/**Function*************************************************************
Synopsis [Transfers fanout to a different node.]
Description [Assumes that the other node currently has no fanouts.]
SideEffects []
SeeAlso []
***********************************************************************/
void Fraig_NodeTransferFanout( Fraig_Node_t * pNodeFrom, Fraig_Node_t * pNodeTo )
{
Fraig_Node_t * pFanout;
assert( pNodeTo->pFanPivot == NULL );
assert( pNodeTo->pFanFanin1 == NULL );
assert( pNodeTo->pFanFanin2 == NULL );
// go through the fanouts and update their fanins
Fraig_NodeForEachFanout( pNodeFrom, pFanout )
{
if ( Fraig_Regular(pFanout->p1) == pNodeFrom )
pFanout->p1 = Fraig_NotCond( pNodeTo, Fraig_IsComplement(pFanout->p1) );
else if ( Fraig_Regular(pFanout->p2) == pNodeFrom )
pFanout->p2 = Fraig_NotCond( pNodeTo, Fraig_IsComplement(pFanout->p2) );
}
// move the pointers
pNodeTo->pFanPivot = pNodeFrom->pFanPivot;
pNodeTo->pFanFanin1 = pNodeFrom->pFanFanin1;
pNodeTo->pFanFanin2 = pNodeFrom->pFanFanin2;
pNodeFrom->pFanPivot = NULL;
pNodeFrom->pFanFanin1 = NULL;
pNodeFrom->pFanFanin2 = NULL;
}
/**Function*************************************************************
Synopsis [The internal AND operation for the two FRAIG nodes.]
Description [This procedure is the core of the FRAIG package, because
it performs the two-step canonicization of FRAIG nodes. The first step
involves the lookup in the structural hash table (which hashes two ANDs
into a node that has them as fanins, if such a node exists). If the node
is not found in the structural hash table, an attempt is made to find a
functionally equivalent node in another hash table (which hashes the
simulation info into the nodes, which has this simulation info). Some
tricks used on the way are described in the comments to the code and
in the paper "FRAIGs: Functionally reduced AND-INV graphs".]
SideEffects []
SeeAlso []
***********************************************************************/
Fraig_Node_t * Fraig_NodeAndCanon( Fraig_Man_t * pMan, Fraig_Node_t * p1, Fraig_Node_t * p2 )
{
Fraig_Node_t * pNodeNew, * pNodeOld, * pNodeRepr;
int fUseSatCheck;
// int RetValue;
// check for trivial cases
if ( p1 == p2 )
return p1;
if ( p1 == Fraig_Not(p2) )
return Fraig_Not(pMan->pConst1);
if ( Fraig_NodeIsConst(p1) )
{
if ( p1 == pMan->pConst1 )
return p2;
return Fraig_Not(pMan->pConst1);
}
if ( Fraig_NodeIsConst(p2) )
{
if ( p2 == pMan->pConst1 )
return p1;
return Fraig_Not(pMan->pConst1);
}
/*
// check for less trivial cases
if ( Fraig_IsComplement(p1) )
{
if ( RetValue = Fraig_NodeIsInSupergate( Fraig_Regular(p1), p2 ) )
{
if ( RetValue == -1 )
pMan->nImplies0++;
else
pMan->nImplies1++;
if ( RetValue == -1 )
return p2;
}
}
else
{
if ( RetValue = Fraig_NodeIsInSupergate( p1, p2 ) )
{
if ( RetValue == 1 )
pMan->nSimplifies1++;
else
pMan->nSimplifies0++;
if ( RetValue == 1 )
return p1;
return Fraig_Not(pMan->pConst1);
}
}
if ( Fraig_IsComplement(p2) )
{
if ( RetValue = Fraig_NodeIsInSupergate( Fraig_Regular(p2), p1 ) )
{
if ( RetValue == -1 )
pMan->nImplies0++;
else
pMan->nImplies1++;
if ( RetValue == -1 )
return p1;
}
}
else
{
if ( RetValue = Fraig_NodeIsInSupergate( p2, p1 ) )
{
if ( RetValue == 1 )
pMan->nSimplifies1++;
else
pMan->nSimplifies0++;
if ( RetValue == 1 )
return p2;
return Fraig_Not(pMan->pConst1);
}
}
*/
// perform level-one structural hashing
if ( Fraig_HashTableLookupS( pMan, p1, p2, &pNodeNew ) ) // the node with these children is found
{
// if the existent node is part of the cone of unused logic
// (that is logic feeding the node which is equivalent to the given node)
// return the canonical representative of this node
// determine the phase of the given node, with respect to its canonical form
pNodeRepr = Fraig_Regular(pNodeNew)->pRepr;
if ( pMan->fFuncRed && pNodeRepr )
return Fraig_NotCond( pNodeRepr, Fraig_IsComplement(pNodeNew) ^ Fraig_NodeComparePhase(Fraig_Regular(pNodeNew), pNodeRepr) );
// otherwise, the node is itself a canonical representative, return it
return pNodeNew;
}
// the same node is not found, but the new one is created
// if one level hashing is requested (without functionality hashing), return
if ( !pMan->fFuncRed )
return pNodeNew;
// check if the new node is unique using the simulation info
if ( pNodeNew->nOnes == 0 || pNodeNew->nOnes == (unsigned)pMan->nWordsRand * 32 )
{
pMan->nSatZeros++;
if ( !pMan->fDoSparse ) // if we do not do sparse functions, skip
return pNodeNew;
// check the sparse function simulation hash table
pNodeOld = Fraig_HashTableLookupF0( pMan, pNodeNew );
if ( pNodeOld == NULL ) // the node is unique (it is added to the table)
return pNodeNew;
}
else
{
// check the simulation hash table
pNodeOld = Fraig_HashTableLookupF( pMan, pNodeNew );
if ( pNodeOld == NULL ) // the node is unique
return pNodeNew;
}
assert( pNodeOld->pRepr == 0 );
// there is another node which looks the same according to simulation
// use SAT to resolve the ambiguity
fUseSatCheck = (pMan->nInspLimit == 0 || Fraig_ManReadInspects(pMan) < pMan->nInspLimit);
if ( fUseSatCheck && Fraig_NodeIsEquivalent( pMan, pNodeOld, pNodeNew, pMan->nBTLimit, 1000000 ) )
{
// set the node to be equivalent with this node
// to prevent loops, only set if the old node is not in the TFI of the new node
// the loop may happen in the following case: suppose
// NodeC = AND(NodeA, NodeB) and at the same time NodeA => NodeB
// in this case, NodeA and NodeC are functionally equivalent
// however, NodeA is a fanin of node NodeC (this leads to the loop)
// add the node to the list of equivalent nodes or dereference it
if ( pMan->fChoicing && !Fraig_CheckTfi( pMan, pNodeOld, pNodeNew ) )
{
// if the old node is not in the TFI of the new node and choicing
// is enabled, add the new node to the list of equivalent ones
pNodeNew->pNextE = pNodeOld->pNextE;
pNodeOld->pNextE = pNodeNew;
}
// set the canonical representative of this node
pNodeNew->pRepr = pNodeOld;
// return the equivalent node
return Fraig_NotCond( pNodeOld, Fraig_NodeComparePhase(pNodeOld, pNodeNew) );
}
// now we add another member to this simulation class
if ( pNodeNew->nOnes == 0 || pNodeNew->nOnes == (unsigned)pMan->nWordsRand * 32 )
{
Fraig_Node_t * pNodeTemp;
assert( pMan->fDoSparse );
pNodeTemp = Fraig_HashTableLookupF0( pMan, pNodeNew );
// assert( pNodeTemp == NULL );
// Fraig_HashTableInsertF0( pMan, pNodeNew );
}
else
{
pNodeNew->pNextD = pNodeOld->pNextD;
pNodeOld->pNextD = pNodeNew;
}
// return the new node
assert( pNodeNew->pRepr == 0 );
return pNodeNew;
}
