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/**CFile****************************************************************
FileName [saigAbs.c]
SystemName [ABC: Logic synthesis and verification system.]
PackageName [Sequential AIG package.]
Synopsis [Proof-based abstraction.]
Author [Alan Mishchenko]
Affiliation [UC Berkeley]
Date [Ver. 1.0. Started - June 20, 2005.]
Revision [$Id: saigAbs.c,v 1.00 2005/06/20 00:00:00 alanmi Exp $]
***********************************************************************/
#include "saig.h"
#include "cnf.h"
#include "satSolver.h"
#include "satStore.h"
////////////////////////////////////////////////////////////////////////
/// DECLARATIONS ///
////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////
/// FUNCTION DEFINITIONS ///
////////////////////////////////////////////////////////////////////////
/**Function*************************************************************
Synopsis [Creates SAT solver for BMC.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
sat_solver * Saig_AbsCreateSolver( Cnf_Dat_t * pCnf, int nFrames )
{
sat_solver * pSat;
Vec_Int_t * vPoLits;
Aig_Obj_t * pObjPo, * pObjLi, * pObjLo;
int f, i, Lit, Lits[2], iVarOld, iVarNew;
// start array of output literals
vPoLits = Vec_IntAlloc( nFrames * Saig_ManPoNum(pCnf->pMan) );
// create the SAT solver
pSat = sat_solver_new();
sat_solver_store_alloc( pSat );
sat_solver_setnvars( pSat, pCnf->nVars * nFrames );
// add clauses for the timeframes
for ( f = 0; f < nFrames; f++ )
{
for ( i = 0; i < pCnf->nClauses; i++ )
{
if ( !sat_solver_addclause( pSat, pCnf->pClauses[i], pCnf->pClauses[i+1] ) )
{
printf( "The BMC problem is trivially UNSAT.\n" );
sat_solver_delete( pSat );
Vec_IntFree( vPoLits );
return NULL;
}
}
// remember output literal
Saig_ManForEachPo( pCnf->pMan, pObjPo, i )
Vec_IntPush( vPoLits, toLit(pCnf->pVarNums[pObjPo->Id]) );
// lift CNF to the next frame
Cnf_DataLift( pCnf, pCnf->nVars );
}
// put CNF back to the original level
Cnf_DataLift( pCnf, - pCnf->nVars * nFrames );
// add auxiliary clauses (output, connectors, initial)
// add output clause
if ( !sat_solver_addclause( pSat, Vec_IntArray(vPoLits), Vec_IntArray(vPoLits) + Vec_IntSize(vPoLits) ) )
assert( 0 );
Vec_IntFree( vPoLits );
// add connecting clauses
for ( f = 0; f < nFrames; f++ )
{
// connect to the previous timeframe
if ( f > 0 )
{
Saig_ManForEachLiLo( pCnf->pMan, pObjLi, pObjLo, i )
{
iVarOld = pCnf->pVarNums[pObjLi->Id] - pCnf->nVars;
iVarNew = pCnf->pVarNums[pObjLo->Id];
// add clauses connecting existing variables
Lits[0] = toLitCond( iVarOld, 0 );
Lits[1] = toLitCond( iVarNew, 1 );
if ( !sat_solver_addclause( pSat, Lits, Lits+2 ) )
assert( 0 );
Lits[0] = toLitCond( iVarOld, 1 );
Lits[1] = toLitCond( iVarNew, 0 );
if ( !sat_solver_addclause( pSat, Lits, Lits+2 ) )
assert( 0 );
}
}
// lift CNF to the next frame
Cnf_DataLift( pCnf, pCnf->nVars );
}
// put CNF back to the original level
Cnf_DataLift( pCnf, - pCnf->nVars * nFrames );
// add unit clauses
Saig_ManForEachLo( pCnf->pMan, pObjLo, i )
{
assert( pCnf->pVarNums[pObjLo->Id] >= 0 );
Lit = toLitCond( pCnf->pVarNums[pObjLo->Id], 1 );
if ( !sat_solver_addclause( pSat, &Lit, &Lit+1 ) )
assert( 0 );
}
sat_solver_store_mark_roots( pSat );
return pSat;
}
/**Function*************************************************************
Synopsis [Finds the set of clauses involved in the UNSAT core.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
Vec_Int_t * Saig_AbsSolverUnsatCore( sat_solver * pSat, int nConfMax, int fVerbose )
{
Vec_Int_t * vCore;
void * pSatCnf;
Intp_Man_t * pManProof;
int RetValue;
// solve the problem
RetValue = sat_solver_solve( pSat, NULL, NULL, (sint64)nConfMax, (sint64)0, (sint64)0, (sint64)0 );
if ( RetValue == l_Undef )
{
printf( "Conflict limit is reached.\n" );
return NULL;
}
if ( RetValue == l_True )
{
printf( "The BMC problem is SAT.\n" );
return NULL;
}
if ( fVerbose )
printf( "SAT solver returned UNSAT after %d conflicts.\n", pSat->stats.conflicts );
assert( RetValue == l_False );
pSatCnf = sat_solver_store_release( pSat );
// derive the UNSAT core
pManProof = Intp_ManAlloc();
vCore = Intp_ManUnsatCore( pManProof, pSatCnf, fVerbose );
Intp_ManFree( pManProof );
Sto_ManFree( pSatCnf );
return vCore;
}
/**Function*************************************************************
Synopsis [Performs proof-based abstraction using BMC of the given depth.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
Vec_Int_t * Saig_AbsCollectRegisters( Cnf_Dat_t * pCnf, int nFrames, Vec_Int_t * vCore )
{
Aig_Obj_t * pObj;
Vec_Int_t * vFlops;
int * pVars, * pFlops;
int i, iClause, iReg, * piLit;
// mark register variables
pVars = ALLOC( int, pCnf->nVars );
for ( i = 0; i < pCnf->nVars; i++ )
pVars[i] = -1;
Saig_ManForEachLi( pCnf->pMan, pObj, i )
pVars[ pCnf->pVarNums[pObj->Id] ] = i;
Saig_ManForEachLo( pCnf->pMan, pObj, i )
pVars[ pCnf->pVarNums[pObj->Id] ] = i;
// mark used registers
pFlops = CALLOC( int, Aig_ManRegNum(pCnf->pMan) );
Vec_IntForEachEntry( vCore, iClause, i )
{
// skip auxiliary clauses
if ( iClause >= pCnf->nClauses * nFrames )
continue;
// consider the clause
iClause = iClause % pCnf->nClauses;
for ( piLit = pCnf->pClauses[iClause]; piLit < pCnf->pClauses[iClause+1]; piLit++ )
{
iReg = pVars[ lit_var(*piLit) ];
if ( iReg >= 0 )
pFlops[iReg] = 1;
}
}
// collect registers
vFlops = Vec_IntAlloc( Aig_ManRegNum(pCnf->pMan) );
for ( i = 0; i < Aig_ManRegNum(pCnf->pMan); i++ )
if ( pFlops[i] )
Vec_IntPush( vFlops, i );
free( pFlops );
free( pVars );
return vFlops;
}
/**Function*************************************************************
Synopsis [Performs proof-based abstraction using BMC of the given depth.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
Aig_Man_t * Saig_ManProofAbstraction( Aig_Man_t * p, int nFrames, int nConfMax, int fVerbose )
{
Aig_Man_t * pResult;
Cnf_Dat_t * pCnf;
sat_solver * pSat;
Vec_Int_t * vCore;
Vec_Int_t * vFlops;
int clk = clock();
assert( Aig_ManRegNum(p) > 0 );
Aig_ManSetPioNumbers( p );
if ( fVerbose )
printf( "Performing proof-based abstraction with %d frames and %d max conflicts.\n", nFrames, nConfMax );
// create CNF for the AIG
pCnf = Cnf_DeriveSimple( p, Aig_ManPoNum(p) );
// create SAT solver for the unrolled AIG
pSat = Saig_AbsCreateSolver( pCnf, nFrames );
// compute UNSAT core
vCore = Saig_AbsSolverUnsatCore( pSat, nConfMax, fVerbose );
sat_solver_delete( pSat );
if ( vCore == NULL )
{
Cnf_DataFree( pCnf );
return NULL;
}
// collect registers
vFlops = Saig_AbsCollectRegisters( pCnf, nFrames, vCore );
Cnf_DataFree( pCnf );
Vec_IntFree( vCore );
if ( fVerbose )
{
printf( "The number of relevant registers is %d (out of %d).\n", Vec_IntSize(vFlops), Aig_ManRegNum(p) );
PRT( "Time", clock() - clk );
}
// create the resulting AIG
pResult = Saig_ManAbstraction( p, vFlops );
Vec_IntFree( vFlops );
return pResult;
}
////////////////////////////////////////////////////////////////////////
/// END OF FILE ///
////////////////////////////////////////////////////////////////////////
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