
+    int q;
+    seed *= 1389796;
+    q = (int)(seed / 2147483647);
+    seed -= (double)q * 2147483647;
+    return seed / 2147483647; }
+
+// Returns a random integer 0 <= x < size. Seed must never be 0.
+static int irand(double seed, int size) {
+    return (int)(drand(seed) * size); }
+
+static void Msat_SolverSort( Msat_Clause_t ** array, int size, double seed );
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Msat_SolverSort the learned clauses in the increasing order of activity.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverSortDB( Msat_Solver_t * p )
+{
+    Msat_ClauseVec_t * pVecClauses;
+    Msat_Clause_t ** pLearned;
+    int nLearned;
+    // read the parameters
+    pVecClauses = Msat_SolverReadLearned( p );
+    nLearned    = Msat_ClauseVecReadSize( pVecClauses );
+    pLearned    = Msat_ClauseVecReadArray( pVecClauses );
+    // Msat_SolverSort the array
+//    qMsat_SolverSort( (void *)pLearned, nLearned, sizeof(Msat_Clause_t *), 
+//            (int (*)(const void *, const void *)) Msat_SolverSortCompare );
+//    printf( "Msat_SolverSorting.\n" );
+    Msat_SolverSort( pLearned, nLearned, 91648253 );
+/*
+    if ( nLearned > 2 )
+    {
+    printf( "Clause 1: %0.20f\n", Msat_ClauseReadActivity(pLearned[0]) );
+    printf( "Clause 2: %0.20f\n", Msat_ClauseReadActivity(pLearned[1]) );
+    printf( "Clause 3: %0.20f\n", Msat_ClauseReadActivity(pLearned[2]) );
+    }
+*/
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Comparison procedure for two clauses.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Msat_SolverSortCompare( Msat_Clause_t ** ppC1, Msat_Clause_t ** ppC2 )
+{
+    float Value1 = Msat_ClauseReadActivity( *ppC1 );
+    float Value2 = Msat_ClauseReadActivity( *ppC2 );
+    if ( Value1 < Value2 )
+        return -1;
+    if ( Value1 > Value2 )
+        return 1;
+    return 0;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Selection sort for small array size.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverSortSelection( Msat_Clause_t ** array, int size )
+{
+    Msat_Clause_t * tmp;
+    int i, j, best_i;
+    for ( i = 0; i < size-1; i++ )
+    {
+        best_i = i;
+        for (j = i+1; j < size; j++)
+        {
+            if ( Msat_ClauseReadActivity(array[j]) < Msat_ClauseReadActivity(array[best_i]) )
+                best_i = j;
+        }
+        tmp = array[i]; array[i] = array[best_i]; array[best_i] = tmp;
+    }
+}
+
+/**Function*************************************************************
+
+  Synopsis    [The original MiniSat sorting procedure.]
+
+  Description [This procedure is used to preserve trace-equivalence
+  with the orignal C++ implemenation of the solver.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_SolverSort( Msat_Clause_t ** array, int size, double seed )
+{
+    if (size <= 15)
+        Msat_SolverSortSelection( array, size );
+    else
+    {
+        Msat_Clause_t *   pivot = array[irand(seed, size)];
+        Msat_Clause_t *   tmp;
+        int              i = -1;
+        int              j = size;
+
+        for(;;)
+        {
+            do i++; while( Msat_ClauseReadActivity(array[i]) < Msat_ClauseReadActivity(pivot) );
+            do j--; while( Msat_ClauseReadActivity(pivot) < Msat_ClauseReadActivity(array[j]) );
+
+            if ( i >= j ) break;
+
+            tmp = array[i]; array[i] = array[j]; array[j] = tmp;
+        }
+        Msat_SolverSort(array    , i     , seed);
+        Msat_SolverSort(&array[i], size-i, seed);
+    }
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/msat/msatVec.c b/src/sat/msat/msatVec.c
new file mode 100644
index 00000000..75f53047
--- /dev/null
+++ b/src/sat/msat/msatVec.c
@@ -0,0 +1,495 @@
+/**CFile****************************************************************
+
+  FileName    [msatVec.c]
+
+  PackageName [A C version of SAT solver MINISAT, originally developed 
+  in C++ by Niklas Een and Niklas Sorensson, Chalmers University of 
+  Technology, Sweden: http://www.cs.chalmers.se/~een/Satzoo.]
+
+  Synopsis    [Integer vector borrowed from Extra.]
+
+  Author      [Alan Mishchenko <alanmi@eecs.berkeley.edu>]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - January 1, 2004.]
+
+  Revision    [$Id: msatVec.c,v 1.0 2004/01/01 1:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include "msatInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+static int Msat_IntVecSortCompare1( int * pp1, int * pp2 );
+static int Msat_IntVecSortCompare2( int * pp1, int * pp2 );
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Allocates a vector with the given capacity.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_IntVec_t * Msat_IntVecAlloc( int nCap )
+{
+    Msat_IntVec_t * p;
+    p = ALLOC( Msat_IntVec_t, 1 );
+    if ( nCap > 0 && nCap < 16 )
+        nCap = 16;
+    p->nSize  = 0;
+    p->nCap   = nCap;
+    p->pArray = p->nCap? ALLOC( int, p->nCap ) : NULL;
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Creates the vector from an integer array of the given size.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_IntVec_t * Msat_IntVecAllocArray( int * pArray, int nSize )
+{
+    Msat_IntVec_t * p;
+    p = ALLOC( Msat_IntVec_t, 1 );
+    p->nSize  = nSize;
+    p->nCap   = nSize;
+    p->pArray = pArray;
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Creates the vector from an integer array of the given size.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_IntVec_t * Msat_IntVecAllocArrayCopy( int * pArray, int nSize )
+{
+    Msat_IntVec_t * p;
+    p = ALLOC( Msat_IntVec_t, 1 );
+    p->nSize  = nSize;
+    p->nCap   = nSize;
+    p->pArray = ALLOC( int, nSize );
+    memcpy( p->pArray, pArray, sizeof(int) * nSize );
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Duplicates the integer array.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_IntVec_t * Msat_IntVecDup( Msat_IntVec_t * pVec )
+{
+    Msat_IntVec_t * p;
+    p = ALLOC( Msat_IntVec_t, 1 );
+    p->nSize  = pVec->nSize;
+    p->nCap   = pVec->nCap;
+    p->pArray = p->nCap? ALLOC( int, p->nCap ) : NULL;
+    memcpy( p->pArray, pVec->pArray, sizeof(int) * pVec->nSize );
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Transfers the array into another vector.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Msat_IntVec_t * Msat_IntVecDupArray( Msat_IntVec_t * pVec )
+{
+    Msat_IntVec_t * p;
+    p = ALLOC( Msat_IntVec_t, 1 );
+    p->nSize  = pVec->nSize;
+    p->nCap   = pVec->nCap;
+    p->pArray = pVec->pArray;
+    pVec->nSize  = 0;
+    pVec->nCap   = 0;
+    pVec->pArray = NULL;
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_IntVecFree( Msat_IntVec_t * p )
+{
+    FREE( p->pArray );
+    FREE( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Fills the vector with given number of entries.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_IntVecFill( Msat_IntVec_t * p, int nSize, int Entry )
+{
+    int i;
+    Msat_IntVecGrow( p, nSize );
+    p->nSize = nSize;
+    for ( i = 0; i < p->nSize; i++ )
+        p->pArray[i] = Entry;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int * Msat_IntVecReleaseArray( Msat_IntVec_t * p )
+{
+    int * pArray = p->pArray;
+    p->nCap = 0;
+    p->nSize = 0;
+    p->pArray = NULL;
+    return pArray;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int * Msat_IntVecReadArray( Msat_IntVec_t * p )
+{
+    return p->pArray;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Msat_IntVecReadSize( Msat_IntVec_t * p )
+{
+    return p->nSize;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Msat_IntVecReadEntry( Msat_IntVec_t * p, int i )
+{
+    assert( i >= 0 && i < p->nSize );
+    return p->pArray[i];
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_IntVecWriteEntry( Msat_IntVec_t * p, int i, int Entry )
+{
+    assert( i >= 0 && i < p->nSize );
+    p->pArray[i] = Entry;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Msat_IntVecReadEntryLast( Msat_IntVec_t * p )
+{
+    return p->pArray[p->nSize-1];
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Resizes the vector to the given capacity.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_IntVecGrow( Msat_IntVec_t * p, int nCapMin )
+{
+    if ( p->nCap >= nCapMin )
+        return;
+    p->pArray = REALLOC( int, p->pArray, nCapMin ); 
+    p->nCap   = nCapMin;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_IntVecShrink( Msat_IntVec_t * p, int nSizeNew )
+{
+    assert( p->nSize >= nSizeNew );
+    p->nSize = nSizeNew;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_IntVecClear( Msat_IntVec_t * p )
+{
+    p->nSize = 0;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_IntVecPush( Msat_IntVec_t * p, int Entry )
+{
+    if ( p->nSize == p->nCap )
+    {
+        if ( p->nCap < 16 )
+            Msat_IntVecGrow( p, 16 );
+        else
+            Msat_IntVecGrow( p, 2 * p->nCap );
+    }
+    p->pArray[p->nSize++] = Entry;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Add the element while ensuring uniqueness.]
+
+  Description [Returns 1 if the element was found, and 0 if it was new. ]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Msat_IntVecPushUnique( Msat_IntVec_t * p, int Entry )
+{
+    int i;
+    for ( i = 0; i < p->nSize; i++ )
+        if ( p->pArray[i] == Entry )
+            return 1;
+    Msat_IntVecPush( p, Entry );
+    return 0;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Inserts the element while sorting in the increasing order.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_IntVecPushUniqueOrder( Msat_IntVec_t * p, int Entry, int fIncrease )
+{
+    int Entry1, Entry2;
+    int i;
+    Msat_IntVecPushUnique( p, Entry );
+    // find the p of the node
+    for ( i = p->nSize-1; i > 0; i-- )
+    {
+        Entry1 = p->pArray[i  ];
+        Entry2 = p->pArray[i-1];
+        if ( fIncrease && Entry1 >= Entry2 || 
+            !fIncrease && Entry1 <= Entry2 )
+            break;
+        p->pArray[i  ] = Entry2;
+        p->pArray[i-1] = Entry1;
+    }
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Returns the last entry and removes it from the list.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Msat_IntVecPop( Msat_IntVec_t * p )
+{
+    assert( p->nSize > 0 );
+    return p->pArray[--p->nSize];
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Sorting the entries by their integer value.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Msat_IntVecSort( Msat_IntVec_t * p, int fReverse )
+{
+    if ( fReverse ) 
+        qsort( (void *)p->pArray, p->nSize, sizeof(int), 
+                (int (*)(const void *, const void *)) Msat_IntVecSortCompare2 );
+    else
+        qsort( (void *)p->pArray, p->nSize, sizeof(int), 
+                (int (*)(const void *, const void *)) Msat_IntVecSortCompare1 );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Comparison procedure for two clauses.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Msat_IntVecSortCompare1( int * pp1, int * pp2 )
+{
+    // for some reason commenting out lines (as shown) led to crashing of the release version
+    if ( *pp1 < *pp2 )
+        return -1;
+    if ( *pp1 > *pp2 ) //
+        return 1;
+    return 0; //
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Comparison procedure for two clauses.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Msat_IntVecSortCompare2( int * pp1, int * pp2 )
+{
+    // for some reason commenting out lines (as shown) led to crashing of the release version
+    if ( *pp1 > *pp2 )
+        return -1;
+    if ( *pp1 < *pp2 ) //
+        return 1;
+    return 0; //
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/proof/pr.c b/src/sat/proof/pr.c
new file mode 100644
index 00000000..2d1ab2d1
--- /dev/null
+++ b/src/sat/proof/pr.c
@@ -0,0 +1,1263 @@
+/**CFile****************************************************************
+
+  FileName    [pr.c]
+
+  SystemName  [ABC: Logic synthesis and verification system.]
+
+  PackageName [Proof recording.]
+
+  Synopsis    [Core procedures of the package.]
+
+  Author      [Alan Mishchenko]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - June 20, 2005.]
+
+  Revision    [$Id: pr.c,v 1.00 2005/06/20 00:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <time.h>
+//#include "vec.h"
+#include "pr.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+typedef unsigned lit;
+
+typedef struct Pr_Cls_t_ Pr_Cls_t;
+struct Pr_Cls_t_
+{
+    unsigned        uTruth;       // interpolant
+    void *          pProof;       // the proof node 
+//    void *          pAntis;       // the anticedents
+    Pr_Cls_t *      pNext;        // the next clause
+    Pr_Cls_t *      pNext0;       // the next 0-watch
+    Pr_Cls_t *      pNext1;       // the next 0-watch
+    int             Id;           // the clause ID
+    unsigned        fA     :  1;  // belongs to A
+    unsigned        fRoot  :  1;  // original clause
+    unsigned        fVisit :  1;  // visited clause
+    unsigned        nLits  : 24;  // the number of literals
+    lit             pLits[0];     // literals of this clause
+};
+
+struct Pr_Man_t_
+{
+    // general data
+    int             fProofWrite;  // writes the proof file
+    int             fProofVerif;  // verifies the proof
+    int             nVars;        // the number of variables
+    int             nVarsAB;      // the number of global variables
+    int             nRoots;       // the number of root clauses
+    int             nClauses;     // the number of all clauses
+    int             nClausesA;    // the number of clauses of A 
+    Pr_Cls_t *      pHead;        // the head clause
+    Pr_Cls_t *      pTail;        // the tail clause
+    Pr_Cls_t *      pLearnt;      // the tail clause
+    Pr_Cls_t *      pEmpty;       // the empty clause
+    // internal BCP
+    int             nRootSize;    // the number of root level assignments
+    int             nTrailSize;   // the number of assignments made 
+    lit *           pTrail;       // chronological order of assignments (size nVars)
+    lit *           pAssigns;     // assignments by variable (size nVars) 
+    char *          pSeens;       // temporary mark (size nVars)
+    char *          pVarTypes;    // variable type (size nVars) [1=A, 0=B, <0=AB]
+    Pr_Cls_t **     pReasons;     // reasons for each assignment (size nVars)          
+    Pr_Cls_t **     pWatches;     // watched clauses for each literal (size 2*nVars)          
+    int             nVarsAlloc;   // the allocated size of arrays
+    // proof recording
+    void *          pManProof;    // proof manager
+    int             Counter;      // counter of resolved clauses
+    // memory management
+    int             nChunkSize;   // the number of bytes in a chunk
+    int             nChunkUsed;   // the number of bytes used in the last chunk
+    char *          pChunkLast;   // the last memory chunk
+    // internal verification
+    lit *           pResLits;     // the literals of the resolvent   
+    int             nResLits;     // the number of literals of the resolvent
+    int             nResLitsAlloc;// the number of literals of the resolvent
+    // runtime stats
+    int             timeBcp;
+    int             timeTrace;
+    int             timeRead;
+    int             timeTotal;
+};
+
+#ifndef PRT
+#define PRT(a,t)  printf("%s = ", (a)); printf("%6.2f sec\n", (float)(t)/(float)(CLOCKS_PER_SEC))
+#endif
+
+// variable assignments 
+static const lit  LIT_UNDEF = 0xffffffff;
+
+// variable/literal conversions (taken from MiniSat)
+static inline lit   toLit    (int v)        { return v + v;  }
+static inline lit   toLitCond(int v, int c) { return v + v + (c != 0); }
+static inline lit   lit_neg  (lit l)        { return l ^ 1;  }
+static inline int   lit_var  (lit l)        { return l >> 1; }
+static inline int   lit_sign (lit l)        { return l & 1;  }
+static inline int   lit_print(lit l)        { return lit_sign(l)? -lit_var(l)-1 : lit_var(l)+1; }
+static inline lit   lit_read (int s)        { return s > 0 ? toLit(s-1) : lit_neg(toLit(-s-1)); }
+static inline int   lit_check(lit l, int n) { return l >= 0 && lit_var(l) < n;                  }
+
+// iterators through the clauses
+#define Pr_ManForEachClause( p, pCls )        for( pCls = p->pHead; pCls; pCls = pCls->pNext )
+#define Pr_ManForEachClauseRoot( p, pCls )    for( pCls = p->pHead; pCls != p->pLearnt; pCls = pCls->pNext )
+#define Pr_ManForEachClauseLearnt( p, pCls )  for( pCls = p->pLearnt; pCls; pCls = pCls->pNext )
+
+// static procedures
+static char *     Pr_ManMemoryFetch( Pr_Man_t * p, int nBytes );
+static void       Pr_ManMemoryStop( Pr_Man_t * p );
+static void       Pr_ManResize( Pr_Man_t * p, int nVarsNew );
+
+// exported procedures
+extern Pr_Man_t * Pr_ManAlloc( int nVarsAlloc );
+extern void       Pr_ManFree( Pr_Man_t * p );
+extern int        Pr_ManAddClause( Pr_Man_t * p, lit * pBeg, lit * pEnd, int fRoot, int fClauseA );
+extern int        Pr_ManProofWrite( Pr_Man_t * p );
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Allocate proof manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Pr_Man_t * Pr_ManAlloc( int nVarsAlloc )
+{
+    Pr_Man_t * p;
+    // allocate the manager
+    p = (Pr_Man_t *)malloc( sizeof(Pr_Man_t) );
+    memset( p, 0, sizeof(Pr_Man_t) );
+    // allocate internal arrays
+    Pr_ManResize( p, nVarsAlloc? nVarsAlloc : 256 );
+    // set the starting number of variables
+    p->nVars = 0;
+    // memory management
+    p->nChunkSize = (1<<16); // use 64K chunks
+    // verification
+    p->nResLitsAlloc = (1<<16);
+    p->pResLits = malloc( sizeof(lit) * p->nResLitsAlloc );
+    // parameters
+    p->fProofWrite = 0;
+    p->fProofVerif = 0;
+    return p;    
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Resize proof manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Pr_ManResize( Pr_Man_t * p, int nVarsNew )
+{
+    // check if resizing is needed
+    if ( p->nVarsAlloc < nVarsNew )
+    {
+        int nVarsAllocOld = p->nVarsAlloc;
+        // find the new size
+        if ( p->nVarsAlloc == 0 )
+            p->nVarsAlloc = 1;
+        while ( p->nVarsAlloc < nVarsNew ) 
+            p->nVarsAlloc *= 2;
+        // resize the arrays
+        p->pTrail    = (lit *)      realloc( p->pTrail,    sizeof(lit) * p->nVarsAlloc );
+        p->pAssigns  = (lit *)      realloc( p->pAssigns,  sizeof(lit) * p->nVarsAlloc );
+        p->pSeens    = (char *)     realloc( p->pSeens,    sizeof(char) * p->nVarsAlloc );
+        p->pVarTypes = (char *)     realloc( p->pVarTypes, sizeof(char) * p->nVarsAlloc );
+        p->pReasons  = (Pr_Cls_t **)realloc( p->pReasons,  sizeof(Pr_Cls_t *) * p->nVarsAlloc );
+        p->pWatches  = (Pr_Cls_t **)realloc( p->pWatches,  sizeof(Pr_Cls_t *) * p->nVarsAlloc*2 );
+        // clean the free space
+        memset( p->pAssigns  + nVarsAllocOld, 0xff, sizeof(lit) * (p->nVarsAlloc - nVarsAllocOld) );
+        memset( p->pSeens    + nVarsAllocOld, 0, sizeof(char) * (p->nVarsAlloc - nVarsAllocOld) );
+        memset( p->pVarTypes + nVarsAllocOld, 0, sizeof(char) * (p->nVarsAlloc - nVarsAllocOld) );
+        memset( p->pReasons  + nVarsAllocOld, 0, sizeof(Pr_Cls_t *) * (p->nVarsAlloc - nVarsAllocOld) );
+        memset( p->pWatches  + nVarsAllocOld, 0, sizeof(Pr_Cls_t *) * (p->nVarsAlloc - nVarsAllocOld)*2 );
+    }
+    // adjust the number of variables
+    if ( p->nVars < nVarsNew )
+        p->nVars = nVarsNew;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Deallocate proof manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Pr_ManFree( Pr_Man_t * p )
+{
+    printf( "Runtime stats:\n" );
+PRT( "Reading ", p->timeRead  );
+PRT( "BCP     ", p->timeBcp   );
+PRT( "Trace   ", p->timeTrace );
+PRT( "TOTAL   ", p->timeTotal );
+
+    Pr_ManMemoryStop( p );
+    free( p->pTrail );
+    free( p->pAssigns );
+    free( p->pSeens );
+    free( p->pVarTypes );
+    free( p->pReasons );
+    free( p->pWatches );
+    free( p->pResLits );
+    free( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Adds one clause to the watcher list.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+static inline void Pr_ManWatchClause( Pr_Man_t * p, Pr_Cls_t * pClause, lit Lit )
+{
+    assert( lit_check(Lit, p->nVars) );
+    if ( pClause->pLits[0] == Lit )
+        pClause->pNext0 = p->pWatches[lit_neg(Lit)];  
+    else
+    {
+        assert( pClause->pLits[1] == Lit );
+        pClause->pNext1 = p->pWatches[lit_neg(Lit)];  
+    }
+    p->pWatches[lit_neg(Lit)] = pClause;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Adds one clause to the manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Pr_ManAddClause( Pr_Man_t * p, lit * pBeg, lit * pEnd, int fRoot, int fClauseA )
+{
+    Pr_Cls_t * pClause;
+    lit Lit, * i, * j;
+    int nSize, VarMax;
+
+    // process the literals
+    if ( pBeg < pEnd )
+    {
+        // insertion sort
+        VarMax = lit_var( *pBeg );
+        for ( i = pBeg + 1; i < pEnd; i++ )
+        {
+            Lit = *i;
+            VarMax = lit_var(Lit) > VarMax ? lit_var(Lit) : VarMax;
+            for ( j = i; j > pBeg && *(j-1) > Lit; j-- )
+                *j = *(j-1);
+            *j = Lit;
+        }
+        // make sure there is no duplicated variables
+        for ( i = pBeg + 1; i < pEnd; i++ )
+            assert( lit_var(*(i-1)) != lit_var(*i) );
+        // resize the manager
+        Pr_ManResize( p, VarMax+1 );
+    }
+
+    // get memory for the clause
+    nSize = sizeof(Pr_Cls_t) + sizeof(lit) * (pEnd - pBeg);
+    pClause = (Pr_Cls_t *)Pr_ManMemoryFetch( p, nSize );
+    memset( pClause, 0, sizeof(Pr_Cls_t) );
+
+    // assign the clause
+    assert( !fClauseA || fRoot ); // clause of A is always a root clause
+    p->nRoots += fRoot;
+    p->nClausesA += fClauseA;
+    pClause->Id = p->nClauses++;
+    pClause->fA = fClauseA;
+    pClause->fRoot = fRoot;
+    pClause->nLits = pEnd - pBeg;
+    memcpy( pClause->pLits, pBeg, sizeof(lit) * (pEnd - pBeg) );
+
+    // add the clause to the list
+    if ( p->pHead == NULL )
+        p->pHead = pClause;
+    if ( p->pTail == NULL )
+        p->pTail = pClause;
+    else
+    {
+        p->pTail->pNext = pClause;
+        p->pTail = pClause;
+    }
+
+    // mark the first learnt clause
+    if ( p->pLearnt == NULL && !pClause->fRoot )
+        p->pLearnt = pClause;
+
+    // add the empty clause
+    if ( pClause->nLits == 0 )
+    {
+        if ( p->pEmpty )
+            printf( "More than one empty clause!\n" );
+        p->pEmpty = pClause;
+    }
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Fetches memory.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+char * Pr_ManMemoryFetch( Pr_Man_t * p, int nBytes )
+{
+    char * pMem;
+    if ( p->pChunkLast == NULL || nBytes > p->nChunkSize - p->nChunkUsed )
+    {
+        pMem = (char *)malloc( p->nChunkSize );
+        *(char **)pMem = p->pChunkLast;
+        p->pChunkLast = pMem;
+        p->nChunkUsed = sizeof(char *);
+    }
+    pMem = p->pChunkLast + p->nChunkUsed;
+    p->nChunkUsed += nBytes;
+    return pMem;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Frees memory manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Pr_ManMemoryStop( Pr_Man_t * p )
+{
+    char * pMem, * pNext;
+    if ( p->pChunkLast == NULL )
+        return;
+    for ( pMem = p->pChunkLast; pNext = *(char **)pMem; pMem = pNext )
+        free( pMem );
+    free( pMem );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Reports memory usage in bytes.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Pr_ManMemoryReport( Pr_Man_t * p )
+{
+    int Total;
+    char * pMem, * pNext;
+    if ( p->pChunkLast == NULL )
+        return 0;
+    Total = p->nChunkUsed; 
+    for ( pMem = p->pChunkLast; pNext = *(char **)pMem; pMem = pNext )
+        Total += p->nChunkSize;
+    return Total;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Records the proof.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Extra_PrintBinary_( FILE * pFile, unsigned Sign[], int nBits )
+{
+    int Remainder, nWords;
+    int w, i;
+
+    Remainder = (nBits%(sizeof(unsigned)*8));
+    nWords    = (nBits/(sizeof(unsigned)*8)) + (Remainder>0);
+
+    for ( w = nWords-1; w >= 0; w-- )
+        for ( i = ((w == nWords-1 && Remainder)? Remainder-1: 31); i >= 0; i-- )
+            fprintf( pFile, "%c", '0' + (int)((Sign[w] & (1<<i)) > 0) );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Prints the interpolant for one clause.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Pr_ManPrintInterOne( Pr_Man_t * p, Pr_Cls_t * pClause )
+{
+    printf( "Clause %2d :  ", pClause->Id );
+    Extra_PrintBinary_( stdout, &pClause->uTruth, (1 << p->nVarsAB) );
+    printf( "\n" );
+}
+
+
+
+/**Function*************************************************************
+
+  Synopsis    [Records implication.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+static inline int Pr_ManEnqueue( Pr_Man_t * p, lit Lit, Pr_Cls_t * pReason )
+{
+    int Var = lit_var(Lit);
+    if ( p->pAssigns[Var] != LIT_UNDEF )
+        return p->pAssigns[Var] == Lit;
+    p->pAssigns[Var] = Lit;
+    p->pReasons[Var] = pReason;
+    p->pTrail[p->nTrailSize++] = Lit;
+//printf( "assigning var %d value %d\n", Var, !lit_sign(Lit) );
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Records implication.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+static inline void Pr_ManCancelUntil( Pr_Man_t * p, int Level )
+{
+    lit Lit;
+    int i, Var;
+    for ( i = p->nTrailSize - 1; i >= Level; i-- )
+    {
+        Lit = p->pTrail[i];
+        Var = lit_var( Lit );
+        p->pReasons[Var] = NULL;
+        p->pAssigns[Var] = LIT_UNDEF;
+//printf( "cancelling var %d\n", Var );
+    }
+    p->nTrailSize = Level;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Propagate one assignment.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+static inline Pr_Cls_t * Pr_ManPropagateOne( Pr_Man_t * p, lit Lit )
+{
+    Pr_Cls_t ** ppPrev, * pCur, * pTemp;
+    lit LitF = lit_neg(Lit);
+    int i;
+    // iterate through the literals
+    ppPrev = p->pWatches + Lit;
+    for ( pCur = p->pWatches[Lit]; pCur; pCur = *ppPrev )
+    {
+        // make sure the false literal is in the second literal of the clause
+        if ( pCur->pLits[0] == LitF )
+        {
+            pCur->pLits[0] = pCur->pLits[1];
+            pCur->pLits[1] = LitF;
+            pTemp = pCur->pNext0;
+            pCur->pNext0 = pCur->pNext1;
+            pCur->pNext1 = pTemp;
+        }
+        assert( pCur->pLits[1] == LitF );
+
+        // if the first literal is true, the clause is satisfied
+        if ( pCur->pLits[0] == p->pAssigns[lit_var(pCur->pLits[0])] )
+        {
+            ppPrev = &pCur->pNext1;
+            continue;
+        }
+
+        // look for a new literal to watch
+        for ( i = 2; i < (int)pCur->nLits; i++ )
+        {
+            // skip the case when the literal is false
+            if ( lit_neg(pCur->pLits[i]) == p->pAssigns[lit_var(pCur->pLits[i])] )
+                continue;
+            // the literal is either true or unassigned - watch it
+            pCur->pLits[1] = pCur->pLits[i];
+            pCur->pLits[i] = LitF;
+            // remove this clause from the watch list of Lit
+            *ppPrev = pCur->pNext1;
+            // add this clause to the watch list of pCur->pLits[i] (now it is pCur->pLits[1])
+            Pr_ManWatchClause( p, pCur, pCur->pLits[1] );
+            break;
+        }
+        if ( i < (int)pCur->nLits ) // found new watch
+            continue;
+
+        // clause is unit - enqueue new implication
+        if ( Pr_ManEnqueue(p, pCur->pLits[0], pCur) )
+        {
+            ppPrev = &pCur->pNext1;
+            continue;
+        }
+
+        // conflict detected - return the conflict clause
+        return pCur;
+    }
+    return NULL;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Propagate the current assignments.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Pr_Cls_t * Pr_ManPropagate( Pr_Man_t * p, int Start )
+{
+    Pr_Cls_t * pClause;
+    int i;
+    int clk = clock();
+    for ( i = Start; i < p->nTrailSize; i++ )
+    {
+        pClause = Pr_ManPropagateOne( p, p->pTrail[i] );
+        if ( pClause )
+        {
+p->timeBcp += clock() - clk;
+            return pClause;
+        }
+    }
+p->timeBcp += clock() - clk;
+    return NULL;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Prints the clause.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Pr_ManPrintClause( Pr_Cls_t * pClause )
+{
+    int i;
+    printf( "Clause ID = %d. Proof = %d. {", pClause->Id, (int)pClause->pProof );
+    for ( i = 0; i < (int)pClause->nLits; i++ )
+        printf( " %d", pClause->pLits[i] );
+    printf( " }\n" );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Prints the resolvent.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Pr_ManPrintResolvent( lit * pResLits, int nResLits )
+{
+    int i;
+    printf( "Resolvent: {" );
+    for ( i = 0; i < nResLits; i++ )
+        printf( " %d", pResLits[i] );
+    printf( " }\n" );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Writes one root clause into a file.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Pr_ManProofWriteOne( Pr_Man_t * p, Pr_Cls_t * pClause )
+{
+    pClause->pProof = (void *)++p->Counter;
+
+    if ( p->fProofWrite )
+    {
+        int v;
+        fprintf( p->pManProof, "%d", (int)pClause->pProof );
+        for ( v = 0; v < (int)pClause->nLits; v++ )
+            fprintf( p->pManProof, " %d", lit_print(pClause->pLits[v]) );
+        fprintf( p->pManProof, " 0 0\n" );
+    }
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Traces the proof for one clause.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Pr_ManProofTraceOne( Pr_Man_t * p, Pr_Cls_t * pConflict, Pr_Cls_t * pFinal )
+{
+    Pr_Cls_t * pReason;
+    int i, v, Var, PrevId;
+    int fPrint = 0;
+    int clk = clock();
+
+    // collect resolvent literals
+    if ( p->fProofVerif )
+    {
+        assert( (int)pConflict->nLits <= p->nResLitsAlloc );
+        memcpy( p->pResLits, pConflict->pLits, sizeof(lit) * pConflict->nLits );
+        p->nResLits = pConflict->nLits;
+    }
+
+    // mark all the variables in the conflict as seen
+    for ( v = 0; v < (int)pConflict->nLits; v++ )
+        p->pSeens[lit_var(pConflict->pLits[v])] = 1;
+
+    // start the anticedents
+//    pFinal->pAntis = Vec_PtrAlloc( 32 );
+//    Vec_PtrPush( pFinal->pAntis, pConflict );
+
+    if ( p->nClausesA )
+        pFinal->uTruth = pConflict->uTruth;
+   
+    // follow the trail backwards
+    PrevId = (int)pConflict->pProof;
+    for ( i = p->nTrailSize - 1; i >= 0; i-- )
+    {
+        // skip literals that are not involved
+        Var = lit_var(p->pTrail[i]);
+        if ( !p->pSeens[Var] )
+            continue;
+        p->pSeens[Var] = 0;
+
+        // skip literals of the resulting clause
+        pReason = p->pReasons[Var];
+        if ( pReason == NULL )
+            continue;
+        assert( p->pTrail[i] == pReason->pLits[0] );
+
+        // add the variables to seen
+        for ( v = 1; v < (int)pReason->nLits; v++ )
+            p->pSeens[lit_var(pReason->pLits[v])] = 1;
+
+
+        // record the reason clause
+        assert( pReason->pProof > 0 );
+        p->Counter++;
+        if ( p->fProofWrite )
+            fprintf( p->pManProof, "%d * %d %d 0\n", p->Counter, PrevId, (int)pReason->pProof );
+        PrevId = p->Counter;
+
+        if ( p->nClausesA )
+        {
+            if ( p->pVarTypes[Var] == 1 ) // var of A
+                pFinal->uTruth |= pReason->uTruth;
+            else
+                pFinal->uTruth &= pReason->uTruth;
+        }
+ 
+        // resolve the temporary resolvent with the reason clause
+        if ( p->fProofVerif )
+        {
+            int v1, v2; 
+            if ( fPrint )
+                Pr_ManPrintResolvent( p->pResLits, p->nResLits );
+            // check that the var is present in the resolvent
+            for ( v1 = 0; v1 < p->nResLits; v1++ )
+                if ( lit_var(p->pResLits[v1]) == Var )
+                    break;
+            if ( v1 == p->nResLits )
+                printf( "Recording clause %d: Cannot find variable %d in the temporary resolvent.\n", pFinal->Id, Var );
+            if ( p->pResLits[v1] != lit_neg(pReason->pLits[0]) )
+                printf( "Recording clause %d: The resolved variable %d is in the wrong polarity.\n", pFinal->Id, Var );
+            // remove this variable from the resolvent
+            assert( lit_var(p->pResLits[v1]) == Var );
+            p->nResLits--;
+            for ( ; v1 < p->nResLits; v1++ )
+                p->pResLits[v1] = p->pResLits[v1+1];
+            // add variables of the reason clause
+            for ( v2 = 1; v2 < (int)pReason->nLits; v2++ )
+            {
+                for ( v1 = 0; v1 < p->nResLits; v1++ )
+                    if ( lit_var(p->pResLits[v1]) == lit_var(pReason->pLits[v2]) )
+                        break;
+                // if it is a new variable, add it to the resolvent
+                if ( v1 == p->nResLits ) 
+                {
+                    if ( p->nResLits == p->nResLitsAlloc )
+                        printf( "Recording clause %d: Ran out of space for intermediate resolvent.\n, pFinal->Id" );
+                    p->pResLits[ p->nResLits++ ] = pReason->pLits[v2];
+                    continue;
+                }
+                // if the variable is the same, the literal should be the same too
+                if ( p->pResLits[v1] == pReason->pLits[v2] )
+                    continue;
+                // the literal is different
+                printf( "Recording clause %d: Trying to resolve the clause with more than one opposite literal.\n", pFinal->Id );
+            }
+        }
+
+//        Vec_PtrPush( pFinal->pAntis, pReason );
+    }
+
+    // unmark all seen variables
+//    for ( i = p->nTrailSize - 1; i >= 0; i-- )
+//        p->pSeens[lit_var(p->pTrail[i])] = 0;
+    // check that the literals are unmarked
+//    for ( i = p->nTrailSize - 1; i >= 0; i-- )
+//        assert( p->pSeens[lit_var(p->pTrail[i])] == 0 );
+
+    // use the resulting clause to check the correctness of resolution
+    if ( p->fProofVerif )
+    {
+        int v1, v2; 
+        if ( fPrint )
+            Pr_ManPrintResolvent( p->pResLits, p->nResLits );
+        for ( v1 = 0; v1 < p->nResLits; v1++ )
+        {
+            for ( v2 = 0; v2 < (int)pFinal->nLits; v2++ )
+                if ( pFinal->pLits[v2] == p->pResLits[v1] )
+                    break;
+            if ( v2 < (int)pFinal->nLits )
+                continue;
+            break;
+        }
+        if ( v1 < p->nResLits )
+        {
+            printf( "Recording clause %d: The final resolvent is wrong.\n", pFinal->Id );
+            Pr_ManPrintClause( pConflict );
+            Pr_ManPrintResolvent( p->pResLits, p->nResLits );
+            Pr_ManPrintClause( pFinal );
+        }
+    }
+p->timeTrace += clock() - clk;
+
+    // return the proof pointer 
+    if ( p->nClausesA )
+    {
+        Pr_ManPrintInterOne( p, pFinal );
+    }
+    return p->Counter;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Records the proof for one clause.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Pr_ManProofRecordOne( Pr_Man_t * p, Pr_Cls_t * pClause )
+{
+    Pr_Cls_t * pConflict;
+    int i;
+
+    // empty clause never ends up there
+    assert( pClause->nLits > 0 );
+    if ( pClause->nLits == 0 )
+        printf( "Error: Empty clause is attempted.\n" );
+
+    // add assumptions to the trail
+    assert( !pClause->fRoot );
+    assert( p->nTrailSize == p->nRootSize );
+    for ( i = 0; i < (int)pClause->nLits; i++ )
+        if ( !Pr_ManEnqueue( p, lit_neg(pClause->pLits[i]), NULL ) )
+        {
+            assert( 0 ); // impossible
+            return 0;
+        }
+
+    // propagate the assumptions
+    pConflict = Pr_ManPropagate( p, p->nRootSize );
+    if ( pConflict == NULL )
+    {
+        assert( 0 ); // cannot prove
+        return 0;
+    }
+
+    // construct the proof
+    pClause->pProof = (void *)Pr_ManProofTraceOne( p, pConflict, pClause );
+
+    // undo to the root level
+    Pr_ManCancelUntil( p, p->nRootSize );
+
+    // add large clauses to the watched lists
+    if ( pClause->nLits > 1 )
+    {
+        Pr_ManWatchClause( p, pClause, pClause->pLits[0] );
+        Pr_ManWatchClause( p, pClause, pClause->pLits[1] );
+        return 1;
+    }
+    assert( pClause->nLits == 1 );
+
+    // if the clause proved is unit, add it and propagate
+    if ( !Pr_ManEnqueue( p, pClause->pLits[0], pClause ) )
+    {
+        assert( 0 ); // impossible
+        return 0;
+    }
+
+    // propagate the assumption
+    pConflict = Pr_ManPropagate( p, p->nRootSize );
+    if ( pConflict )
+    {
+        // construct the proof
+        p->pEmpty->pProof = (void *)Pr_ManProofTraceOne( p, pConflict, p->pEmpty );
+        printf( "Found last conflict after adding unit clause number %d!\n", pClause->Id );
+        return 0;
+    }
+
+    // update the root level
+    p->nRootSize = p->nTrailSize;
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Propagate the root clauses.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Pr_ManProcessRoots( Pr_Man_t * p )
+{
+    Pr_Cls_t * pClause;
+    int Counter;
+
+    // make sure the root clauses are preceeding the learnt clauses
+    Counter = 0;
+    Pr_ManForEachClause( p, pClause )
+    {
+        assert( (int)pClause->fA    == (Counter < (int)p->nClausesA) );
+        assert( (int)pClause->fRoot == (Counter < (int)p->nRoots)    );
+        Counter++;
+    }
+    assert( p->nClauses == Counter );
+
+    // make sure the last clause if empty
+    assert( p->pTail->nLits == 0 );
+
+    // go through the root unit clauses
+    p->nTrailSize = 0;
+    Pr_ManForEachClauseRoot( p, pClause )
+    {
+        // create watcher lists for the root clauses
+        if ( pClause->nLits > 1 )
+        {
+            Pr_ManWatchClause( p, pClause, pClause->pLits[0] );
+            Pr_ManWatchClause( p, pClause, pClause->pLits[1] );
+        }
+        // empty clause and large clauses
+        if ( pClause->nLits != 1 )
+            continue;
+        // unit clause
+        assert( lit_check(pClause->pLits[0], p->nVars) );
+        if ( !Pr_ManEnqueue( p, pClause->pLits[0], pClause ) )
+        {
+            // detected root level conflict
+            printf( "Pr_ManProcessRoots(): Detected a root-level conflict\n" );
+            assert( 0 );
+            return 0;
+        }
+    }
+
+    // propagate the root unit clauses
+    pClause = Pr_ManPropagate( p, 0 );
+    if ( pClause )
+    {
+        // detected root level conflict
+        printf( "Pr_ManProcessRoots(): Detected a root-level conflict\n" );
+        assert( 0 );
+        return 0;
+    }
+
+    // set the root level
+    p->nRootSize = p->nTrailSize;
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Records the proof.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Pr_ManPrepareInter( Pr_Man_t * p )
+{
+    unsigned uTruths[5] = { 0xAAAAAAAA, 0xCCCCCCCC, 0xF0F0F0F0, 0xFF00FF00, 0xFFFF0000 };
+    Pr_Cls_t * pClause;
+    int Var, v;
+
+    // mark the variable encountered in the clauses of A
+    Pr_ManForEachClauseRoot( p, pClause )
+    {
+        if ( !pClause->fA )
+            break;
+        for ( v = 0; v < (int)pClause->nLits; v++ )
+            p->pVarTypes[lit_var(pClause->pLits[v])] = 1;
+    }
+
+    // check variables that appear in clauses of B
+    p->nVarsAB = 0;
+    Pr_ManForEachClauseRoot( p, pClause )
+    {
+        if ( pClause->fA )
+            continue;
+        for ( v = 0; v < (int)pClause->nLits; v++ )
+        {
+            Var = lit_var(pClause->pLits[v]);
+            if ( p->pVarTypes[Var] == 1 ) // var of A
+            {
+                // change it into a global variable
+                p->nVarsAB++;
+                p->pVarTypes[Var] = -1;
+            }
+        }
+    }
+
+    // order global variables
+    p->nVarsAB = 0;
+    for ( v = 0; v < p->nVars; v++ )
+        if ( p->pVarTypes[v] == -1 )
+            p->pVarTypes[v] -= p->nVarsAB++;
+printf( "There are %d global variables.\n", p->nVarsAB );
+
+    // set interpolants for root clauses
+    Pr_ManForEachClauseRoot( p, pClause )
+    {
+        if ( !pClause->fA ) // clause of B
+        {
+            pClause->uTruth = ~0;
+            Pr_ManPrintInterOne( p, pClause );
+            continue;
+        }
+        // clause of A
+        pClause->uTruth = 0;
+        for ( v = 0; v < (int)pClause->nLits; v++ )
+        {
+            Var = lit_var(pClause->pLits[v]);
+            if ( p->pVarTypes[Var] < 0 ) // global var
+            {
+                if ( lit_sign(pClause->pLits[v]) ) // negative var
+                    pClause->uTruth |= ~uTruths[ -p->pVarTypes[Var]-1 ];
+                else
+                    pClause->uTruth |= uTruths[ -p->pVarTypes[Var]-1 ];
+            }
+        }
+        Pr_ManPrintInterOne( p, pClause );
+    }
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Records the proof.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Pr_ManProofWrite( Pr_Man_t * p )
+{
+    Pr_Cls_t * pClause;
+    int RetValue = 1;
+
+    // propagate root level assignments
+    Pr_ManProcessRoots( p );
+
+    // prepare the interpolant computation
+    if ( p->nClausesA )
+        Pr_ManPrepareInter( p );
+
+    // construct proof for each clause
+    // start the proof
+    if ( p->fProofWrite )
+        p->pManProof = fopen( "proof.cnf_", "w" );
+    p->Counter = 0;
+
+    // write the root clauses
+    Pr_ManForEachClauseRoot( p, pClause )
+        Pr_ManProofWriteOne( p, pClause );
+
+    // consider each learned clause
+    Pr_ManForEachClauseLearnt( p, pClause )
+    {
+        if ( !Pr_ManProofRecordOne( p, pClause ) )
+        {
+            RetValue = 0;
+            break;
+        }
+    }
+
+    if ( p->nClausesA )
+    {
+        printf( "Interpolant:  " );
+    }
+
+
+    // stop the proof
+    if ( p->fProofWrite )
+    {
+        fclose( p->pManProof );
+        p->pManProof = NULL;    
+    }
+    return RetValue;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Reads clauses from file.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Pr_Man_t * Pr_ManProofRead( char * pFileName )
+{
+    Pr_Man_t * p = NULL;
+    char * pCur, * pBuffer = NULL;
+    int * pArray = NULL;
+    FILE * pFile;
+    int RetValue, Counter, nNumbers, Temp;
+    int nClauses, nClausesA, nRoots, nVars;
+
+    // open the file
+    pFile = fopen( pFileName, "r" );
+    if ( pFile == NULL )
+    {
+        printf( "Count not open input file \"%s\".\n", pFileName );
+        return NULL;
+    }
+
+    // read the file
+    pBuffer = (char *)malloc( (1<<16) );
+    for ( Counter = 0; fgets( pBuffer, (1<<16), pFile ); )
+    {
+        if ( pBuffer[0] == 'c' )
+            continue;
+        if ( pBuffer[0] == 'p' )
+        {
+            assert( p == NULL );
+            nClausesA = 0;
+            RetValue = sscanf( pBuffer + 1, "%d %d %d %d", &nVars, &nClauses, &nRoots, &nClausesA );
+            if ( RetValue != 3 && RetValue != 4 )
+            {
+                printf( "Wrong input file format.\n" );
+            }
+            p = Pr_ManAlloc( nVars );
+            pArray = (int *)malloc( sizeof(int) * (nVars + 10) );
+            continue;
+        }
+        // skip empty lines
+        for ( pCur = pBuffer; *pCur; pCur++ )
+            if ( !(*pCur == ' ' || *pCur == '\t' || *pCur == '\r' || *pCur == '\n') )
+                break;
+        if ( *pCur == 0 )
+            continue;
+        // scan the numbers from file
+        nNumbers = 0;
+        pCur = pBuffer;
+        while ( *pCur )
+        {
+            // skip spaces
+            for ( ; *pCur && *pCur == ' '; pCur++ );
+            // read next number
+            Temp = 0;
+            sscanf( pCur, "%d", &Temp );
+            if ( Temp == 0 )
+                break;
+            pArray[ nNumbers++ ] = lit_read( Temp );
+            // skip non-spaces
+            for ( ; *pCur && *pCur != ' '; pCur++ );
+        }
+        // add the clause
+        if ( !Pr_ManAddClause( p, pArray, pArray + nNumbers, Counter < nRoots, Counter < nClausesA ) )
+        {
+            printf( "Bad clause number %d.\n", Counter );
+            return NULL;
+        }
+        // count the clauses
+        Counter++;
+    }
+    // check the number of clauses
+    if ( Counter != nClauses )
+        printf( "Expected %d clauses but read %d.\n", nClauses, Counter );
+
+    // finish
+    if ( pArray ) free( pArray );
+    if ( pBuffer ) free( pBuffer );
+    fclose( pFile );
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Records the proof.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+/*
+int Pr_ManProofCount_rec( Pr_Cls_t * pClause )
+{
+    Pr_Cls_t * pNext;
+    int i, Counter;    
+    if ( pClause->fRoot )
+        return 0;
+    if ( pClause->fVisit )
+        return 0;
+    pClause->fVisit = 1;
+    // count the number of visited clauses
+    Counter = 1;
+    Vec_PtrForEachEntry( pClause->pAntis, pNext, i )
+        Counter += Pr_ManProofCount_rec( pNext );
+    return Counter;
+}
+*/
+
+/**Function*************************************************************
+
+  Synopsis    [Records the proof.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Pr_ManProofTest( char * pFileName )
+{
+    Pr_Man_t * p;
+    int clk, clkTotal = clock();
+
+clk = clock();
+    p = Pr_ManProofRead( pFileName );
+p->timeRead = clock() - clk;
+    if ( p == NULL )
+        return 0;
+
+    Pr_ManProofWrite( p );
+
+    // print stats
+/*
+    nUsed = Pr_ManProofCount_rec( p->pEmpty );
+    printf( "Roots = %d. Learned = %d. Total = %d. Steps = %d.  Ave = %.2f.  Used = %d. Ratio = %.2f. \n", 
+        p->nRoots, p->nClauses-p->nRoots, p->nClauses, p->Counter,  
+        1.0*(p->Counter-p->nRoots)/(p->nClauses-p->nRoots),
+        nUsed, 1.0*nUsed/(p->nClauses-p->nRoots)  );
+*/
+    printf( "Vars = %d. Roots = %d. Learned = %d. Resol steps = %d.  Ave = %.2f.  Mem = %.2f Mb\n", 
+        p->nVars, p->nRoots, p->nClauses-p->nRoots, p->Counter,  
+        1.0*(p->Counter-p->nRoots)/(p->nClauses-p->nRoots), 
+        1.0*Pr_ManMemoryReport(p)/(1<<20) );
+
+p->timeTotal = clock() - clkTotal;
+    Pr_ManFree( p );
+    return 1;
+}
+
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/sat/proof/pr.h b/src/sat/proof/pr.h
new file mode 100644
index 00000000..1e71a2d3
--- /dev/null
+++ b/src/sat/proof/pr.h
@@ -0,0 +1,65 @@
+/**CFile****************************************************************
+
+  FileName    [pr.h]
+
+  SystemName  [ABC: Logic synthesis and verification system.]
+
+  PackageName [Proof recording.]
+
+  Synopsis    [External declarations.]
+
+  Author      [Alan Mishchenko]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - June 20, 2005.]
+
+  Revision    [$Id: pr.h,v 1.00 2005/06/20 00:00:00 alanmi Exp $]
+
+***********************************************************************/
+ 
+#ifndef __PR_H__
+#define __PR_H__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifdef _WIN32
+#define inline __inline // compatible with MS VS 6.0
+#endif
+
+////////////////////////////////////////////////////////////////////////
+///                          INCLUDES                                ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                         PARAMETERS                               ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                         BASIC TYPES                              ///
+////////////////////////////////////////////////////////////////////////
+
+typedef struct Pr_Man_t_ Pr_Man_t;
+
+////////////////////////////////////////////////////////////////////////
+///                      MACRO DEFINITIONS                           ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                    FUNCTION DECLARATIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/*=== pr.c ==========================================================*/
+ 
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
diff --git a/src/sat/proof/stats.txt b/src/sat/proof/stats.txt
new file mode 100644
index 00000000..470b1630
--- /dev/null
+++ b/src/sat/proof/stats.txt
@@ -0,0 +1,66 @@
+UC Berkeley, ABC 1.01 (compiled Jan 20 2007 16:47:34)
+abc.rc: No such file or directory
+Loaded "abc.rc" from the parent directory.
+abc 01> test
+Found last conflict after adding unit clause number 10229!
+Roots = 7184. Learned = 3047. Total = 10231. Steps = 196361.  Ave = 62.09.  Used = 2224. Ratio = 0.73.
+Runtime stats:
+Reading  =   0.03 sec
+BCP      =   0.32 sec
+Trace    =   0.06 sec
+TOTAL    =   0.43 sec
+abc 01> test
+Found last conflict after adding unit clause number 7676!
+Roots = 6605. Learned = 1073. Total = 7678. Steps = 52402.  Ave = 42.68.  Used = 1011. Ratio = 0.94.
+Runtime stats:
+Reading  =   0.01 sec
+BCP      =   0.02 sec
+Trace    =   0.02 sec
+TOTAL    =   0.06 sec
+abc 01> test
+Found last conflict after adding unit clause number 37868!
+Roots = 15443. Learned = 22427. Total = 37870. Steps = 2365472.  Ave = 104.79.  Used = 19763. Ratio = 0.88.
+Runtime stats:
+Reading  =   0.20 sec
+BCP      =  14.67 sec
+Trace    =   0.56 sec
+TOTAL    =  15.74 sec
+abc 01>
+
+
+abc 05> wb ibm_bmc/len25u_renc.blif
+abc 05> ps
+(no name)    : i/o =  348/   1  lat =    0  nd =  3648  bdd  = 15522  lev = 246
+abc 05> sat -v
+==================================[MINISAT]===================================
+| Conflicts |     ORIGINAL     |              LEARNT              | Progress |
+|           | Clauses Literals |   Limit Clauses Literals  Lit/Cl |          |
+==============================================================================
+|         0 |   17413    54996 |    5804       0        0     0.0 |  0.000 % |
+|       100 |   17413    54996 |    6384     100      606     6.1 |  0.417 % |
+|       250 |   17413    54996 |    7023     250     1586     6.3 |  0.417 % |
+|       476 |   17413    54996 |    7725     476     3288     6.9 |  0.417 % |
+|       813 |   17413    54996 |    8498     813     7586     9.3 |  0.417 % |
+|      1319 |   17403    54970 |    9347    1318    14848    11.3 |  0.442 % |
+|      2078 |   17403    54970 |   10282    2076    40186    19.4 |  0.466 % |
+|      3217 |   17397    54948 |   11310    3208    99402    31.0 |  0.466 % |
+|      4926 |   17392    54930 |   12441    4911   131848    26.8 |  0.491 % |
+|      7489 |   17392    54930 |   13686    7474   204217    27.3 |  0.491 % |
+|     11336 |   17357    54829 |   15054   11310   332863    29.4 |  0.638 % |
+|     17103 |   17346    54794 |   16559    9130   203029    22.2 |  0.687 % |
+|     25752 |   17288    54606 |   18215    9083   176982    19.5 |  0.834 % |
+|     38727 |   17266    54536 |   20037   12674   278949    22.0 |  0.883 % |
+|     58188 |   17240    54453 |   22041   11905   255255    21.4 |  0.957 % |
+==============================================================================
+Start =   15. Conf =  79435. Dec = 130967. Prop = 24083434. Insp = 136774586.
+Total runtime =   18.66 sec.  Var select =    0.00 sec.  Var update =    0.00 sec.
+UNSATISFIABLE  Time =  18.69 sec
+abc 05>
+abc 05> test
+Found last conflict after adding unit clause number 96902!
+Roots = 17469. Learned = 79435. Total = 96904. Steps = 9700042.  Ave = 121.89.  Used = 57072. Ratio = 0.72.
+Runtime stats:
+Reading  =   1.26 sec
+BCP      = 204.99 sec
+Trace    =   2.85 sec
+TOTAL    = 209.85 sec
\ No newline at end of file