/src/opt/dar/darBalance.c

/**CFile****************************************************************

  FileName    [darBalance.c]

  SystemName  [ABC: Logic synthesis and verification system.]

  PackageName [DAG-aware AIG rewriting.]

  Synopsis    [Algebraic AIG balancing.]

  Author      [Alan Mishchenko]
  
  Affiliation [UC Berkeley]

  Date        [Ver. 1.0. Started - April 28, 2007.]

  Revision    [$Id: darBalance.c,v 1.00 2007/04/28 00:00:00 alanmi Exp $]

***********************************************************************/

#include "darInt.h"
#include "misc/tim/tim.h"

ABC_NAMESPACE_IMPL_START


////////////////////////////////////////////////////////////////////////
///                        DECLARATIONS                              ///
////////////////////////////////////////////////////////////////////////

//#define USE_LUTSIZE_BALANCE

////////////////////////////////////////////////////////////////////////
///                     FUNCTION DEFINITIONS                         ///
////////////////////////////////////////////////////////////////////////

/**Function*************************************************************

  Synopsis    [Uniqifies the node.]

  Description []
               
  SideEffects []

  SeeAlso     []

***********************************************************************/
int Dar_ObjCompareLits( Aig_Obj_t ** pp1, Aig_Obj_t ** pp2 )
{
    int Diff = Aig_ObjToLit(*pp1) - Aig_ObjToLit(*pp2);
    if ( Diff < 0 )
        return -1;
    if ( Diff > 0 ) 
        return 1;
    return 0; 
}
void Dar_BalanceUniqify( Aig_Obj_t * pObj, Vec_Ptr_t * vNodes, int fExor )
{
    Aig_Obj_t * pTemp, * pTempNext;
    int i, k;
    // sort the nodes by their literal
    Vec_PtrSort( vNodes, (int (*)())Dar_ObjCompareLits );
    // remove duplicates
    k = 0;
    Vec_PtrForEachEntry( Aig_Obj_t *, vNodes, pTemp, i )
    {
        if ( i + 1 == Vec_PtrSize(vNodes) )
        {
            Vec_PtrWriteEntry( vNodes, k++, pTemp );
            break;
        }
        pTempNext = (Aig_Obj_t *)Vec_PtrEntry( vNodes, i+1 );
        if ( !fExor && pTemp == Aig_Not(pTempNext) ) // pos_lit & neg_lit = 0
        {
            Vec_PtrClear( vNodes );
            return;
        }
        if ( pTemp != pTempNext )  // save if different
            Vec_PtrWriteEntry( vNodes, k++, pTemp );
        else if ( fExor ) // in case of XOR, remove identical
            i++;
    }
    Vec_PtrShrink( vNodes, k );
    if ( Vec_PtrSize(vNodes) < 2 )

        return;

    // check that there is no duplicates
    pTemp = (Aig_Obj_t *)Vec_PtrEntry( vNodes, 0 );
    Vec_PtrForEachEntryStart( Aig_Obj_t *, vNodes, pTempNext, i, 1 )
    {
        assert( pTemp != pTempNext );
        pTemp = pTempNext;
    }
}

/**Function*************************************************************

  Synopsis    [Collects the nodes of the supergate.]

  Description []
               
  SideEffects []

  SeeAlso     []

***********************************************************************/
void Dar_BalanceCone_rec( Aig_Obj_t * pRoot, Aig_Obj_t * pObj, Vec_Ptr_t * vSuper )
{
    if ( pObj != pRoot && (Aig_IsComplement(pObj) || Aig_ObjType(pObj) != Aig_ObjType(pRoot) || Aig_ObjRefs(pObj) > 1 || Vec_PtrSize(vSuper) > 10000) )
        Vec_PtrPush( vSuper, pObj );
    else
    {
        assert( !Aig_IsComplement(pObj) );
        assert( Aig_ObjIsNode(pObj) );
        // go through the branches
        Dar_BalanceCone_rec( pRoot, Aig_ObjReal_rec( Aig_ObjChild0(pObj) ), vSuper );
        Dar_BalanceCone_rec( pRoot, Aig_ObjReal_rec( Aig_ObjChild1(pObj) ), vSuper );
    }
}
Vec_Ptr_t * Dar_BalanceCone( Aig_Obj_t * pObj, Vec_Vec_t * vStore, int Level )
{
    Vec_Ptr_t * vNodes;
    assert( !Aig_IsComplement(pObj) );
    assert( Aig_ObjIsNode(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
    Dar_BalanceCone_rec( pObj, pObj, vNodes );
    // remove duplicates
    Dar_BalanceUniqify( pObj, vNodes, Aig_ObjIsExor(pObj) );
    return vNodes;
}


/**Function*************************************************************

  Synopsis    [Collects the nodes of the supergate.]

  Description []
               
  SideEffects []

  SeeAlso     []

***********************************************************************/
/*
int Dar_BalanceCone_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 )
    {
        if ( Aig_ObjIsExor(pRoot) )
        {
            assert( !Aig_IsComplement(pObj) );
            // check if the node occurs in the same polarity
            Vec_PtrRemove( vSuper, pObj );
            Aig_Regular(pObj)->fMarkB = 0;
//printf( " Duplicated EXOR input!!! " );
            return 1;
        }
        else
        {
            // 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_PtrSize(vSuper) > 10000) )
    {
        Vec_PtrPush( vSuper, pObj );
        Aig_Regular(pObj)->fMarkB = 1;
        return 0;
    }
    assert( !Aig_IsComplement(pObj) );
    assert( Aig_ObjIsNode(pObj) );
    // go through the branches
    RetValue1 = Dar_BalanceCone_rec( pRoot, Aig_ObjReal_rec( Aig_ObjChild0(pObj) ), vSuper );
    RetValue2 = Dar_BalanceCone_rec( pRoot, Aig_ObjReal_rec( Aig_ObjChild1(pObj) ), vSuper );
    if ( RetValue1 == -1 || RetValue2 == -1 )
        return -1;
    // return 1 if at least one branch has a duplicate
    return RetValue1 || RetValue2;
}
Vec_Ptr_t * Dar_BalanceCone( 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 = Dar_BalanceCone_rec( pObj, pObj, vNodes );
    assert( RetValue != 0 || vNodes->nSize > 1 );
    // unmark the visited nodes
    Vec_PtrForEachEntry( Aig_Obj_t *, 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    [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 Dar_BalanceFindLeft( 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 = (Aig_Obj_t *)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 = (Aig_Obj_t *)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 = (Aig_Obj_t *)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 Dar_BalancePermute( 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 = (Aig_Obj_t *)Vec_PtrEntry( vSuper, RightBound + 1 );
    pObj2 = (Aig_Obj_t *)Vec_PtrEntry( vSuper, RightBound     );
    if ( Aig_Regular(pObj1) == p->pConst1 || Aig_Regular(pObj2) == p->pConst1 || Aig_Regular(pObj1) == Aig_Regular(pObj2) )
        return;
    // find the first node that can be shared
    for ( i = RightBound; i >= LeftBound; i-- )
    {
        pObj3 = (Aig_Obj_t *)Vec_PtrEntry( vSuper, i );
        if ( Aig_Regular(pObj3) == p->pConst1 )
        {
            Vec_PtrWriteEntry( vSuper, i,          pObj2 );
            Vec_PtrWriteEntry( vSuper, RightBound, pObj3 );
            return;
        }
        if ( Aig_Regular(pObj1) == Aig_Regular(pObj3) )
        {
            if ( pObj3 == pObj2 )
                return;
            Vec_PtrWriteEntry( vSuper, i,          pObj2 );
            Vec_PtrWriteEntry( vSuper, RightBound, pObj3 );
            return;
        }
        pGhost = Aig_ObjCreateGhost( p, pObj1, pObj3, fExor? AIG_OBJ_EXOR : AIG_OBJ_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 = Aig_ManRandom(0) % (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    [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;
    Diff = Aig_ObjId(Aig_Regular(*pp1)) - Aig_ObjId(Aig_Regular(*pp2));
    if ( Diff > 0 )
        return -1;
    if ( Diff < 0 ) 
        return 1;
    return 0; 
}

/**Function*************************************************************

  Synopsis    [Inserts a new node in the order by levels.]

  Description []
               
  SideEffects []

  SeeAlso     []

***********************************************************************/
void Dar_BalancePushUniqueOrderByLevel( Vec_Ptr_t * vStore, Aig_Obj_t * pObj, int fExor )
{
    Aig_Obj_t * pObj1, * pObj2;
    int i;
    if ( Vec_PtrPushUnique(vStore, pObj) )
    {
        if ( fExor )
            Vec_PtrRemove(vStore, pObj);
        return;
    }
    // find the p of the node
    for ( i = vStore->nSize-1; i > 0; i-- )
    {
        pObj1 = (Aig_Obj_t *)vStore->pArray[i  ];
        pObj2 = (Aig_Obj_t *)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;
    }
}

/**Function*************************************************************

  Synopsis    [Builds implication supergate.]

  Description []
               
  SideEffects []

  SeeAlso     []

***********************************************************************/
Aig_Obj_t * Dar_BalanceBuildSuper( 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, (int (*)(void))Aig_NodeCompareLevelsDecrease );
    // balance the nodes
    while ( vSuper->nSize > 1 )
    {
        // find the left bound on the node to be paired
        LeftBound = (!fUpdateLevel)? 0 : Dar_BalanceFindLeft( vSuper );
        // find the node that can be shared (if no such node, randomize choice)
        Dar_BalancePermute( p, vSuper, LeftBound, Type == AIG_OBJ_EXOR );
        // pull out the last two nodes
        pObj1 = (Aig_Obj_t *)Vec_PtrPop(vSuper);
        pObj2 = (Aig_Obj_t *)Vec_PtrPop(vSuper);
        Dar_BalancePushUniqueOrderByLevel( vSuper, Aig_Oper(p, pObj1, pObj2, Type), Type == AIG_OBJ_EXOR );
    }
    return (Aig_Obj_t *)Vec_PtrEntry(vSuper, 0);
}


/**Function*************************************************************

  Synopsis    [Returns affective support size.]

  Description []
               
  SideEffects []

  SeeAlso     []

***********************************************************************/
int Aig_BaseSize( Aig_Man_t * p, Aig_Obj_t * pObj, int nLutSize )
{
    int nBaseSize;
    pObj = Aig_Regular(pObj);
    if ( Aig_ObjIsConst1(pObj) )
        return 0;
    if ( Aig_ObjLevel(pObj) >= nLutSize )
        return 1;
    nBaseSize = Aig_SupportSize( p, pObj );
    if ( nBaseSize >= nLutSize )
        return 1;
    return nBaseSize;
}

/**Function*************************************************************

  Synopsis    [Builds implication supergate.]

  Description []
               
  SideEffects []

  SeeAlso     []

***********************************************************************/
Aig_Obj_t * Dar_BalanceBuildSuperTop( Aig_Man_t * p, Vec_Ptr_t * vSuper, Aig_Type_t Type, int fUpdateLevel, int nLutSize )
{
    Vec_Ptr_t * vSubset;
    Aig_Obj_t * pObj;
    int i, nBaseSizeAll, nBaseSize;
    assert( vSuper->nSize > 1 );
    // sort the new nodes by level in the decreasing order
    Vec_PtrSort( vSuper, (int (*)(void))Aig_NodeCompareLevelsDecrease );
    // add one LUT at a time
    while ( Vec_PtrSize(vSuper) > 1 )
    {
        // isolate the group of nodes with nLutSize inputs
        nBaseSizeAll = 0;
        vSubset = Vec_PtrAlloc( nLutSize );
        Vec_PtrForEachEntryReverse( Aig_Obj_t *, vSuper, pObj, i )
        {
            nBaseSize = Aig_BaseSize( p, pObj, nLutSize );
            if ( nBaseSizeAll + nBaseSize > nLutSize && Vec_PtrSize(vSubset) > 1 )
                break;
            nBaseSizeAll += nBaseSize;
            Vec_PtrPush( vSubset, pObj );
        }
        // remove them from vSuper
        Vec_PtrShrink( vSuper, Vec_PtrSize(vSuper) - Vec_PtrSize(vSubset) );
        // create the new supergate
        pObj = Dar_BalanceBuildSuper( p, vSubset, Type, fUpdateLevel );
        Vec_PtrFree( vSubset );
        // add the new output
        Dar_BalancePushUniqueOrderByLevel( vSuper, pObj, Type == AIG_OBJ_EXOR );
    }
    return (Aig_Obj_t *)Vec_PtrEntry(vSuper, 0);
}

/**Function*************************************************************

  Synopsis    [Returns the new node constructed.]

  Description []
               
  SideEffects []

  SeeAlso     []

***********************************************************************/
Aig_Obj_t * Dar_Balance_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) );
    assert( !Aig_ObjIsBuf(pObjOld) );
    // return if the result is known
    if ( pObjOld->pData )
        return (Aig_Obj_t *)pObjOld->pData;
    assert( Aig_ObjIsNode(pObjOld) );
    // get the implication supergate
    vSuper = Dar_BalanceCone( pObjOld, vStore, Level );
    // check if supergate contains two nodes in the opposite polarity
    if ( vSuper->nSize == 0 )
        return (Aig_Obj_t *)(pObjOld->pData = Aig_ManConst0(pNew));
    // for each old node, derive the new well-balanced node
    for ( i = 0; i < Vec_PtrSize(vSuper); i++ )
    {
        pObjNew = Dar_Balance_rec( pNew, Aig_Regular((Aig_Obj_t *)vSuper->pArray[i]), vStore, Level + 1, fUpdateLevel );

        if ( pObjNew == NULL )

            return NULL;
        vSuper->pArray[i] = Aig_NotCond( pObjNew, Aig_IsComplement((Aig_Obj_t *)vSuper->pArray[i]) );
    }
    // check for exactly one node

    if ( vSuper->nSize == 1 )

        return (Aig_Obj_t *)Vec_PtrEntry(vSuper, 0);

    // build the supergate
#ifdef USE_LUTSIZE_BALANCE
    pObjNew = Dar_BalanceBuildSuperTop( pNew, vSuper, Aig_ObjType(pObjOld), fUpdateLevel, 6 );
#else
    pObjNew = Dar_BalanceBuildSuper( pNew, vSuper, Aig_ObjType(pObjOld), fUpdateLevel );
#endif

    if ( pNew->Time2Quit && !(Aig_Regular(pObjNew)->Id & 255) && Abc_Clock() > pNew->Time2Quit )

        return NULL;
    // make sure the balanced node is not assigned
//    assert( pObjOld->Level >= Aig_Regular(pObjNew)->Level );
    assert( pObjOld->pData == NULL );

    return (Aig_Obj_t *)(pObjOld->pData = pObjNew);
}

/**Function*************************************************************

  Synopsis    [Performs algebraic balancing of the AIG.]

  Description []
               
  SideEffects []

  SeeAlso     []

***********************************************************************/
Aig_Man_t * Dar_ManBalance( Aig_Man_t * p, int fUpdateLevel )
{
    Aig_Man_t * pNew;
    Aig_Obj_t * pObj, * pDriver, * pObjNew;
    Vec_Vec_t * vStore;
    int i;
    assert( Aig_ManVerifyTopoOrder(p) );
    // create the new manager 
    pNew = Aig_ManStart( Aig_ManObjNumMax(p) );
    pNew->pName = Abc_UtilStrsav( p->pName );
    pNew->pSpec = Abc_UtilStrsav( p->pSpec );
    pNew->nAsserts = p->nAsserts;
    pNew->nConstrs = p->nConstrs;

    pNew->nBarBufs = p->nBarBufs;

    pNew->Time2Quit = p->Time2Quit;
    if ( p->vFlopNums )
        pNew->vFlopNums = Vec_IntDup( p->vFlopNums );
    // map the PI nodes
    Aig_ManCleanData( p );
    Aig_ManConst1(p)->pData = Aig_ManConst1(pNew);
    vStore = Vec_VecAlloc( 50 );
    if ( p->pManTime != NULL )
    {
        float arrTime;
        Tim_ManIncrementTravId( (Tim_Man_t *)p->pManTime );
        Aig_ManSetCioIds( p );
        Aig_ManForEachObj( p, pObj, i )
        {
            if ( Aig_ObjIsNode(pObj) || Aig_ObjIsConst1(pObj) )
                continue;
            if ( Aig_ObjIsCi(pObj) )
            {
                // copy the PI
                pObjNew = Aig_ObjCreateCi(pNew); 
                pObj->pData = pObjNew;
                // set the arrival time of the new PI
                arrTime = Tim_ManGetCiArrival( (Tim_Man_t *)p->pManTime, Aig_ObjCioId(pObj) );
                pObjNew->Level = (int)arrTime;
            }
            else if ( Aig_ObjIsCo(pObj) )
            {
                // perform balancing
                pDriver = Aig_ObjReal_rec( Aig_ObjChild0(pObj) );
                pObjNew = Dar_Balance_rec( pNew, Aig_Regular(pDriver), vStore, 0, fUpdateLevel );

                if ( pObjNew == NULL )

                {

                    Vec_VecFree( vStore );

                    Aig_ManStop( pNew );

                    return NULL;

                }
                pObjNew = Aig_NotCond( pObjNew, Aig_IsComplement(pDriver) );
                // save arrival time of the output
                arrTime = (float)Aig_Regular(pObjNew)->Level;
                Tim_ManSetCoArrival( (Tim_Man_t *)p->pManTime, Aig_ObjCioId(pObj), arrTime );
                // create PO
                pObjNew = Aig_ObjCreateCo( pNew, pObjNew );
            }
            else
                assert( 0 );
        }
        Aig_ManCleanCioIds( p );
        pNew->pManTime = Tim_ManDup( (Tim_Man_t *)p->pManTime, 0 );
    }
    else
    {

        Aig_ManForEachCi( p, pObj, i )
        {
            pObjNew = Aig_ObjCreateCi(pNew); 
            pObjNew->Level = pObj->Level;
            pObj->pData = pObjNew;
        }
        if ( p->nBarBufs == 0 )

        {

            Aig_ManForEachCo( p, pObj, i )
            {
                pDriver = Aig_ObjReal_rec( Aig_ObjChild0(pObj) );
                pObjNew = Dar_Balance_rec( pNew, Aig_Regular(pDriver), vStore, 0, fUpdateLevel );
                if ( pObjNew == NULL )

                {

                    Vec_VecFree( vStore );

                    Aig_ManStop( pNew );

                    return NULL;

                }

                pObjNew = Aig_NotCond( pObjNew, Aig_IsComplement(pDriver) );
                pObjNew = Aig_ObjCreateCo( pNew, pObjNew );
            }

        }

        else

        {

            Vec_Ptr_t * vLits = Vec_PtrStart( Aig_ManCoNum(p) );

            Aig_ManForEachCo( p, pObj, i )

            {

                int k = i < p->nBarBufs ? Aig_ManCoNum(p) - p->nBarBufs + i : i - p->nBarBufs;

                pObj = Aig_ManCo( p, k );

                pDriver = Aig_ObjReal_rec( Aig_ObjChild0(pObj) );

                pObjNew = Dar_Balance_rec( pNew, Aig_Regular(pDriver), vStore, 0, fUpdateLevel );

                if ( pObjNew == NULL )

                {

                    Vec_VecFree( vStore );

                    Aig_ManStop( pNew );

                    return NULL;

                }

                pObjNew = Aig_NotCond( pObjNew, Aig_IsComplement(pDriver) );

                Vec_PtrWriteEntry( vLits, k, pObjNew );

                if ( i < p->nBarBufs )

                    Aig_ManCi(pNew, Aig_ManCiNum(p) - p->nBarBufs + i)->Level = Aig_Regular(pObjNew)->Level;

            }

            Aig_ManForEachCo( p, pObj, i )

                Aig_ObjCreateCo( pNew, (Aig_Obj_t *)Vec_PtrEntry(vLits, i) );

            Vec_PtrFree(vLits);

        }
    }
    Vec_VecFree( vStore );
    // remove dangling nodes
    Aig_ManCleanup( pNew );
    Aig_ManSetRegNum( pNew, Aig_ManRegNum(p) );
    // check the resulting AIG
    if ( !Aig_ManCheck(pNew) )
        printf( "Dar_ManBalance(): The check has failed.\n" );
    return pNew;
}

/**Function*************************************************************

  Synopsis    [Reproduces script "compress2".]

  Description []
               
  SideEffects []

  SeeAlso     []

***********************************************************************/
Aig_Man_t * Dar_ManBalanceXor( Aig_Man_t * pAig, int fExor, int fUpdateLevel, int fVerbose )
{
    Aig_Man_t * pAigXor, * pRes;
    if ( fExor )
    {
        pAigXor = Aig_ManDupExor( pAig );
        if ( fVerbose )
            Dar_BalancePrintStats( pAigXor );
        pRes = Dar_ManBalance( pAigXor, fUpdateLevel );
        Aig_ManStop( pAigXor );
    }
    else
    {
        pRes = Dar_ManBalance( pAig, fUpdateLevel );
    }
    return pRes;
}

/**Function*************************************************************

  Synopsis    [Inserts a new node in the order by levels.]

  Description []
               
  SideEffects []

  SeeAlso     []

***********************************************************************/
void Dar_BalancePrintStats( Aig_Man_t * p )
{
    Vec_Ptr_t * vSuper;
    Aig_Obj_t * pObj, * pTemp;
    int i, k;
    if ( Aig_ManExorNum(p) == 0 )
    {
        printf( "There is no EXOR gates.\n" );
        return;
    }
    Aig_ManForEachExor( p, pObj, i )
    {
        Aig_ObjFanin0(pObj)->fMarkA = 1;
        Aig_ObjFanin1(pObj)->fMarkA = 1;
        assert( !Aig_ObjFaninC0(pObj) );
        assert( !Aig_ObjFaninC1(pObj) );
    }
    vSuper = Vec_PtrAlloc( 1000 );
    Aig_ManForEachExor( p, pObj, i )
    {
        if ( pObj->fMarkA && pObj->nRefs == 1 )
            continue;
        Vec_PtrClear( vSuper );
        Dar_BalanceCone_rec( pObj, pObj, vSuper );
        Vec_PtrForEachEntry( Aig_Obj_t *, vSuper, pTemp, k )
            pTemp->fMarkB = 0;
        if ( Vec_PtrSize(vSuper) < 3 )
            continue;
        printf( "  %d(", Vec_PtrSize(vSuper) );
        Vec_PtrForEachEntry( Aig_Obj_t *, vSuper, pTemp, k )
            printf( " %d", pTemp->Level );
        printf( " )" );
    }
    Vec_PtrFree( vSuper );
    Aig_ManForEachObj( p, pObj, i )
        pObj->fMarkA = 0;
    printf( "\n" );
}

////////////////////////////////////////////////////////////////////////
///                       END OF FILE                                ///
////////////////////////////////////////////////////////////////////////


ABC_NAMESPACE_IMPL_END