src/sat/msat/msatSolverSearch.c File Reference

#include "msatInt.h"

Include dependency graph for msatSolverSearch.c:

Go to the source code of this file.

Functions
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)
bool	Msat_SolverAssume (Msat_Solver_t *p, Msat_Lit_t Lit)
void	Msat_SolverCancelUntil (Msat_Solver_t *p, int Level)
bool	Msat_SolverEnqueue (Msat_Solver_t *p, Msat_Lit_t Lit, Msat_Clause_t *pC)
Msat_Clause_t *	Msat_SolverPropagate (Msat_Solver_t *p)
bool	Msat_SolverSimplifyDB (Msat_Solver_t *p)
void	Msat_SolverRemoveLearned (Msat_Solver_t *p)
void	Msat_SolverRemoveMarked (Msat_Solver_t *p)
Msat_Type_t	Msat_SolverSearch (Msat_Solver_t *p, int nConfLimit, int nLearnedLimit, int nBackTrackLimit, Msat_SearchParams_t *pPars)

---

Function Documentation

void Msat_SolverAnalyze	(	Msat_Solver_t *	p,
		Msat_Clause_t *	pC,
		Msat_IntVec_t *	vLits_out,
		int *	pLevel_out
	)			[static]

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 []

Definition at line 452 of file msatSolverSearch.c.

{
    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); 
    }
}

bool Msat_SolverAssume	(	Msat_Solver_t *	p,
		Msat_Lit_t	Lit
	)

FUNCTION DEFINITIONS ///Function*************************************************************

Synopsis [Makes the next assumption (Lit).]

Description [Returns FALSE if immediate conflict.]

SideEffects []

SeeAlso []

Definition at line 48 of file msatSolverSearch.c.

{
    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 );
}

void Msat_SolverCancel

(

Msat_Solver_t *

p

)

[static]

Function*************************************************************

Synopsis [Reverts to the state before last Msat_SolverAssume().]

Description []

SideEffects []

SeeAlso []

Definition at line 97 of file msatSolverSearch.c.

{
    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 );
}

void Msat_SolverCancelUntil	(	Msat_Solver_t *	p,
		int	Level
	)

Function*************************************************************

Synopsis [Reverts to the state at given level.]

Description []

SideEffects []

SeeAlso []

Definition at line 125 of file msatSolverSearch.c.

{
    while ( Msat_IntVecReadSize(p->vTrailLim) > Level )
        Msat_SolverCancel(p);
}

bool Msat_SolverEnqueue	(	Msat_Solver_t *	p,
		Msat_Lit_t	Lit,
		Msat_Clause_t *	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 []

Definition at line 170 of file msatSolverSearch.c.

{
    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;
}

Msat_Clause_t* Msat_SolverPropagate

(

Msat_Solver_t *

p

)

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 []

Definition at line 214 of file msatSolverSearch.c.

{
    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;
}

Msat_Clause_t * Msat_SolverRecord	(	Msat_Solver_t *	p,
		Msat_IntVec_t *	vLits
	)			[static]

Function*************************************************************

Synopsis [Record a clause and drive backtracking.]

Description [vLits[0] must contain the asserting literal.]

SideEffects []

SeeAlso []

Definition at line 143 of file msatSolverSearch.c.

{
    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;
}

void Msat_SolverReduceDB

(

Msat_Solver_t *

p

)

[static]

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 []

Definition at line 329 of file msatSolverSearch.c.

{
    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 );
}

void Msat_SolverRemoveLearned

(

Msat_Solver_t *

p

)

Function*************************************************************

Synopsis [Removes the learned clauses.]

Description []

SideEffects []

SeeAlso []

Definition at line 368 of file msatSolverSearch.c.

{
    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;
}

void Msat_SolverRemoveMarked

(

Msat_Solver_t *

p

)

Function*************************************************************

Synopsis [Removes the recently added clauses.]

Description []

SideEffects []

SeeAlso []

Definition at line 400 of file msatSolverSearch.c.

{
    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 );
*/
}

Msat_Type_t Msat_SolverSearch	(	Msat_Solver_t *	p,
		int	nConfLimit,
		int	nLearnedLimit,
		int	nBackTrackLimit,
		Msat_SearchParams_t *	pPars
	)

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 []

Definition at line 532 of file msatSolverSearch.c.

{
    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 );
            }
        }
    }
}

bool Msat_SolverSimplifyDB

(

Msat_Solver_t *

p

)

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 []

Definition at line 279 of file msatSolverSearch.c.

{
    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;
}

void Msat_SolverUndoOne

(

Msat_Solver_t *

p

)

[static]

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

] DECLARATIONS ///

Function*************************************************************

Synopsis [Reverts one variable binding on the trail.]

Description []

SideEffects []

SeeAlso []

Definition at line 70 of file msatSolverSearch.c.

{
    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)); 
}