Improvements to buffering and sizing.

5 files changed, 290 insertions, 20 deletions

diff --git a/src/base/abc/abc.h b/src/base/abc/abc.h
index bd0c5bba..a9178f38 100644
--- a/src/base/abc/abc.h
+++ b/src/base/abc/abc.h
@@ -387,8 +387,8 @@ static inline Abc_Obj_t * Abc_ObjChild0Data( Abc_Obj_t * pObj )      { return Ab
 static inline Abc_Obj_t * Abc_ObjChild1Data( Abc_Obj_t * pObj )      { return Abc_ObjNotCond( (Abc_Obj_t *)Abc_ObjFanin1(pObj)->pData, Abc_ObjFaninC1(pObj) );    }
 static inline Abc_Obj_t * Abc_ObjFromLit( Abc_Ntk_t * p, int iLit )  { return Abc_ObjNotCond( Abc_NtkObj(p, Abc_Lit2Var(iLit)), Abc_LitIsCompl(iLit) );           }
 static inline int         Abc_ObjToLit( Abc_Obj_t * p )              { return Abc_Var2Lit( Abc_ObjId(Abc_ObjRegular(p)), Abc_ObjIsComplement(p) );                }
-static inline int         Abc_ObjFaninPhase( Abc_Obj_t * p, int i )  { assert(p->pNtk->vPhases); return (Vec_IntEntry(p->pNtk->vPhases, Abc_ObjId(p)) >> i) & 1;  } 
-static inline void        Abc_ObjFaninFlipPhase( Abc_Obj_t * p,int i){ assert(p->pNtk->vPhases); *Vec_IntEntryP(p->pNtk->vPhases, Abc_ObjId(p)) ^= (1 << i);      } 
+static inline int         Abc_ObjFaninPhase( Abc_Obj_t * p, int i )  { assert(p->pNtk->vPhases); assert( i >= 0 && i < Abc_ObjFaninNum(p) ); return (Vec_IntEntry(p->pNtk->vPhases, Abc_ObjId(p)) >> i) & 1;  } 
+static inline void        Abc_ObjFaninFlipPhase( Abc_Obj_t * p,int i){ assert(p->pNtk->vPhases); assert( i >= 0 && i < Abc_ObjFaninNum(p) ); *Vec_IntEntryP(p->pNtk->vPhases, Abc_ObjId(p)) ^= (1 << i);      } 
 
 // checking the AIG node types
 static inline int         Abc_AigNodeIsConst( Abc_Obj_t * pNode )    { assert(Abc_NtkIsStrash(Abc_ObjRegular(pNode)->pNtk));  return Abc_ObjRegular(pNode)->Type == ABC_OBJ_CONST1;       }
diff --git a/src/map/scl/scl.c b/src/map/scl/scl.c
index e9c4d22c..e2b3d1ce 100644
--- a/src/map/scl/scl.c
+++ b/src/map/scl/scl.c
@@ -37,10 +37,11 @@ static int Scl_CommandStime   ( Abc_Frame_t * pAbc, int argc, char **argv );
 static int Scl_CommandTopo    ( Abc_Frame_t * pAbc, int argc, char **argv );
 static int Scl_CommandBuffer  ( Abc_Frame_t * pAbc, int argc, char **argv );
 static int Scl_CommandUnBuffer( Abc_Frame_t * pAbc, int argc, char **argv );
-static int Scl_CommandUpsize  ( Abc_Frame_t * pAbc, int argc, char **argv );
-static int Scl_CommandDnsize  ( Abc_Frame_t * pAbc, int argc, char **argv );
 static int Scl_CommandMinsize ( Abc_Frame_t * pAbc, int argc, char **argv );
 static int Scl_CommandMaxsize ( Abc_Frame_t * pAbc, int argc, char **argv );
+static int Scl_CommandUpsize  ( Abc_Frame_t * pAbc, int argc, char **argv );
+static int Scl_CommandDnsize  ( Abc_Frame_t * pAbc, int argc, char **argv );
+static int Scl_CommandBsize   ( Abc_Frame_t * pAbc, int argc, char **argv );
 static int Scl_CommandPrintBuf( Abc_Frame_t * pAbc, int argc, char **argv );
 
 ////////////////////////////////////////////////////////////////////////
@@ -73,6 +74,7 @@ void Scl_Init( Abc_Frame_t * pAbc )
     Cmd_CommandAdd( pAbc, "SCL mapping",  "maxsize",     Scl_CommandMaxsize,  1 ); 
     Cmd_CommandAdd( pAbc, "SCL mapping",  "upsize",      Scl_CommandUpsize,   1 ); 
     Cmd_CommandAdd( pAbc, "SCL mapping",  "dnsize",      Scl_CommandDnsize,   1 ); 
+    Cmd_CommandAdd( pAbc, "SCL mapping",  "bsize",       Scl_CommandBsize,    1 ); 
     Cmd_CommandAdd( pAbc, "SCL mapping",  "print_buf",   Scl_CommandPrintBuf, 0 ); 
 }
 void Scl_End( Abc_Frame_t * pAbc )
@@ -571,17 +573,18 @@ int Scl_CommandBuffer( Abc_Frame_t * pAbc, int argc, char ** argv )
 {
     Abc_Ntk_t * pNtk = Abc_FrameReadNtk(pAbc);
     Abc_Ntk_t * pNtkRes;
-    int FanMin, FanMax, fAddInvs, fUseInvs, fBufPis;
+    int FanMin, FanMax, FanMaxR, fAddInvs, fUseInvs, fBufPis;
     int c, fVerbose;
     int fOldAlgo = 0;
     FanMin   =  6;
     FanMax   = 14;
+    FanMaxR  =  0;
     fAddInvs =  0;
     fUseInvs =  0;
     fBufPis  =  0;
     fVerbose =  0;
     Extra_UtilGetoptReset();
-    while ( ( c = Extra_UtilGetopt( argc, argv, "NMaixpvh" ) ) != EOF )
+    while ( ( c = Extra_UtilGetopt( argc, argv, "NMRaixpvh" ) ) != EOF )
     {
         switch ( c )
         {
@@ -607,6 +610,17 @@ int Scl_CommandBuffer( Abc_Frame_t * pAbc, int argc, char ** argv )
             if ( FanMax < 0 ) 
                 goto usage;
             break;
+        case 'R':
+            if ( globalUtilOptind >= argc )
+            {
+                Abc_Print( -1, "Command line switch \"-R\" should be followed by a positive integer.\n" );
+                goto usage;
+            }
+            FanMaxR = atoi(argv[globalUtilOptind]);
+            globalUtilOptind++;
+            if ( FanMaxR < 0 ) 
+                goto usage;
+            break;
         case 'a':
             fOldAlgo ^= 1;
             break;
@@ -649,7 +663,7 @@ int Scl_CommandBuffer( Abc_Frame_t * pAbc, int argc, char ** argv )
     if ( fAddInvs )
         pNtkRes = Abc_SclBufferPhase( pNtk, fVerbose );
     else if ( fOldAlgo )
-        pNtkRes = Abc_SclPerformBuffering( pNtk, FanMax, fUseInvs, fVerbose );
+        pNtkRes = Abc_SclPerformBuffering( pNtk, FanMaxR, FanMax, fUseInvs, fVerbose );
     else
         pNtkRes = Abc_SclBufPerform( pNtk, FanMin, FanMax, fBufPis, fVerbose );
     if ( pNtkRes == NULL )
@@ -662,10 +676,11 @@ int Scl_CommandBuffer( Abc_Frame_t * pAbc, int argc, char ** argv )
     return 0;
 
 usage:
-    fprintf( pAbc->Err, "usage: buffer [-NM num] [-aixpvh]\n" );
+    fprintf( pAbc->Err, "usage: buffer [-NMR num] [-aixpvh]\n" );
     fprintf( pAbc->Err, "\t           performs buffering of the mapped network\n" );
     fprintf( pAbc->Err, "\t-N <num> : the min fanout considered by the algorithm [default = %d]\n", FanMin );
     fprintf( pAbc->Err, "\t-M <num> : the max allowed fanout count of node/buffer [default = %d]\n", FanMax );
+    fprintf( pAbc->Err, "\t-R <num> : the max allowed fanout count of root node [default = %d]\n", FanMaxR );
     fprintf( pAbc->Err, "\t-a       : toggle using old algorithm [default = %s]\n", fOldAlgo? "yes": "no" );
     fprintf( pAbc->Err, "\t-i       : toggle adding interters instead of buffering [default = %s]\n", fAddInvs? "yes": "no" );
     fprintf( pAbc->Err, "\t-x       : toggle using interters instead of buffers [default = %s]\n", fUseInvs? "yes": "no" );
@@ -1248,6 +1263,94 @@ usage:
   SeeAlso     []
 
 ***********************************************************************/
+int Scl_CommandBsize( Abc_Frame_t * pAbc, int argc, char **argv )
+{
+    extern Abc_Ntk_t * Abc_SclBuffSizeStep( SC_Lib * pLib, Abc_Ntk_t * pNtk, int nTreeCRatio, int fUseWireLoads );
+    Abc_Ntk_t * pNtkRes;
+    int c;
+    int fUseWireLoads = 1;
+    int nTreeCRatio   = 0;
+
+    Extra_UtilGetoptReset();
+    while ( ( c = Extra_UtilGetopt( argc, argv, "Xch" ) ) != EOF )
+    {
+        switch ( c )
+        {
+            case 'X':
+                if ( globalUtilOptind >= argc )
+                {
+                    Abc_Print( -1, "Command line switch \"-X\" should be followed by a positive integer.\n" );
+                    goto usage;
+                }
+                nTreeCRatio = atoi(argv[globalUtilOptind]);
+                globalUtilOptind++;
+                if ( nTreeCRatio < 0 ) 
+                    goto usage;
+                break;
+            case 'c':
+                fUseWireLoads ^= 1;
+                break;
+           case 'h':
+                goto usage;
+            default:
+                goto usage;
+        }
+    }
+
+    if ( Abc_FrameReadNtk(pAbc) == NULL )
+    {
+        fprintf( pAbc->Err, "There is no current network.\n" );
+        return 1;
+    }
+    if ( !Abc_NtkHasMapping(Abc_FrameReadNtk(pAbc)) )
+    {
+        fprintf( pAbc->Err, "The current network is not mapped.\n" );
+        return 1;
+    }
+    if ( !Abc_SclCheckNtk(Abc_FrameReadNtk(pAbc), 0) )
+    {
+        fprintf( pAbc->Err, "The current network is not in a topo order (run \"topo\").\n" );
+        return 1;
+    }
+    if ( pAbc->pLibScl == NULL )
+    {
+        fprintf( pAbc->Err, "There is no Liberty library available.\n" );
+        return 1;
+    }
+    if ( Abc_FrameReadNtk(pAbc)->vPhases == 0 )
+    {
+        fprintf( pAbc->Err, "There is no phases available.\n" );
+        return 1;
+    }
+    pNtkRes = Abc_SclBuffSizeStep( (SC_Lib *)pAbc->pLibScl, Abc_FrameReadNtk(pAbc), nTreeCRatio, fUseWireLoads );
+    if ( pNtkRes == NULL )
+    {
+        Abc_Print( -1, "The command has failed.\n" );
+        return 1;
+    }
+    Abc_FrameReplaceCurrentNetwork( pAbc, pNtkRes );
+    return 0;
+
+usage:
+    fprintf( pAbc->Err, "usage: bsize [-X num] [-ch]\n" );
+    fprintf( pAbc->Err, "\t         performs STA using Liberty library\n" );
+    fprintf( pAbc->Err, "\t-X     : min Cout/Cave ratio for tree estimations [default = %d]\n", nTreeCRatio );
+    fprintf( pAbc->Err, "\t-c     : toggle using wire-loads if specified [default = %s]\n", fUseWireLoads? "yes": "no" );
+    fprintf( pAbc->Err, "\t-h     : print the help massage\n" );
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    []
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
 int Scl_CommandPrintBuf( Abc_Frame_t * pAbc, int argc, char **argv )
 {
     Abc_Ntk_t * pNtk = Abc_FrameReadNtk(pAbc);
diff --git a/src/map/scl/sclBuffer.c b/src/map/scl/sclBuffer.c
index 9dc43499..83a305bd 100644
--- a/src/map/scl/sclBuffer.c
+++ b/src/map/scl/sclBuffer.c
@@ -78,6 +78,28 @@ static inline int  Abc_BufEdgeSlack( Buf_Man_t * p, Abc_Obj_t * pObj, Abc_Obj_t
 
 /**Function*************************************************************
 
+  Synopsis    [Make sure fanins of gates are not duplicated.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Abc_SclReportDupFanins( Abc_Ntk_t * pNtk )
+{
+    Abc_Obj_t * pObj, * pFanin, * pFanin2;
+    int i, k, k2;
+    Abc_NtkForEachNode( pNtk, pObj, i )
+        Abc_ObjForEachFanin( pObj, pFanin, k )
+            Abc_ObjForEachFanin( pObj, pFanin2, k2 )
+                if ( k != k2 && pFanin == pFanin2 )
+                    printf( "Node %d has dup fanin %d.\n", i, Abc_ObjId(pFanin) );    
+}
+
+/**Function*************************************************************
+
   Synopsis    [Removes buffers and inverters.]
 
   Description []
@@ -244,6 +266,7 @@ Abc_Ntk_t * Abc_SclUnBufferPhase( Abc_Ntk_t * pNtk, int fVerbose )
     pNtkNew = Abc_NtkDupDfs( pNtk );
     if ( fVerbose )
         printf( "Max depth = %d.\n", Abc_SclCountMaxPhases(pNtkNew) );
+    Abc_SclReportDupFanins( pNtkNew );
     return pNtkNew;
 }
 
@@ -292,6 +315,20 @@ int Abc_SclCheckNtk( Abc_Ntk_t * p, int fVerbose )
   SeeAlso     []
 
 ***********************************************************************/
+void Abc_NodeInvUpdateFanPolarity( Abc_Obj_t * pObj )
+{
+    Abc_Obj_t * pFanout;
+    int i;
+    assert( Abc_SclObjIsBufInv(pObj) );
+    Abc_ObjForEachFanout( pObj, pFanout, i )
+    {
+        if ( Abc_SclObjIsBufInv(pFanout) )
+            Abc_NodeInvUpdateFanPolarity( pFanout );
+        else
+            Abc_ObjFaninFlipPhase( pFanout, Abc_NodeFindFanin(pFanout, pObj) );
+    }
+}
+
 int Abc_NodeCompareLevels( Abc_Obj_t ** pp1, Abc_Obj_t ** pp2 )
 {
     int Diff = Abc_ObjLevel(*pp1) - Abc_ObjLevel(*pp2);
@@ -364,12 +401,16 @@ Abc_Obj_t * Abc_SclPerformBufferingOne( Abc_Obj_t * pObj, int Degree, int fUseIn
     Vec_PtrFree( vFanouts );
     Abc_ObjAddFanin( pBuffer, pObj );
     pBuffer->Level = Abc_SclComputeReverseLevel( pBuffer );
+    if ( fUseInvs )
+        Abc_NodeInvUpdateFanPolarity( pBuffer );
     return pBuffer;
 }
-void Abc_SclPerformBuffering_rec( Abc_Obj_t * pObj, int Degree, int fUseInvs, int fVerbose )
+void Abc_SclPerformBuffering_rec( Abc_Obj_t * pObj, int DegreeR, int Degree, int fUseInvs, int fVerbose )
 {
+    Vec_Ptr_t * vFanouts;
+    Abc_Obj_t * pBuffer;
     Abc_Obj_t * pFanout;
-    int i;
+    int i, nOldFanNum;
     if ( Abc_NodeIsTravIdCurrent( pObj ) )
         return;
     Abc_NodeSetTravIdCurrent( pObj );
@@ -379,14 +420,32 @@ void Abc_SclPerformBuffering_rec( Abc_Obj_t * pObj, int Degree, int fUseInvs, in
     assert( Abc_ObjIsCi(pObj) || Abc_ObjIsNode(pObj) );
     // buffer fanouts and collect reverse levels
     Abc_ObjForEachFanout( pObj, pFanout, i )
-        Abc_SclPerformBuffering_rec( pFanout, Degree, fUseInvs, fVerbose );
+        Abc_SclPerformBuffering_rec( pFanout, DegreeR, Degree, fUseInvs, fVerbose );
     // perform buffering as long as needed
+    nOldFanNum = Abc_ObjFanoutNum(pObj);
     while ( Abc_ObjFanoutNum(pObj) > Degree )
         Abc_SclPerformBufferingOne( pObj, Degree, fUseInvs, fVerbose );
+    // add yet another level of buffers
+    if ( DegreeR && nOldFanNum > DegreeR )
+    {
+        if ( fUseInvs )
+            pBuffer = Abc_NtkCreateNodeInv( pObj->pNtk, NULL );
+        else
+            pBuffer = Abc_NtkCreateNodeBuf( pObj->pNtk, NULL );
+        vFanouts = Vec_PtrAlloc( Abc_ObjFanoutNum(pObj) );
+        Abc_NodeCollectFanouts( pObj, vFanouts );
+        Vec_PtrForEachEntry( Abc_Obj_t *, vFanouts, pFanout, i )
+            Abc_ObjPatchFanin( pFanout, pObj, pBuffer );
+        Vec_PtrFree( vFanouts );
+        Abc_ObjAddFanin( pBuffer, pObj );
+        pBuffer->Level = Abc_SclComputeReverseLevel( pBuffer );
+        if ( fUseInvs )
+            Abc_NodeInvUpdateFanPolarity( pBuffer );
+    }
     // compute the new level of the node
     pObj->Level = Abc_SclComputeReverseLevel( pObj );
 }
-Abc_Ntk_t * Abc_SclPerformBuffering( Abc_Ntk_t * p, int Degree, int fUseInvs, int fVerbose )
+Abc_Ntk_t * Abc_SclPerformBuffering( Abc_Ntk_t * p, int DegreeR, int Degree, int fUseInvs, int fVerbose )
 {
     Vec_Int_t * vCiLevs;
     Abc_Ntk_t * pNew;
@@ -394,7 +453,11 @@ Abc_Ntk_t * Abc_SclPerformBuffering( Abc_Ntk_t * p, int Degree, int fUseInvs, in
     int i;
     assert( Abc_NtkHasMapping(p) );
     if ( fUseInvs )
+    {
         printf( "Warning!!! Using inverters instead of buffers.\n" );
+        if ( p->vPhases == NULL )
+            printf( "The phases are not given. The result will not verify.\n" );
+    }
     // remember CI levels
     vCiLevs = Vec_IntAlloc( Abc_NtkCiNum(p) );
     Abc_NtkForEachCi( p, pObj, i )
@@ -402,13 +465,16 @@ Abc_Ntk_t * Abc_SclPerformBuffering( Abc_Ntk_t * p, int Degree, int fUseInvs, in
     // perform buffering
     Abc_NtkIncrementTravId( p );        
     Abc_NtkForEachCi( p, pObj, i )
-        Abc_SclPerformBuffering_rec( pObj, Degree, fUseInvs, fVerbose );
+        Abc_SclPerformBuffering_rec( pObj, DegreeR, Degree, fUseInvs, fVerbose );
     // recompute logic levels
     Abc_NtkForEachCi( p, pObj, i )
         pObj->Level = Vec_IntEntry( vCiLevs, i );
     Abc_NtkForEachNode( p, pObj, i )
         Abc_ObjLevelNew( pObj );
     Vec_IntFree( vCiLevs );
+    // if phases are present
+    if ( p->vPhases )
+        Vec_IntFillExtra( p->vPhases, Abc_NtkObjNumMax(p), 0 );
     // duplication in topo order
     pNew = Abc_NtkDupDfs( p );
     Abc_SclCheckNtk( pNew, fVerbose );
diff --git a/src/map/scl/sclSize.c b/src/map/scl/sclSize.c
index 2efa22ee..86c81589 100644
--- a/src/map/scl/sclSize.c
+++ b/src/map/scl/sclSize.c
@@ -20,6 +20,7 @@
 
 #include "sclSize.h"
 #include "map/mio/mio.h"
+#include "misc/vec/vecWec.h"
 
 ABC_NAMESPACE_IMPL_START
 
@@ -121,7 +122,7 @@ static inline void Abc_SclTimeNodePrint( SC_Man * p, Abc_Obj_t * pObj, int fRise
     printf( "Cout =%5.0f ff  ", Abc_SclObjLoadFf(p, pObj, fRise >= 0 ? fRise : 0 ) );
     printf( "Cmax =%5.0f ff  ", pCell ? SC_CellPin(pCell, pCell->n_inputs)->max_out_cap : 0.0 );
     printf( "G =%5.1f  ",       pCell ? Abc_SclObjLoadAve(p, pObj) / SC_CellPinCap(pCell, 0) : 0.0 );
-    printf( "SL =%5.1f ps",     Abc_SclObjSlack(p, pObj) );
+    printf( "SL =%5.1f ps",     Abc_SclObjSlackPs(p, pObj) );
     printf( "\n" );
 }
 void Abc_SclTimeNtkPrint( SC_Man * p, int fShowAll, int fPrintPath )
@@ -201,6 +202,11 @@ static inline void Abc_SclDeptFanin( SC_Man * p, SC_Timing * pTime, Abc_Obj_t *
     SC_Pair * pDepOut  = Abc_SclObjDept( p, pObj );
     Scl_LibPinDeparture( pTime, pDepIn, pSlewIn, pLoad, pDepOut );
 }
+static inline float Abc_SclObjLoadValue( SC_Man * p, Abc_Obj_t * pObj )
+{
+//    float Value = Abc_MaxFloat(pLoad->fall, pLoad->rise) / (p->EstLoadAve * p->EstLoadMax);
+    return 0.5 * (Abc_SclObjLoad(p, pObj)->fall + Abc_SclObjLoad(p, pObj)->rise) / (p->EstLoadAve * p->EstLoadMax);
+}
 void Abc_SclTimeNode( SC_Man * p, Abc_Obj_t * pObj, int fDept )
 {
     SC_Timings * pRTime;
@@ -213,8 +219,7 @@ void Abc_SclTimeNode( SC_Man * p, Abc_Obj_t * pObj, int fDept )
     float LoadFall = pLoad->fall;
     float DeptRise = 0;
     float DeptFall = 0;
-//    float Value = Abc_MaxFloat(pLoad->fall, pLoad->rise) / (p->EstLoadAve * p->EstLoadMax);
-    float Value = 0.5 * (pLoad->fall + pLoad->rise) / (p->EstLoadAve * p->EstLoadMax);
+    float Value = p->EstLoadMax ? Abc_SclObjLoadValue( p, pObj ) : 0;
     if ( Abc_ObjIsCo(pObj) )
     {
         if ( !fDept )
@@ -325,8 +330,6 @@ void Abc_SclTimeNtkRecompute( SC_Man * p, float * pArea, float * pDelay, int fRe
             p->pSlack[i] = Abc_MaxFloat( 0.0, Abc_SclObjGetSlack(p, pObj, D) );
         }
     }
-    if ( p->nEstNodes )
-        printf( "Estimated nodes = %d.\n", p->nEstNodes );
 }
 
 /**Function*************************************************************
@@ -626,7 +629,7 @@ void Abc_SclPrintBuffersOne( SC_Man * p, Abc_Obj_t * pObj, int nOffset )
     printf( "%6.0f ps)  ",     Abc_SclObjTimePs(p, pObj, 0) );
     printf( "l =%5.0f ff  ",   Abc_SclObjLoadFf(p, pObj, 0 ) );
     printf( "s =%5.0f ps   ",  Abc_SclObjSlewPs(p, pObj, 0 ) );
-    printf( "sl =%5.0f ps   ", Abc_SclObjSlack(p, pObj) );
+    printf( "sl =%5.0f ps   ", Abc_SclObjSlackPs(p, pObj) );
     if ( nOffset == 0 )
     {
     printf( "L =%5.0f ff   ",  SC_LibCapFf( p->pLib, Abc_SclCountNonBufferLoad(p, pObj) ) );
@@ -698,6 +701,103 @@ int Abc_SclInputDriveOk( SC_Man * p, Abc_Obj_t * pObj, SC_Cell * pCell )
     return 1;
 }
 
+/**Function*************************************************************
+
+  Synopsis    [Select nodes that need to be buffered.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Vec_Wec_t * Abc_SclSelectSplitNodes( SC_Man * p, Abc_Ntk_t * pNtk )
+{
+    Vec_Wec_t * vSplits;
+    Vec_Int_t * vCrits, * vNonCrits, * vLevel;
+    Abc_Obj_t * pObj, * pFanout;
+    int i, k;
+    assert( p->EstLoadMax > 0 );
+    vCrits = Vec_IntAlloc( 1000 );
+    vNonCrits = Vec_IntAlloc( 1000 );
+    vSplits = Vec_WecAlloc( 1000 );
+    Abc_NtkForEachNodeCi( pNtk, pObj, i )
+    {
+        if ( Abc_SclObjLoadValue(p, pObj) < 1 )
+        {
+//            printf( "%d ", Abc_ObjFanoutNum(pObj) );
+            continue;
+        }
+/*
+        printf( "%d : %.0f   ", i, 0.5 * (Abc_SclObjLoad(p, pObj)->fall + Abc_SclObjLoad(p, pObj)->rise) );
+        Abc_ObjForEachFanout( pObj, pFanout, k )
+            printf( "%.1f ", Abc_SclGatePinCapAve(p->pLib, Abc_SclObjCell(p, pFanout)) );
+        printf( "\n" );
+*/
+        // skip non-critical nodes
+//        if ( Abc_SclObjSlack(p, pObj) > 100 )
+//            continue;
+        // collect non-critical fanouts of the node
+        Vec_IntClear( vCrits );
+        Vec_IntClear( vNonCrits );
+        Abc_ObjForEachFanout( pObj, pFanout, k )
+            if ( Abc_SclObjSlack(p, pFanout) < 100 )
+                Vec_IntPush( vCrits, Abc_ObjId(pFanout) );
+            else
+                Vec_IntPush( vNonCrits, Abc_ObjId(pFanout) );
+//        assert( Vec_IntSize(vNonCrits) < Abc_ObjFanoutNum(pObj) );
+        // skip if there is nothing to split
+//        if ( Vec_IntSize(vNonCrits) < 2 )
+//            continue;
+        // remember them
+        vLevel = Vec_WecPushLevel( vSplits );
+        Vec_IntPush( vLevel, i );
+        Vec_IntAppend( vLevel, vCrits );
+        // remember them
+        vLevel = Vec_WecPushLevel( vSplits );
+        Vec_IntPush( vLevel, i );
+        Vec_IntAppend( vLevel, vNonCrits );
+    }
+    Vec_IntFree( vCrits );
+    Vec_IntFree( vNonCrits );
+    // print out
+    printf( "Collected %d nodes to split.\n", Vec_WecSize(vSplits) );
+    return vSplits;
+}
+void Abc_SclPerformSplit( SC_Man * p, Abc_Ntk_t * pNtk, Vec_Wec_t * vSplits )
+{
+    Abc_Obj_t * pObj, * pObjInv, * pFanout;
+    Vec_Int_t * vLevel;
+    int i, k;
+    assert( pNtk->vPhases != NULL );
+    Vec_WecForEachLevel( vSplits, vLevel, i )
+    {
+        pObj = Abc_NtkObj( pNtk, Vec_IntEntry(vLevel, 0) );
+        pObjInv = Abc_NtkCreateNodeInv( pNtk, pObj );
+        Abc_NtkForEachObjVecStart( vLevel, pNtk, pFanout, k, 1 )
+        {
+            Abc_ObjFaninFlipPhase( pFanout, Abc_NodeFindFanin(pFanout, pObj) );
+            Abc_ObjPatchFanin( pFanout, pObj, pObjInv );
+        }
+    }
+    Vec_IntFillExtra( pNtk->vPhases, Abc_NtkObjNumMax(pNtk), 0 );
+}
+Abc_Ntk_t * Abc_SclBuffSizeStep( SC_Lib * pLib, Abc_Ntk_t * pNtk, int nTreeCRatio, int fUseWireLoads )
+{
+    SC_Man * p;
+    Vec_Wec_t * vSplits;
+    p = Abc_SclManStart( pLib, pNtk, fUseWireLoads, 1, 0, nTreeCRatio );
+    Abc_SclTimeNtkPrint( p, 0, 0 );
+    if ( p->nEstNodes )
+        printf( "Estimated nodes = %d.\n", p->nEstNodes );
+    vSplits = Abc_SclSelectSplitNodes( p, pNtk );
+    Abc_SclPerformSplit( p, pNtk, vSplits );
+    Vec_WecFree( vSplits );
+    Abc_SclManFree( p );
+    return Abc_NtkDupDfs( pNtk );
+}
+
 ////////////////////////////////////////////////////////////////////////
 ///                       END OF FILE                                ///
 ////////////////////////////////////////////////////////////////////////
diff --git a/src/map/scl/sclSize.h b/src/map/scl/sclSize.h
index c467ba1c..9656b55a 100644
--- a/src/map/scl/sclSize.h
+++ b/src/map/scl/sclSize.h
@@ -122,6 +122,7 @@ static inline int       Abc_SclObjLegal( SC_Man * p, Abc_Obj_t * pObj, float D )
 static inline double    Abc_SclObjLoadFf( SC_Man * p, Abc_Obj_t * pObj, int fRise ) { return SC_LibCapFf( p->pLib, fRise ? Abc_SclObjLoad(p, pObj)->rise : Abc_SclObjLoad(p, pObj)->fall); }
 static inline double    Abc_SclObjTimePs( SC_Man * p, Abc_Obj_t * pObj, int fRise ) { return SC_LibTimePs(p->pLib, fRise ? Abc_SclObjTime(p, pObj)->rise : Abc_SclObjTime(p, pObj)->fall); }
 static inline double    Abc_SclObjSlewPs( SC_Man * p, Abc_Obj_t * pObj, int fRise ) { return SC_LibTimePs(p->pLib, fRise ? Abc_SclObjSlew(p, pObj)->rise : Abc_SclObjSlew(p, pObj)->fall); }
+static inline double    Abc_SclObjSlackPs( SC_Man * p, Abc_Obj_t * pObj )           { return SC_LibTimePs(p->pLib, Abc_SclObjSlack(p, pObj));                        }
 
 ////////////////////////////////////////////////////////////////////////
 ///                     FUNCTION DEFINITIONS                         ///
@@ -397,7 +398,7 @@ extern Abc_Ntk_t *   Abc_SclUnBufferPerform( Abc_Ntk_t * pNtk, int fVerbose );
 extern Abc_Ntk_t *   Abc_SclUnBufferPhase( Abc_Ntk_t * pNtk, int fVerbose );
 extern Abc_Ntk_t *   Abc_SclBufferPhase( Abc_Ntk_t * pNtk, int fVerbose );
 extern int           Abc_SclCheckNtk( Abc_Ntk_t * p, int fVerbose );
-extern Abc_Ntk_t *   Abc_SclPerformBuffering( Abc_Ntk_t * p, int Degree, int fUseInvs, int fVerbose );
+extern Abc_Ntk_t *   Abc_SclPerformBuffering( Abc_Ntk_t * p, int DegreeR, int Degree, int fUseInvs, int fVerbose );
 extern Abc_Ntk_t *   Abc_SclBufPerform( Abc_Ntk_t * pNtk, int FanMin, int FanMax, int fBufPis, int fVerbose );
 /*=== sclDnsize.c ===============================================================*/
 extern void          Abc_SclDnsizePerform( SC_Lib * pLib, Abc_Ntk_t * pNtk, SC_SizePars * pPars );