src/bdd/dsd/dsdCheck.c

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#include "dsdInt.h"


typedef struct Dsd_Cache_t_  Dds_Cache_t;
typedef struct Dsd_Entry_t_  Dsd_Entry_t;

struct Dsd_Cache_t_
{
    Dsd_Entry_t *     pTable;
    int               nTableSize;
    int               nSuccess;
    int               nFailure;
};

struct Dsd_Entry_t_
{
        DdNode * bX[5];
};

static Dds_Cache_t * pCache;

static int Dsd_CheckRootFunctionIdentity_rec( DdManager * dd, DdNode * bF1, DdNode * bF2, DdNode * bC1, DdNode * bC2 );


void Dsd_CheckCacheAllocate( int nEntries )
{
        int nRequested;

    pCache = ALLOC( Dds_Cache_t, 1 );
    memset( pCache, 0, sizeof(Dds_Cache_t) );

        // check what is the size of the current cache
    nRequested = Cudd_Prime( nEntries );
        if ( pCache->nTableSize != nRequested )
        { // the current size is different
                // deallocate the old, allocate the new
                if ( pCache->nTableSize )
                        Dsd_CheckCacheDeallocate();
                // allocate memory for the hash table
                pCache->nTableSize = nRequested;
                pCache->pTable = ALLOC( Dsd_Entry_t, nRequested );
        }
        // otherwise, there is no need to allocate, just clean
        Dsd_CheckCacheClear();
//      printf( "\nThe number of allocated cache entries = %d.\n\n", pCache->nTableSize );
}

void Dsd_CheckCacheDeallocate()
{
        free( pCache->pTable );
    free( pCache );
}

void Dsd_CheckCacheClear()
{
        int i;
        for ( i = 0; i < pCache->nTableSize; i++ )
                pCache->pTable[0].bX[0] = NULL;
}


int Dsd_CheckRootFunctionIdentity( DdManager * dd, DdNode * bF1, DdNode * bF2, DdNode * bC1, DdNode * bC2 )
{
        int RetValue;
//      pCache->nSuccess = 0;
//      pCache->nFailure = 0;
        RetValue = Dsd_CheckRootFunctionIdentity_rec(dd, bF1, bF2, bC1, bC2);
//      printf( "Cache success = %d. Cache failure = %d.\n", pCache->nSuccess, pCache->nFailure );
        return RetValue;
}

int Dsd_CheckRootFunctionIdentity_rec( DdManager * dd, DdNode * bF1, DdNode * bF2, DdNode * bC1, DdNode * bC2 )
{
        unsigned HKey;

        // if either bC1 or bC2 is zero, the test is true
//      if ( bC1 == b0 || bC2 == b0 )  return 1;
        assert( bC1 != b0 );
        assert( bC2 != b0 );

        // if both bC1 and bC2 are one - perform comparison
        if ( bC1 == b1 && bC2 == b1 )  return (int)( bF1 == bF2 );

        if ( bF1 == b0 )
                return Cudd_bddLeq( dd, bC2, Cudd_Not(bF2) );

        if ( bF1 == b1 )
                return Cudd_bddLeq( dd, bC2, bF2 );

        if ( bF2 == b0 )
                return Cudd_bddLeq( dd, bC1, Cudd_Not(bF1) );

        if ( bF2 == b1 )
                return Cudd_bddLeq( dd, bC1, bF1 );

        // otherwise, keep expanding

        // check cache
//      HKey = _Hash( ((unsigned)bF1), ((unsigned)bF2), ((unsigned)bC1), ((unsigned)bC2) );
        HKey = hashKey4( bF1, bF2, bC1, bC2, pCache->nTableSize );
        if ( pCache->pTable[HKey].bX[0] == bF1 && 
                 pCache->pTable[HKey].bX[1] == bF2 && 
                 pCache->pTable[HKey].bX[2] == bC1 && 
                 pCache->pTable[HKey].bX[3] == bC2 )
        {
                pCache->nSuccess++;
                return (int)pCache->pTable[HKey].bX[4]; // the last bit records the result (yes/no)
        }
        else
        {

                // determine the top variables
                int RetValue;
                DdNode * bA[4]  = { bF1, bF2, bC1, bC2 }; // arguments
                DdNode * bAR[4] = { Cudd_Regular(bF1), Cudd_Regular(bF2), Cudd_Regular(bC1), Cudd_Regular(bC2) }; // regular arguments
                int CurLevel[4] = { cuddI(dd,bAR[0]->index), cuddI(dd,bAR[1]->index), cuddI(dd,bAR[2]->index), cuddI(dd,bAR[3]->index) };
                int TopLevel = CUDD_CONST_INDEX;
                int i;
                DdNode * bE[4], * bT[4];
                DdNode * bF1next, * bF2next, * bC1next, * bC2next;

                pCache->nFailure++;

                // determine the top level
                for ( i = 0; i < 4; i++ )
                        if ( TopLevel > CurLevel[i] )
                                 TopLevel = CurLevel[i];

                // compute the cofactors
                for ( i = 0; i < 4; i++ )
                if ( TopLevel == CurLevel[i] )
                {
                        if ( bA[i] != bAR[i] ) // complemented
                        {
                                bE[i] = Cudd_Not(cuddE(bAR[i]));
                                bT[i] = Cudd_Not(cuddT(bAR[i]));
                        }
                        else
                        {
                                bE[i] = cuddE(bAR[i]);
                                bT[i] = cuddT(bAR[i]);
                        }
                }
                else
                        bE[i] = bT[i] = bA[i];

                // solve subproblems
                // three cases are possible

                // (1) the top var belongs to both C1 and C2
                //     in this case, any cofactor of F1 and F2 will do, 
                //     as long as the corresponding cofactor of C1 and C2 is not equal to 0
                if ( TopLevel == CurLevel[2] && TopLevel == CurLevel[3] ) 
                {
                        if ( bE[2] != b0 ) // C1
                        {
                                bF1next = bE[0];
                                bC1next = bE[2];
                        }
                        else
                        {
                                bF1next = bT[0];
                                bC1next = bT[2];
                        }
                        if ( bE[3] != b0 ) // C2
                        {
                                bF2next = bE[1];
                                bC2next = bE[3];
                        }
                        else
                        {
                                bF2next = bT[1];
                                bC2next = bT[3];
                        }
                        RetValue = Dsd_CheckRootFunctionIdentity_rec( dd, bF1next, bF2next, bC1next, bC2next );
                }
                // (2) the top var belongs to either C1 or C2
                //     in this case normal splitting of cofactors
                else if ( TopLevel == CurLevel[2] && TopLevel != CurLevel[3] ) 
                {
                        if ( bE[2] != b0 ) // C1
                        {
                                bF1next = bE[0];
                                bC1next = bE[2];
                        }
                        else
                        {
                                bF1next = bT[0];
                                bC1next = bT[2];
                        }
                        // split around this variable
                        RetValue = Dsd_CheckRootFunctionIdentity_rec( dd, bF1next, bE[1], bC1next, bE[3] );
                        if ( RetValue == 1 ) // test another branch; otherwise, there is no need to test
                                RetValue = Dsd_CheckRootFunctionIdentity_rec( dd, bF1next, bT[1], bC1next, bT[3] );
                }
                else if ( TopLevel != CurLevel[2] && TopLevel == CurLevel[3] ) 
                {
                        if ( bE[3] != b0 ) // C2
                        {
                                bF2next = bE[1];
                                bC2next = bE[3];
                        }
                        else
                        {
                                bF2next = bT[1];
                                bC2next = bT[3];
                        }
                        // split around this variable
                        RetValue = Dsd_CheckRootFunctionIdentity_rec( dd, bE[0], bF2next, bE[2], bC2next );
                        if ( RetValue == 1 ) // test another branch; otherwise, there is no need to test
                                RetValue = Dsd_CheckRootFunctionIdentity_rec( dd, bT[0], bF2next, bT[2], bC2next );
                }
                // (3) the top var does not belong to C1 and C2
                //     in this case normal splitting of cofactors
                else // if ( TopLevel != CurLevel[2] && TopLevel != CurLevel[3] )
                {
                        // split around this variable
                        RetValue = Dsd_CheckRootFunctionIdentity_rec( dd, bE[0], bE[1], bE[2], bE[3] );
                        if ( RetValue == 1 ) // test another branch; otherwise, there is no need to test
                                RetValue = Dsd_CheckRootFunctionIdentity_rec( dd, bT[0], bT[1], bT[2], bT[3] );
                }

                // set cache
                for ( i = 0; i < 4; i++ )
                        pCache->pTable[HKey].bX[i] = bA[i];
                pCache->pTable[HKey].bX[4] = (DdNode*)RetValue;

                return RetValue;
        }
}

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