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abc/src/temp/aig/aigBalance.c

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/**CFile****************************************************************
FileName [aigBalance.c]
SystemName [ABC: Logic synthesis and verification system.]
PackageName [Minimalistic And-Inverter Graph package.]
Synopsis [Algebraic AIG balancing.]
Author [Alan Mishchenko]
Affiliation [UC Berkeley]
Date [Ver. 1.0. Started - May 11, 2006.]
Revision [$Id: aigBalance.c,v 1.00 2006/05/11 00:00:00 alanmi Exp $]
***********************************************************************/
#include "aig.h"
////////////////////////////////////////////////////////////////////////
/// DECLARATIONS ///
////////////////////////////////////////////////////////////////////////
static Aig_Obj_t * Aig_NodeBalance_rec( Aig_Man_t * pNew, Aig_Obj_t * pObj, Vec_Vec_t * vStore, int Level, int fUpdateLevel );
static Vec_Ptr_t * Aig_NodeBalanceCone( Aig_Obj_t * pObj, Vec_Vec_t * vStore, int Level );
static int Aig_NodeBalanceFindLeft( Vec_Ptr_t * vSuper );
static void Aig_NodeBalancePermute( Aig_Man_t * p, Vec_Ptr_t * vSuper, int LeftBound, int fExor );
static void Aig_NodeBalancePushUniqueOrderByLevel( Vec_Ptr_t * vStore, Aig_Obj_t * pObj );
////////////////////////////////////////////////////////////////////////
/// FUNCTION DEFINITIONS ///
////////////////////////////////////////////////////////////////////////
/**Function*************************************************************
Synopsis [Performs algebraic balancing of the AIG.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
Aig_Man_t * Aig_ManBalance( Aig_Man_t * p, int fUpdateLevel )
{
Aig_Man_t * pNew;
Aig_Obj_t * pObj, * pObjNew;
Vec_Vec_t * vStore;
int i;
// create the new manager
pNew = Aig_ManStart();
pNew->fRefCount = 0;
// map the PI nodes
Aig_ManCleanData( p );
Aig_ManConst1(p)->pData = Aig_ManConst1(pNew);
Aig_ManForEachPi( p, pObj, i )
pObj->pData = Aig_ObjCreatePi(pNew);
// balance the AIG
vStore = Vec_VecAlloc( 50 );
Aig_ManForEachPo( p, pObj, i )
{
pObjNew = Aig_NodeBalance_rec( pNew, Aig_ObjFanin0(pObj), vStore, 0, fUpdateLevel );
Aig_ObjCreatePo( pNew, Aig_NotCond( pObjNew, Aig_ObjFaninC0(pObj) ) );
}
Vec_VecFree( vStore );
// remove dangling nodes
// Aig_ManCreateRefs( pNew );
// if ( i = Aig_ManCleanup( pNew ) )
// printf( "Cleanup after balancing removed %d dangling nodes.\n", i );
// check the resulting AIG
if ( !Aig_ManCheck(pNew) )
printf( "Aig_ManBalance(): The check has failed.\n" );
return pNew;
}
/**Function*************************************************************
Synopsis [Returns the new node constructed.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
Aig_Obj_t * Aig_NodeBalance_rec( Aig_Man_t * pNew, Aig_Obj_t * pObjOld, Vec_Vec_t * vStore, int Level, int fUpdateLevel )
{
Aig_Obj_t * pObjNew;
Vec_Ptr_t * vSuper;
int i;
assert( !Aig_IsComplement(pObjOld) );
// return if the result is known
if ( pObjOld->pData )
return pObjOld->pData;
assert( Aig_ObjIsNode(pObjOld) );
// get the implication supergate
vSuper = Aig_NodeBalanceCone( pObjOld, vStore, Level );
// check if supergate contains two nodes in the opposite polarity
if ( vSuper->nSize == 0 )
return pObjOld->pData = Aig_ManConst0(pNew);
if ( Vec_PtrSize(vSuper) < 2 )
printf( "BUG!\n" );
// for each old node, derive the new well-balanced node
for ( i = 0; i < Vec_PtrSize(vSuper); i++ )
{
pObjNew = Aig_NodeBalance_rec( pNew, Aig_Regular(vSuper->pArray[i]), vStore, Level + 1, fUpdateLevel );
vSuper->pArray[i] = Aig_NotCond( pObjNew, Aig_IsComplement(vSuper->pArray[i]) );
}
// build the supergate
pObjNew = Aig_NodeBalanceBuildSuper( pNew, vSuper, Aig_ObjType(pObjOld), fUpdateLevel );
// make sure the balanced node is not assigned
// assert( pObjOld->Level >= Aig_Regular(pObjNew)->Level );
assert( pObjOld->pData == NULL );
return pObjOld->pData = pObjNew;
}
/**Function*************************************************************
Synopsis [Collects the nodes of the supergate.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Aig_NodeBalanceCone_rec( Aig_Obj_t * pRoot, Aig_Obj_t * pObj, Vec_Ptr_t * vSuper )
{
int RetValue1, RetValue2, i;
// check if the node is visited
if ( Aig_Regular(pObj)->fMarkB )
{
// check if the node occurs in the same polarity
for ( i = 0; i < vSuper->nSize; i++ )
if ( vSuper->pArray[i] == pObj )
return 1;
// check if the node is present in the opposite polarity
for ( i = 0; i < vSuper->nSize; i++ )
if ( vSuper->pArray[i] == Aig_Not(pObj) )
return -1;
assert( 0 );
return 0;
}
// if the new node is complemented or a PI, another gate begins
if ( pObj != pRoot && (Aig_IsComplement(pObj) || Aig_ObjType(pObj) != Aig_ObjType(pRoot) || Aig_ObjRefs(pObj) > 1) )
{
Vec_PtrPush( vSuper, pObj );
Aig_Regular(pObj)->fMarkB = 1;
return 0;
}
assert( !Aig_IsComplement(pObj) );
assert( Aig_ObjIsNode(pObj) );
// go through the branches
RetValue1 = Aig_NodeBalanceCone_rec( pRoot, Aig_ObjChild0(pObj), vSuper );
RetValue2 = Aig_NodeBalanceCone_rec( pRoot, Aig_ObjChild1(pObj), vSuper );
if ( RetValue1 == -1 || RetValue2 == -1 )
return -1;
// return 1 if at least one branch has a duplicate
return RetValue1 || RetValue2;
}
/**Function*************************************************************
Synopsis [Collects the nodes of the supergate.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
Vec_Ptr_t * Aig_NodeBalanceCone( Aig_Obj_t * pObj, Vec_Vec_t * vStore, int Level )
{
Vec_Ptr_t * vNodes;
int RetValue, i;
assert( !Aig_IsComplement(pObj) );
// extend the storage
if ( Vec_VecSize( vStore ) <= Level )
Vec_VecPush( vStore, Level, 0 );
// get the temporary array of nodes
vNodes = Vec_VecEntry( vStore, Level );
Vec_PtrClear( vNodes );
// collect the nodes in the implication supergate
RetValue = Aig_NodeBalanceCone_rec( pObj, pObj, vNodes );
assert( vNodes->nSize > 1 );
// unmark the visited nodes
Vec_PtrForEachEntry( vNodes, pObj, i )
Aig_Regular(pObj)->fMarkB = 0;
// if we found the node and its complement in the same implication supergate,
// return empty set of nodes (meaning that we should use constant-0 node)
if ( RetValue == -1 )
vNodes->nSize = 0;
return vNodes;
}
/**Function*************************************************************
Synopsis [Procedure used for sorting the nodes in decreasing order of levels.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Aig_NodeCompareLevelsDecrease( Aig_Obj_t ** pp1, Aig_Obj_t ** pp2 )
{
int Diff = Aig_ObjLevel(Aig_Regular(*pp1)) - Aig_ObjLevel(Aig_Regular(*pp2));
if ( Diff > 0 )
return -1;
if ( Diff < 0 )
return 1;
return 0;
}
/**Function*************************************************************
Synopsis [Builds implication supergate.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
Aig_Obj_t * Aig_NodeBalanceBuildSuper( Aig_Man_t * p, Vec_Ptr_t * vSuper, Aig_Type_t Type, int fUpdateLevel )
{
Aig_Obj_t * pObj1, * pObj2;
int LeftBound;
assert( vSuper->nSize > 1 );
// sort the new nodes by level in the decreasing order
Vec_PtrSort( vSuper, Aig_NodeCompareLevelsDecrease );
// balance the nodes
while ( vSuper->nSize > 1 )
{
// find the left bound on the node to be paired
LeftBound = (!fUpdateLevel)? 0 : Aig_NodeBalanceFindLeft( vSuper );
// find the node that can be shared (if no such node, randomize choice)
Aig_NodeBalancePermute( p, vSuper, LeftBound, Type == AIG_EXOR );
// pull out the last two nodes
pObj1 = Vec_PtrPop(vSuper);
pObj2 = Vec_PtrPop(vSuper);
Aig_NodeBalancePushUniqueOrderByLevel( vSuper, Aig_Oper(p, pObj1, pObj2, Type) );
}
return Vec_PtrEntry(vSuper, 0);
}
/**Function*************************************************************
Synopsis [Finds the left bound on the next candidate to be paired.]
Description [The nodes in the array are in the decreasing order of levels.
The last node in the array has the smallest level. By default it would be paired
with the next node on the left. However, it may be possible to pair it with some
other node on the left, in such a way that the new node is shared. This procedure
finds the index of the left-most node, which can be paired with the last node.]
SideEffects []
SeeAlso []
***********************************************************************/
int Aig_NodeBalanceFindLeft( Vec_Ptr_t * vSuper )
{
Aig_Obj_t * pObjRight, * pObjLeft;
int Current;
// if two or less nodes, pair with the first
if ( Vec_PtrSize(vSuper) < 3 )
return 0;
// set the pointer to the one before the last
Current = Vec_PtrSize(vSuper) - 2;
pObjRight = Vec_PtrEntry( vSuper, Current );
// go through the nodes to the left of this one
for ( Current--; Current >= 0; Current-- )
{
// get the next node on the left
pObjLeft = Vec_PtrEntry( vSuper, Current );
// if the level of this node is different, quit the loop
if ( Aig_ObjLevel(Aig_Regular(pObjLeft)) != Aig_ObjLevel(Aig_Regular(pObjRight)) )
break;
}
Current++;
// get the node, for which the equality holds
pObjLeft = Vec_PtrEntry( vSuper, Current );
assert( Aig_ObjLevel(Aig_Regular(pObjLeft)) == Aig_ObjLevel(Aig_Regular(pObjRight)) );
return Current;
}
/**Function*************************************************************
Synopsis [Moves closer to the end the node that is best for sharing.]
Description [If there is no node with sharing, randomly chooses one of
the legal nodes.]
SideEffects []
SeeAlso []
***********************************************************************/
void Aig_NodeBalancePermute( Aig_Man_t * p, Vec_Ptr_t * vSuper, int LeftBound, int fExor )
{
Aig_Obj_t * pObj1, * pObj2, * pObj3, * pGhost;
int RightBound, i;
// get the right bound
RightBound = Vec_PtrSize(vSuper) - 2;
assert( LeftBound <= RightBound );
if ( LeftBound == RightBound )
return;
// get the two last nodes
pObj1 = Vec_PtrEntry( vSuper, RightBound + 1 );
pObj2 = Vec_PtrEntry( vSuper, RightBound );
if ( Aig_Regular(pObj1) == p->pConst1 || Aig_Regular(pObj2) == p->pConst1 )
return;
// find the first node that can be shared
for ( i = RightBound; i >= LeftBound; i-- )
{
pObj3 = Vec_PtrEntry( vSuper, i );
if ( Aig_Regular(pObj3) == p->pConst1 )
{
Vec_PtrWriteEntry( vSuper, i, pObj2 );
Vec_PtrWriteEntry( vSuper, RightBound, pObj3 );
return;
}
pGhost = Aig_ObjCreateGhost( p, pObj1, pObj3, fExor? AIG_EXOR : AIG_AND );
if ( Aig_TableLookup( p, pGhost ) )
{
if ( pObj3 == pObj2 )
return;
Vec_PtrWriteEntry( vSuper, i, pObj2 );
Vec_PtrWriteEntry( vSuper, RightBound, pObj3 );
return;
}
}
/*
// we did not find the node to share, randomize choice
{
int Choice = rand() % (RightBound - LeftBound + 1);
pObj3 = Vec_PtrEntry( vSuper, LeftBound + Choice );
if ( pObj3 == pObj2 )
return;
Vec_PtrWriteEntry( vSuper, LeftBound + Choice, pObj2 );
Vec_PtrWriteEntry( vSuper, RightBound, pObj3 );
}
*/
}
/**Function*************************************************************
Synopsis [Inserts a new node in the order by levels.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
void Aig_NodeBalancePushUniqueOrderByLevel( Vec_Ptr_t * vStore, Aig_Obj_t * pObj )
{
Aig_Obj_t * pObj1, * pObj2;
int i;
if ( Vec_PtrPushUnique(vStore, pObj) )
return;
// find the p of the node
for ( i = vStore->nSize-1; i > 0; i-- )
{
pObj1 = vStore->pArray[i ];
pObj2 = vStore->pArray[i-1];
if ( Aig_ObjLevel(Aig_Regular(pObj1)) <= Aig_ObjLevel(Aig_Regular(pObj2)) )
break;
vStore->pArray[i ] = pObj2;
vStore->pArray[i-1] = pObj1;
}
}
////////////////////////////////////////////////////////////////////////
/// END OF FILE ///
////////////////////////////////////////////////////////////////////////
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