Shrink for 6-LUTs.

13 files changed, 1642 insertions, 7 deletions

diff --git a/Makefile b/Makefile
index c533aeeb..7ea37b2c 100644
--- a/Makefile
+++ b/Makefile
@@ -20,7 +20,7 @@ MODULES := \
 	src/opt/ret src/opt/res src/opt/lpk src/opt/nwk src/opt/rwt \
 	src/opt/cgt src/opt/csw src/opt/dar src/opt/dau \
 	src/sat/bsat src/sat/csat src/sat/msat src/sat/psat src/sat/cnf src/sat/bmc \
-	src/bool/bdc src/bool/deco src/bool/dec src/bool/kit src/bool/lucky \
+	src/bool/bdc src/bool/deco src/bool/dec src/bool/kit src/bool/lucky src/bool/rsb \
 	src/proof/pdr src/proof/int src/proof/bbr src/proof/llb src/proof/live \
 	src/proof/cec src/proof/dch src/proof/fraig src/proof/fra src/proof/ssw \
 	src/proof/abs \
diff --git a/abclib.dsp b/abclib.dsp
index 979f6bcf..6c2d3ee6 100644
--- a/abclib.dsp
+++ b/abclib.dsp
@@ -3543,6 +3543,10 @@ SOURCE=.\src\aig\gia\giaShrink.c
 # End Source File
 # Begin Source File
 
+SOURCE=.\src\aig\gia\giaShrink6.c
+# End Source File
+# Begin Source File
+
 SOURCE=.\src\aig\gia\giaSim.c
 # End Source File
 # Begin Source File
@@ -3786,6 +3790,26 @@ SOURCE=.\src\bool\lucky\luckySwap.c
 SOURCE=.\src\bool\lucky\luckySwapIJ.c
 # End Source File
 # End Group
+# Begin Group "rsb"
+
+# PROP Default_Filter ""
+# Begin Source File
+
+SOURCE=.\src\bool\rsb\rsb.h
+# End Source File
+# Begin Source File
+
+SOURCE=.\src\bool\rsb\rsbDec6.c
+# End Source File
+# Begin Source File
+
+SOURCE=.\src\bool\rsb\rsbInt.h
+# End Source File
+# Begin Source File
+
+SOURCE=.\src\bool\rsb\rsbMan.c
+# End Source File
+# End Group
 # End Group
 # Begin Group "prove"
 
diff --git a/src/aig/gia/gia.h b/src/aig/gia/gia.h
index 23afc45e..eb3bedab 100644
--- a/src/aig/gia/gia.h
+++ b/src/aig/gia/gia.h
@@ -980,6 +980,7 @@ extern Gia_Man_t *         Gia_ManSeqCleanup( Gia_Man_t * p );
 extern Gia_Man_t *         Gia_ManSeqStructSweep( Gia_Man_t * p, int fConst, int fEquiv, int fVerbose );
 /*=== giaShrink.c ===========================================================*/
 extern Gia_Man_t *         Gia_ManPerformMapShrink( Gia_Man_t * p, int fKeepLevel, int fVerbose );
+extern Gia_Man_t *         Gia_ManMapShrink6( Gia_Man_t * p, int fKeepLevel, int fVerbose );
 /*=== giaSort.c ============================================================*/
 extern int *               Gia_SortFloats( float * pArray, int * pPerm, int nSize );
 /*=== giaSim.c ============================================================*/
diff --git a/src/aig/gia/giaShrink.c b/src/aig/gia/giaShrink.c
index 487f9aa6..69dec67c 100644
--- a/src/aig/gia/giaShrink.c
+++ b/src/aig/gia/giaShrink.c
@@ -85,7 +85,8 @@ Gia_Man_t * Gia_ManPerformMapShrink( Gia_Man_t * p, int fKeepLevel, int fVerbose
         if ( Gia_ObjIsCi(pObj) )
         {
             pObj->Value = Gia_ManAppendCi( pNew );
-            Gia_ObjSetLevel( pNew, Gia_ObjFromLit(pNew, Gia_ObjValue(pObj)), Gia_ObjLevel(p, pObj) );
+            if ( p->vLevels )
+                Gia_ObjSetLevel( pNew, Gia_ObjFromLit(pNew, Gia_ObjValue(pObj)), Gia_ObjLevel(p, pObj) );
         }
         else if ( Gia_ObjIsCo(pObj) )
         {
diff --git a/src/aig/gia/giaShrink6.c b/src/aig/gia/giaShrink6.c
new file mode 100644
index 00000000..0d7f7541
--- /dev/null
+++ b/src/aig/gia/giaShrink6.c
@@ -0,0 +1,481 @@
+/**CFile****************************************************************
+
+  FileName    [giaShrink6.c]
+
+  SystemName  [ABC: Logic synthesis and verification system.]
+
+  PackageName [Scalable AIG package.]
+
+  Synopsis    [Implementation of DAG-aware unmapping for 6-input cuts.]
+
+  Author      [Alan Mishchenko]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - June 20, 2005.]
+
+  Revision    [$Id: giaShrink6.c,v 1.00 2005/06/20 00:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include "gia.h"
+#include "bool/bdc/bdc.h"
+#include "bool/rsb/rsb.h"
+//#include "misc/util/utilTruth.h"
+
+ABC_NAMESPACE_IMPL_START
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+static word Truth[8] = {
+    ABC_CONST(0xAAAAAAAAAAAAAAAA),
+    ABC_CONST(0xCCCCCCCCCCCCCCCC),
+    ABC_CONST(0xF0F0F0F0F0F0F0F0),
+    ABC_CONST(0xFF00FF00FF00FF00),
+    ABC_CONST(0xFFFF0000FFFF0000),
+    ABC_CONST(0xFFFFFFFF00000000),
+    ABC_CONST(0x0000000000000000),
+    ABC_CONST(0xFFFFFFFFFFFFFFFF)
+};
+
+// fanout structure
+typedef struct Shr_Fan_t_ Shr_Fan_t;
+struct Shr_Fan_t_
+{
+    int                iFan;           // fanout ID
+    int                Next;           // next structure
+};
+
+// operation manager
+typedef struct Shr_Man_t_ Shr_Man_t;
+struct Shr_Man_t_
+{
+    Gia_Man_t *        pGia;           // user's AIG
+    Gia_Man_t *        pNew;           // constructed AIG
+    int                nDivMax;        // max number of divisors
+    int                nNewSize;       // max growth size
+    // dynamic fanout (can only grow)
+    Vec_Wrd_t *        vFanMem;        // fanout memory
+    Vec_Int_t *        vObj2Fan;       // fanout
+    Shr_Fan_t *        pFanTemp;       // temporary fanout
+    // divisors
+    Vec_Int_t *        vDivs;          // divisors
+    Vec_Int_t *        vPrio;          // priority queue
+    Vec_Int_t *        vDivResub;      // resubstitution
+    Vec_Int_t *        vLeaves;        // cut leaves
+    // truth tables
+    Vec_Wrd_t *        vTruths;        // truth tables
+    Vec_Wrd_t *        vDivTruths;     // truth tables
+    // bidecomposition
+    Rsb_Man_t *        pManRsb;
+    Bdc_Man_t *        pManDec;       
+    Bdc_Par_t          Pars;
+};
+
+#define Shr_ObjForEachFanout( p, iNode, iFan )                      \
+    for ( iFan = Shr_ManFanIterStart(p, iNode); iFan; iFan = Shr_ManFanIterNext(p) )
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Shr_Man_t * Shr_ManAlloc( Gia_Man_t * pGia )
+{
+    Shr_Man_t * p;
+    p = ABC_CALLOC( Shr_Man_t, 1 );
+    p->nDivMax     = 64;
+    p->nNewSize    = 3 * Gia_ManObjNum(pGia) / 2;
+    p->pGia        = pGia;
+    p->vFanMem     = Vec_WrdAlloc( 1000 );   Vec_WrdPush(p->vFanMem, -1); 
+    p->vObj2Fan    = Vec_IntStart( p->nNewSize );
+    p->vDivs       = Vec_IntAlloc( 1000 );
+    p->vPrio       = Vec_IntAlloc( 1000 );
+    p->vTruths     = Vec_WrdStart( p->nNewSize );
+    p->vDivTruths  = Vec_WrdAlloc( 100 );
+    p->vDivResub   = Vec_IntAlloc( 6 );
+    p->vLeaves     = Vec_IntAlloc( 6 );
+    // start new manager
+    p->pNew        = Gia_ManStart( p->nNewSize );
+    p->pNew->pName = Abc_UtilStrsav( pGia->pName );
+    p->pNew->pSpec = Abc_UtilStrsav( pGia->pSpec );
+    Gia_ManHashAlloc( p->pNew );
+    Gia_ManCleanLevels( p->pNew, p->nNewSize );
+    // allocate traversal IDs
+    p->pNew->nObjs = p->nNewSize;
+    Gia_ManIncrementTravId( p->pNew );
+    p->pNew->nObjs = 1;
+    // start decompostion
+    p->Pars.nVarsMax = 6;
+    p->Pars.fVerbose = 0;
+    p->pManDec = Bdc_ManAlloc( &p->Pars );
+    p->pManRsb = Rsb_ManAlloc( 6, p->nDivMax, 4, 1 );
+    return p;
+}
+Gia_Man_t * Shr_ManFree( Shr_Man_t * p )
+{
+    // prepare the manager
+    Gia_Man_t * pTemp;
+    Gia_ManHashStop( p->pNew );
+    Vec_IntFreeP( &p->pNew->vLevels );
+    if ( Gia_ManHasDangling(p->pNew) )
+    {
+        p->pNew = Gia_ManCleanup( pTemp = p->pNew );
+        if ( Gia_ManAndNum(p->pNew) != Gia_ManAndNum(pTemp) )
+            printf( "Gia_ManShrink6() node reduction after sweep %6d -> %6d.\n", Gia_ManAndNum(pTemp), Gia_ManAndNum(p->pNew) );
+        Gia_ManStop( pTemp );
+    }
+    Gia_ManSetRegNum( p->pNew, Gia_ManRegNum(p->pGia) );
+    pTemp = p->pNew; p->pNew = NULL;
+    // free data structures
+    Rsb_ManFree( p->pManRsb );
+    Bdc_ManFree( p->pManDec );
+    Gia_ManStopP( &p->pNew );
+    Vec_WrdFree( p->vFanMem );
+    Vec_IntFree( p->vObj2Fan );
+    Vec_IntFree( p->vDivs );
+    Vec_IntFree( p->vPrio );
+    Vec_WrdFree( p->vTruths );
+    Vec_WrdFree( p->vDivTruths );
+    Vec_IntFree( p->vDivResub );
+    Vec_IntFree( p->vLeaves );
+    ABC_FREE( p );
+    return pTemp;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Fanout manipulation.]
+
+  Description []
+
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+static inline void Shr_ManAddFanout( Shr_Man_t * p, int iFanin, int iFanout )
+{
+    Shr_Fan_t FanStr;
+    FanStr.iFan = iFanout;
+    FanStr.Next = Vec_IntEntry(p->vObj2Fan, iFanin);
+    Vec_IntWriteEntry( p->vObj2Fan, iFanin, Vec_WrdSize(p->vFanMem) );
+    Vec_WrdPush(p->vFanMem, *((word *)&FanStr) );
+}
+static inline int Shr_ManFanIterStart( Shr_Man_t * p, int iNode )
+{
+    if ( Vec_IntEntry(p->vObj2Fan, iNode) == 0 )
+        return 0;
+    p->pFanTemp = (Shr_Fan_t *)Vec_WrdEntryP( p->vFanMem, Vec_IntEntry(p->vObj2Fan, iNode) );
+    return p->pFanTemp->iFan;
+}
+static inline int Shr_ManFanIterNext( Shr_Man_t * p )
+{
+    if ( p->pFanTemp->Next == 0 )
+        return 0;
+    p->pFanTemp = (Shr_Fan_t *)Vec_WrdEntryP( p->vFanMem, p->pFanTemp->Next );
+    return p->pFanTemp->iFan;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Collect divisors.]
+
+  Description []
+
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+static inline int Shr_ManDivPushOrderByLevel( Shr_Man_t * p, int iDiv )
+{
+    int iPlace, * pArray;
+    Vec_IntPush( p->vPrio, iDiv );
+    if ( Vec_IntSize(p->vPrio) == 1 )
+        return 0;
+    pArray = Vec_IntArray(p->vPrio);
+    for ( iPlace = Vec_IntSize(p->vPrio) - 1; iPlace > 0; iPlace-- )
+        if ( Gia_ObjLevel(p->pNew, Gia_ManObj(p->pNew, pArray[iPlace-1])) > 
+             Gia_ObjLevel(p->pNew, Gia_ManObj(p->pNew, pArray[iPlace])) )
+             ABC_SWAP( int, pArray[iPlace-1], pArray[iPlace] )
+        else
+            break;
+    return iPlace; // the place of the new divisor
+}
+static inline int Shr_ManCollectDivisors( Shr_Man_t * p, Vec_Int_t * vLeaves, int Limit )
+{
+    Gia_Obj_t * pFan;
+    int i, iDiv, iFan, iPlace;
+    assert( Limit > 6 );
+    Vec_IntClear( p->vDivs );
+    Vec_IntClear( p->vPrio );
+    Gia_ManIncrementTravId( p->pNew );
+    Vec_IntForEachEntry( vLeaves, iDiv, i )
+    {
+        Vec_IntPush( p->vDivs, iDiv );
+        Shr_ManDivPushOrderByLevel( p, iDiv );
+        Gia_ObjSetTravIdCurrentId( p->pNew, iDiv );
+    }
+    Vec_IntForEachEntry( p->vPrio, iDiv, i )
+    {
+        assert( Gia_ObjIsTravIdCurrentId(p->pNew, iDiv) );
+        Shr_ObjForEachFanout( p, iDiv, iFan )
+        {
+            if ( Gia_ObjIsTravIdCurrentId(p->pNew, iFan) )
+                continue;
+            pFan = Gia_ManObj( p->pNew, iFan );
+            assert( Gia_ObjIsAnd(pFan) );
+            assert( Gia_ObjLevel(p->pNew, Gia_ManObj(p->pNew, iDiv)) < Gia_ObjLevel(p->pNew, pFan) );
+            if ( !Gia_ObjIsTravIdCurrentId(p->pNew, Gia_ObjFaninId0(pFan, iFan)) ||
+                 !Gia_ObjIsTravIdCurrentId(p->pNew, Gia_ObjFaninId1(pFan, iFan)) )
+                continue;
+            Vec_IntPush( p->vDivs, iFan );
+            Gia_ObjSetTravIdCurrentId( p->pNew, iFan );
+            iPlace = Shr_ManDivPushOrderByLevel( p, iFan );
+            assert( i < iPlace );
+            if ( Vec_IntSize(p->vDivs) == Limit )
+                return Vec_IntSize(p->vDivs);
+        }
+    }
+    return Vec_IntSize(p->vDivs);
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Resynthesizes nodes using bi-decomposition.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Shr_ObjPerformBidec( Shr_Man_t * p, Bdc_Man_t * pManDec, Gia_Man_t * pNew, Vec_Int_t * vLeafLits, word uTruth1, word uTruthC )
+{
+    Bdc_Fun_t * pFunc;
+    Gia_Obj_t * pObj;
+    int i, iVar, iLit, nNodes, iLast;
+    int nVars = Vec_IntSize(vLeafLits);
+    assert( uTruth1 != 0 && uTruthC != 0 );
+    Bdc_ManDecompose( pManDec, (unsigned *)&uTruth1, (unsigned *)&uTruthC, nVars, NULL, 1000 );
+    Bdc_FuncSetCopyInt( Bdc_ManFunc(pManDec, 0), 1 );
+    Vec_IntForEachEntry( vLeafLits, iVar, i )
+        Bdc_FuncSetCopyInt( Bdc_ManFunc(pManDec, i+1), Abc_Var2Lit(iVar, 0) );
+    nNodes = Bdc_ManNodeNum( pManDec );
+    for ( i = nVars + 1; i < nNodes; i++ )
+    {
+        pFunc = Bdc_ManFunc( pManDec, i );
+        iLast = Gia_ManObjNum(pNew);
+        iLit  = Gia_ManHashAnd( pNew, Bdc_FunFanin0Copy(pFunc), Bdc_FunFanin1Copy(pFunc) );
+        Bdc_FuncSetCopyInt( pFunc, iLit );
+        if ( iLast == Gia_ManObjNum(pNew) )
+            continue;
+        assert( iLast + 1 == Gia_ManObjNum(pNew) );
+        pObj = Gia_ManObj(pNew, Abc_Lit2Var(iLit));
+        Gia_ObjSetAndLevel( pNew, pObj );
+        Shr_ManAddFanout( p, Gia_ObjFaninId0p(pNew, pObj), Gia_ObjId(pNew, pObj) );
+        Shr_ManAddFanout( p, Gia_ObjFaninId1p(pNew, pObj), Gia_ObjId(pNew, pObj) );
+        assert( Gia_ManObjNum(pNew) < p->nNewSize );
+    }
+    return Bdc_FunObjCopy( Bdc_ManRoot(pManDec) );
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Compute truth table.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+word Shr_ManComputeTruth6_rec( Gia_Man_t * p, int iNode, Vec_Wrd_t * vTruths )
+{
+    Gia_Obj_t * pObj;
+    word Truth0, Truth1;
+    if ( Gia_ObjIsTravIdCurrentId(p, iNode) )
+        return Vec_WrdEntry(vTruths, iNode);
+    Gia_ObjSetTravIdCurrentId(p, iNode);
+    pObj = Gia_ManObj( p, iNode );
+    assert( Gia_ObjIsAnd(pObj) );
+    Truth0 = Shr_ManComputeTruth6_rec( p, Gia_ObjFaninId0p(p, pObj), vTruths );
+    Truth1 = Shr_ManComputeTruth6_rec( p, Gia_ObjFaninId1p(p, pObj), vTruths );
+    if ( Gia_ObjFaninC0(pObj) )
+        Truth0 = ~Truth0;
+    if ( Gia_ObjFaninC1(pObj) )
+        Truth1 = ~Truth1;
+    Vec_WrdWriteEntry( vTruths, iNode, Truth0 & Truth1 );
+    return Truth0 & Truth1;
+}
+word Shr_ManComputeTruth6( Gia_Man_t * p, Gia_Obj_t * pObj, Vec_Int_t * vLeaves, Vec_Wrd_t * vTruths )
+{
+    int i, iLeaf;
+    assert( Gia_ObjIsAnd(pObj) );
+    Gia_ManIncrementTravId( p );
+    Vec_IntForEachEntry( vLeaves, iLeaf, i )
+    {
+        Gia_ObjSetTravIdCurrentId( p, iLeaf );
+        Vec_WrdWriteEntry( vTruths, iLeaf, Truth[i] );
+    }
+    return Shr_ManComputeTruth6_rec( p, Gia_ObjId(p, pObj), vTruths );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Compute truth table.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Shr_ManComputeTruths( Gia_Man_t * p, int nVars, Vec_Int_t * vDivs, Vec_Wrd_t * vDivTruths, Vec_Wrd_t * vTruths )
+{
+    Gia_Obj_t * pObj;
+    word Truth0, Truth1;//, Truthh;
+    int i, iDiv;
+    Vec_WrdClear( vDivTruths );
+    Vec_IntForEachEntryStop( vDivs, iDiv, i, nVars )
+    {
+        Vec_WrdWriteEntry( vTruths, iDiv, Truth[i] );
+        Vec_WrdPush( vDivTruths, Truth[i] );
+    }
+    Vec_IntForEachEntryStart( vDivs, iDiv, i, nVars )
+    {
+        pObj = Gia_ManObj( p, iDiv );
+        Truth0 = Vec_WrdEntry( vTruths, Gia_ObjFaninId0(pObj, iDiv) );
+        Truth1 = Vec_WrdEntry( vTruths, Gia_ObjFaninId1(pObj, iDiv) );
+        if ( Gia_ObjFaninC0(pObj) )
+            Truth0 = ~Truth0;
+        if ( Gia_ObjFaninC1(pObj) )
+            Truth1 = ~Truth1;
+        Vec_WrdWriteEntry( vTruths, iDiv, Truth0 & Truth1 );
+        Vec_WrdPush( vDivTruths, Truth0 & Truth1 );
+
+//        Truthh = Truth0 & Truth1;
+//        Abc_TtPrintBinary( &Truthh, nVars );   //printf( "\n" );
+//        Kit_DsdPrintFromTruth( &Truthh, nVars );    printf( "\n" );
+    }
+//    printf( "\n" );
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Gia_Man_t * Gia_ManMapShrink6( Gia_Man_t * p, int fKeepLevel, int fVerbose )
+{
+    Shr_Man_t * pMan;
+    Gia_Obj_t * pObj, * pFanin;
+    word uTruth, uTruth0, uTruth1;
+    int i, k, nDivs, iNode;
+    int RetValue, Counter1 = 0, Counter2 = 0;
+    clock_t clk = clock();
+    assert( p->pMapping != NULL );
+    pMan = Shr_ManAlloc( p );
+    Gia_ManFillValue( p );
+    Gia_ManConst0(p)->Value = 0;
+    Gia_ManForEachObj1( p, pObj, i )
+    {
+        if ( Gia_ObjIsCi(pObj) )
+        {
+            pObj->Value = Gia_ManAppendCi( pMan->pNew );
+            if ( p->vLevels )
+                Gia_ObjSetLevel( pMan->pNew, Gia_ObjFromLit(pMan->pNew, Gia_ObjValue(pObj)), Gia_ObjLevel(p, pObj) );
+        }
+        else if ( Gia_ObjIsCo(pObj) )
+        {
+            pObj->Value = Gia_ManAppendCo( pMan->pNew, Gia_ObjFanin0Copy(pObj) );
+        }
+        else if ( Gia_ObjIsLut(p, i) )
+        {
+            // collect leaves of this gate  
+            Vec_IntClear( pMan->vLeaves );
+            Gia_LutForEachFanin( p, i, iNode, k )
+                Vec_IntPush( pMan->vLeaves, iNode );
+            assert( Vec_IntSize(pMan->vLeaves) <= 6 );
+            // compute truth table 
+            uTruth = Shr_ManComputeTruth6( pMan->pGia, pObj, pMan->vLeaves, pMan->vTruths );
+            assert( pObj->Value == ~0 );
+            if ( uTruth == 0 || ~uTruth == 0 )
+                pObj->Value = Abc_LitNotCond( 0, ~uTruth == 0 );
+            else
+                Gia_ManForEachObjVec( pMan->vLeaves, p, pFanin, k )
+                    if ( uTruth == Truth[k] || ~uTruth == Truth[k] )
+                        pObj->Value = Abc_LitNotCond( pFanin->Value, ~uTruth == Truth[k] );
+            if ( pObj->Value != ~0 )
+                continue;
+            // translate into new nodes
+            Gia_ManForEachObjVec( pMan->vLeaves, p, pFanin, k )
+            {
+                if ( Abc_LitIsCompl(pFanin->Value) )
+                    uTruth = ((uTruth & Truth[k]) >> (1 << k)) | ((uTruth & ~Truth[k]) << (1 << k));
+                Vec_IntWriteEntry( pMan->vLeaves, k, Abc_Lit2Var(pFanin->Value) );
+            }
+            // compute divisors
+            nDivs = Shr_ManCollectDivisors( pMan, pMan->vLeaves, pMan->nDivMax );
+            assert( nDivs <= pMan->nDivMax );
+            // compute truth tables
+            Shr_ManComputeTruths( pMan->pNew, Vec_IntSize(pMan->vLeaves), pMan->vDivs, pMan->vDivTruths, pMan->vTruths );
+            // perform resubstitution
+            RetValue = Rsb_ManPerformResub6( pMan->pManRsb, Vec_IntSize(pMan->vLeaves), uTruth, pMan->vDivTruths, &uTruth0, &uTruth1, 0 );
+            if ( RetValue ) // resub exists
+            {
+                Vec_Int_t * vResult = Rsb_ManGetFanins(pMan->pManRsb);
+                Vec_IntClear( pMan->vDivResub );
+                Vec_IntForEachEntry( vResult, iNode, k )
+                    Vec_IntPush( pMan->vDivResub, Vec_IntEntry(pMan->vDivs, iNode) );
+                pObj->Value = Shr_ObjPerformBidec( pMan, pMan->pManDec, pMan->pNew, pMan->vDivResub, uTruth1, uTruth0 | uTruth1 );
+                Counter1++;
+            }
+            else
+            {
+                pObj->Value = Shr_ObjPerformBidec( pMan, pMan->pManDec, pMan->pNew, pMan->vLeaves, uTruth, ~(word)0 );
+                Counter2++;
+            }
+        }
+    }
+    if ( fVerbose )
+    {
+        printf( "Performed %d resubs and %d decomps.  ", Counter1, Counter2 );
+        printf( "Gain in AIG nodes = %d.  ", Gia_ManObjNum(p)-Gia_ManObjNum(pMan->pNew) );
+        ABC_PRT( "Runtime", clock() - clk );
+    }
+    return Shr_ManFree( pMan );
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
+ABC_NAMESPACE_IMPL_END
+
diff --git a/src/aig/gia/module.make b/src/aig/gia/module.make
index 17147f49..5cb60633 100644
--- a/src/aig/gia/module.make
+++ b/src/aig/gia/module.make
@@ -31,6 +31,7 @@ SRC +=    src/aig/gia/giaAig.c \
     src/aig/gia/giaRetime.c \
     src/aig/gia/giaScl.c \
     src/aig/gia/giaShrink.c \
+    src/aig/gia/giaShrink6.c \
     src/aig/gia/giaSim.c \
     src/aig/gia/giaSim2.c \
     src/aig/gia/giaSort.c \
diff --git a/src/base/abci/abc.c b/src/base/abci/abc.c
index d972b506..b913e04e 100644
--- a/src/base/abci/abc.c
+++ b/src/base/abci/abc.c
@@ -26155,7 +26155,8 @@ usage:
 ***********************************************************************/
 int Abc_CommandAbc9Shrink( Abc_Frame_t * pAbc, int argc, char ** argv )
 {
-    Gia_Man_t * pTemp;
+    Gia_Man_t * pTemp = NULL;
+    int nLutSize;
     int c,fVerbose = 0;
     int fKeepLevel = 0;
     Extra_UtilGetoptReset();
@@ -26185,8 +26186,15 @@ int Abc_CommandAbc9Shrink( Abc_Frame_t * pAbc, int argc, char ** argv )
         Abc_Print( -1, "Abc_CommandAbc9Shrink(): Mapping of the AIG is not defined.\n" );
         return 1;
     }
-    pTemp = Gia_ManPerformMapShrink( pAbc->pGia, fKeepLevel, fVerbose );
-    Abc_FrameUpdateGia( pAbc, pTemp );
+    nLutSize = Gia_ManLutSizeMax( pAbc->pGia );
+    if ( nLutSize <= 4 )
+        pTemp = Gia_ManPerformMapShrink( pAbc->pGia, fKeepLevel, fVerbose );
+    else if ( nLutSize <= 6 )
+        pTemp = Gia_ManMapShrink6( pAbc->pGia, fKeepLevel, fVerbose );
+    else
+        Abc_Print( -1, "Abc_CommandAbc9Shrink(): Works only for 4-LUTs and 6-LUTs.\n" );
+    if ( pTemp )
+        Abc_FrameUpdateGia( pAbc, pTemp );
     return 0;
 
 usage:
diff --git a/src/bool/rsb/module.make b/src/bool/rsb/module.make
new file mode 100644
index 00000000..0011e6a5
--- /dev/null
+++ b/src/bool/rsb/module.make
@@ -0,0 +1,2 @@
+SRC +=    src/bool/rsb/rsbDec6.c \
+    src/bool/rsb/rsbMan.c
diff --git a/src/bool/rsb/rsb.h b/src/bool/rsb/rsb.h
new file mode 100644
index 00000000..e0b92d30
--- /dev/null
+++ b/src/bool/rsb/rsb.h
@@ -0,0 +1,65 @@
+/**CFile****************************************************************
+
+  FileName    [rsb.h]
+
+  SystemName  [ABC: Logic synthesis and verification system.]
+
+  PackageName [Truth-table based resubstitution.]
+
+  Synopsis    [External declarations.]
+
+  Author      [Alan Mishchenko]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - June 20, 2005.]
+
+  Revision    [$Id: rsb.h,v 1.00 2005/06/20 00:00:00 alanmi Exp $]
+
+***********************************************************************/
+ 
+#ifndef ABC__bool_Rsb_h
+#define ABC__bool_Rsb_h
+
+
+////////////////////////////////////////////////////////////////////////
+///                          INCLUDES                                ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                         PARAMETERS                               ///
+////////////////////////////////////////////////////////////////////////
+
+ABC_NAMESPACE_HEADER_START
+
+////////////////////////////////////////////////////////////////////////
+///                         BASIC TYPES                              ///
+////////////////////////////////////////////////////////////////////////
+
+typedef struct Rsb_Man_t_ Rsb_Man_t;
+
+////////////////////////////////////////////////////////////////////////
+///                      MACRO DEFINITIONS                           ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                    FUNCTION DECLARATIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/*=== rsbMan.c ==========================================================*/
+extern Rsb_Man_t *  Rsb_ManAlloc( int nLeafMax, int nDivMax, int nDecMax, int fVerbose );
+extern void         Rsb_ManFree( Rsb_Man_t * p );
+extern Vec_Int_t *  Rsb_ManGetFanins( Rsb_Man_t * p );
+extern Vec_Int_t *  Rsb_ManGetFaninsOld( Rsb_Man_t * p );
+/*=== rsbDec6.c ==========================================================*/
+extern int          Rsb_ManPerformResub6( Rsb_Man_t * p, int nVars, word uTruth, Vec_Wrd_t * vDivTruths, word * puTruth0, word * puTruth1, int fVerbose );
+
+
+ABC_NAMESPACE_HEADER_END
+
+#endif
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
diff --git a/src/bool/rsb/rsbDec6.c b/src/bool/rsb/rsbDec6.c
new file mode 100644
index 00000000..90f88938
--- /dev/null
+++ b/src/bool/rsb/rsbDec6.c
@@ -0,0 +1,733 @@
+/**CFile****************************************************************
+
+  FileName    [rsbDec6.c]
+
+  SystemName  [ABC: Logic synthesis and verification system.]
+
+  PackageName [Truth-table-based resubstitution.]
+
+  Synopsis    [Implementation of the algorithm.]
+
+  Author      [Alan Mishchenko]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - June 20, 2005.]
+
+  Revision    [$Id: rsbDec6.c,v 1.00 2005/06/20 00:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include "rsbInt.h"
+
+ABC_NAMESPACE_IMPL_START
+
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+static inline unsigned Rsb_DecTry0( word c ) 
+{
+    return (unsigned)(c != 0);
+}
+static inline unsigned Rsb_DecTry1( word c, word f1 ) 
+{
+    return (Rsb_DecTry0(c&f1) << 1) | Rsb_DecTry0(c&~f1);
+}
+static inline unsigned Rsb_DecTry2( word c, word f1, word f2 ) 
+{
+    return (Rsb_DecTry1(c&f2, f1) << 2) | Rsb_DecTry1(c&~f2, f1);
+}
+static inline unsigned Rsb_DecTry3( word c, word f1, word f2, word f3 ) 
+{
+    return (Rsb_DecTry2(c&f3, f1, f2) << 4) | Rsb_DecTry2(c&~f3, f1, f2);
+}
+static inline unsigned Rsb_DecTry4( word c, word f1, word f2, word f3, word f4 ) 
+{
+    return (Rsb_DecTry3(c&f4, f1, f2, f3) << 8) | Rsb_DecTry3(c&~f4, f1, f2, f3);
+}
+static inline unsigned Rsb_DecTry5( word c, word f1, word f2, word f3, word f4, word f5 ) 
+{
+    return (Rsb_DecTry4(c&f5, f1, f2, f3, f4) << 16) | Rsb_DecTry4(c&~f5, f1, f2, f3, f4);
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+static inline int Rsb_DecTryCex( word * g, int iCexA, int iCexB ) 
+{
+    return Abc_TtGetBit(g, iCexA) == Abc_TtGetBit(g, iCexB);
+}
+static inline void Rsb_DecVerifyCex( word * f, word ** g, int nGs, int iCexA, int iCexB ) 
+{
+    int i;
+    // f distinquished it
+    if ( Rsb_DecTryCex( f, iCexA, iCexB ) )
+        printf( "Verification of CEX has failed: f(A) == f(B)!!!\n" );
+    // g do not distinguish it
+    for ( i = 0; i < nGs; i++ )
+        if ( !Rsb_DecTryCex( g[i], iCexA, iCexB ) )
+            printf( "Verification of CEX has failed: g[%d](A) != g[%d](B)!!!\n", i, i );
+}
+static inline void Rsb_DecRecordCex( word ** g, int nGs, int iCexA, int iCexB, word * pCexes, int nCexes ) 
+{
+    int i;
+    assert( nCexes < 64 );
+    for ( i = 0; i < nGs; i++ )
+        if ( Rsb_DecTryCex(g[i], iCexA, iCexB) )
+            Abc_TtSetBit( pCexes + i, nCexes );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Checks decomposability of f with divisors g.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+static inline word Rsb_DecCofactor( word ** g, int nGs, int w, int iMint ) 
+{
+    int i;
+    word Cof = ~(word)0;
+    for ( i = 0; i < nGs; i++ )
+        Cof &=  ((iMint >> i) & 1) ? g[i][w] : ~g[i][w];
+    return Cof;
+}
+unsigned Rsb_DecCheck( int nVars, word * f, word ** g, int nGs, unsigned * pPat, int * pCexA, int * pCexB ) 
+{
+    word CofA, CofB;
+    int nWords = Abc_TtWordNum( nVars );
+    int w, k, iMint, iShift = ( 1 << nGs );
+    unsigned uMask = (~(unsigned)0) >> (32-iShift);
+    unsigned uTotal = 0;
+    assert( nGs > 0 && nGs < 5 );
+    for ( w = 0; w < nWords; w++ )
+    {
+        // generate decomposition pattern
+        if ( nGs == 1 )
+            pPat[w] = Rsb_DecTry2( ~(word)0, g[0][w], f[w] );
+        else if ( nGs == 2 )
+            pPat[w] = Rsb_DecTry3( ~(word)0, g[0][w], g[1][w], f[w] );
+        else if ( nGs == 3 )
+            pPat[w] = Rsb_DecTry4( ~(word)0, g[0][w], g[1][w], g[2][w], f[w] );
+        else if ( nGs == 4 )
+            pPat[w] = Rsb_DecTry5( ~(word)0, g[0][w], g[1][w], g[2][w], g[3][w], f[w] );
+        // check if it is consistent
+        iMint = Abc_Tt6FirstBit( (pPat[w] >> iShift) & pPat[w] & uMask );
+        if ( iMint >= 0 )
+        {   // generate a cex
+            CofA = Rsb_DecCofactor( g, nGs, w, iMint );
+            assert( (~f[w] & CofA) && (f[w] & CofA) );
+            *pCexA = w * 64 + Abc_Tt6FirstBit( ~f[w] & CofA );
+            *pCexB = w * 64 + Abc_Tt6FirstBit(  f[w] & CofA );
+            return 0;
+        }
+        uTotal |= pPat[w];
+        if ( w == 0 )
+            continue;
+        // check if it is consistent with other patterns seen so far
+        iMint = Abc_Tt6FirstBit( (uTotal >> iShift) & uTotal & uMask );
+        if ( iMint == -1 )
+            continue;
+        // find an overlap and generate a cex
+        for ( k = 0; k < w; k++ )
+        {
+            iMint = Abc_Tt6FirstBit( ((pPat[k] | pPat[w]) >> iShift) & (pPat[k] | pPat[w]) & uMask );
+            if ( iMint == -1 )
+                continue;
+            CofA = Rsb_DecCofactor( g, nGs, k, iMint );
+            CofB = Rsb_DecCofactor( g, nGs, w, iMint );
+            if ( (~f[k] & CofA) && (f[w] & CofB) )
+            {
+                *pCexA = k * 64 + Abc_Tt6FirstBit( ~f[k] & CofA );
+                *pCexB = w * 64 + Abc_Tt6FirstBit(  f[w] & CofB );
+            }
+            else
+            {
+                assert( (f[k] & CofA) && (~f[w] & CofB) );
+                *pCexA = k * 64 + Abc_Tt6FirstBit(  f[k] & CofA );
+                *pCexB = w * 64 + Abc_Tt6FirstBit( ~f[w] & CofB );
+            }
+            return 0;
+        }
+    }
+    return uTotal;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Rsb_DecPrintTable( word * pCexes, int nGs, int nGsAll, Vec_Int_t * vTries ) 
+{
+    int pCands[16], nCands;
+    int i, c, Cand, iStart = 0;
+    if ( Vec_IntSize(vTries) == 0 )
+        return;
+
+//    printf( "\n" );
+    for ( i = 0; i < 4; i++ )
+        printf( "    " );
+    printf( "  " );
+    for ( i = 0; i < nGs; i++ )
+        printf( "%d", (i % 100) / 10 );
+    printf( "|" );
+    for ( ; i < nGsAll; i++ )
+        printf( "%d", (i % 100) / 10 );
+    printf( "\n" );
+
+    for ( i = 0; i < 4; i++ )
+        printf( "    " );
+    printf( "  " );
+    for ( i = 0; i < nGs; i++ )
+        printf( "%d", i % 10 );
+    printf( "|" );
+    for ( ; i < nGsAll; i++ )
+        printf( "%d", i % 10 );
+    printf( "\n" );
+    printf( "\n" );
+
+    for ( c = 0; iStart < Vec_IntSize(vTries); c++ )
+    {
+        // collect candidates
+        for ( i = 0; i < 4; i++ )
+            pCands[i] = -1;
+        nCands = 0;
+        Vec_IntForEachEntryStart( vTries, Cand, i, iStart )
+            if ( Cand == -1 )
+            {
+                iStart = i + 1;
+                break;
+            }
+            else
+                pCands[nCands++] = Cand;
+        assert( nCands <= 4 );
+        // print them
+        for ( i = 0; i < 4; i++ )
+            if ( pCands[i] >= 0 )
+                printf( "%4d", pCands[i] );
+            else
+                printf( "    " );
+        // print the bit-string
+        printf( "  " );
+        for ( i = 0; i < nGs; i++ )
+            printf( "%c", Abc_TtGetBit( pCexes + i, c ) ? '.' : '+' );
+        printf( "|" );
+        for ( ; i < nGsAll; i++ )
+            printf( "%c", Abc_TtGetBit( pCexes + i, c ) ? '.' : '+' );
+        printf( "  %3d\n", c );
+    }
+    printf( "\n" );
+
+    // write the number of ones
+    for ( i = 0; i < 4; i++ )
+        printf( "    " );
+    printf( "  " );
+    for ( i = 0; i < nGs; i++ )
+        printf( "%d", Abc_TtCountOnes(pCexes[i]) / 10 );
+    printf( "|" );
+    for ( ; i < nGsAll; i++ )
+        printf( "%d", Abc_TtCountOnes(pCexes[i]) / 10 );
+    printf( "\n" );
+
+    for ( i = 0; i < 4; i++ )
+        printf( "    " );
+    printf( "  " );
+    for ( i = 0; i < nGs; i++ )
+        printf( "%d", Abc_TtCountOnes(pCexes[i]) % 10 );
+    printf( "|" );
+    for ( ; i < nGsAll; i++ )
+        printf( "%d", Abc_TtCountOnes(pCexes[i]) % 10 );
+    printf( "\n" );
+    printf( "\n" );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Init ]
+
+  Description [Returns the numbers of the decomposition functions and 
+  the truth table of a function up to 4 variables.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Rsb_DecInitCexes( int nVars, word * f, word ** g, int nGs, int nGsAll, word * pCexes, Vec_Int_t * vTries ) 
+{
+    int nWords = Abc_TtWordNum( nVars );
+    int ValueB = Abc_TtGetBit( f, 0 );
+    int ValueE = Abc_TtGetBit( f, 64*nWords-1 );
+    int iCexT0, iCexT1, iCexF0, iCexF1;
+
+    iCexT0 = ValueB  ? 0           : Abc_TtFindFirstBit( f, nVars );
+    iCexT1 = ValueE  ? 64*nWords-1 : Abc_TtFindLastBit( f, nVars );
+
+    iCexF0 = !ValueB ? 0           : Abc_TtFindFirstZero( f, nVars );
+    iCexF1 = !ValueE ? 64*nWords-1 : Abc_TtFindLastZero( f, nVars );
+
+    assert( !Rsb_DecTryCex( f, iCexT0, iCexF0 ) );
+    assert( !Rsb_DecTryCex( f, iCexT0, iCexF1 ) );
+    assert( !Rsb_DecTryCex( f, iCexT1, iCexF0 ) );
+    assert( !Rsb_DecTryCex( f, iCexT1, iCexF1 ) );
+
+    Rsb_DecRecordCex( g, nGsAll, iCexT0, iCexF0, pCexes, 0 );
+    Rsb_DecRecordCex( g, nGsAll, iCexT0, iCexF1, pCexes, 1 );
+    Rsb_DecRecordCex( g, nGsAll, iCexT1, iCexF0, pCexes, 2 );
+    Rsb_DecRecordCex( g, nGsAll, iCexT1, iCexF1, pCexes, 3 );
+
+    if ( vTries )
+    {
+    Vec_IntPush( vTries, -1 );
+    Vec_IntPush( vTries, -1 );
+    Vec_IntPush( vTries, -1 );
+    Vec_IntPush( vTries, -1 );
+    }
+    return 4;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Finds a setset of gs to decompose f.]
+
+  Description [Returns the numbers of the decomposition functions and 
+  the truth table of a function up to 4 variables.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+unsigned Rsb_DecPerformInt( Rsb_Man_t * p, int nVars, word * f, word ** g, int nGs, int nGsAll ) 
+{
+    word * pCexes = Vec_WrdArray(p->vCexes);
+    unsigned * pPat = (unsigned *)Vec_IntArray(p->vDecPats);
+    /*
+    The following filtering hueristic can be used:
+    after the first round (if there is more than 5 cexes, 
+    remove all the divisors, except fanins of the node
+    This should lead to a speadup without sacrifying quality.
+
+    Another idea is to precompute several counter-examples
+    like the first and last 0 and 1 mints of the function
+    which yields 4 cexes.
+    */
+
+    word * pDivs[16];
+    unsigned uTruth = 0;
+    int i, k, j, n, iCexA, iCexB, nCexes = 0;
+    memset( pCexes, 0, sizeof(word) * nGsAll );  
+    Vec_IntClear( p->vTries );
+    // populate the counter-examples with the three most obvious
+//    nCexes = Rsb_DecInitCexes( nVars, f, g, nGs, nGsAll, pCexes, vTries );
+    // start by checking each function
+    p->vFanins->nSize = 1;
+    for ( i = 0; i < nGs; i++ )
+    {
+        if ( pCexes[i] )
+            continue;
+        pDivs[0] = g[i];  p->vFanins->pArray[0] = i;
+        uTruth = Rsb_DecCheck( nVars, f, pDivs, Vec_IntSize(p->vFanins), pPat, &iCexA, &iCexB );
+        if ( uTruth )
+            return uTruth;
+        if ( nCexes == 64 )
+            return 0;
+        Rsb_DecVerifyCex( f, pDivs, Vec_IntSize(p->vFanins), iCexA, iCexB );
+        Rsb_DecRecordCex( g, nGsAll, iCexA, iCexB, pCexes, nCexes++ );
+        if ( !p->fVerbose )
+            continue;
+        Vec_IntPush( p->vTries, i );
+        Vec_IntPush( p->vTries, -1 );
+    }
+    if ( p->nDecMax == 1 )
+        return 0;
+    // continue by checking pairs
+    p->vFanins->nSize = 2;
+    for ( i = 1; i < nGs; i++ )
+    for ( k = 0; k < i; k++ )
+    {
+        if ( pCexes[i] & pCexes[k] )
+            continue;
+        pDivs[0] = g[i];  p->vFanins->pArray[0] = i;
+        pDivs[1] = g[k];  p->vFanins->pArray[1] = k;
+        uTruth = Rsb_DecCheck( nVars, f, pDivs, Vec_IntSize(p->vFanins), pPat, &iCexA, &iCexB );
+        if ( uTruth )
+            return uTruth;
+        if ( nCexes == 64 )
+            return 0;
+        Rsb_DecVerifyCex( f, pDivs, Vec_IntSize(p->vFanins), iCexA, iCexB );
+        Rsb_DecRecordCex( g, nGsAll, iCexA, iCexB, pCexes, nCexes++ );
+        if ( !p->fVerbose )
+            continue;
+        Vec_IntPush( p->vTries, i );
+        Vec_IntPush( p->vTries, k );
+        Vec_IntPush( p->vTries, -1 );
+    }
+    if ( p->nDecMax == 2 )
+        return 0;
+    // continue by checking triples
+    p->vFanins->nSize = 3;
+    for ( i = 2; i < nGs; i++ )
+    for ( k = 1; k < i; k++ )
+    for ( j = 0; j < k; j++ )
+    {
+        if ( pCexes[i] & pCexes[k] & pCexes[j] )
+            continue;
+        pDivs[0] = g[i];  p->vFanins->pArray[0] = i;
+        pDivs[1] = g[k];  p->vFanins->pArray[1] = k;
+        pDivs[2] = g[j];  p->vFanins->pArray[2] = j;
+        uTruth = Rsb_DecCheck( nVars, f, pDivs, Vec_IntSize(p->vFanins), pPat, &iCexA, &iCexB );
+        if ( uTruth )
+            return uTruth;
+        if ( nCexes == 64 )
+            return 0;
+        Rsb_DecVerifyCex( f, pDivs, Vec_IntSize(p->vFanins), iCexA, iCexB );
+        Rsb_DecRecordCex( g, nGsAll, iCexA, iCexB, pCexes, nCexes++ );
+        if ( !p->fVerbose )
+            continue;
+        Vec_IntPush( p->vTries, i );
+        Vec_IntPush( p->vTries, k );
+        Vec_IntPush( p->vTries, j );
+        Vec_IntPush( p->vTries, -1 );
+    }
+    if ( p->nDecMax == 3 )
+        return 0;
+    // continue by checking quadras
+    p->vFanins->nSize = 4;
+    for ( i = 3; i < nGs; i++ )
+    for ( k = 2; k < i; k++ )
+    for ( j = 1; j < k; j++ )
+    for ( n = 0; n < j; n++ )
+    {
+        if ( pCexes[i] & pCexes[k] & pCexes[j] & pCexes[n] )
+            continue;
+        pDivs[0] = g[i];  p->vFanins->pArray[0] = i;
+        pDivs[1] = g[k];  p->vFanins->pArray[1] = k;
+        pDivs[2] = g[j];  p->vFanins->pArray[2] = j;
+        pDivs[3] = g[n];  p->vFanins->pArray[3] = n;
+        uTruth = Rsb_DecCheck( nVars, f, pDivs, Vec_IntSize(p->vFanins), pPat, &iCexA, &iCexB );
+        if ( uTruth )
+            return uTruth;
+        if ( nCexes == 64 )
+            return 0;
+        Rsb_DecVerifyCex( f, pDivs, Vec_IntSize(p->vFanins), iCexA, iCexB );
+        Rsb_DecRecordCex( g, nGsAll, iCexA, iCexB, pCexes, nCexes++ );
+        if ( !p->fVerbose )
+            continue;
+        Vec_IntPush( p->vTries, i );
+        Vec_IntPush( p->vTries, k );
+        Vec_IntPush( p->vTries, j );
+        Vec_IntPush( p->vTries, n );
+        Vec_IntPush( p->vTries, -1 );
+    }
+//    printf( "%d ", nCexes );
+    if ( p->nDecMax == 4 )
+        return 0;
+    return 0;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Verifies 4-input decomposition.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Rsb_DecPrintFunc( Rsb_Man_t * p, unsigned Truth4, word * f, word ** ppGs, int nGs, int nVarsAll )
+{
+    int nVars  =  Vec_IntSize(p->vFanins);
+    word Copy  =  Truth4;
+    word wOn   =  Abc_Tt6Stretch( Copy >> (1 << nVars), nVars );
+    word wOnDc = ~Abc_Tt6Stretch( Copy, nVars );
+    word wIsop =  Abc_Tt6Isop( wOn, wOnDc, nVars );
+    int i;
+
+    printf( "Offset : " );
+    Abc_TtPrintBinary( &Copy, nVars );  //printf( "\n" );
+    Copy >>= (1 << nVars);
+    printf( "Onset  : " );
+    Abc_TtPrintBinary( &Copy, nVars );  //printf( "\n" );
+    printf( "Result : " );
+    Abc_TtPrintBinary( &wIsop, nVars ); //printf( "\n" );
+    Kit_DsdPrintFromTruth( (unsigned *)&wIsop, nVars );  printf( "\n" );
+
+    // print functions
+    printf( "Func   : " );
+    Abc_TtPrintBinary( f, nVarsAll );   //printf( "\n" );
+    Kit_DsdPrintFromTruth( (unsigned *)f, nVarsAll );    printf( "\n" );
+    for ( i = 0; i < nGs; i++ )
+    {
+        printf( "Div%3d : ", i );
+        Kit_DsdPrintFromTruth( (unsigned *)ppGs[i], nVarsAll );  printf( "\n" );
+    }
+    printf( "Solution : " );
+    for ( i = 0; i < Vec_IntSize(p->vFanins); i++ )
+        printf( "%d ", Vec_IntEntry(p->vFanins, i) );
+    printf( "\n" );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Verifies 4-input decomposition.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Rsb_DecVerify( Rsb_Man_t * p, int nVars, word * f, word ** g, int nGs, unsigned Truth4, word * pTemp1, word * pTemp2 )
+{
+    word * pFanins[16];
+    int b, m, Num, nSuppSize;
+    int nWords = Abc_TtWordNum(nVars);
+    Truth4 >>= (1 << Vec_IntSize(p->vFanins));
+    Truth4 = (unsigned)Abc_Tt6Stretch( (word)Truth4, Vec_IntSize(p->vFanins) );
+//Kit_DsdPrintFromTruth( (unsigned *)&Truth4, Vec_IntSize(p->vFanins) );
+//printf( "\n" );
+//    nSuppSize = Rsb_Word6SupportSize( Truth4 );
+//    assert( nSuppSize == Vec_IntSize(p->vFanins) );
+    nSuppSize = Vec_IntSize(p->vFanins);
+    // collect the fanins
+    Vec_IntForEachEntry( p->vFanins, Num, b )
+    {
+        assert( Num < nGs );
+        pFanins[b] = g[Num];
+    }
+    // create the or of ands
+    Abc_TtClear( pTemp1, nWords );
+    for ( m = 0; m < (1<<nSuppSize); m++ )
+    {
+        if ( ((Truth4 >> m) & 1) == 0 )
+            continue;
+        Abc_TtFill( pTemp2, nWords );
+        for ( b = 0; b < nSuppSize; b++ )
+            if ( (m >> b) & 1 )
+                Abc_TtAnd( pTemp2, pTemp2, pFanins[b], nWords, 0 );
+            else
+                Abc_TtSharp( pTemp2, pTemp2, pFanins[b], nWords );
+        Abc_TtOr( pTemp1, pTemp1, pTemp2, nWords );
+    }
+    // check the function
+    if ( !Abc_TtEqual( pTemp1, f, nWords ) )
+        printf( "Verification failed.\n" );
+//    else
+//        printf( "Verification passed.\n" );
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Finds a setset of gs to decompose f.]
+
+  Description [Returns the numbers of the decomposition functions and 
+  the truth table of a function up to 4 variables.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+unsigned Rsb_ManPerform( Rsb_Man_t * p, int nVars, word * f, word ** g, int nGs, int nGsAll, int fVerbose0 ) 
+{
+    word * pCexes = Vec_WrdArray(p->vCexes);
+    unsigned * pPat = (unsigned *)Vec_IntArray(p->vDecPats);
+    int fVerbose = 0;//(nGs > 40);
+    Vec_Int_t * vTries = NULL;
+    unsigned uTruth;
+
+    // verify original decomposition
+    if ( Vec_IntSize(p->vFaninsOld) && Vec_IntSize(p->vFaninsOld) <= 4 )
+    {
+        word * pDivs[8];
+        int i, Entry, iCexA, iCexB;
+        Vec_IntForEachEntry( p->vFaninsOld, Entry, i )
+            pDivs[i] = g[Entry];
+        uTruth = Rsb_DecCheck( nVars, f, pDivs, Vec_IntSize(p->vFaninsOld), pPat, &iCexA, &iCexB );
+//        assert( uTruth != 0 );
+        if ( fVerbose )
+        {
+            printf( "Verified orig decomp with %d vars {", Vec_IntSize(p->vFaninsOld) );
+            Vec_IntForEachEntry( p->vFaninsOld, Entry, i )
+                printf( " %d", Entry );
+            printf( " }\n" );
+        }
+        if ( uTruth )
+        {
+//            if ( fVerbose )
+//                Rsb_DecPrintFunc( p, uTruth );
+        }
+        else 
+        {
+            printf( "Verified orig decomp with %d vars {", Vec_IntSize(p->vFaninsOld) );
+            Vec_IntForEachEntry( p->vFaninsOld, Entry, i )
+                printf( " %d", Entry );
+            printf( " }\n" );
+            printf( "Verification FAILED.\n" );
+        }
+    }
+    // start tries
+if ( fVerbose )
+vTries = Vec_IntAlloc( 100 );
+    assert( nGs < nGsAll );
+    uTruth = Rsb_DecPerformInt( p, nVars, f, g, nGs, nGsAll );
+
+    if ( uTruth )
+    {
+        if ( fVerbose )
+        {
+            int i, Entry;
+            printf( "Found decomp with %d vars {", Vec_IntSize(p->vFanins) );
+            Vec_IntForEachEntry( p->vFanins, Entry, i )
+                printf( " %d", Entry );
+            printf( " }\n" );
+//            Rsb_DecPrintFunc( p, uTruth );
+//            Rsb_DecVerify( nVars, f, g, nGs, p->vFanins, uTruth, g[nGsAll], g[nGsAll+1] );
+        }
+    }
+    else 
+    {
+        Vec_IntShrink( p->vFanins, 0 );
+        if ( fVerbose )
+        printf( "Did not find decomposition with 4 variables.\n" );
+    }
+
+if ( fVerbose )
+Rsb_DecPrintTable( pCexes, nGs, nGsAll, vTries );
+if ( fVerbose )
+Vec_IntFree( vTries );
+    if ( fVerbose && Vec_IntSize(p->vFaninsOld) && Vec_IntSize(p->vFaninsOld) <= 4 && Vec_IntSize(p->vFaninsOld) > Vec_IntSize(p->vFanins) )
+    {
+        int s = 0;
+    }
+    return uTruth;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Rsb_ManPerformResub6( Rsb_Man_t * p, int nVarsAll, word uTruth, Vec_Wrd_t * vDivTruths, word * puTruth0, word * puTruth1, int fVerbose )
+{
+    word * pGs[64];
+    unsigned uTruthRes;
+    int i, nVars, nGs = Vec_WrdSize(vDivTruths);
+    for ( i = 0; i < nGs; i++ )
+        pGs[i] = Vec_WrdEntryP(vDivTruths,i);
+    uTruthRes = Rsb_DecPerformInt( p, nVarsAll, &uTruth, pGs, nGs, nGs );
+    if ( uTruthRes == 0 )
+        return 0;
+
+    if ( fVerbose )
+        Rsb_DecPrintFunc( p, uTruthRes, &uTruth, pGs, nGs, nVarsAll );
+    if ( fVerbose )
+        Rsb_DecPrintTable( Vec_WrdArray(p->vCexes), nGs, nGs, p->vTries );
+
+    nVars = Vec_IntSize(p->vFanins);
+    *puTruth0 = Abc_Tt6Stretch( uTruthRes,                 nVars );
+    *puTruth1 = Abc_Tt6Stretch( uTruthRes >> (1 << nVars), nVars );
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Rsb_ManPerformResub6Test()
+{
+    Rsb_Man_t * p;
+    Vec_Wrd_t * vDivTruths;
+    int RetValue;
+    word a = s_Truths6[0];
+    word b = s_Truths6[1];
+    word c = s_Truths6[2];
+    word d = s_Truths6[3];
+    word e = s_Truths6[4];
+    word f = s_Truths6[5];
+    word ab = a & b;
+    word cd = c & d;
+    word ef = e & f;
+    word F = ab | cd | ef;
+    word uTruth0, uTruth1;
+
+    vDivTruths = Vec_WrdAlloc( 100 );
+    Vec_WrdPush( vDivTruths, a );
+    Vec_WrdPush( vDivTruths, b );
+    Vec_WrdPush( vDivTruths, c );
+    Vec_WrdPush( vDivTruths, d );
+    Vec_WrdPush( vDivTruths, e );
+    Vec_WrdPush( vDivTruths, f );
+    Vec_WrdPush( vDivTruths, ab );
+    Vec_WrdPush( vDivTruths, cd );
+    Vec_WrdPush( vDivTruths, ef );
+
+    p = Rsb_ManAlloc( 6, 64, 4, 1 );
+
+    RetValue = Rsb_ManPerformResub6( p, 6, F, vDivTruths, &uTruth0, &uTruth1, 1 );
+
+    Rsb_ManFree( p );
+    Vec_WrdFree( vDivTruths );
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
+ABC_NAMESPACE_IMPL_END
+
diff --git a/src/bool/rsb/rsbInt.h b/src/bool/rsb/rsbInt.h
new file mode 100644
index 00000000..862ce8c7
--- /dev/null
+++ b/src/bool/rsb/rsbInt.h
@@ -0,0 +1,84 @@
+/**CFile****************************************************************
+
+  FileName    [rsbInt.h]
+
+  SystemName  [ABC: Logic synthesis and verification system.]
+
+  PackageName [Truth-table based resubstitution.]
+
+  Synopsis    [Internal declarations.]
+
+  Author      [Alan Mishchenko]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - June 20, 2005.]
+
+  Revision    [$Id: rsbInt.h,v 1.00 2005/06/20 00:00:00 alanmi Exp $]
+
+***********************************************************************/
+ 
+#ifndef ABC__bool_RsbInt_h
+#define ABC__bool_RsbInt_h
+
+
+////////////////////////////////////////////////////////////////////////
+///                          INCLUDES                                ///
+////////////////////////////////////////////////////////////////////////
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#include "misc/vec/vec.h"
+#include "misc/util/utilTruth.h"
+#include "bool/kit/kit.h"
+#include "rsb.h"
+
+////////////////////////////////////////////////////////////////////////
+///                         PARAMETERS                               ///
+////////////////////////////////////////////////////////////////////////
+
+ABC_NAMESPACE_HEADER_START
+
+////////////////////////////////////////////////////////////////////////
+///                         BASIC TYPES                              ///
+////////////////////////////////////////////////////////////////////////
+
+// truth table computation manager
+struct Rsb_Man_t_
+{
+    // parameters
+    int                nLeafMax;     // the max number of leaves of a cut
+    int                nDivMax;      // the max number of divisors to collect
+    int                nDecMax;      // the max number of decompositions
+    int                fVerbose;     // verbosity level
+    // decomposition
+    Vec_Wrd_t *        vCexes;       // counter-examples
+    Vec_Int_t *        vDecPats;     // decomposition patterns
+    Vec_Int_t *        vFanins;      // the result of decomposition
+    Vec_Int_t *        vFaninsOld;   // original fanins
+    Vec_Int_t *        vTries;       // intermediate
+};
+
+////////////////////////////////////////////////////////////////////////
+///                      MACRO DEFINITIONS                           ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                    FUNCTION DECLARATIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/*=== rsbMan.c ==========================================================*/
+
+ABC_NAMESPACE_HEADER_END
+
+
+
+#endif
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
diff --git a/src/bool/rsb/rsbMan.c b/src/bool/rsb/rsbMan.c
new file mode 100644
index 00000000..0d91cca4
--- /dev/null
+++ b/src/bool/rsb/rsbMan.c
@@ -0,0 +1,99 @@
+/**CFile****************************************************************
+
+  FileName    [rsbMan.c]
+
+  SystemName  [ABC: Logic synthesis and verification system.]
+
+  PackageName [Truth-table based resubstitution.]
+
+  Synopsis    [Manager maintenance.]
+
+  Author      [Alan Mishchenko]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - June 20, 2005.]
+
+  Revision    [$Id: rsbMan.c,v 1.00 2005/06/20 00:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include "rsbInt.h"
+
+ABC_NAMESPACE_IMPL_START
+
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Rsb_Man_t * Rsb_ManAlloc( int nLeafMax, int nDivMax, int nDecMax, int fVerbose )
+{
+    Rsb_Man_t * p;
+    assert( nLeafMax <= 20 );
+    assert( nDivMax  <= 200 );
+    p = ABC_CALLOC( Rsb_Man_t, 1 );
+    p->nLeafMax   = nLeafMax;
+    p->nDivMax    = nDivMax;
+    p->nDecMax    = nDecMax;
+    p->fVerbose   = fVerbose;
+    // decomposition
+    p->vCexes     = Vec_WrdAlloc( nDivMax + 150 );
+    p->vDecPats   = Vec_IntAlloc( Abc_TtWordNum(nLeafMax) );
+    p->vFanins    = Vec_IntAlloc( 10 );
+    p->vFaninsOld = Vec_IntAlloc( 10 );
+    p->vTries     = Vec_IntAlloc( 10 );
+    return p;
+}
+void Rsb_ManFree( Rsb_Man_t * p )
+{
+    Vec_WrdFree( p->vCexes );
+    Vec_IntFree( p->vDecPats );
+    Vec_IntFree( p->vFanins );
+    Vec_IntFree( p->vFaninsOld );
+    Vec_IntFree( p->vTries );
+    ABC_FREE( p );
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Vec_Int_t * Rsb_ManGetFanins( Rsb_Man_t * p )
+{
+    return p->vFanins;
+}
+Vec_Int_t * Rsb_ManGetFaninsOld( Rsb_Man_t * p )
+{
+    return p->vFaninsOld;
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
+ABC_NAMESPACE_IMPL_END
+
diff --git a/src/misc/util/utilTruth.h b/src/misc/util/utilTruth.h
index 4275912f..0072a808 100644
--- a/src/misc/util/utilTruth.h
+++ b/src/misc/util/utilTruth.h
@@ -116,6 +116,18 @@ static inline int  Abc_TtHexDigitNum( int nVars ) { return nVars <= 2 ? 1 : 1 <<
   SeeAlso     []
 
 ***********************************************************************/
+static inline void Abc_TtClear( word * pOut, int nWords )
+{
+    int w;
+    for ( w = 0; w < nWords; w++ )
+        pOut[w] = 0;
+}
+static inline void Abc_TtFill( word * pOut, int nWords )
+{
+    int w;
+    for ( w = 0; w < nWords; w++ )
+        pOut[w] = ~(word)0;
+}
 static inline void Abc_TtNot( word * pOut, int nWords )
 {
     int w;
@@ -142,6 +154,18 @@ static inline void Abc_TtAnd( word * pOut, word * pIn1, word * pIn2, int nWords,
         for ( w = 0; w < nWords; w++ )
             pOut[w] = pIn1[w] & pIn2[w];
 }
+static inline void Abc_TtSharp( word * pOut, word * pIn1, word * pIn2, int nWords )
+{
+    int w;
+    for ( w = 0; w < nWords; w++ )
+        pOut[w] = pIn1[w] & ~pIn2[w];
+}
+static inline void Abc_TtOr( word * pOut, word * pIn1, word * pIn2, int nWords )
+{
+    int w;
+    for ( w = 0; w < nWords; w++ )
+        pOut[w] = pIn1[w] | pIn2[w];
+}
 static inline void Abc_TtXor( word * pOut, word * pIn1, word * pIn2, int nWords, int fCompl )
 {
     int w;
@@ -756,10 +780,10 @@ static inline int Abc_TtReadHex( word * pTruth, char * pString )
 static inline void Abc_TtPrintBinary( word * pTruth, int nVars )
 {
     word * pThis, * pLimit = pTruth + Abc_TtWordNum(nVars);
-    int k;
+    int k, Limit = Abc_MinInt( 64, (1 << nVars) );
     assert( nVars >= 2 );
     for ( pThis = pTruth; pThis < pLimit; pThis++ )
-        for ( k = 0; k < 64; k++ )
+        for ( k = 0; k < Limit; k++ )
             printf( "%d", Abc_InfoHasBit( (unsigned *)pThis, k ) );
     printf( "\n" );
 }
@@ -1109,6 +1133,75 @@ static inline int Abc_TtCountOnes( word x )
   SeeAlso     []
 
 ***********************************************************************/
+static inline int Abc_Tt6FirstBit( word t )
+{
+    int n = 0;
+    if ( t == 0 ) return -1;
+    if ( (t & 0x00000000FFFFFFFF) == 0 ) { n += 32; t >>= 32; }
+    if ( (t & 0x000000000000FFFF) == 0 ) { n += 16; t >>= 16; }
+    if ( (t & 0x00000000000000FF) == 0 ) { n +=  8; t >>=  8; }
+    if ( (t & 0x000000000000000F) == 0 ) { n +=  4; t >>=  4; }
+    if ( (t & 0x0000000000000003) == 0 ) { n +=  2; t >>=  2; }
+    if ( (t & 0x0000000000000001) == 0 ) { n++; }
+    return n;
+}
+static inline int Abc_Tt6LastBit( word t )
+{
+    int n = 0;
+    if ( t == 0 ) return -1;
+    if ( (t & 0xFFFFFFFF00000000) == 0 ) { n += 32; t <<= 32; }
+    if ( (t & 0xFFFF000000000000) == 0 ) { n += 16; t <<= 16; }
+    if ( (t & 0xFF00000000000000) == 0 ) { n +=  8; t <<=  8; }
+    if ( (t & 0xF000000000000000) == 0 ) { n +=  4; t <<=  4; }
+    if ( (t & 0xC000000000000000) == 0 ) { n +=  2; t <<=  2; }
+    if ( (t & 0x8000000000000000) == 0 ) { n++; }
+    return 63-n;
+}
+static inline int Abc_TtFindFirstBit( word * pIn, int nVars )
+{
+    int w, nWords = Abc_TtWordNum(nVars);
+    for ( w = 0; w < nWords; w++ )
+        if ( pIn[w] )
+            return 64*w + Abc_Tt6FirstBit(pIn[w]);
+    return -1;
+}
+static inline int Abc_TtFindFirstZero( word * pIn, int nVars )
+{
+    int w, nWords = Abc_TtWordNum(nVars);
+    for ( w = 0; w < nWords; w++ )
+        if ( ~pIn[w] )
+            return 64*w + Abc_Tt6FirstBit(~pIn[w]);
+    return -1;
+}
+static inline int Abc_TtFindLastBit( word * pIn, int nVars )
+{
+    int w, nWords = Abc_TtWordNum(nVars);
+    for ( w = nWords - 1; w >= 0; w-- )
+        if ( pIn[w] )
+            return 64*w + Abc_Tt6LastBit(pIn[w]);
+    return -1;
+}
+static inline int Abc_TtFindLastZero( word * pIn, int nVars )
+{
+    int w, nWords = Abc_TtWordNum(nVars);
+    for ( w = nWords - 1; w >= 0; w-- )
+        if ( ~pIn[w] )
+            return 64*w + Abc_Tt6LastBit(~pIn[w]);
+    return -1;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
 static inline void Abc_TtReverseVars( word * pTruth, int nVars )
 {
     int k;
@@ -1146,6 +1239,49 @@ static inline void Abc_TtReverseBits( word * pTruth, int nVars )
 }
 
 
+/**Function*************************************************************
+
+  Synopsis    [Computes ISOP for 6 variables or less.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+static inline word Abc_Tt6Isop( word uOn, word uOnDc, int nVars )
+{
+    word uOn0, uOn1, uOnDc0, uOnDc1, uRes0, uRes1, uRes2;
+    int Var;
+    assert( nVars <= 5 );
+    assert( (uOn & ~uOnDc) == 0 );
+    if ( uOn == 0 )
+        return 0;
+    if ( uOnDc == ~(word)0 )
+        return ~(word)0;
+    assert( nVars > 0 );
+    // find the topmost var
+    for ( Var = nVars-1; Var >= 0; Var-- )
+        if ( Abc_Tt6HasVar( uOn, Var ) || Abc_Tt6HasVar( uOnDc, Var ) )
+             break;
+    assert( Var >= 0 );
+    // cofactor
+    uOn0   = Abc_Tt6Cofactor0( uOn,   Var );
+    uOn1   = Abc_Tt6Cofactor1( uOn  , Var );
+    uOnDc0 = Abc_Tt6Cofactor0( uOnDc, Var );
+    uOnDc1 = Abc_Tt6Cofactor1( uOnDc, Var );
+    // solve for cofactors
+    uRes0 = Abc_Tt6Isop( uOn0 & ~uOnDc1, uOnDc0, Var );
+    uRes1 = Abc_Tt6Isop( uOn1 & ~uOnDc0, uOnDc1, Var );
+    uRes2 = Abc_Tt6Isop( (uOn0 & ~uRes0) | (uOn1 & ~uRes1), uOnDc0 & uOnDc1, Var );
+    // derive the final truth table
+    uRes2 |= (uRes0 & s_Truths6Neg[Var]) | (uRes1 & s_Truths6[Var]);
+    assert( (uOn & ~uRes2) == 0 );
+    assert( (uRes2 & ~uOnDc) == 0 );
+    return uRes2;
+}
+
 /*=== utilTruth.c ===========================================================*/