Backward reachability using circuit cofactoring.

src/aig/gia/giaCCof.c

+/**CFile****************************************************************
+
+  FileName    [giaCCof.c]
+
+  SystemName  [ABC: Logic synthesis and verification system.]
+
+  PackageName [Scalable AIG package.]
+
+  Synopsis    [Backward reachability using circuit cofactoring.]
+
+  Author      [Alan Mishchenko]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - June 20, 2005.]
+
+  Revision    [$Id: giaCCof.c,v 1.00 2005/06/20 00:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include "gia.h"
+#include "satSolver.h"
+
+ABC_NAMESPACE_IMPL_START
+
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+typedef struct Ccf_Man_t_ Ccf_Man_t; // manager
+struct Ccf_Man_t_
+{
+    // user data
+    Gia_Man_t *   pGia;         // single output AIG manager
+    int           nFrameMax;    // maximum number of frames
+    int           nConfMax;     // maximum number of conflicts
+    int           nTimeMax;     // maximum runtime in seconds
+    int           fVerbose;     // verbose flag
+    // internal data
+    sat_solver *  pSat;         // SAT solver
+    Gia_Man_t *   pFrames;      // unrolled timeframes
+    Vec_Int_t *   vIdToFra;     // maps GIA obj IDs into frame obj IDs
+    Vec_Int_t *   vOrder;       // map Num to Id
+    Vec_Int_t *   vFraLims;     // frame limits
+};
+
+extern Vec_Int_t * Gia_VtaCollect( Gia_Man_t * p, Vec_Int_t ** pvFraLims, Vec_Int_t ** pvRoots );
+
+static inline int  Gia_ObjFrames( Ccf_Man_t * p, int f, Gia_Obj_t * pObj )             { assert( Vec_IntEntry(p->vIdToFra, f*Gia_ManObjNum(p->pGia)+Gia_ObjId(p->pGia,pObj)) >= 0 ); return Vec_IntEntry(p->vIdToFra, f*Gia_ManObjNum(p->pGia)+Gia_ObjId(p->pGia,pObj));     }
+static inline void Gia_ObjSetFrames( Ccf_Man_t * p, int f, Gia_Obj_t * pObj, int Lit ) { Vec_IntWriteEntry(p->vIdToFra, f*Gia_ManObjNum(p->pGia)+Gia_ObjId(p->pGia,pObj), Lit);  }
+
+static inline int  Gia_ObjChild0Frames( Ccf_Man_t * p, int f, Gia_Obj_t * pObj )       { return Gia_LitNotCond(Gia_ObjFrames(p, f, Gia_ObjFanin0(pObj)), Gia_ObjFaninC0(pObj));  }
+static inline int  Gia_ObjChild1Frames( Ccf_Man_t * p, int f, Gia_Obj_t * pObj )       { return Gia_LitNotCond(Gia_ObjFrames(p, f, Gia_ObjFanin1(pObj)), Gia_ObjFaninC1(pObj));  }
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+static inline int sat_solver_add_const( sat_solver * pSat, int iVar, int fCompl )
+{
+    lit Lits[1];
+    int Cid;
+    assert( iVar >= 0 );
+
+    Lits[0] = toLitCond( iVar, fCompl );
+    Cid = sat_solver_addclause( pSat, Lits, Lits + 1 );
+    assert( Cid );
+    return 1;
+}
+static inline int sat_solver_add_buffer( sat_solver * pSat, int iVarA, int iVarB, int fCompl )
+{
+    lit Lits[2];
+    int Cid;
+    assert( iVarA >= 0 && iVarB >= 0 );
+
+    Lits[0] = toLitCond( iVarA, 0 );
+    Lits[1] = toLitCond( iVarB, !fCompl );
+    Cid = sat_solver_addclause( pSat, Lits, Lits + 2 );
+    assert( Cid );
+
+    Lits[0] = toLitCond( iVarA, 1 );
+    Lits[1] = toLitCond( iVarB, fCompl );
+    Cid = sat_solver_addclause( pSat, Lits, Lits + 2 );
+    assert( Cid );
+    return 2;
+}
+static inline int sat_solver_add_and( sat_solver * pSat, int iVar, int iVar0, int iVar1, int fCompl0, int fCompl1 )
+{
+    lit Lits[3];
+    int Cid;
+
+    Lits[0] = toLitCond( iVar, 1 );
+    Lits[1] = toLitCond( iVar0, fCompl0 );
+    Cid = sat_solver_addclause( pSat, Lits, Lits + 2 );
+    assert( Cid );
+
+    Lits[0] = toLitCond( iVar, 1 );
+    Lits[1] = toLitCond( iVar1, fCompl1 );
+    Cid = sat_solver_addclause( pSat, Lits, Lits + 2 );
+    assert( Cid );
+
+    Lits[0] = toLitCond( iVar, 0 );
+    Lits[1] = toLitCond( iVar0, !fCompl0 );
+    Lits[2] = toLitCond( iVar1, !fCompl1 );
+    Cid = sat_solver_addclause( pSat, Lits, Lits + 3 );
+    assert( Cid );
+    return 3;
+}
+static inline int sat_solver_add_xor( sat_solver * pSat, int iVarA, int iVarB, int iVarC, int fCompl )
+{
+    lit Lits[3];
+    int Cid;
+    assert( iVarA >= 0 && iVarB >= 0 && iVarC >= 0 );
+
+    Lits[0] = toLitCond( iVarA, !fCompl );
+    Lits[1] = toLitCond( iVarB, 1 );
+    Lits[2] = toLitCond( iVarC, 1 );
+    Cid = sat_solver_addclause( pSat, Lits, Lits + 3 );
+    assert( Cid );
+
+    Lits[0] = toLitCond( iVarA, !fCompl );
+    Lits[1] = toLitCond( iVarB, 0 );
+    Lits[2] = toLitCond( iVarC, 0 );
+    Cid = sat_solver_addclause( pSat, Lits, Lits + 3 );
+    assert( Cid );
+
+    Lits[0] = toLitCond( iVarA, fCompl );
+    Lits[1] = toLitCond( iVarB, 1 );
+    Lits[2] = toLitCond( iVarC, 0 );
+    Cid = sat_solver_addclause( pSat, Lits, Lits + 3 );
+    assert( Cid );
+
+    Lits[0] = toLitCond( iVarA, fCompl );
+    Lits[1] = toLitCond( iVarB, 0 );
+    Lits[2] = toLitCond( iVarC, 1 );
+    Cid = sat_solver_addclause( pSat, Lits, Lits + 3 );
+    assert( Cid );
+    return 4;
+}
+static inline int sat_solver_add_constraint( sat_solver * pSat, int iVar, int fCompl )
+{
+    lit Lits[2];
+    int Cid;
+    assert( iVar >= 0 );
+
+    Lits[0] = toLitCond( iVar, fCompl );
+    Lits[1] = toLitCond( iVar+1, 0 );
+    Cid = sat_solver_addclause( pSat, Lits, Lits + 2 );
+    assert( Cid );
+
+    Lits[0] = toLitCond( iVar, fCompl );
+    Lits[1] = toLitCond( iVar+1, 1 );
+    Cid = sat_solver_addclause( pSat, Lits, Lits + 2 );
+    assert( Cid );
+    return 2;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Create manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Ccf_Man_t * Ccf_ManStart( Gia_Man_t * pGia, int nFrameMax, int nConfMax, int nTimeMax, int fVerbose )
+{
+    Ccf_Man_t * p;
+    assert( nFrameMax > 0 );
+    p = ABC_CALLOC( Ccf_Man_t, 1 );
+    p->pGia       = pGia;
+    p->nFrameMax  = nFrameMax;    
+    p->nConfMax   = nConfMax;
+    p->nTimeMax   = nTimeMax;
+    p->fVerbose   = fVerbose;
+    // internal data
+    p->pFrames    = Gia_ManStart( 10000 );
+    Gia_ManHashAlloc( p->pFrames );
+    p->vOrder     = Gia_VtaCollect( pGia, &p->vFraLims, NULL );
+    p->vIdToFra   = Vec_IntAlloc( 0 );
+    p->pSat       = sat_solver_new();
+    sat_solver_setnvars( p->pSat, 10000 );
+    return p;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Delete manager.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Ccf_ManStop( Ccf_Man_t * p )
+{
+    Vec_IntFreeP( &p->vIdToFra );
+    Vec_IntFreeP( &p->vOrder );
+    Vec_IntFreeP( &p->vFraLims );
+    sat_solver_delete( p->pSat );
+    Gia_ManStopP( &p->pFrames );
+    ABC_FREE( p );
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Extends the solver.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Gia_ManCofExtendSolver( Ccf_Man_t * p )
+{
+    Gia_Obj_t * pObj;
+    int i;
+    // add SAT clauses
+    for ( i = sat_solver_nvars(p->pSat); i < Gia_ManObjNum(p->pFrames); i++ )
+    {
+        pObj = Gia_ManObj( p->pGia, i );
+        if ( Gia_ObjIsAnd(pObj) )
+            sat_solver_add_and( p->pSat, i, 
+                Gia_ObjFaninId0(pObj, i), 
+                Gia_ObjFaninId1(pObj, i), 
+                Gia_ObjFaninC0(pObj), 
+                Gia_ObjFaninC1(pObj) ); 
+    }
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Adds logic of one timeframe to the manager.]
+
+  Description [Returns literal of the property output.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Gia_ManCofAddTimeFrame( Ccf_Man_t * p, int fMax )
+{
+    Gia_Obj_t * pObj;
+    int i, f, Beg, End, Lit;
+    assert( fMax > 0 && fMax <= p->nFrameMax );
+    assert( Vec_IntSize(p->vIdToFra) == (fMax - 1) * Gia_ManObjNum(p->pGia) );
+    // add to the mapping of nodes
+    Vec_IntFillExtra( p->vIdToFra, fMax * Gia_ManObjNum(p->pGia), -1 );
+    // add nodes to each time-frame
+    for ( f = 0; f < fMax; f++ )
+    {
+        if ( Vec_IntSize(p->vFraLims) >= fMax-f )
+            continue;
+        Beg = Vec_IntEntry( p->vFraLims, fMax-f-1 );
+        End = Vec_IntEntry( p->vFraLims, fMax-f );
+        for ( i = Beg; i < End; i++ )
+        {
+            pObj = Gia_ManObj( p->pGia, Vec_IntEntry(p->vOrder, i) );
+            if ( Gia_ObjIsAnd(pObj) )
+                Lit = Gia_ManHashAnd( p->pFrames, Gia_ObjChild0Frames(p, f, pObj), Gia_ObjChild1Frames(p, f, pObj) );
+            else if ( Gia_ObjIsRo(p->pGia, pObj) && f > 0 )
+                Lit = Gia_ObjChild0Frames(p, f-1, Gia_ObjRoToRi(p->pGia, pObj));
+            else if ( Gia_ObjIsCi(pObj) )
+            {
+                Lit = Gia_ManAppendCi(p->pFrames);
+                // mark primary input
+                Gia_ManObj(p->pFrames, Gia_Lit2Var(Lit))->fMark0 = Gia_ObjIsPi(p->pGia, pObj);
+            }
+            else assert( 0 );
+            Gia_ObjSetFrames( p, f, pObj, Lit );
+        }
+    }
+    // add SAT clauses
+    Gia_ManCofExtendSolver( p );
+    // return output literal
+    return Gia_ObjChild0Frames( p, fMax-1, Gia_ManPo(p->pGia, 0) );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Cofactor the circuit w.r.t. the given assignment.]
+
+  Description [Assumes that the solver has just returned SAT.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Gia_ManCofOneDerive_rec( Ccf_Man_t * p, Gia_Obj_t * pObj )
+{
+    if ( ~pObj->Value )
+        return pObj->Value;
+    assert( Gia_ObjIsCi(pObj) || Gia_ObjIsAnd(pObj) );
+    if ( Gia_ObjIsAnd(pObj) )
+    {
+        Gia_ManCofOneDerive_rec( p, Gia_ObjFanin0(pObj) );
+        Gia_ManCofOneDerive_rec( p, Gia_ObjFanin1(pObj) );
+        pObj->Value = Gia_ManHashAnd( p->pFrames, Gia_ObjFanin0Copy(pObj), Gia_ObjFanin1Copy(pObj) );
+    }
+    else if ( pObj->fMark0 ) // PI
+        pObj->Value = sat_solver_var_value( p->pSat, Gia_ObjId(p->pGia, pObj) );
+    else
+        pObj->Value = Gia_Var2Lit( Gia_ObjId(p->pGia, pObj), 0 );
+    return pObj->Value;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Cofactor the circuit w.r.t. the given assignment.]
+
+  Description [Assumes that the solver has just returned SAT.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Gia_ManCofOneDerive( Ccf_Man_t * p, int LitProp )
+{
+    Gia_Obj_t * pObj;
+    int LitOut;
+    // get the property node
+    pObj = Gia_ManObj( p->pFrames, Gia_Lit2Var(LitProp) );
+    // derive the cofactor
+    Gia_ManFillValue( p->pFrames );
+    LitOut = Gia_ManCofOneDerive_rec( p, pObj );
+    LitOut = Gia_LitNotCond(LitOut, Gia_LitIsCompl(LitProp));
+    // add new PO for the cofactor
+    Gia_ManAppendCo( p->pFrames, LitOut );
+    // add SAT clauses
+    Gia_ManCofExtendSolver( p );
+    // return negative literal of the cofactor
+    return Gia_LitNot(LitOut);
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Enumerates backward reachable states.]
+
+  Description [Return -1 if resource limit is reached. Returns 1 
+  if computation converged (there is no more reachable states).
+  Returns 0 if no more states to enumerate.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Gia_ManCofGetReachable( Ccf_Man_t * p, int Lit )
+{
+    int RetValue;
+    // try solving for the first time and quit if converged
+    RetValue = sat_solver_solve( p->pSat, &Lit, &Lit + 1, p->nConfMax, 0, 0, 0 );
+    if ( RetValue == l_False )
+        return 1;
+    // iterate circuit cofactoring
+    while ( RetValue == 0 )
+    {
+        // derive cofactor
+        int LitOut = Gia_ManCofOneDerive( p, Lit );
+        // add the blocking clause
+        RetValue = sat_solver_addclause( p->pSat, &LitOut, &LitOut + 1 );
+        assert( RetValue );
+        // try solving again
+        RetValue = sat_solver_solve( p->pSat, &Lit, &Lit + 1, p->nConfMax, 0, 0, 0 );
+    }
+    if ( RetValue == l_Undef )
+        return -1;
+    return 0;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Gia_Man_t * Gia_ManCofTest( Gia_Man_t * pGia, int nFrameMax, int nConfMax, int nTimeMax, int fVerbose )
+{
+    Gia_Man_t * pNew;
+    Ccf_Man_t * p;
+    int f, Lit, RetValue;
+    assert( Gia_ManPoNum(pGia) == 1 );
+    // create reachability manager
+    p = Ccf_ManStart( pGia, nFrameMax, nConfMax, nTimeMax, fVerbose );
+    // perform backward image computation
+    for ( f = 0; f < nFrameMax; f++ )
+    {
+        if ( fVerbose )
+            printf( "ITER %3d :\n", f );
+        // derives new timeframe and returns the property literal
+        Lit = Gia_ManCofAddTimeFrame( p, f+1 );
+        // derives cofactors of the property literal till all states are blocked
+        RetValue = Gia_ManCofGetReachable( p, Lit );
+        if ( RetValue )
+            break;
+    }
+    // report the result
+    if ( f == nFrameMax )
+        printf( "Completed %d frames without converging.\n", f );
+    else if ( RetValue == 1 )
+        printf( "Backward reachability converged after %d iterations.\n", f );
+    else if ( RetValue == -1 )
+        printf( "Conflict limit or timeout is reached after %d frames.\n", f );
+
+    // get the resulting AIG manager
+    Gia_ManHashStop( p->pFrames );
+    Gia_ManCleanMark0( p->pFrames );
+    pNew = p->pFrames;  p->pFrames = NULL;
+    Ccf_ManStop( p );
+    pNew = Gia_ManCleanup( pGia = pNew );
+    Gia_ManStop( pGia );
+
+//    if ( fVerbose )
+        Gia_ManPrintStats( pNew, 0 );
+    return pNew;   
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
+ABC_NAMESPACE_IMPL_END
+