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/**CFile****************************************************************
FileName [darCnf.c]
SystemName [ABC: Logic synthesis and verification system.]
PackageName [DAG-aware AIG rewriting.]
Synopsis []
Author [Alan Mishchenko]
Affiliation [UC Berkeley]
Date [Ver. 1.0. Started - April 28, 2007.]
Revision [$Id: darCnf.c,v 1.00 2007/04/28 00:00:00 alanmi Exp $]
***********************************************************************/
#include "dar.h"
////////////////////////////////////////////////////////////////////////
/// DECLARATIONS ///
////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////
/// FUNCTION DEFINITIONS ///
////////////////////////////////////////////////////////////////////////
/**Function*************************************************************
Synopsis [Dereferences the cut.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
static inline void Dar_CurDeref2( Dar_Man_t * p, Dar_Cut_t * pCut )
{
Dar_Obj_t * pLeaf;
int i;
Dar_CutForEachLeaf( p, pCut, pLeaf, i )
{
assert( pLeaf->nRefs > 0 );
pLeaf->nRefs--;
}
}
/**Function*************************************************************
Synopsis [References the cut.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
static inline void Dar_CurRef2( Dar_Man_t * p, Dar_Cut_t * pCut )
{
Dar_Obj_t * pLeaf;
int i;
Dar_CutForEachLeaf( p, pCut, pLeaf, i )
pLeaf->nRefs++;
}
/**Function*************************************************************
Synopsis [Computes area of the first level.]
Description [The cut need to be derefed.]
SideEffects []
SeeAlso []
***********************************************************************/
void Dar_CutDeref( Dar_Man_t * p, Dar_Cut_t * pCut )
{
Dar_Obj_t * pLeaf;
int i;
Dar_CutForEachLeaf( p, pCut, pLeaf, i )
{
assert( pLeaf->nRefs > 0 );
if ( --pLeaf->nRefs > 0 || !Dar_ObjIsAnd(pLeaf) )
continue;
Dar_CutDeref( p, Dar_ObjBestCut(pLeaf) );
}
}
/**Function*************************************************************
Synopsis [Computes area of the first level.]
Description [The cut need to be derefed.]
SideEffects []
SeeAlso []
***********************************************************************/
int Dar_CutRef( Dar_Man_t * p, Dar_Cut_t * pCut )
{
Dar_Obj_t * pLeaf;
int i, Area = pCut->Cost;
Dar_CutForEachLeaf( p, pCut, pLeaf, i )
{
assert( pLeaf->nRefs >= 0 );
if ( pLeaf->nRefs++ > 0 || !Dar_ObjIsAnd(pLeaf) )
continue;
Area += Dar_CutRef( p, Dar_ObjBestCut(pLeaf) );
}
return Area;
}
/**Function*************************************************************
Synopsis [Computes exact area of the cut.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Dar_CutArea( Dar_Man_t * p, Dar_Cut_t * pCut )
{
int Area = Dar_CutRef( p, pCut );
Dar_CutDeref( p, pCut );
return Area;
}
/**Function*************************************************************
Synopsis [Returns 1 if the second cut is better.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
static inline int Dar_CutCompare( Dar_Cut_t * pC0, Dar_Cut_t * pC1 )
{
if ( pC0->Area < pC1->Area - 0.0001 )
return -1;
if ( pC0->Area > pC1->Area + 0.0001 ) // smaller area flow is better
return 1;
/*
if ( pC0->NoRefs < pC1->NoRefs )
return -1;
if ( pC0->NoRefs > pC1->NoRefs ) // fewer non-referenced fanins is better
return 1;
*/
// if ( pC0->FanRefs / pC0->nLeaves > pC1->FanRefs / pC1->nLeaves )
// return -1;
// if ( pC0->FanRefs / pC0->nLeaves < pC1->FanRefs / pC1->nLeaves )
return 1; // larger average fanin ref-counter is better
// return 0;
}
/**Function*************************************************************
Synopsis [Returns the cut with the smallest area flow.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
Dar_Cut_t * Dar_ObjFindBestCut( Dar_Obj_t * pObj )
{
Dar_Cut_t * pCut, * pCutBest;
int i;
pCutBest = NULL;
Dar_ObjForEachCut( pObj, pCut, i )
if ( pCutBest == NULL || Dar_CutCompare(pCutBest, pCut) == 1 )
pCutBest = pCut;
return pCutBest;
}
/**Function*************************************************************
Synopsis [Computes area flow of the cut.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
void Dar_CutAssignAreaFlow( Dar_Man_t * p, Dar_Cut_t * pCut )
{
Dar_Obj_t * pLeaf;
int i;
pCut->Area = (float)pCut->Cost;
pCut->NoRefs = 0;
pCut->FanRefs = 0;
Dar_CutForEachLeaf( p, pCut, pLeaf, i )
{
if ( !Dar_ObjIsNode(pLeaf) )
continue;
if ( pLeaf->nRefs == 0 )
{
pCut->Area += Dar_ObjBestCut(pLeaf)->Area;
// pCut->NoRefs++;
}
else
{
pCut->Area += Dar_ObjBestCut(pLeaf)->Area / pLeaf->nRefs;
// if ( pCut->FanRefs + pLeaf->nRefs > 15 )
// pCut->FanRefs = 15;
// else
// pCut->FanRefs += pLeaf->nRefs;
}
}
}
/**Function*************************************************************
Synopsis [Computes area flow of the cut.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
void Dar_CutAssignArea( Dar_Man_t * p, Dar_Cut_t * pCut )
{
Dar_Obj_t * pLeaf;
int i;
pCut->Area = (float)pCut->Cost;
pCut->NoRefs = 0;
pCut->FanRefs = 0;
Dar_CutForEachLeaf( p, pCut, pLeaf, i )
{
if ( !Dar_ObjIsNode(pLeaf) )
continue;
if ( pLeaf->nRefs == 0 )
{
pCut->Area += Dar_ObjBestCut(pLeaf)->Cost;
pCut->NoRefs++;
}
else
{
if ( pCut->FanRefs + pLeaf->nRefs > 15 )
pCut->FanRefs = 15;
else
pCut->FanRefs += pLeaf->nRefs;
}
}
}
/**Function*************************************************************
Synopsis [Computes area, references, and nodes used in the mapping.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Dar_ManScanMapping_rec( Dar_Man_t * p, Dar_Obj_t * pObj, Vec_Ptr_t * vMapped )
{
Dar_Obj_t * pLeaf;
Dar_Cut_t * pCutBest;
int aArea, i;
if ( pObj->nRefs++ || Dar_ObjIsPi(pObj) || Dar_ObjIsConst1(pObj) )
return 0;
assert( Dar_ObjIsAnd(pObj) );
// collect the node first to derive pre-order
if ( vMapped )
{
// printf( "%d ", Dar_ObjBestCut(pObj)->Cost );
Vec_PtrPush( vMapped, pObj );
}
// visit the transitive fanin of the selected cut
pCutBest = Dar_ObjBestCut(pObj);
aArea = pCutBest->Cost;
Dar_CutForEachLeaf( p, pCutBest, pLeaf, i )
aArea += Dar_ManScanMapping_rec( p, pLeaf, vMapped );
return aArea;
}
/**Function*************************************************************
Synopsis [Computes area, references, and nodes used in the mapping.]
Description [Collects the nodes in reverse topological order in array
p->vMapping.]
SideEffects []
SeeAlso []
***********************************************************************/
Vec_Ptr_t * Dar_ManScanMapping( Dar_Man_t * p, int fCollect )
{
Vec_Ptr_t * vMapped = NULL;
Dar_Obj_t * pObj;
int i;
// clean all references
Dar_ManForEachObj( p, pObj, i )
pObj->nRefs = 0;
// allocate the array
if ( fCollect )
vMapped = Vec_PtrAlloc( 1000 );
// collect nodes reachable from POs in the DFS order through the best cuts
p->aArea = 0;
Dar_ManForEachPo( p, pObj, i )
p->aArea += Dar_ManScanMapping_rec( p, Dar_ObjFanin0(pObj), vMapped );
printf( "Variables = %d. Clauses = %6d.\n", vMapped? Vec_PtrSize(vMapped) : 0, p->aArea );
return vMapped;
}
/**Function*************************************************************
Synopsis []
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Dar_ManMapForCnf( Dar_Man_t * p )
{
Dar_Obj_t * pObj;
Dar_Cut_t * pCut;
int i, k;
// visit the nodes in the topological order and update their best cuts
Dar_ManForEachObj( p, pObj, i )
{
if ( !Dar_ObjIsNode(pObj) )
continue;
// if ( pObj->nRefs )
// continue;
// if the node is used, dereference its cut
if ( pObj->nRefs )
Dar_CutDeref( p, Dar_ObjBestCut(pObj) );
// evaluate the cuts of this node
Dar_ObjForEachCut( pObj, pCut, k )
// Dar_CutAssignArea( p, pCut );
// Dar_CutAssignAreaFlow( p, pCut );
pCut->Area = (float)Dar_CutArea( p, pCut );
// find a new good cut
Dar_ObjSetBestCut( pObj, Dar_ObjFindBestCut(pObj) );
// if the node is used, reference its cut
if ( pObj->nRefs )
Dar_CutRef( p, Dar_ObjBestCut(pObj) );
}
return 1;
}
/**Function*************************************************************
Synopsis [Returns the number of literals in the SOP.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Dar_SopCountLiterals( char * pSop, int nCubes )
{
int nLits = 0, Cube, i, b;
for ( i = 0; i < nCubes; i++ )
{
Cube = pSop[i];
for ( b = 3; b >= 0; b-- )
{
if ( Cube % 3 != 2 )
nLits++;
Cube = Cube / 3;
}
}
return nLits;
}
/**Function*************************************************************
Synopsis [Writes the cube and returns the number of literals in it.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Dar_SopWriteCube( char Cube, int * pVars, int fCompl, int * pLiterals )
{
int nLits = 4, b;
for ( b = 3; b >= 0; b-- )
{
if ( Cube % 3 == 0 )
*pLiterals++ = 2 * pVars[b] + 1 ^ fCompl;
else if ( Cube % 3 == 1 )
*pLiterals++ = 2 * pVars[b] + fCompl;
else
nLits--;
Cube = Cube / 3;
}
return nLits;
}
/**Function*************************************************************
Synopsis []
Description []
SideEffects []
SeeAlso []
***********************************************************************/
Dar_Cnf_t * Dar_ManWriteCnf( Dar_Man_t * p, Vec_Ptr_t * vMapped )
{
Dar_Cnf_t * pCnf;
Dar_Obj_t * pObj;
Dar_Cut_t * pCut;
int OutVar, pVars[4], * pLits, ** pClas;
unsigned uTruth;
int i, k, nLiterals, nClauses, nCubes, Number;
// count the number of literals and clauses
nLiterals = 1 + Dar_ManPoNum( p );
nClauses = 1 + Dar_ManPoNum( p );
Vec_PtrForEachEntry( vMapped, pObj, i )
{
assert( Dar_ObjIsNode(pObj) );
pCut = Dar_ObjBestCut( pObj );
// positive polarity of the cut
uTruth = pCut->uTruth;
nLiterals += Dar_SopCountLiterals( p->pSops[uTruth], p->pSopSizes[uTruth] ) + p->pSopSizes[uTruth];
nClauses += p->pSopSizes[uTruth];
// negative polarity of the cut
uTruth = 0xFFFF & ~pCut->uTruth;
nLiterals += Dar_SopCountLiterals( p->pSops[uTruth], p->pSopSizes[uTruth] ) + p->pSopSizes[uTruth];
nClauses += p->pSopSizes[uTruth];
}
// allocate CNF
pCnf = ALLOC( Dar_Cnf_t, 1 );
memset( pCnf, 0, sizeof(Dar_Cnf_t) );
pCnf->nLiterals = nLiterals;
pCnf->nClauses = nClauses;
pCnf->pClauses = ALLOC( int *, nClauses );
pCnf->pClauses[0] = ALLOC( int, nLiterals );
pCnf->pVarNums = ALLOC( int, 1+Dar_ManObjIdMax(p) );
// set variable numbers
Number = 0;
memset( pCnf->pVarNums, 0xff, sizeof(int) * (1+Dar_ManObjIdMax(p)) );
Vec_PtrForEachEntry( vMapped, pObj, i )
pCnf->pVarNums[pObj->Id] = Number++;
Dar_ManForEachPi( p, pObj, i )
pCnf->pVarNums[pObj->Id] = Number++;
pCnf->pVarNums[Dar_ManConst1(p)->Id] = Number++;
// assign the clauses
pLits = pCnf->pClauses[0];
pClas = pCnf->pClauses;
Vec_PtrForEachEntry( vMapped, pObj, i )
{
pCut = Dar_ObjBestCut( pObj );
// write variables of this cut
OutVar = pCnf->pVarNums[ pObj->Id ];
for ( k = 0; k < (int)pCut->nLeaves; k++ )
{
pVars[k] = pCnf->pVarNums[ pCut->pLeaves[k] ];
assert( pVars[k] <= Dar_ManObjIdMax(p) );
}
// positive polarity of the cut
uTruth = pCut->uTruth;
nCubes = p->pSopSizes[uTruth];
// write the cubes
for ( k = 0; k < nCubes; k++ )
{
*pClas++ = pLits;
*pLits++ = 2 * pVars[OutVar] + 1;
pLits += Dar_SopWriteCube( p->pSops[uTruth][k], pVars, 0, pLits );
}
// negative polarity of the cut
uTruth = 0xFFFF & ~pCut->uTruth;
nCubes = p->pSopSizes[uTruth];
// write the cubes
for ( k = 0; k < nCubes; k++ )
{
*pClas++ = pLits;
*pLits++ = 2 * pVars[OutVar];
pLits += Dar_SopWriteCube( p->pSops[uTruth][k], pVars, 1, pLits );
}
}
// write the output literals
Dar_ManForEachPo( p, pObj, i )
{
OutVar = pCnf->pVarNums[ Dar_ObjFanin0(pObj)->Id ];
*pClas++ = pLits;
*pLits++ = 2 * pVars[OutVar] + Dar_ObjFaninC0(pObj);
}
// write the constant literal
OutVar = pCnf->pVarNums[ Dar_ManConst1(p)->Id ];
assert( OutVar <= Dar_ManObjIdMax(p) );
*pClas++ = pLits;
*pLits++ = 2 * pVars[OutVar];
// verify that the correct number of literals and clauses was written
assert( pLits - pCnf->pClauses[0] == nLiterals );
assert( pClas - pCnf->pClauses == nClauses );
return pCnf;
}
/**Function*************************************************************
Synopsis []
Description []
SideEffects []
SeeAlso []
***********************************************************************/
void Dar_CnfFree( Dar_Cnf_t * pCnf )
{
if ( pCnf == NULL )
return;
free( pCnf->pClauses[0] );
free( pCnf->pClauses );
free( pCnf->pVarNums );
free( pCnf );
}
/**Function*************************************************************
Synopsis []
Description []
SideEffects []
SeeAlso []
***********************************************************************/
void Dar_ManExploreMapping( Dar_Man_t * p )
{
extern int Dar_ManLargeCutEval( Dar_Man_t * p, Dar_Obj_t * pRoot, Dar_Cut_t * pCutR, Dar_Cut_t * pCutL, int Leaf );
int nNew, Gain, nGain = 0, nVars = 0;
Dar_Obj_t * pObj, * pLeaf;
Dar_Cut_t * pCutBest, * pCut;
int i, k, a, b, Counter;
Dar_ManForEachObj( p, pObj, i )
{
if ( !Dar_ObjIsNode(pObj) )
continue;
if ( pObj->nRefs == 0 )
continue;
pCutBest = Dar_ObjBestCut(pObj);
Dar_CutForEachLeaf( p, pCutBest, pLeaf, k )
{
if ( !Dar_ObjIsNode(pLeaf) )
continue;
assert( pLeaf->nRefs != 0 );
if ( pLeaf->nRefs != 1 )
continue;
pCut = Dar_ObjBestCut(pLeaf);
/*
// find how many common variable they have
Counter = 0;
for ( a = 0; a < (int)pCut->nLeaves; a++ )
{
for ( b = 0; b < (int)pCutBest->nLeaves; b++ )
if ( pCut->pLeaves[a] == pCutBest->pLeaves[b] )
break;
if ( b == (int)pCutBest->nLeaves )
continue;
Counter++;
}
printf( "%d ", Counter );
*/
// find the new truth table after collapsing these two cuts
nNew = Dar_ManLargeCutEval( p, pObj, pCutBest, pCut, pLeaf->Id );
// printf( "%d+%d=%d:%d(%d) ", pCutBest->Cost, pCut->Cost,
// pCutBest->Cost+pCut->Cost, nNew, pCutBest->Cost+pCut->Cost-nNew );
Gain = pCutBest->Cost+pCut->Cost-nNew;
if ( Gain > 0 )
{
nGain += Gain;
nVars++;
}
}
}
printf( "Total gain = %d. Vars = %d.\n", nGain, nVars );
}
/**Function*************************************************************
Synopsis []
Description []
SideEffects []
SeeAlso []
***********************************************************************/
Dar_Cnf_t * Dar_ManDeriveCnf( Dar_Man_t * p )
{
Dar_Cnf_t * pCnf = NULL;
Vec_Ptr_t * vMapped;
int i, nIters = 2;
int clk;
// derive SOPs for all 4-variable functions
clk = clock();
Dar_LibReadMsops( &p->pSopSizes, &p->pSops );
PRT( "setup", clock() - clk );
// generate cuts for all nodes, assign cost, and find best cuts
// (used pObj->pNext for storing the best cut of the node!)
clk = clock();
Dar_ManComputeCuts( p );
PRT( "cuts ", clock() - clk );
// iteratively improve area flow
for ( i = 0; i < nIters; i++ )
{
clk = clock();
Dar_ManScanMapping( p, 0 );
Dar_ManMapForCnf( p );
PRT( "iter ", clock() - clk );
}
// write the file
vMapped = Dar_ManScanMapping( p, 1 );
clk = clock();
Dar_ManExploreMapping( p );
PRT( "exten", clock() - clk );
// pCnf = Dar_ManWriteCnf( p, vMapped );
Vec_PtrFree( vMapped );
// clean up
Dar_ManCutsFree( p );
return pCnf;
}
////////////////////////////////////////////////////////////////////////
/// END OF FILE ///
////////////////////////////////////////////////////////////////////////
|
