Version abc90315

1 files changed, 566 insertions, 78 deletions

diff --git a/src/base/abci/abcLutmin.c b/src/base/abci/abcLutmin.c
index 6906e2c4..41ee25fe 100644
--- a/src/base/abci/abcLutmin.c
+++ b/src/base/abci/abcLutmin.c
@@ -20,6 +20,12 @@
 
 #include "abc.h"
 
+/* 
+    Implememented here is the algorithm for minimal-LUT decomposition
+    described in the paper: T. Sasao et al. "On the number of LUTs 
+    to implement logic functions", To appear in Proc. IWLS'09.
+*/
+
 ////////////////////////////////////////////////////////////////////////
 ///                        DECLARATIONS                              ///
 ////////////////////////////////////////////////////////////////////////
@@ -30,6 +36,254 @@
 
 /**Function*************************************************************
 
+  Synopsis    [Implements 2:1 MUX using one 3-LUT.]
+
+  Description [The fanins are (c, d0, d1).]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Abc_Obj_t * Abc_NtkBddMux21( Abc_Ntk_t * pNtkNew, Abc_Obj_t * pFanins[] )
+{
+    DdManager * dd = pNtkNew->pManFunc;
+    Abc_Obj_t * pNode;
+    DdNode * bSpin, * bCof0, * bCof1;
+    pNode = Abc_NtkCreateNode( pNtkNew );
+    Abc_ObjAddFanin( pNode, pFanins[0] );
+    Abc_ObjAddFanin( pNode, pFanins[1] );
+    Abc_ObjAddFanin( pNode, pFanins[2] );
+    bSpin = Cudd_bddIthVar(dd, 0);
+    bCof0 = Cudd_bddIthVar(dd, 1); 
+    bCof1 = Cudd_bddIthVar(dd, 2); 
+    pNode->pData = Cudd_bddIte( dd, bSpin, bCof1, bCof0 );  Cudd_Ref( pNode->pData ); 
+    return pNode;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Implements 4:1 MUX using one 6-LUT.]
+
+  Description [The fanins are (c0, c1, d00, d01, d10, d11).]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Abc_Obj_t * Abc_NtkBddMux411( Abc_Ntk_t * pNtkNew, Abc_Obj_t * pFanins[] )
+{
+    DdManager * dd = pNtkNew->pManFunc;
+    Abc_Obj_t * pNode;
+    DdNode * bSpin, * bCof0, * bCof1;
+    pNode = Abc_NtkCreateNode( pNtkNew );
+    Abc_ObjAddFanin( pNode, pFanins[0] );
+    Abc_ObjAddFanin( pNode, pFanins[1] );
+    Abc_ObjAddFanin( pNode, pFanins[2] );
+    Abc_ObjAddFanin( pNode, pFanins[3] );
+    Abc_ObjAddFanin( pNode, pFanins[4] );
+    Abc_ObjAddFanin( pNode, pFanins[5] );
+    bSpin = Cudd_bddIthVar(dd, 1);
+    bCof0 = Cudd_bddIte( dd, bSpin, Cudd_bddIthVar(dd, 3), Cudd_bddIthVar(dd, 2) ); Cudd_Ref( bCof0 );
+    bCof1 = Cudd_bddIte( dd, bSpin, Cudd_bddIthVar(dd, 5), Cudd_bddIthVar(dd, 4) ); Cudd_Ref( bCof1 );
+    bSpin = Cudd_bddIthVar(dd, 0);
+    pNode->pData = Cudd_bddIte( dd, bSpin, bCof1, bCof0 );  Cudd_Ref( pNode->pData ); 
+    Cudd_RecursiveDeref( dd, bCof0 );
+    Cudd_RecursiveDeref( dd, bCof1 );
+    return pNode;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Implementes 4:1 MUX using two 4-LUTs.]
+
+  Description [The fanins are (c0, c1, d00, d01, d10, d11).]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Abc_Obj_t * Abc_NtkBddMux412( Abc_Ntk_t * pNtkNew, Abc_Obj_t * pFanins[] )
+{
+    DdManager * dd = pNtkNew->pManFunc;
+    Abc_Obj_t * pNodeBot, * pNodeTop;
+    DdNode * bSpin, * bCof0, * bCof1;
+    // bottom node
+    pNodeBot = Abc_NtkCreateNode( pNtkNew );
+    Abc_ObjAddFanin( pNodeBot, pFanins[0] );
+    Abc_ObjAddFanin( pNodeBot, pFanins[1] );
+    Abc_ObjAddFanin( pNodeBot, pFanins[2] );
+    Abc_ObjAddFanin( pNodeBot, pFanins[3] );
+    bSpin = Cudd_bddIthVar(dd, 0);
+    bCof0 = Cudd_bddIte( dd, Cudd_bddIthVar(dd, 1), Cudd_bddIthVar(dd, 3), Cudd_bddIthVar(dd, 2) ); Cudd_Ref( bCof0 );
+    bCof1 = Cudd_bddIthVar(dd, 1);
+    pNodeBot->pData = Cudd_bddIte( dd, bSpin, bCof1, bCof0 );  Cudd_Ref( pNodeBot->pData ); 
+    Cudd_RecursiveDeref( dd, bCof0 );
+    // top node
+    pNodeTop = Abc_NtkCreateNode( pNtkNew );
+    Abc_ObjAddFanin( pNodeTop, pFanins[0] );
+    Abc_ObjAddFanin( pNodeTop, pNodeBot   );
+    Abc_ObjAddFanin( pNodeTop, pFanins[4] );
+    Abc_ObjAddFanin( pNodeTop, pFanins[5] );
+    bSpin = Cudd_bddIthVar(dd, 0);
+    bCof0 = Cudd_bddIthVar(dd, 1);
+    bCof1 = Cudd_bddIte( dd, Cudd_bddIthVar(dd, 1), Cudd_bddIthVar(dd, 3), Cudd_bddIthVar(dd, 2) ); Cudd_Ref( bCof1 );
+    pNodeTop->pData = Cudd_bddIte( dd, bSpin, bCof1, bCof0 );  Cudd_Ref( pNodeTop->pData ); 
+    Cudd_RecursiveDeref( dd, bCof1 );
+    return pNodeTop;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Implementes 4:1 MUX using two 4-LUTs.]
+
+  Description [The fanins are (c0, c1, d00, d01, d10, d11).]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Abc_Obj_t * Abc_NtkBddMux412a( Abc_Ntk_t * pNtkNew, Abc_Obj_t * pFanins[] )
+{
+    DdManager * dd = pNtkNew->pManFunc;
+    Abc_Obj_t * pNodeBot, * pNodeTop;
+    DdNode * bSpin, * bCof0, * bCof1;
+    // bottom node
+    pNodeBot = Abc_NtkCreateNode( pNtkNew );
+    Abc_ObjAddFanin( pNodeBot, pFanins[1] );
+    Abc_ObjAddFanin( pNodeBot, pFanins[2] );
+    Abc_ObjAddFanin( pNodeBot, pFanins[3] );
+    bSpin = Cudd_bddIthVar(dd, 0);
+    bCof0 = Cudd_bddIthVar(dd, 1);
+    bCof1 = Cudd_bddIthVar(dd, 2);
+    pNodeBot->pData = Cudd_bddIte( dd, bSpin, bCof1, bCof0 );  Cudd_Ref( pNodeBot->pData ); 
+    // top node
+    pNodeTop = Abc_NtkCreateNode( pNtkNew );
+    Abc_ObjAddFanin( pNodeTop, pFanins[0] );
+    Abc_ObjAddFanin( pNodeTop, pFanins[1] );
+    Abc_ObjAddFanin( pNodeTop, pNodeBot   );
+    Abc_ObjAddFanin( pNodeTop, pFanins[4] );
+    Abc_ObjAddFanin( pNodeTop, pFanins[5] );
+    bSpin = Cudd_bddIthVar(dd, 0);
+    bCof0 = Cudd_bddIthVar(dd, 2);
+    bCof1 = Cudd_bddIte( dd, Cudd_bddIthVar(dd, 1), Cudd_bddIthVar(dd, 4), Cudd_bddIthVar(dd, 3) ); Cudd_Ref( bCof1 );
+    pNodeTop->pData = Cudd_bddIte( dd, bSpin, bCof1, bCof0 );  Cudd_Ref( pNodeTop->pData ); 
+    Cudd_RecursiveDeref( dd, bCof1 );
+    return pNodeTop;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Implements 4:1 MUX using three 2:1 MUXes.]
+
+  Description [The fanins are (c0, c1, d00, d01, d10, d11).]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Abc_Obj_t * Abc_NtkBddMux413( Abc_Ntk_t * pNtkNew, Abc_Obj_t * pFanins[] )
+{
+    Abc_Obj_t * pNodesBot[3], * pNodesTop[3];
+    // left bottom
+    pNodesBot[0] = pFanins[1];
+    pNodesBot[1] = pFanins[2];
+    pNodesBot[2] = pFanins[3];
+    pNodesTop[1] = Abc_NtkBddMux21( pNtkNew, pNodesBot );
+    // right bottom
+    pNodesBot[0] = pFanins[1];
+    pNodesBot[1] = pFanins[4];
+    pNodesBot[2] = pFanins[5];
+    pNodesTop[2] = Abc_NtkBddMux21( pNtkNew, pNodesBot );
+    // top node
+    pNodesTop[0] = pFanins[0];
+    return Abc_NtkBddMux21( pNtkNew, pNodesTop );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Finds unique cofactors of the function on the given level.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+DdNode * Abc_NtkBddCofactors_rec( DdManager * dd, DdNode * bNode, int iCof, int iLevel, int nLevels )
+{
+    DdNode * bNode0, * bNode1;
+    if ( Cudd_IsConstant(bNode) || iLevel == nLevels )
+        return bNode;
+    if ( Cudd_ReadPerm( dd, Cudd_NodeReadIndex(bNode) ) > iLevel )
+    {
+        bNode0 = bNode;
+        bNode1 = bNode;
+    }
+    else if ( Cudd_IsComplement(bNode) )
+    {
+        bNode0 = Cudd_Not(cuddE(Cudd_Regular(bNode)));
+        bNode1 = Cudd_Not(cuddT(Cudd_Regular(bNode)));
+    }
+    else
+    {
+        bNode0 = cuddE(bNode);
+        bNode1 = cuddT(bNode);
+    }
+    if ( (iCof >> (nLevels-1-iLevel)) & 1 )
+        return Abc_NtkBddCofactors_rec( dd, bNode1, iCof, iLevel + 1, nLevels );
+    return Abc_NtkBddCofactors_rec( dd, bNode0, iCof, iLevel + 1, nLevels );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Finds unique cofactors of the function on the given level.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Vec_Ptr_t * Abc_NtkBddCofactors( DdManager * dd, DdNode * bNode, int Level )
+{
+    Vec_Ptr_t * vCofs;
+    int i, nCofs = (1<<Level);
+    assert( Level > 0 && Level < 10 );
+    vCofs = Vec_PtrAlloc( 8 );
+    for ( i = 0; i < nCofs; i++ )
+        Vec_PtrPush( vCofs, Abc_NtkBddCofactors_rec( dd, bNode, i, 0, Level ) );
+    return vCofs;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Comparison procedure for two integers.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+static int Vec_PtrSortCompare( void ** pp1, void ** pp2 )
+{
+    if ( *pp1 < *pp2 )
+        return -1;
+    if ( *pp1 > *pp2 )
+        return 1;
+    return 0;
+}
+
+/**Function*************************************************************
+
   Synopsis    [Converts the node to MUXes.]
 
   Description []
@@ -39,27 +293,43 @@
   SeeAlso     []
 
 ***********************************************************************/
-Abc_Obj_t * Abc_NtkCreateNodeLut( Abc_Ntk_t * pNtkNew, DdManager * dd, DdNode * bFunc, Abc_Obj_t * pNode, int nLutSize )
+Abc_Obj_t * Abc_NtkCreateCofLut( Abc_Ntk_t * pNtkNew, DdManager * dd, DdNode * bCof, Abc_Obj_t * pNode, int Level )
 {
+    int fVerbose = 0;
     DdNode * bFuncNew;
     Abc_Obj_t * pNodeNew;
-    int i, nStart = ABC_MIN( 0, Abc_ObjFaninNum(pNode) - nLutSize );
+    int i;
+    assert( Abc_ObjFaninNum(pNode) > Level );
     // create a new node
     pNodeNew = Abc_NtkCreateNode( pNtkNew );
     // add the fanins in the order, in which they appear in the reordered manager
-    for ( i = nStart; i < Abc_ObjFaninNum(pNode); i++ )
+    for ( i = Level; i < Abc_ObjFaninNum(pNode); i++ )
         Abc_ObjAddFanin( pNodeNew, Abc_ObjFanin(pNode, i)->pCopy );
+if ( fVerbose )
+{
+Extra_bddPrint( dd, bCof );
+printf( "\n" );
+printf( "\n" );
+}
     // transfer the function
-    bFuncNew = Extra_bddMove( dd, bFunc, nStart );  Cudd_Ref( bFuncNew );
-    assert( Cudd_SupportSize(dd, bFuncNew) <= nLutSize );
+    bFuncNew = Extra_bddMove( dd, bCof, -Level );  Cudd_Ref( bFuncNew );
+if ( fVerbose )
+{
+Extra_bddPrint( dd, bFuncNew );
+printf( "\n" );
+printf( "\n" );
+}
     pNodeNew->pData = Extra_TransferLevelByLevel( dd, pNtkNew->pManFunc, bFuncNew );  Cudd_Ref( pNodeNew->pData );
+//Extra_bddPrint( pNtkNew->pManFunc, pNodeNew->pData );
+//printf( "\n" );
+//printf( "\n" );
     Cudd_RecursiveDeref( dd, bFuncNew );
     return pNodeNew;
 }
 
 /**Function*************************************************************
 
-  Synopsis    [Converts the node to MUXes.]
+  Synopsis    [Performs one step of Ashenhurst-Curtis decomposition.]
 
   Description []
                
@@ -68,36 +338,164 @@ Abc_Obj_t * Abc_NtkCreateNodeLut( Abc_Ntk_t * pNtkNew, DdManager * dd, DdNode *
   SeeAlso     []
 
 ***********************************************************************/
-Abc_Obj_t * Abc_NodeBddToMuxesLut_rec( DdManager * dd, DdNode * bFunc, Abc_Ntk_t * pNtkNew, st_table * tBdd2Node, Abc_Obj_t * pNode, int nLutSize )
-{
-    Abc_Obj_t * pNodeNew, * pNodeNew0, * pNodeNew1, * pNodeNewC;
-    assert( !Cudd_IsComplement(bFunc) );
-    if ( bFunc == b1 )
-        return Abc_NtkCreateNodeConst1(pNtkNew);
-    if ( st_lookup( tBdd2Node, (char *)bFunc, (char **)&pNodeNew ) )
-        return pNodeNew;
-    if ( dd->perm[bFunc->index] >= Abc_ObjFaninNum(pNode) - nLutSize )
-    {
-        pNodeNew = Abc_NtkCreateNodeLut( pNtkNew, dd, bFunc, pNode, nLutSize );
-        st_insert( tBdd2Node, (char *)bFunc, (char *)pNodeNew );
-        return pNodeNew;
-    }
-    // solve for the children nodes
-    pNodeNew0 = Abc_NodeBddToMuxesLut_rec( dd, Cudd_Regular(cuddE(bFunc)), pNtkNew, tBdd2Node, pNode, nLutSize );
-    if ( Cudd_IsComplement(cuddE(bFunc)) )
-        pNodeNew0 = Abc_NtkCreateNodeInv( pNtkNew, pNodeNew0 );
-    pNodeNew1 = Abc_NodeBddToMuxesLut_rec( dd, cuddT(bFunc), pNtkNew, tBdd2Node, pNode, nLutSize );
-    if ( !st_lookup( tBdd2Node, (char *)Cudd_bddIthVar(dd, bFunc->index), (char **)&pNodeNewC ) )
-        assert( 0 );
-    // create the MUX node
-    pNodeNew = Abc_NtkCreateNodeMux( pNtkNew, pNodeNewC, pNodeNew1, pNodeNew0 );
-    st_insert( tBdd2Node, (char *)bFunc, (char *)pNodeNew );
+Abc_Obj_t * Abc_NtkBddCurtis( Abc_Ntk_t * pNtkNew, Abc_Obj_t * pNode, Vec_Ptr_t * vCofs, Vec_Ptr_t * vUniq )
+{
+    DdManager * ddOld = pNode->pNtk->pManFunc;
+    DdManager * ddNew = pNtkNew->pManFunc;
+    DdNode * bCof, * bUniq, * bMint, * bTemp, * bFunc, * bBits[10], ** pbCodeVars;
+    Abc_Obj_t * pNodeNew = NULL, * pNodeBS[10];
+    int nLutSize = Extra_Base2Log( Vec_PtrSize(vCofs) );
+    int nBits    = Extra_Base2Log( Vec_PtrSize(vUniq) );
+    int b, c, u, i;
+    assert( nBits + 2 <= nLutSize );
+    assert( nLutSize < Abc_ObjFaninNum(pNode) );
+    // start BDDs for the decompoosed blocks
+    for ( b = 0; b < nBits; b++ )
+        bBits[b] = Cudd_ReadLogicZero(ddNew), Cudd_Ref( bBits[b] );
+    // add each bound set minterm to one of the blccks
+    Vec_PtrForEachEntry( vCofs, bCof, c )
+    {
+        Vec_PtrForEachEntry( vUniq, bUniq, u )
+            if ( bUniq == bCof )
+                break;
+        assert( u < Vec_PtrSize(vUniq) );
+        for ( b = 0; b < nBits; b++ )
+        {
+            if ( ((u >> b) & 1) == 0 )
+                continue;
+            bMint = Extra_bddBitsToCube( ddNew, c, nLutSize, ddNew->vars, 1 );  Cudd_Ref( bMint );
+            bBits[b] = Cudd_bddOr( ddNew, bTemp = bBits[b], bMint );  Cudd_Ref( bBits[b] );
+            Cudd_RecursiveDeref( ddNew, bTemp );
+            Cudd_RecursiveDeref( ddNew, bMint );
+        }
+    }
+    // create bound set nodes
+    for ( b = 0; b < nBits; b++ )
+    {
+        pNodeBS[b] = Abc_NtkCreateNode( pNtkNew );
+        for ( i = 0; i < nLutSize; i++ )
+            Abc_ObjAddFanin( pNodeBS[b], Abc_ObjFanin(pNode, i)->pCopy );
+        pNodeBS[b]->pData = bBits[b]; // takes ref
+    }
+    // create composition node
+    pNodeNew = Abc_NtkCreateNode( pNtkNew );
+    // add free set variables first
+    for ( i = nLutSize; i < Abc_ObjFaninNum(pNode); i++ )
+        Abc_ObjAddFanin( pNodeNew, Abc_ObjFanin(pNode, i)->pCopy );
+    // add code bit variables next
+    for ( b = 0; b < nBits; b++ )
+        Abc_ObjAddFanin( pNodeNew, pNodeBS[b] );
+    // derive function of the composition node
+    bFunc = Cudd_ReadLogicZero(ddNew); Cudd_Ref( bFunc );
+    pbCodeVars = ddNew->vars + Abc_ObjFaninNum(pNode) - nLutSize;
+    Vec_PtrForEachEntry( vUniq, bUniq, u )
+    {
+        bUniq = Extra_bddMove( ddOld, bUniq, -nLutSize );                   Cudd_Ref( bUniq );
+        bUniq = Extra_TransferLevelByLevel( ddOld, ddNew, bTemp = bUniq );  Cudd_Ref( bUniq );
+        Cudd_RecursiveDeref( ddOld, bTemp );
+
+        bMint = Extra_bddBitsToCube( ddNew, u, nBits, pbCodeVars, 0 );  Cudd_Ref( bMint );
+        bMint = Cudd_bddAnd( ddNew, bTemp = bMint, bUniq );  Cudd_Ref( bMint );
+        Cudd_RecursiveDeref( ddNew, bTemp );
+        Cudd_RecursiveDeref( ddNew, bUniq );
+
+        bFunc = Cudd_bddOr( ddNew, bTemp = bFunc, bMint );  Cudd_Ref( bFunc );
+        Cudd_RecursiveDeref( ddNew, bTemp );
+        Cudd_RecursiveDeref( ddNew, bMint );
+    }
+    pNodeNew->pData = bFunc; // takes ref
     return pNodeNew;
 }
 
 /**Function*************************************************************
 
-  Synopsis    [Converts the node to MUXes.]
+  Synopsis    [Tries to decompose using cofactoring into two LUTs.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Abc_Obj_t * Abc_NtkBddFindCofactor( Abc_Ntk_t * pNtkNew, Abc_Obj_t * pNode, int nLutSize )
+{
+    Abc_Obj_t * pNodeBot, * pNodeTop;
+    DdManager * ddOld = pNode->pNtk->pManFunc;
+    DdManager * ddNew = pNtkNew->pManFunc;
+    DdNode * bCof0, * bCof1, * bSupp, * bTemp, * bVar;
+    DdNode * bCof0n, * bCof1n;
+    int i, iCof, iFreeVar, fCof1Smaller = -1;
+    assert( Abc_ObjFaninNum(pNode) == nLutSize + 1 );
+    for ( iCof = 0; iCof < Abc_ObjFaninNum(pNode); iCof++ )
+    {
+        bVar  = Cudd_bddIthVar( ddOld, iCof );
+        bCof0 = Cudd_Cofactor( ddOld, pNode->pData, Cudd_Not(bVar) );  Cudd_Ref( bCof0 );
+        bCof1 = Cudd_Cofactor( ddOld, pNode->pData, bVar  );           Cudd_Ref( bCof1 );
+        if ( Cudd_SupportSize( ddOld, bCof0 ) <= nLutSize - 2 )
+        {
+            fCof1Smaller = 0;
+            break;
+        }
+        if ( Cudd_SupportSize( ddOld, bCof1 ) <= nLutSize - 2 )
+        {
+            fCof1Smaller = 1;
+            break;
+        }
+        Cudd_RecursiveDeref( ddOld, bCof0 );
+        Cudd_RecursiveDeref( ddOld, bCof1 );
+    }
+    if ( iCof == Abc_ObjFaninNum(pNode) )
+        return NULL;
+    // find unused variable
+    bSupp = Cudd_Support( ddOld, fCof1Smaller? bCof1 : bCof0 );   Cudd_Ref( bSupp );
+    iFreeVar = -1;
+    for ( i = 0; i < Abc_ObjFaninNum(pNode); i++ )
+    {
+        assert( i == Cudd_ReadPerm(ddOld, i) );
+        if ( i == iCof )
+            continue;
+        for ( bTemp = bSupp; !Cudd_IsConstant(bTemp); bTemp = cuddT(bTemp) )
+            if ( i == (int)Cudd_NodeReadIndex(bTemp) )
+                break;
+        if ( Cudd_IsConstant(bTemp) )
+        {
+            iFreeVar = i;
+            break;
+        }
+    }
+    assert( iFreeVar != iCof && iFreeVar < Abc_ObjFaninNum(pNode) );
+    Cudd_RecursiveDeref( ddOld, bSupp );
+    // transfer the cofactors
+    bCof0n = Extra_TransferLevelByLevel( ddOld, ddNew, bCof0 ); Cudd_Ref( bCof0n );
+    bCof1n = Extra_TransferLevelByLevel( ddOld, ddNew, bCof1 ); Cudd_Ref( bCof1n );
+    Cudd_RecursiveDeref( ddOld, bCof0 );
+    Cudd_RecursiveDeref( ddOld, bCof1 );
+    // create bottom node
+    pNodeBot = Abc_NtkCreateNode( pNtkNew );
+    for ( i = 0; i < Abc_ObjFaninNum(pNode); i++ )
+        Abc_ObjAddFanin( pNodeBot, Abc_ObjFanin(pNode, i)->pCopy );
+    pNodeBot->pData = fCof1Smaller? bCof0n : bCof1n;
+    // create top node
+    pNodeTop = Abc_NtkCreateNode( pNtkNew );
+    for ( i = 0; i < Abc_ObjFaninNum(pNode); i++ )
+        if ( i == iFreeVar )           
+            Abc_ObjAddFanin( pNodeTop, pNodeBot );
+        else
+            Abc_ObjAddFanin( pNodeTop, Abc_ObjFanin(pNode, i)->pCopy );
+    // derive the new function
+    pNodeTop->pData = Cudd_bddIte( ddNew, 
+        Cudd_bddIthVar(ddNew, iCof), 
+        fCof1Smaller? bCof1n : Cudd_bddIthVar(ddNew, iFreeVar), 
+        fCof1Smaller? Cudd_bddIthVar(ddNew, iFreeVar) : bCof0n );
+    Cudd_Ref( pNodeTop->pData );
+    Cudd_RecursiveDeref( ddNew, fCof1Smaller? bCof1n : bCof0n );
+    return pNodeTop;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Decompose the function once.]
 
   Description []
                
@@ -106,23 +504,64 @@ Abc_Obj_t * Abc_NodeBddToMuxesLut_rec( DdManager * dd, DdNode * bFunc, Abc_Ntk_t
   SeeAlso     []
 
 ***********************************************************************/
-Abc_Obj_t * Abc_NodeBddToMuxesLut( Abc_Ntk_t * pNtkNew, Abc_Obj_t * pNodeOld, int nLutSize )
+Abc_Obj_t * Abc_NtkBddDecompose( Abc_Ntk_t * pNtkNew, Abc_Obj_t * pNode, int nLutSize, int fVerbose )
 {
-    DdManager * dd = pNodeOld->pNtk->pManFunc;
-    DdNode * bFunc = pNodeOld->pData;
-    Abc_Obj_t * pFaninOld, * pNodeNew;
-    st_table * tBdd2Node;
+    Vec_Ptr_t * vCofs, * vUniq;
+    DdManager * dd = pNode->pNtk->pManFunc;
+    DdNode * bCof;
+    Abc_Obj_t * pNodeNew = NULL;
+    Abc_Obj_t * pCofs[20];
     int i;
-    // create the table mapping BDD nodes into the ABC nodes
-    tBdd2Node = st_init_table( st_ptrcmp, st_ptrhash );
-    // add the constant and the elementary vars
-    Abc_ObjForEachFanin( pNodeOld, pFaninOld, i )
-        st_insert( tBdd2Node, (char *)Cudd_bddIthVar(dd, i), (char *)pFaninOld->pCopy );
-    // create the new nodes recursively
-    pNodeNew = Abc_NodeBddToMuxesLut_rec( dd, Cudd_Regular(bFunc), pNtkNew, tBdd2Node, pNodeOld, nLutSize );
-    st_free_table( tBdd2Node );
-    if ( Cudd_IsComplement(bFunc) )
-        pNodeNew = Abc_NtkCreateNodeInv( pNtkNew, pNodeNew );
+    assert( Abc_ObjFaninNum(pNode) > nLutSize );
+    // try to decompose with two LUTs (the best case for Supp = LutSize + 1)
+    if ( Abc_ObjFaninNum(pNode) == nLutSize + 1 )
+    {
+
+        pNodeNew = Abc_NtkBddFindCofactor( pNtkNew, pNode, nLutSize );
+        if ( pNodeNew != NULL )
+        {
+            if ( fVerbose )
+            printf( "Decomposing %d-input node %d using MUX.\n",
+                Abc_ObjFaninNum(pNode), Abc_ObjId(pNode) );
+            return pNodeNew;
+        }
+
+    }
+    // cofactor w.r.t. the bound set variables
+    vCofs = Abc_NtkBddCofactors( dd, pNode->pData, nLutSize );
+    vUniq = Vec_PtrDup( vCofs );
+    Vec_PtrUniqify( vUniq, (int (*)())Vec_PtrSortCompare );
+    // only perform decomposition with it is support reduring with two less vars
+    if( Vec_PtrSize(vUniq) > (1 << (nLutSize-2)) )
+    {
+        Vec_PtrFree( vCofs );
+        vCofs = Abc_NtkBddCofactors( dd, pNode->pData, 2 );
+        if ( fVerbose )
+        printf( "Decomposing %d-input node %d using cofactoring with %d cofactors.\n",
+            Abc_ObjFaninNum(pNode), Abc_ObjId(pNode), Vec_PtrSize(vCofs) );
+        // implement the cofactors
+        pCofs[0] = Abc_ObjFanin(pNode, 0)->pCopy;
+        pCofs[1] = Abc_ObjFanin(pNode, 1)->pCopy;
+        Vec_PtrForEachEntry( vCofs, bCof, i )
+            pCofs[2+i] = Abc_NtkCreateCofLut( pNtkNew, dd, bCof, pNode, 2 );
+        if ( nLutSize == 4 )
+            pNodeNew = Abc_NtkBddMux412( pNtkNew, pCofs );
+        else if ( nLutSize == 5 )
+            pNodeNew = Abc_NtkBddMux412a( pNtkNew, pCofs );
+        else if ( nLutSize == 6 )
+            pNodeNew = Abc_NtkBddMux411( pNtkNew, pCofs );
+        else  assert( 0 );
+    }
+    // alternative decompose using MUX-decomposition
+    else
+    {
+        if ( fVerbose )
+        printf( "Decomposing %d-input node %d using Curtis with %d unique columns.\n",
+            Abc_ObjFaninNum(pNode), Abc_ObjId(pNode), Vec_PtrSize(vUniq) );
+        pNodeNew = Abc_NtkBddCurtis( pNtkNew, pNode, vCofs, vUniq );
+    }
+    Vec_PtrFree( vCofs );
+    Vec_PtrFree( vUniq );
     return pNodeNew;
 }
 
@@ -137,20 +576,24 @@ Abc_Obj_t * Abc_NodeBddToMuxesLut( Abc_Ntk_t * pNtkNew, Abc_Obj_t * pNodeOld, in
   SeeAlso     []
 
 ***********************************************************************/
-void Abc_NtkLutminConstruct( Abc_Ntk_t * pNtkClp, Abc_Ntk_t * pNtkDec, int nLutSize )
+void Abc_NtkLutminConstruct( Abc_Ntk_t * pNtkClp, Abc_Ntk_t * pNtkDec, int nLutSize, int fVerbose )
 {
-    Abc_Obj_t * pObj, * pDriver;
-    int i;
-    Abc_NtkForEachCo( pNtkClp, pObj, i )
+    Vec_Ptr_t * vNodes;
+    Abc_Obj_t * pNode, * pFanin;
+    int i, k;
+    vNodes = Abc_NtkDfs( pNtkClp, 0 );
+    Vec_PtrForEachEntry( vNodes, pNode, i )
     {
-        pDriver = Abc_ObjFanin0( pObj );
-        if ( !Abc_ObjIsNode(pDriver) )
-            continue;
-        if ( Abc_ObjFaninNum(pDriver) == 0 )
-            pDriver->pCopy = Abc_NtkDupObj( pNtkDec, pDriver, 0 );
+        if ( Abc_ObjFaninNum(pNode) <= nLutSize )
+        {
+            pNode->pCopy = Abc_NtkDupObj( pNtkDec, pNode, 0 );
+            Abc_ObjForEachFanin( pNode, pFanin, k )
+                Abc_ObjAddFanin( pNode->pCopy, pFanin->pCopy );
+        }
         else
-            pDriver->pCopy = Abc_NodeBddToMuxesLut( pNtkDec, pDriver, nLutSize );
+            pNode->pCopy = Abc_NtkBddDecompose( pNtkDec, pNode, nLutSize, fVerbose );
     }
+    Vec_PtrFree( vNodes );
 }
 
 /**Function*************************************************************
@@ -164,42 +607,87 @@ void Abc_NtkLutminConstruct( Abc_Ntk_t * pNtkClp, Abc_Ntk_t * pNtkDec, int nLutS
   SeeAlso     []
 
 ***********************************************************************/
-Abc_Ntk_t * Abc_NtkLutmin( Abc_Ntk_t * pNtk, int nLutSize, int fVerbose )
+Abc_Ntk_t * Abc_NtkLutminInt( Abc_Ntk_t * pNtk, int nLutSize, int fVerbose )
 {
     extern void Abc_NtkBddReorder( Abc_Ntk_t * pNtk, int fVerbose );
-    Abc_Ntk_t * pNtkDec, * pNtkClp, * pTemp;
-    // collapse the network and reorder BDDs
-    if ( Abc_NtkIsStrash(pNtk) )
-        pTemp = Abc_NtkDup( pNtk );
-    else
-        pTemp = Abc_NtkStrash( pNtk, 0, 1, 0 );
-    pNtkClp = Abc_NtkCollapse( pTemp, 10000, 0, 1, 0 );
-    Abc_NtkDelete( pTemp );
-    if ( pNtkClp == NULL )
-        return NULL;
-    if ( !Abc_NtkIsBddLogic(pNtkClp) )
-        Abc_NtkToBdd( pNtkClp );
-    Abc_NtkBddReorder( pNtkClp, fVerbose );
+    Abc_Ntk_t * pNtkDec;
+    // minimize BDDs
+//    Abc_NtkBddReorder( pNtk, fVerbose );
+    Abc_NtkBddReorder( pNtk, 0 );
     // decompose one output at a time
-    pNtkDec = Abc_NtkStartFrom( pNtkClp, ABC_NTK_LOGIC, ABC_FUNC_BDD );
+    pNtkDec = Abc_NtkStartFrom( pNtk, ABC_NTK_LOGIC, ABC_FUNC_BDD );
     // make sure the new manager has enough inputs
-    Cudd_bddIthVar( pNtkDec->pManFunc, nLutSize );
+    Cudd_bddIthVar( pNtkDec->pManFunc, Abc_NtkGetFaninMax(pNtk) );
     // put the results into the new network (save new CO drivers in old CO drivers)
-    Abc_NtkLutminConstruct( pNtkClp, pNtkDec, nLutSize );
+    Abc_NtkLutminConstruct( pNtk, pNtkDec, nLutSize, fVerbose );
     // finalize the new network
-    Abc_NtkFinalize( pNtkClp, pNtkDec );
-    Abc_NtkDelete( pNtkClp );
+    Abc_NtkFinalize( pNtk, pNtkDec );
     // make the network minimum base
     Abc_NtkMinimumBase( pNtkDec );
+    return pNtkDec;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Performs minimum-LUT decomposition of the network.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Abc_Ntk_t * Abc_NtkLutmin( Abc_Ntk_t * pNtkInit, int nLutSize, int fVerbose )
+{
+    extern bool Abc_NtkFraigSweep( Abc_Ntk_t * pNtk, int fUseInv, int fExdc, int fVerbose, int fVeryVerbose );
+    Abc_Ntk_t * pNtkNew, * pTemp;
+    int i;
+    if ( nLutSize < 4 )
+    {
+        printf( "The LUT count (%d) should be at least 4.\n", nLutSize );
+        return NULL;
+    }
+    if ( nLutSize > 6 )
+    {
+        printf( "The LUT count (%d) should not exceed 6.\n", nLutSize );
+        return NULL;
+    }
+    // create internal representation
+    if ( Abc_NtkIsStrash(pNtkInit) )
+        pNtkNew = Abc_NtkDup( pNtkInit );
+    else
+        pNtkNew = Abc_NtkStrash( pNtkInit, 0, 1, 0 );
+    // collapse the network 
+    pNtkNew = Abc_NtkCollapse( pTemp = pNtkNew, 10000, 0, 1, 0 );
+    Abc_NtkDelete( pTemp );
+    if ( pNtkNew == NULL )
+        return NULL;
+    // convert it to BDD
+    if ( !Abc_NtkIsBddLogic(pNtkNew) )
+        Abc_NtkToBdd( pNtkNew );
+    // iterate decomposition
+    for ( i = 0; Abc_NtkGetFaninMax(pNtkNew) > nLutSize; i++ )
+    {
+        if ( fVerbose )
+            printf( "*** Iteration %d:\n", i+1 );
+        if ( fVerbose )
+            printf( "Decomposing network with %d nodes and %d max fanin count for K = %d.\n", 
+                Abc_NtkNodeNum(pNtkNew), Abc_NtkGetFaninMax(pNtkNew), nLutSize );
+        pNtkNew = Abc_NtkLutminInt( pTemp = pNtkNew, nLutSize, fVerbose );
+        Abc_NtkDelete( pTemp );
+    }
     // fix the problem with complemented and duplicated CO edges
-    Abc_NtkLogicMakeSimpleCos( pNtkDec, 0 );
+    Abc_NtkLogicMakeSimpleCos( pNtkNew, 0 );
+    // merge functionally equivalent nodes
+    Abc_NtkFraigSweep( pNtkNew, 1, 0, 0, 0 );
     // make sure everything is okay
-    if ( !Abc_NtkCheck( pNtkDec ) )
+    if ( !Abc_NtkCheck( pNtkNew ) )
     {
         printf( "Abc_NtkLutmin: The network check has failed.\n" );
         return 0;
     }
-    return pNtkDec;
+    return pNtkNew;
 }
 
 ////////////////////////////////////////////////////////////////////////