Version abc61111

10 files changed, 1188 insertions, 256 deletions

diff --git a/src/opt/ret/module.make b/src/opt/ret/module.make
index 9ac0bf1f..c65021c4 100644
--- a/src/opt/ret/module.make
+++ b/src/opt/ret/module.make
@@ -1,8 +1,7 @@
-SRC +=  src/opt/dec/retArea.c \
-        src/opt/dec/retBwd.c \
-        src/opt/dec/retCore.c \
-        src/opt/dec/retDelay.c \
-        src/opt/dec/retFlow.c \
-        src/opt/dec/retFwd.c \
-        src/opt/dec/retInit.c
+SRC +=  src/opt/ret/retArea.c \
+        src/opt/ret/retCore.c \
+        src/opt/ret/retDelay.c \
+        src/opt/ret/retFlow.c \
+        src/opt/ret/retIncrem.c \
+        src/opt/ret/retInit.c
 
diff --git a/src/opt/ret/retArea.c b/src/opt/ret/retArea.c
index 7f93b87b..41d19592 100644
--- a/src/opt/ret/retArea.c
+++ b/src/opt/ret/retArea.c
@@ -50,38 +50,36 @@ extern Abc_Ntk_t * Abc_NtkAttachBottom( Abc_Ntk_t * pNtkTop, Abc_Ntk_t * pNtkBot
   SeeAlso     []
 
 ***********************************************************************/
-int Abc_NtkRetimeMinArea( Abc_Ntk_t * pNtk, int fVerbose )
+int Abc_NtkRetimeMinArea( Abc_Ntk_t * pNtk, int fForwardOnly, int fBackwardOnly, int fVerbose )
 {
-    Abc_Ntk_t * pNtkTotal = NULL, * pNtkBottom, * pNtkMiter;
-    Vec_Int_t * vValues;
+    Abc_Ntk_t * pNtkTotal = NULL, * pNtkBottom;
+    Vec_Int_t * vValuesNew = NULL, * vValues;
     int nLatches = Abc_NtkLatchNum(pNtk);
+    assert( !fForwardOnly || !fBackwardOnly );
     // there should not be black boxes
     assert( Abc_NtkIsSopLogic(pNtk) );
     assert( Abc_NtkLatchNum(pNtk) == Vec_PtrSize(pNtk->vBoxes) );
     // reorder CI/CO/latch inputs
     Abc_NtkOrderCisCos( pNtk );
     // perform forward retiming
-    vValues = Abc_NtkCollectLatchValues( pNtk );
 //    Abc_NtkRetimeMinAreaFwd( pNtk, fVerbose );
-    pNtkTotal = Abc_NtkRetimeMinAreaBwd( pNtk, fVerbose );
-
-//    while ( Abc_NtkRetimeMinAreaFwd( pNtk, fVerbose ) );
+//    pNtkTotal = Abc_NtkRetimeMinAreaBwd( pNtk, fVerbose );
+    if ( !fBackwardOnly )
+        while ( Abc_NtkRetimeMinAreaFwd( pNtk, fVerbose ) );
+    // remember initial values
+    vValues = Abc_NtkCollectLatchValues( pNtk );
     // perform backward retiming
-//    while ( pNtkBottom = Abc_NtkRetimeMinAreaBwd( pNtk, fVerbose ) )
-//        pNtkTotal = Abc_NtkAttachBottom( pNtkTotal, pNtkBottom );  
+    if ( !fForwardOnly )
+//        pNtkTotal = Abc_NtkRetimeMinAreaBwd( pNtk, fVerbose );
+        while ( pNtkBottom = Abc_NtkRetimeMinAreaBwd( pNtk, fVerbose ) )
+            pNtkTotal = Abc_NtkAttachBottom( pNtkTotal, pNtkBottom );  
     // compute initial values
-    if ( pNtkTotal )
-    {
-        // convert the target network to AIG
-        Abc_NtkLogicToAig( pNtkTotal );
-        // get the miter
-        pNtkMiter = Abc_NtkCreateTarget( pNtkTotal, pNtkTotal->vCos, vValues );
-        Abc_NtkDelete( pNtkTotal );
-        // get the initial values
-        Abc_NtkRetimeInitialValues( pNtk, pNtkMiter, fVerbose );
-        Abc_NtkDelete( pNtkMiter );
-    }
-    Vec_IntFree( vValues );
+    vValuesNew = Abc_NtkRetimeInitialValues( pNtkTotal, vValues, fVerbose );
+    if ( pNtkTotal ) Abc_NtkDelete( pNtkTotal );
+    // insert new initial values
+    Abc_NtkInsertLatchValues( pNtk, vValuesNew );
+    if ( vValuesNew ) Vec_IntFree( vValuesNew );
+    if ( vValues )    Vec_IntFree( vValues );
     // fix the COs
     Abc_NtkLogicMakeSimpleCos( pNtk, 0 );
     // check for correctness
@@ -311,46 +309,6 @@ void Abc_NtkRetimeMinAreaRemoveBuffers( Abc_Ntk_t * pNtk, Vec_Ptr_t * vBuffers )
 
 /**Function*************************************************************
 
-  Synopsis    [Computes the results of simulating one node.]
-
-  Description [Assumes that fanins have pCopy set to the input values.]
-               
-  SideEffects []
-
-  SeeAlso     []
-
-***********************************************************************/
-int Abc_ObjSopSimulate( Abc_Obj_t * pObj )
-{
-    char * pCube, * pSop = pObj->pData;
-    int nVars, Value, v, ResOr, ResAnd, ResVar;
-    assert( pSop && !Abc_SopIsExorType(pSop) );
-    // simulate the SOP of the node
-    ResOr = 0;
-    nVars = Abc_SopGetVarNum(pSop);
-    Abc_SopForEachCube( pSop, nVars, pCube )
-    {
-        ResAnd = 1;
-        Abc_CubeForEachVar( pCube, Value, v )
-        {
-            if ( Value == '0' )
-                ResVar = 1 ^ ((int)Abc_ObjFanin(pObj, v)->pCopy);
-            else if ( Value == '1' )
-                ResVar = (int)Abc_ObjFanin(pObj, v)->pCopy;
-            else
-                continue;
-            ResAnd &= ResVar;
-        }
-        ResOr |= ResAnd;
-    }
-    // complement the result if necessary
-    if ( !Abc_SopGetPhase(pSop) )
-        ResOr ^= 1;
-    return ResOr;
-}
-
-/**Function*************************************************************
-
   Synopsis    [Compute initial values.]
 
   Description []
@@ -369,7 +327,7 @@ int Abc_NtkRetimeMinAreaInitValue_rec( Abc_Obj_t * pObj )
         return (int)pObj->pCopy;
     Abc_NodeSetTravIdCurrent(pObj);
     // consider the case of a latch output
-    if ( Abc_ObjIsBi(pObj) )
+    if ( Abc_ObjIsBo(pObj) )
     {
         assert( Abc_ObjIsLatch(Abc_ObjFanin0(pObj)) );
         pObj->pCopy = (void *)Abc_NtkRetimeMinAreaInitValue_rec( Abc_ObjFanin0(pObj) );
@@ -431,8 +389,11 @@ Abc_Obj_t * Abc_NtkRetimeMinAreaConstructNtk_rec( Abc_Ntk_t * pNtkNew, Abc_Obj_t
         return pObj->pCopy;
     Abc_NodeSetTravIdCurrent(pObj);
     // consider the case of a latch output
-    if ( Abc_ObjIsBo(pObj) )
-        return Abc_NtkRetimeMinAreaConstructNtk_rec( pNtkNew, Abc_ObjFanin0(pObj) );
+    if ( Abc_ObjIsBi(pObj) )
+    {
+        pObj->pCopy = Abc_NtkRetimeMinAreaConstructNtk_rec( pNtkNew, Abc_ObjFanin0(pObj) );
+        return pObj->pCopy;
+    }
     assert( Abc_ObjIsNode(pObj) );
     // visit the fanins
     Abc_ObjForEachFanin( pObj, pFanin, i )
@@ -462,7 +423,7 @@ Abc_Ntk_t * Abc_NtkRetimeMinAreaConstructNtk( Abc_Ntk_t * pNtk, Vec_Ptr_t * vMin
     int i;
     // create new network
     pNtkNew = Abc_NtkAlloc( ABC_NTK_LOGIC, ABC_FUNC_SOP, 1 );
-    // set mapping of new latches into the PIs of the network
+    // map new latches into PIs of the new network
     Abc_NtkIncrementTravId(pNtk);
     Vec_PtrForEachEntry( vMinCut, pObj, i )
     {
@@ -475,6 +436,9 @@ Abc_Ntk_t * Abc_NtkRetimeMinAreaConstructNtk( Abc_Ntk_t * pNtk, Vec_Ptr_t * vMin
         pObjNew = Abc_NtkRetimeMinAreaConstructNtk_rec( pNtkNew, Abc_ObjFanin0(pObj) );
         Abc_ObjAddFanin( Abc_NtkCreatePo(pNtkNew), pObjNew );
     }
+    // unmark the nodes in the cut
+    Vec_PtrForEachEntry( vMinCut, pObj, i )
+        Abc_NodeSetTravIdPrevious( pObj );
     // assign dummy node names
     Abc_NtkAddDummyPiNames( pNtkNew );
     Abc_NtkAddDummyPoNames( pNtkNew );
@@ -485,6 +449,76 @@ Abc_Ntk_t * Abc_NtkRetimeMinAreaConstructNtk( Abc_Ntk_t * pNtk, Vec_Ptr_t * vMin
 
 /**Function*************************************************************
 
+  Synopsis    [Mark the inside of the min-cut with current traversal ID.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Abc_NtkRetimeMinAreaMarkInside_rec( Abc_Obj_t * pObj, int fForward )
+{
+    Abc_Obj_t * pNext;
+    int i;
+    // skip visited nodes
+    if ( Abc_NodeIsTravIdCurrent(pObj) )
+        return;
+    Abc_NodeSetTravIdCurrent( pObj );
+    // make sure we never reach PIs/POs/latches
+    if ( Abc_ObjIsPi(pObj) || Abc_ObjIsPo(pObj) || Abc_ObjIsLatch(pObj) )
+        printf( "Abc_NtkRetimeMinAreaMarkInside(): The set of nodes is not a cut. Internal error!!!\n" );
+    // continue to explore the cone
+    if ( fForward )
+    {
+        Abc_ObjForEachFanout( pObj, pNext, i )
+            Abc_NtkRetimeMinAreaMarkInside_rec( pNext, fForward );
+    }
+    else
+    {
+        Abc_ObjForEachFanin( pObj, pNext, i )
+            Abc_NtkRetimeMinAreaMarkInside_rec( pNext, fForward );
+    }
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Marks the inside of the min-cut with current traversal ID.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Abc_NtkRetimeMinAreaMarkInside( Abc_Ntk_t * pNtk, Vec_Ptr_t * vMinCut, int fForward )
+{
+    Abc_Obj_t * pObj;
+    int i;
+    // mark the mincut
+    Abc_NtkIncrementTravId(pNtk);
+    Vec_PtrForEachEntry( vMinCut, pObj, i )
+        Abc_NodeSetTravIdCurrent( pObj );
+    // mark the area inside of the cut
+    if ( fForward )
+    {
+        Abc_NtkForEachLatch( pNtk, pObj, i )
+            Abc_NtkRetimeMinAreaMarkInside_rec( Abc_ObjFanout0(pObj), fForward );
+    }
+    else
+    {
+        Abc_NtkForEachLatch( pNtk, pObj, i )
+            Abc_NtkRetimeMinAreaMarkInside_rec( Abc_ObjFanin0(pObj), fForward );
+        // unmark the nodes in the cut
+        Vec_PtrForEachEntry( vMinCut, pObj, i )
+            Abc_NodeSetTravIdPrevious( pObj );
+    }
+}
+
+/**Function*************************************************************
+
   Synopsis    [Updates the network after backward retiming.]
 
   Description []
@@ -496,9 +530,11 @@ Abc_Ntk_t * Abc_NtkRetimeMinAreaConstructNtk( Abc_Ntk_t * pNtk, Vec_Ptr_t * vMin
 ***********************************************************************/
 void Abc_NtkRetimeMinAreaUpdateLatches( Abc_Ntk_t * pNtk, Vec_Ptr_t * vMinCut, int fForward )
 {
-    Vec_Ptr_t * vCis, * vCos, * vBoxes, * vBoxesNew, * vFanouts;
-    Abc_Obj_t * pObj, * pLatch, * pLatchIn, * pLatchOut, * pFanout;
+    Vec_Ptr_t * vCis, * vCos, * vBoxes, * vBoxesNew, * vNodes;
+    Abc_Obj_t * pObj, * pLatch, * pLatchIn, * pLatchOut, * pNext;
     int i, k;
+    // mark the inside of min-cut with new trav ID
+    Abc_NtkRetimeMinAreaMarkInside( pNtk, vMinCut, fForward );
     // create new latches
     Vec_PtrShrink( pNtk->vCis, Abc_NtkCiNum(pNtk) - Abc_NtkLatchNum(pNtk) );
     Vec_PtrShrink( pNtk->vCos, Abc_NtkCoNum(pNtk) - Abc_NtkLatchNum(pNtk) );
@@ -511,8 +547,7 @@ void Abc_NtkRetimeMinAreaUpdateLatches( Abc_Ntk_t * pNtk, Vec_Ptr_t * vMinCut, i
         if ( !Abc_ObjIsLatch(pObj) )
             Vec_PtrPush( vBoxesNew, pObj );
     // create or reuse latches
-    Abc_NtkIncrementTravId(pNtk);
-    vFanouts = Vec_PtrAlloc( 100 );
+    vNodes = Vec_PtrAlloc( 100 );
     Vec_PtrForEachEntry( vMinCut, pObj, i )
     {
         if ( Abc_ObjIsCi(pObj) && fForward )
@@ -520,7 +555,7 @@ void Abc_NtkRetimeMinAreaUpdateLatches( Abc_Ntk_t * pNtk, Vec_Ptr_t * vMinCut, i
             pLatchOut = pObj;
             pLatch    = Abc_ObjFanin0(pLatchOut);
             pLatchIn  = Abc_ObjFanin0(pLatch);
-            assert( Abc_ObjIsBi(pLatchOut) && Abc_ObjIsLatch(pLatch) && Abc_ObjIsBo(pLatchIn) );
+            assert( Abc_ObjIsBo(pLatchOut) && Abc_ObjIsLatch(pLatch) && Abc_ObjIsBi(pLatchIn) );
             // mark the latch as reused
             Abc_NodeSetTravIdCurrent( pLatch );
         }
@@ -529,15 +564,15 @@ void Abc_NtkRetimeMinAreaUpdateLatches( Abc_Ntk_t * pNtk, Vec_Ptr_t * vMinCut, i
             pLatchIn  = pObj;
             pLatch    = Abc_ObjFanout0(pLatchIn);
             pLatchOut = Abc_ObjFanout0(pLatch);
-            assert( Abc_ObjIsBi(pLatchOut) && Abc_ObjIsLatch(pLatch) && Abc_ObjIsBo(pLatchIn) );
+            assert( Abc_ObjIsBo(pLatchOut) && Abc_ObjIsLatch(pLatch) && Abc_ObjIsBi(pLatchIn) );
             // mark the latch as reused
             Abc_NodeSetTravIdCurrent( pLatch );
         }
         else
         {
-            pLatchOut = Abc_NtkCreateBi(pNtk);
+            pLatchOut = Abc_NtkCreateBo(pNtk);
             pLatch    = Abc_NtkCreateLatch(pNtk);
-            pLatchIn  = Abc_NtkCreateBo(pNtk);
+            pLatchIn  = Abc_NtkCreateBi(pNtk);
             Abc_ObjAssignName( pLatchOut, Abc_ObjName(pLatchOut), NULL );
             Abc_ObjAssignName( pLatchIn,  Abc_ObjName(pLatchIn), NULL );
             // connect
@@ -545,16 +580,20 @@ void Abc_NtkRetimeMinAreaUpdateLatches( Abc_Ntk_t * pNtk, Vec_Ptr_t * vMinCut, i
             Abc_ObjAddFanin( pLatch, pLatchIn );
             if ( fForward )
             {
-                Abc_ObjTransferFanout( pObj, pLatchOut );
                 pLatch->pData = (void *)(pObj->pCopy? ABC_INIT_ONE : ABC_INIT_ZERO);
+                // redirect edges to the unvisited fanouts of the node
+                Abc_NodeCollectFanouts( pObj, vNodes );
+                Vec_PtrForEachEntry( vNodes, pNext, k )
+                    if ( !Abc_NodeIsTravIdCurrent(pNext) )
+                        Abc_ObjPatchFanin( pNext, pObj, pLatchOut );
             }
             else
             {
-                // redirect unmarked edges
-                Abc_NodeCollectFanouts( pObj, vFanouts );
-                Vec_PtrForEachEntry( vFanouts, pFanout, k )
-                    if ( !pFanout->fMarkA )
-                        Abc_ObjPatchFanin( pFanout, pObj, pLatchOut );
+                // redirect edges to the visited fanouts of the node
+                Abc_NodeCollectFanouts( pObj, vNodes );
+                Vec_PtrForEachEntry( vNodes, pNext, k )
+                    if ( Abc_NodeIsTravIdCurrent(pNext) )
+                        Abc_ObjPatchFanin( pNext, pObj, pLatchOut );
             }
             // connect latch to the node
             Abc_ObjAddFanin( pLatchIn, pObj );
@@ -563,7 +602,7 @@ void Abc_NtkRetimeMinAreaUpdateLatches( Abc_Ntk_t * pNtk, Vec_Ptr_t * vMinCut, i
         Vec_PtrPush( vBoxesNew, pLatch );
         Vec_PtrPush( vCos, pLatchIn );
     }
-    Vec_PtrFree( vFanouts );
+    Vec_PtrFree( vNodes );
     // remove useless latches
     Vec_PtrForEachEntry( vBoxes, pObj, i )
     {
@@ -574,7 +613,8 @@ void Abc_NtkRetimeMinAreaUpdateLatches( Abc_Ntk_t * pNtk, Vec_Ptr_t * vMinCut, i
         pLatchOut = Abc_ObjFanout0(pObj);
         pLatch    = pObj;
         pLatchIn  = Abc_ObjFanin0(pObj);
-        Abc_ObjTransferFanout( pLatchOut, Abc_ObjFanin0(pLatchIn) );
+        if ( Abc_ObjFanoutNum(pLatchOut) > 0 )
+            Abc_ObjTransferFanout( pLatchOut, Abc_ObjFanin0(pLatchIn) );
         Abc_NtkDeleteObj( pLatchOut );
         Abc_NtkDeleteObj( pObj );
         Abc_NtkDeleteObj( pLatchIn );
diff --git a/src/opt/ret/retBwd.c b/src/opt/ret/retBwd.c
deleted file mode 100644
index 7eefc4e0..00000000
--- a/src/opt/ret/retBwd.c
+++ /dev/null
@@ -1,65 +0,0 @@
-/**CFile****************************************************************
-
-  FileName    [retBwd.c]
-
-  SystemName  [ABC: Logic synthesis and verification system.]
-
-  PackageName [Retiming package.]
-
-  Synopsis    [Most backward retiming.]
-
-  Author      [Alan Mishchenko]
-  
-  Affiliation [UC Berkeley]
-
-  Date        [Ver. 1.0. Started - Oct 31, 2006.]
-
-  Revision    [$Id: retBwd.c,v 1.00 2006/10/31 00:00:00 alanmi Exp $]
-
-***********************************************************************/
-
-#include "retInt.h"
-
-////////////////////////////////////////////////////////////////////////
-///                        DECLARATIONS                              ///
-////////////////////////////////////////////////////////////////////////
-
-////////////////////////////////////////////////////////////////////////
-///                     FUNCTION DEFINITIONS                         ///
-////////////////////////////////////////////////////////////////////////
-
-/**Function*************************************************************
-
-  Synopsis    []
-
-  Description []
-               
-  SideEffects []
-
-  SeeAlso     []
-
-***********************************************************************/
-int Abc_NtkRetimeBackward( Abc_Ntk_t * pNtk, int fVerbose )
-{
-    printf( "Not implemented.\n" );
-    return 0;
-}
-
-/**Function*************************************************************
-
-  Synopsis    []
-
-  Description []
-               
-  SideEffects []
-
-  SeeAlso     []
-
-***********************************************************************/
-
-
-////////////////////////////////////////////////////////////////////////
-///                       END OF FILE                                ///
-////////////////////////////////////////////////////////////////////////
-
-
diff --git a/src/opt/ret/retCore.c b/src/opt/ret/retCore.c
index 541f5962..8ef4e79b 100644
--- a/src/opt/ret/retCore.c
+++ b/src/opt/ret/retCore.c
@@ -24,6 +24,8 @@
 ///                        DECLARATIONS                              ///
 ////////////////////////////////////////////////////////////////////////
 
+int timeRetime = 0;
+
 ////////////////////////////////////////////////////////////////////////
 ///                     FUNCTION DEFINITIONS                         ///
 ////////////////////////////////////////////////////////////////////////
@@ -39,36 +41,74 @@
   SeeAlso     []
 
 ***********************************************************************/
-int Abc_NtkRetime( Abc_Ntk_t * pNtk, int Mode, int fVerbose )
+int Abc_NtkRetime( Abc_Ntk_t * pNtk, int Mode, int fForwardOnly, int fBackwardOnly, int fVerbose )
 {
-    int RetValue;
+    int nLatches = Abc_NtkLatchNum(pNtk);
+    int nLevels  = Abc_NtkGetLevelNum(pNtk);
+    int RetValue = 0, clkTotal = clock();
     assert( Mode > 0 && Mode < 6 );
+    assert( !fForwardOnly || !fBackwardOnly );
     // perform forward retiming
     switch ( Mode )
     {
     case 1: // forward 
-        RetValue = Abc_NtkRetimeForward( pNtk, fVerbose );
+        RetValue = Abc_NtkRetimeIncremental( pNtk, 1, 0, fVerbose );
         break;
     case 2: // backward 
-        RetValue = Abc_NtkRetimeBackward( pNtk, fVerbose );
+        RetValue = Abc_NtkRetimeIncremental( pNtk, 0, 0, fVerbose );
         break;
     case 3: // min-area 
-        RetValue = Abc_NtkRetimeMinArea( pNtk, fVerbose );
+        RetValue = Abc_NtkRetimeMinArea( pNtk, fForwardOnly, fBackwardOnly, fVerbose );
         break;
     case 4: // min-delay
-        RetValue = Abc_NtkRetimeMinDelay( pNtk, fVerbose );
+        if ( !fBackwardOnly )
+            RetValue += Abc_NtkRetimeIncremental( pNtk, 1, 1, fVerbose );
+        if ( !fForwardOnly )
+            RetValue += Abc_NtkRetimeIncremental( pNtk, 0, 1, fVerbose );
         break;
     case 5: // min-area + min-delay
-        RetValue  = Abc_NtkRetimeMinArea( pNtk, fVerbose );
-        RetValue += Abc_NtkRetimeMinDelay( pNtk, fVerbose );
+        RetValue  = Abc_NtkRetimeMinArea( pNtk, fForwardOnly, fBackwardOnly, fVerbose );
+        if ( !fBackwardOnly )
+            RetValue += Abc_NtkRetimeIncremental( pNtk, 1, 1, fVerbose );
+        if ( !fForwardOnly )
+            RetValue += Abc_NtkRetimeIncremental( pNtk, 0, 1, fVerbose );
         break;
     default:
         printf( "Unknown retiming option.\n" );
         break;
     }
+    if ( fVerbose )
+    {
+        printf( "Reduction in area = %3d. Reduction in delay = %3d. ", 
+            nLatches - Abc_NtkLatchNum(pNtk), nLevels - Abc_NtkGetLevelNum(pNtk) );
+        PRT( "Total runtime", clock() - clkTotal );
+    }
+    timeRetime = clock() - clkTotal;
     return RetValue;
 }
 
+/**Function*************************************************************
+
+  Synopsis    [Used for automated debugging.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Abc_NtkRetimeDebug( Abc_Ntk_t * pNtk )
+{
+    extern int Abc_NtkSecFraig( Abc_Ntk_t * pNtk1, Abc_Ntk_t * pNtk2, int nSeconds, int nFrames, int fVerbose );
+    Abc_Ntk_t * pNtkRet;
+    assert( Abc_NtkIsLogic(pNtk) );
+    Abc_NtkLogicToSop( pNtk, 0 );
+    pNtkRet = Abc_NtkDup( pNtk );
+    Abc_NtkRetime( pNtkRet, 3, 0, 1, 0 );
+    return !Abc_NtkSecFraig( pNtk, pNtkRet, 10000, 3, 0 );
+}
+
 ////////////////////////////////////////////////////////////////////////
 ///                       END OF FILE                                ///
 ////////////////////////////////////////////////////////////////////////
diff --git a/src/opt/ret/retDelay.c b/src/opt/ret/retDelay.c
index b7ccc570..d2d87447 100644
--- a/src/opt/ret/retDelay.c
+++ b/src/opt/ret/retDelay.c
@@ -24,30 +24,44 @@
 ///                        DECLARATIONS                              ///
 ////////////////////////////////////////////////////////////////////////
 
+static int Abc_NtkRetimeMinDelayTry( Abc_Ntk_t * pNtk, int fForward, int fInitial, int nIterLimit, int * pIterBest, int fVerbose );
+static int Abc_NtkRetimeTiming( Abc_Ntk_t * pNtk, int fForward, Vec_Ptr_t * vCritical );
+static int Abc_NtkRetimeTiming_rec( Abc_Obj_t * pObj, int fForward );
+
 ////////////////////////////////////////////////////////////////////////
 ///                     FUNCTION DEFINITIONS                         ///
 ////////////////////////////////////////////////////////////////////////
 
 /**Function*************************************************************
 
-  Synopsis    []
+  Synopsis    [Retimes incrementally for minimum delay.]
 
-  Description []
+  Description [This procedure cannot be called in the application code
+  because it assumes that the network is preprocessed by removing LIs/LOs.]
                
   SideEffects []
 
   SeeAlso     []
 
 ***********************************************************************/
-int Abc_NtkRetimeMinDelay( Abc_Ntk_t * pNtk, int fVerbose )
+int Abc_NtkRetimeMinDelay( Abc_Ntk_t * pNtk, Abc_Ntk_t * pNtkCopy, int nIterLimit, int fForward, int fVerbose )
 {
-    printf( "Not implemented.\n" );
-    return 0;
+    int IterBest, DelayBest;
+    int IterBest2, DelayBest2;
+    // try to find the best delay iteration on a copy
+    DelayBest = Abc_NtkRetimeMinDelayTry( pNtkCopy, fForward, 0, nIterLimit, &IterBest, fVerbose );
+    if ( IterBest == 0 )
+        return 1;
+    // perform the given number of iterations on the original network
+    DelayBest2 = Abc_NtkRetimeMinDelayTry( pNtk, fForward, 1, IterBest, &IterBest2, fVerbose );
+    assert( DelayBest == DelayBest2 );
+    assert( IterBest == IterBest2 );
+    return 1;
 }
 
 /**Function*************************************************************
 
-  Synopsis    []
+  Synopsis    [Returns the best delay and the number of best iteration.]
 
   Description []
                
@@ -56,7 +70,217 @@ int Abc_NtkRetimeMinDelay( Abc_Ntk_t * pNtk, int fVerbose )
   SeeAlso     []
 
 ***********************************************************************/
+int Abc_NtkRetimeMinDelayTry( Abc_Ntk_t * pNtk, int fForward, int fInitial, int nIterLimit, int * pIterBest, int fVerbose )
+{
+    Abc_Ntk_t * pNtkNew = NULL;
+    Vec_Ptr_t * vCritical;
+    Vec_Int_t * vValues;
+    Abc_Obj_t * pObj;
+    int i, k, IterBest, DelayCur, DelayBest, DelayStart;
+    // transfer intitial values
+    if ( fInitial )
+    {
+        if ( fForward )
+            Abc_NtkRetimeTranferToCopy( pNtk );
+        else
+        {
+            // save initial value of the latches
+            vValues = Abc_NtkRetimeCollectLatchValues( pNtk );
+            // start the network for initial value computation
+            pNtkNew = Abc_NtkRetimeBackwardInitialStart( pNtk );
+        }
+    }
+    // find the best iteration
+    DelayBest = ABC_INFINITY; IterBest = 0;
+    vCritical = Vec_PtrAlloc( 100 );
+    for ( i = 0; ; i++ )
+    {
+        // perform moves for the timing-critical nodes
+        DelayCur = Abc_NtkRetimeTiming( pNtk, fForward, vCritical );
+        if ( i == 0 )
+            DelayStart = DelayCur;
+        // record this position if it has the best delay
+        if ( DelayBest > DelayCur )
+        {
+            DelayBest = DelayCur;
+            IterBest = i;
+        }
+        // quit after timing analysis
+        if ( i == nIterLimit )
+            break;
+        // try retiming to improve the delay
+        Vec_PtrForEachEntry( vCritical, pObj, k )
+            if ( Abc_NtkRetimeNodeIsEnabled(pObj, fForward) )
+                Abc_NtkRetimeNode( pObj, fForward, fInitial );
+    }
+    Vec_PtrFree( vCritical );
+    // transfer the initial state back to the latches
+    if ( fInitial )
+    {
+        if ( fForward )
+            Abc_NtkRetimeTranferFromCopy( pNtk );
+        else
+        {
+            Abc_NtkRetimeBackwardInitialFinish( pNtk, pNtkNew, vValues, fVerbose );
+            Abc_NtkDelete( pNtkNew );
+            Vec_IntFree( vValues );
+        }
+    }
+    if ( !fInitial && fVerbose )
+        printf( "%s : Starting delay = %3d.  Final delay = %3d.  IterBest = %2d (out of %2d).\n", 
+            fForward? "Forward " : "Backward", DelayStart, DelayBest, IterBest, nIterLimit );
+    *pIterBest = IterBest;
+    return DelayBest;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Returns the set of timing-critical nodes.]
 
+  Description [Performs static timing analysis on the network. Uses 
+  unit-delay model.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Abc_NtkRetimeTiming( Abc_Ntk_t * pNtk, int fForward, Vec_Ptr_t * vCritical )
+{
+    Vec_Ptr_t * vLatches;
+    Abc_Obj_t * pObj, * pNext;
+    int i, k, LevelCur, LevelMax = 0;
+    // mark all objects except nodes
+    Abc_NtkIncrementTravId(pNtk);
+    vLatches = Vec_PtrAlloc( Abc_NtkLatchNum(pNtk) );
+    Abc_NtkForEachObj( pNtk, pObj, i )
+    {
+        if ( Abc_ObjIsLatch(pObj) )
+            Vec_PtrPush( vLatches, pObj );
+        if ( Abc_ObjIsNode(pObj) )
+            continue;
+        pObj->Level = 0;
+        Abc_NodeSetTravIdCurrent( pObj );
+    }
+    // perform analysis from CIs/COs
+    if ( fForward )
+    {
+        Vec_PtrForEachEntry( vLatches, pObj, i )
+        {
+            Abc_ObjForEachFanout( pObj, pNext, k )
+            {
+                LevelCur = Abc_NtkRetimeTiming_rec( pNext, fForward );
+                if ( LevelMax < LevelCur )
+                    LevelMax = LevelCur;
+            }
+        }
+        Abc_NtkForEachPi( pNtk, pObj, i )
+        {
+            Abc_ObjForEachFanout( pObj, pNext, k )
+            {
+                LevelCur = Abc_NtkRetimeTiming_rec( pNext, fForward );
+                if ( LevelMax < LevelCur )
+                    LevelMax = LevelCur;
+            }
+        }
+    }
+    else
+    {
+        Vec_PtrForEachEntry( vLatches, pObj, i )
+        {
+            LevelCur = Abc_NtkRetimeTiming_rec( Abc_ObjFanin0(pObj), fForward );
+            if ( LevelMax < LevelCur )
+                LevelMax = LevelCur;
+        }
+        Abc_NtkForEachPo( pNtk, pObj, i )
+        {
+            LevelCur = Abc_NtkRetimeTiming_rec( Abc_ObjFanin0(pObj), fForward );
+            if ( LevelMax < LevelCur )
+                LevelMax = LevelCur;
+        }
+    }
+    // collect timing critical nodes, which should be retimed forward/backward
+    Vec_PtrClear( vCritical );
+    Abc_NtkIncrementTravId(pNtk);
+    if ( fForward )
+    {
+        Vec_PtrForEachEntry( vLatches, pObj, i )
+        {
+            Abc_ObjForEachFanout( pObj, pNext, k )
+            {
+                if ( Abc_NodeIsTravIdCurrent(pNext) )
+                    continue;
+                if ( LevelMax != (int)pNext->Level )
+                    continue;
+                // new critical node
+                Vec_PtrPush( vCritical, pNext );
+                Abc_NodeSetTravIdCurrent( pNext );
+            }
+        }
+    }
+    else
+    {
+        Vec_PtrForEachEntry( vLatches, pObj, i )
+        {
+            Abc_ObjForEachFanin( pObj, pNext, k )
+            {
+                if ( Abc_NodeIsTravIdCurrent(pNext) )
+                    continue;
+                if ( LevelMax != (int)pNext->Level )
+                    continue;
+                // new critical node
+                Vec_PtrPush( vCritical, pNext );
+                Abc_NodeSetTravIdCurrent( pNext );
+            }
+        }
+    }
+    Vec_PtrFree( vLatches );
+    return LevelMax;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Recursively performs timing analysis.]
+
+  Description [Performs static timing analysis on the network. Uses 
+  unit-delay model.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Abc_NtkRetimeTiming_rec( Abc_Obj_t * pObj, int fForward )
+{
+    Abc_Obj_t * pNext;
+    int i, LevelCur, LevelMax = 0;
+    // skip visited nodes
+    if ( Abc_NodeIsTravIdCurrent(pObj) )
+        return pObj->Level;
+    Abc_NodeSetTravIdCurrent(pObj);
+    // visit the next nodes
+    if ( fForward )
+    {
+        Abc_ObjForEachFanout( pObj, pNext, i )
+        {
+            LevelCur = Abc_NtkRetimeTiming_rec( pNext, fForward );
+            if ( LevelMax < LevelCur )
+                LevelMax = LevelCur;
+        }
+    }
+    else
+    {
+        Abc_ObjForEachFanin( pObj, pNext, i )
+        {
+            LevelCur = Abc_NtkRetimeTiming_rec( pNext, fForward );
+            if ( LevelMax < LevelCur )
+                LevelMax = LevelCur;
+        }
+    }
+//    printf( "Node %3d -> Level %3d.\n", pObj->Id, LevelMax + 1 );
+    pObj->Level = LevelMax + 1;
+    return pObj->Level;
+}
 
 ////////////////////////////////////////////////////////////////////////
 ///                       END OF FILE                                ///
diff --git a/src/opt/ret/retFlow.c b/src/opt/ret/retFlow.c
index 9b8393f3..642a1f69 100644
--- a/src/opt/ret/retFlow.c
+++ b/src/opt/ret/retFlow.c
@@ -126,9 +126,12 @@ Vec_Ptr_t * Abc_NtkMaxFlow( Abc_Ntk_t * pNtk, int fForward, int fVerbose )
         printf( "Abc_NtkMaxFlow() error! The computed min-cut is not a cut!\n" );
 
     // report the results
+    if ( fVerbose )
+    {
     printf( "Latches = %6d. %s max-flow = %6d.  Min-cut = %6d.  ", 
         Abc_NtkLatchNum(pNtk), fForward? "Forward " : "Backward", Flow, Vec_PtrSize(vMinCut) );
 PRT( "Time", clock() - clk );
+    }
 
 //    Abc_NtkMaxFlowPrintCut( vMinCut );
     return vMinCut;
@@ -377,6 +380,15 @@ int Abc_NtkMaxFlowVerifyCut( Abc_Ntk_t * pNtk, Vec_Ptr_t * vMinCut, int fForward
                 return 0;
         }
     }
+/*
+    {
+        // count the volume of the cut
+        int Counter = 0;
+        Abc_NtkForEachObj( pNtk, pObj, i )
+            Counter += Abc_NodeIsTravIdCurrent( pObj );
+        printf( "Volume = %d.\n", Counter );
+    }
+*/
     return 1;
 }
 
diff --git a/src/opt/ret/retFwd.c b/src/opt/ret/retFwd.c
deleted file mode 100644
index c33abc30..00000000
--- a/src/opt/ret/retFwd.c
+++ /dev/null
@@ -1,65 +0,0 @@
-/**CFile****************************************************************
-
-  FileName    [retFwd.c]
-
-  SystemName  [ABC: Logic synthesis and verification system.]
-
-  PackageName [Retiming package.]
-
-  Synopsis    [Most forward retiming.]
-
-  Author      [Alan Mishchenko]
-  
-  Affiliation [UC Berkeley]
-
-  Date        [Ver. 1.0. Started - Oct 31, 2006.]
-
-  Revision    [$Id: retFwd.c,v 1.00 2006/10/31 00:00:00 alanmi Exp $]
-
-***********************************************************************/
-
-#include "retInt.h"
-
-////////////////////////////////////////////////////////////////////////
-///                        DECLARATIONS                              ///
-////////////////////////////////////////////////////////////////////////
-
-////////////////////////////////////////////////////////////////////////
-///                     FUNCTION DEFINITIONS                         ///
-////////////////////////////////////////////////////////////////////////
-
-/**Function*************************************************************
-
-  Synopsis    []
-
-  Description []
-               
-  SideEffects []
-
-  SeeAlso     []
-
-***********************************************************************/
-int Abc_NtkRetimeForward( Abc_Ntk_t * pNtk, int fVerbose )
-{
-    printf( "Not implemented.\n" );
-    return 0;
-}
-
-/**Function*************************************************************
-
-  Synopsis    []
-
-  Description []
-               
-  SideEffects []
-
-  SeeAlso     []
-
-***********************************************************************/
-
-
-////////////////////////////////////////////////////////////////////////
-///                       END OF FILE                                ///
-////////////////////////////////////////////////////////////////////////
-
-
diff --git a/src/opt/ret/retIncrem.c b/src/opt/ret/retIncrem.c
new file mode 100644
index 00000000..d2ad6a72
--- /dev/null
+++ b/src/opt/ret/retIncrem.c
@@ -0,0 +1,460 @@
+/**CFile****************************************************************
+
+  FileName    [retIncrem.c]
+
+  SystemName  [ABC: Logic synthesis and verification system.]
+
+  PackageName [Retiming package.]
+
+  Synopsis    [Incremental retiming in one direction.]
+
+  Author      [Alan Mishchenko]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - Oct 31, 2006.]
+
+  Revision    [$Id: retIncrem.c,v 1.00 2006/10/31 00:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include "retInt.h"
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+static st_table * Abc_NtkRetimePrepareLatches( Abc_Ntk_t * pNtk );
+static int Abc_NtkRetimeFinalizeLatches( Abc_Ntk_t * pNtk, st_table * tLatches, int nIdMaxStart );
+static int Abc_NtkRetimeOneWay( Abc_Ntk_t * pNtk, int fForward, int fVerbose );
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Performs retiming in one direction.]
+
+  Description [Currently does not retime over black boxes.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Abc_NtkRetimeIncremental( Abc_Ntk_t * pNtk, int fForward, int fMinDelay, int fVerbose )
+{
+    Abc_Ntk_t * pNtkCopy = NULL;
+    Vec_Ptr_t * vBoxes;
+    st_table * tLatches;
+    int nLatches = Abc_NtkLatchNum(pNtk);
+    int nIdMaxStart = Abc_NtkObjNumMax(pNtk);
+    int RetValue, nIterLimit;
+    if ( Abc_NtkNodeNum(pNtk) == 0 )
+        return 0;
+    // reorder CI/CO/latch inputs
+    Abc_NtkOrderCisCos( pNtk );
+    if ( fMinDelay ) 
+    {
+        nIterLimit = 2 * Abc_NtkGetLevelNum(pNtk);
+        pNtkCopy = Abc_NtkDup( pNtk );
+        tLatches = Abc_NtkRetimePrepareLatches( pNtkCopy );
+        st_free_table( tLatches );
+    }
+    // collect latches and remove CIs/COs
+    tLatches = Abc_NtkRetimePrepareLatches( pNtk );
+    // save boxes
+    vBoxes = pNtk->vBoxes;  pNtk->vBoxes = NULL;
+    // perform the retiming
+    if ( fMinDelay )
+        Abc_NtkRetimeMinDelay( pNtk, pNtkCopy, nIterLimit, fForward, fVerbose );
+    else
+        Abc_NtkRetimeOneWay( pNtk, fForward, fVerbose );
+    if ( fMinDelay ) 
+        Abc_NtkDelete( pNtkCopy );
+    // share the latches
+    Abc_NtkRetimeShareLatches( pNtk );    
+    // restore boxes
+    pNtk->vBoxes = vBoxes;
+    // finalize the latches
+    RetValue = Abc_NtkRetimeFinalizeLatches( pNtk, tLatches, nIdMaxStart );
+    st_free_table( tLatches );
+    if ( RetValue == 0 )
+        return 0;
+    // fix the COs
+    Abc_NtkLogicMakeSimpleCos( pNtk, 0 );
+    // check for correctness
+    if ( !Abc_NtkCheck( pNtk ) )
+        fprintf( stdout, "Abc_NtkRetimeForward(): Network check has failed.\n" );
+    // return the number of latches saved
+    return nLatches - Abc_NtkLatchNum(pNtk);
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Prepares the network for retiming.]
+
+  Description [Hash latches into their number in the original network.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+st_table * Abc_NtkRetimePrepareLatches( Abc_Ntk_t * pNtk )
+{
+    st_table * tLatches;
+    Abc_Obj_t * pLatch, * pLatchIn, * pLatchOut, * pFanin;
+    int i, nOffSet = Abc_NtkBoxNum(pNtk) - Abc_NtkLatchNum(pNtk);
+    // collect latches and remove CIs/COs
+    tLatches = st_init_table( st_ptrcmp, st_ptrhash );
+    Abc_NtkForEachLatch( pNtk, pLatch, i )
+    {
+        // map latch into its true number
+        st_insert( tLatches, (void *)pLatch, (void *)(i-nOffSet) );
+        // disconnect LI     
+        pLatchIn = Abc_ObjFanin0(pLatch);
+        pFanin = Abc_ObjFanin0(pLatchIn);
+        Abc_ObjTransferFanout( pLatchIn, pFanin );
+        Abc_ObjDeleteFanin( pLatchIn, pFanin );
+        // disconnect LO     
+        pLatchOut = Abc_ObjFanout0(pLatch);
+        pFanin = Abc_ObjFanin0(pLatchOut);
+        Abc_ObjTransferFanout( pLatchOut, pFanin );
+        Abc_ObjDeleteFanin( pLatchOut, pFanin );
+    }
+    return tLatches;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Finalizes the latches after retiming.]
+
+  Description [Reuses the LIs/LOs for old latches.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Abc_NtkRetimeFinalizeLatches( Abc_Ntk_t * pNtk, st_table * tLatches, int nIdMaxStart )
+{
+    Vec_Ptr_t * vCisOld, * vCosOld, * vBoxesOld, * vCisNew, * vCosNew, * vBoxesNew;
+    Abc_Obj_t * pObj, * pLatch, * pLatchIn, * pLatchOut;
+    int i, Index;
+    // create new arrays
+    vCisOld   = pNtk->vCis;    pNtk->vCis   = NULL;  vCisNew   = Vec_PtrAlloc( 100 );
+    vCosOld   = pNtk->vCos;    pNtk->vCos   = NULL;  vCosNew   = Vec_PtrAlloc( 100 );  
+    vBoxesOld = pNtk->vBoxes;  pNtk->vBoxes = NULL;  vBoxesNew = Vec_PtrAlloc( 100 );
+    // copy boxes and their CIs/COs
+    Vec_PtrForEachEntryStop( vCisOld, pObj, i, Vec_PtrSize(vCisOld) - st_count(tLatches) )
+        Vec_PtrPush( vCisNew, pObj );
+    Vec_PtrForEachEntryStop( vCosOld, pObj, i, Vec_PtrSize(vCosOld) - st_count(tLatches) )
+        Vec_PtrPush( vCosNew, pObj );
+    Vec_PtrForEachEntryStop( vBoxesOld, pObj, i, Vec_PtrSize(vBoxesOld) - st_count(tLatches) )
+        Vec_PtrPush( vBoxesNew, pObj );
+    // go through the latches
+    Abc_NtkForEachObj( pNtk, pLatch, i )
+    {
+        if ( !Abc_ObjIsLatch(pLatch) )
+            continue;
+        if ( Abc_ObjId(pLatch) >= (unsigned)nIdMaxStart )
+        {
+            // this is a new latch 
+            pLatchIn  = Abc_NtkCreateBi(pNtk);
+            pLatchOut = Abc_NtkCreateBo(pNtk);
+            Abc_ObjAssignName( pLatchIn,  Abc_ObjName(pLatchIn), NULL );
+            Abc_ObjAssignName( pLatchOut, Abc_ObjName(pLatchOut), NULL );
+        }
+        else
+        {
+            // this is an old latch 
+            // get its number in the original order
+            if ( !st_lookup( tLatches, (char *)pLatch, (char **)&Index ) )
+            {
+                printf( "Abc_NtkRetimeFinalizeLatches(): Internal error.\n" );
+                return 0;
+            }
+            assert( pLatch == Vec_PtrEntry(vBoxesOld, Vec_PtrSize(vBoxesOld) - st_count(tLatches) + Index) );
+            // reconnect with the old LIs/LOs
+            pLatchIn  = Vec_PtrEntry( vCosOld, Vec_PtrSize(vCosOld) - st_count(tLatches) + Index );
+            pLatchOut = Vec_PtrEntry( vCisOld, Vec_PtrSize(vCisOld) - st_count(tLatches) + Index );
+        }
+        // connect
+        Abc_ObjAddFanin( pLatchIn, Abc_ObjFanin0(pLatch) );
+        Abc_ObjPatchFanin( pLatch, Abc_ObjFanin0(pLatch), pLatchIn );
+        Abc_ObjTransferFanout( pLatch, pLatchOut );
+        Abc_ObjAddFanin( pLatchOut, pLatch );
+        // add to the arrays
+        Vec_PtrPush( vCisNew, pLatchOut );
+        Vec_PtrPush( vCosNew, pLatchIn );
+        Vec_PtrPush( vBoxesNew, pLatch );
+    }
+    // free useless Cis/Cos
+    Vec_PtrForEachEntry( vCisOld, pObj, i )
+        if ( !Abc_ObjIsPi(pObj) && Abc_ObjFaninNum(pObj) == 0 && Abc_ObjFanoutNum(pObj) == 0 )
+            Abc_NtkDeleteObj(pObj);
+    Vec_PtrForEachEntry( vCosOld, pObj, i )
+        if ( !Abc_ObjIsPo(pObj) && Abc_ObjFaninNum(pObj) == 0 && Abc_ObjFanoutNum(pObj) == 0 )
+            Abc_NtkDeleteObj(pObj);
+    // set the new arrays
+    pNtk->vCis   = vCisNew;   Vec_PtrFree( vCisOld );
+    pNtk->vCos   = vCosNew;   Vec_PtrFree( vCosOld );
+    pNtk->vBoxes = vBoxesNew; Vec_PtrFree( vBoxesOld );
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Performs retiming one way, forward or backward.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Abc_NtkRetimeOneWay( Abc_Ntk_t * pNtk, int fForward, int fVerbose )
+{
+    Abc_Ntk_t * pNtkNew;
+    Vec_Int_t * vValues;
+    Abc_Obj_t * pObj;
+    int i, fChanges, nTotalMoves = 0, nTotalMovesLimit = 5000;
+    if ( fForward )
+        Abc_NtkRetimeTranferToCopy( pNtk );
+    else
+    {
+        // save initial values of the latches
+        vValues = Abc_NtkRetimeCollectLatchValues( pNtk );
+        // start the network for initial value computation
+        pNtkNew = Abc_NtkRetimeBackwardInitialStart( pNtk );
+    }
+    // try to move latches forward whenever possible
+    do {
+        fChanges = 0;
+        Abc_NtkForEachObj( pNtk, pObj, i )
+        {
+            if ( !Abc_ObjIsNode(pObj) )
+                continue;
+            if ( Abc_NtkRetimeNodeIsEnabled( pObj, fForward ) )
+            {
+                Abc_NtkRetimeNode( pObj, fForward, 1 );
+                fChanges = 1;
+                nTotalMoves++;
+                if ( nTotalMoves >= nTotalMovesLimit )
+                {
+                    printf( "Stopped after %d latch moves.\n", nTotalMoves );
+                    break;
+                }
+            }
+        }
+    } while ( fChanges && nTotalMoves < nTotalMovesLimit );
+    // transfer the initial state back to the latches
+    if ( fForward )
+        Abc_NtkRetimeTranferFromCopy( pNtk );
+    else
+    {
+        Abc_NtkRetimeBackwardInitialFinish( pNtk, pNtkNew, vValues, fVerbose );
+        Abc_NtkDelete( pNtkNew );
+        Vec_IntFree( vValues );
+    }
+    return 0;
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Returns 1 if retiming forward/backward is possible.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Abc_NtkRetimeNodeIsEnabled( Abc_Obj_t * pObj, int fForward )
+{
+    Abc_Obj_t * pNext;
+    int i;
+    assert( Abc_ObjIsNode(pObj) );
+    if ( fForward )
+    {
+        Abc_ObjForEachFanin( pObj, pNext, i )
+            if ( !Abc_ObjIsLatch(pNext) )
+                return 0;
+    }
+    else
+    {
+        Abc_ObjForEachFanout( pObj, pNext, i )
+            if ( !Abc_ObjIsLatch(pNext) )
+                return 0;
+    }
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Retimes the node backward or forward.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Abc_NtkRetimeNode( Abc_Obj_t * pObj, int fForward, int fInitial )
+{
+    Abc_Ntk_t * pNtkNew = NULL;
+    Vec_Ptr_t * vNodes;
+    Abc_Obj_t * pNext, * pLatch;
+    int i;
+    vNodes = Vec_PtrAlloc( 10 );
+    if ( fForward )
+    {
+        // compute the initial value
+        if ( fInitial )
+            pObj->pCopy = (void *)Abc_ObjSopSimulate( pObj );
+        // collect fanins
+        Abc_NodeCollectFanins( pObj, vNodes );
+        // make the node point to the fanins fanins
+        Vec_PtrForEachEntry( vNodes, pNext, i )
+        {
+            assert( Abc_ObjIsLatch(pNext) );
+            Abc_ObjPatchFanin( pObj, pNext, Abc_ObjFanin0(pNext) );
+            if ( Abc_ObjFanoutNum(pNext) == 0 )
+                Abc_NtkDeleteObj(pNext);            
+        }
+        // add a new latch on top
+        pNext = Abc_NtkCreateLatch(pObj->pNtk);
+        Abc_ObjTransferFanout( pObj, pNext );
+        Abc_ObjAddFanin( pNext, pObj );
+        // set the initial value
+        if ( fInitial )
+            pNext->pCopy = pObj->pCopy;
+    }
+    else
+    {
+        // compute the initial value
+        if ( fInitial )
+        {
+            pNtkNew = Abc_ObjFanout0(pObj)->pCopy->pNtk;
+            Abc_NtkDupObj( pNtkNew, pObj, 0 );
+            Abc_ObjForEachFanout( pObj, pNext, i )
+            {
+                assert( Abc_ObjFaninNum(pNext->pCopy) == 0 );
+                Abc_ObjAddFanin( pNext->pCopy, pObj->pCopy );
+            }
+        }
+        // collect fanouts
+        Abc_NodeCollectFanouts( pObj, vNodes );
+        // make the fanouts fanouts point to the node
+        Vec_PtrForEachEntry( vNodes, pNext, i )
+        {
+            assert( Abc_ObjIsLatch(pNext) );
+            Abc_ObjTransferFanout( pNext, pObj );
+            Abc_NtkDeleteObj( pNext );  
+        }
+        // add new latches to the fanins
+        Abc_ObjForEachFanin( pObj, pNext, i )
+        {
+            pLatch = Abc_NtkCreateLatch(pObj->pNtk);
+            Abc_ObjPatchFanin( pObj, pNext, pLatch );
+            Abc_ObjAddFanin( pLatch, pNext );
+            // create buffer isomorphic to this latch
+            if ( fInitial )
+            {
+                pLatch->pCopy = Abc_NtkCreateNodeBuf( pNtkNew, NULL );
+                Abc_ObjAddFanin( pObj->pCopy, pLatch->pCopy );
+            }
+        }
+    }
+    Vec_PtrFree( vNodes );
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Returns the number of compatible fanout latches.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Abc_NtkRetimeCheckCompatibleLatchFanouts( Abc_Obj_t * pObj )
+{
+    Abc_Obj_t * pFanout;
+    int i, nLatches = 0, Init = -1;
+    Abc_ObjForEachFanout( pObj, pFanout, i )
+    {
+        if ( !Abc_ObjIsLatch(pFanout) )
+            continue;
+        if ( Init == -1 )
+        {
+            Init = (int)pObj->pData;
+            nLatches++;
+        }
+        else if ( Init == (int)pObj->pData )
+            nLatches++;
+    }
+    return nLatches;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Retimes the node backward or forward.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Abc_NtkRetimeShareLatches( Abc_Ntk_t * pNtk )
+{
+    Vec_Ptr_t * vNodes;
+    Abc_Obj_t * pFanin, * pLatch, * pLatchTop, * pLatchCur;
+    int i, k;
+    vNodes = Vec_PtrAlloc( 10 );
+    // consider latch fanins
+    Abc_NtkForEachObj( pNtk, pLatch, i )
+    {
+        if ( !Abc_ObjIsLatch(pLatch) )
+            continue;
+        pFanin = Abc_ObjFanin0(pLatch);
+        if ( Abc_NtkRetimeCheckCompatibleLatchFanouts(pFanin) <= 1 )
+            continue;
+        // get the first latch
+        Abc_ObjForEachFanout( pFanin, pLatchTop, k )
+            if ( Abc_ObjIsLatch(pLatchTop) )
+                break;
+        assert( Abc_ObjIsLatch(pLatchTop) );
+        // redirect compatible fanout latches to the first latch
+        Abc_NodeCollectFanouts( pFanin, vNodes );
+        Vec_PtrForEachEntry( vNodes, pLatchCur, k )
+        {
+            if ( pLatchCur == pLatchTop )
+                continue;
+            if ( !Abc_ObjIsLatch(pLatchCur) )
+                continue;
+            if ( pLatchCur->pData != pLatchTop->pData )
+                continue;
+            // redirect the fanouts
+            Abc_ObjTransferFanout( pLatchCur, pLatchTop );
+            Abc_NtkDeleteObj(pLatchCur);
+        }
+    }
+    Vec_PtrFree( vNodes );
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
diff --git a/src/opt/ret/retInit.c b/src/opt/ret/retInit.c
index 169d5a63..3eb80da1 100644
--- a/src/opt/ret/retInit.c
+++ b/src/opt/ret/retInit.c
@@ -1,12 +1,12 @@
 /**CFile****************************************************************
 
-  FileName    [ret_.c]
+  FileName    [retInit.c]
 
   SystemName  [ABC: Logic synthesis and verification system.]
 
   PackageName [Retiming package.]
 
-  Synopsis    []
+  Synopsis    [Initial state computation for backward retiming.]
 
   Author      [Alan Mishchenko]
   
@@ -14,7 +14,7 @@
 
   Date        [Ver. 1.0. Started - Oct 31, 2006.]
 
-  Revision    [$Id: ret_.c,v 1.00 2006/10/31 00:00:00 alanmi Exp $]
+  Revision    [$Id: retInit.c,v 1.00 2006/10/31 00:00:00 alanmi Exp $]
 
 ***********************************************************************/
 
@@ -24,6 +24,8 @@
 ///                        DECLARATIONS                              ///
 ////////////////////////////////////////////////////////////////////////
 
+static int Abc_NtkRetimeVerifyModel( Abc_Ntk_t * pNtkCone, Vec_Int_t * vValues, int * pModel );
+
 ////////////////////////////////////////////////////////////////////////
 ///                     FUNCTION DEFINITIONS                         ///
 ////////////////////////////////////////////////////////////////////////
@@ -39,29 +41,306 @@
   SeeAlso     []
 
 ***********************************************************************/
-void Abc_NtkRetimeInitialValues( Abc_Ntk_t * pNtk, Abc_Ntk_t * pNtkMiter, int fVerbose )
+Vec_Int_t * Abc_NtkRetimeInitialValues( Abc_Ntk_t * pNtkCone, Vec_Int_t * vValues, int fVerbose )
 {
-    Abc_Obj_t * pLatch;
-    int * pModel, RetValue, clk, i;
+    Vec_Int_t * vSolution;
+    Abc_Ntk_t * pNtkMiter, * pNtkLogic;
+    int RetValue, clk;
+    if ( pNtkCone == NULL )
+        return Vec_IntDup( vValues );
+    // convert the target network to AIG
+    pNtkLogic = Abc_NtkDup( pNtkCone );
+    Abc_NtkLogicToAig( pNtkLogic );
+    // get the miter
+    pNtkMiter = Abc_NtkCreateTarget( pNtkLogic, pNtkLogic->vCos, vValues );
     if ( fVerbose )
-        printf( "The number of ANDs in the AIG = %5d.\n", Abc_NtkNodeNum(pNtkMiter) );
+        printf( "The miter for initial state computation has %d AIG nodes. ", Abc_NtkNodeNum(pNtkMiter) );
     // solve the miter
-clk = clock();
+    clk = clock();
     RetValue = Abc_NtkMiterSat( pNtkMiter, (sint64)500000, (sint64)50000000, 0, 0, NULL, NULL );
-if ( fVerbose && clock() - clk > 100 )
-{
-PRT( "SAT solving time", clock() - clk );
-}
+    if ( fVerbose ) 
+        { PRT( "SAT solving time", clock() - clk ); }
     // analyze the result
     if ( RetValue == 1 )
         printf( "Abc_NtkRetimeInitialValues(): The problem is unsatisfiable. DC latch values are used.\n" );
     else if ( RetValue == -1 )
         printf( "Abc_NtkRetimeInitialValues(): The SAT problem timed out. DC latch values are used.\n" );
+    else if ( !Abc_NtkRetimeVerifyModel( pNtkCone, vValues, pNtkMiter->pModel ) )
+        printf( "Abc_NtkRetimeInitialValues(): The computed counter-example is incorrect.\n" );
     // set the values of the latches
-    pModel = pNtkMiter->pModel;  pNtkMiter->pModel = NULL;
-    Abc_NtkForEachLatch( pNtk, pLatch, i )
-        pLatch->pData = (void *)(pModel? (pModel[i]? ABC_INIT_ONE : ABC_INIT_ZERO) : ABC_INIT_DC);
-    FREE( pModel );
+    vSolution = RetValue? NULL : Vec_IntAllocArray( pNtkMiter->pModel, Abc_NtkPiNum(pNtkLogic) );
+    pNtkMiter->pModel = NULL;
+    Abc_NtkDelete( pNtkMiter );
+    Abc_NtkDelete( pNtkLogic );
+    return vSolution;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Computes the results of simulating one node.]
+
+  Description [Assumes that fanins have pCopy set to the input values.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Abc_ObjSopSimulate( Abc_Obj_t * pObj )
+{
+    char * pCube, * pSop = pObj->pData;
+    int nVars, Value, v, ResOr, ResAnd, ResVar;
+    assert( pSop && !Abc_SopIsExorType(pSop) );
+    // simulate the SOP of the node
+    ResOr = 0;
+    nVars = Abc_SopGetVarNum(pSop);
+    Abc_SopForEachCube( pSop, nVars, pCube )
+    {
+        ResAnd = 1;
+        Abc_CubeForEachVar( pCube, Value, v )
+        {
+            if ( Value == '0' )
+                ResVar = 1 ^ ((int)Abc_ObjFanin(pObj, v)->pCopy);
+            else if ( Value == '1' )
+                ResVar = (int)Abc_ObjFanin(pObj, v)->pCopy;
+            else
+                continue;
+            ResAnd &= ResVar;
+        }
+        ResOr |= ResAnd;
+    }
+    // complement the result if necessary
+    if ( !Abc_SopGetPhase(pSop) )
+        ResOr ^= 1;
+    return ResOr;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Verifies the counter-example.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Abc_NtkRetimeVerifyModel( Abc_Ntk_t * pNtkCone, Vec_Int_t * vValues, int * pModel )
+{
+    Vec_Ptr_t * vNodes;
+    Abc_Obj_t * pObj;
+    int i, Counter = 0;
+    assert( Abc_NtkIsSopLogic(pNtkCone) );
+    // set the PIs
+    Abc_NtkForEachPi( pNtkCone, pObj, i )
+        pObj->pCopy = (void *)pModel[i];
+    // simulate the internal nodes
+    vNodes = Abc_NtkDfs( pNtkCone, 0 );
+    Vec_PtrForEachEntry( vNodes, pObj, i )
+        pObj->pCopy = (void *)Abc_ObjSopSimulate( pObj );
+    Vec_PtrFree( vNodes );
+    // compare the outputs
+    Abc_NtkForEachPo( pNtkCone, pObj, i )
+        pObj->pCopy = Abc_ObjFanin0(pObj)->pCopy;
+    Abc_NtkForEachPo( pNtkCone, pObj, i )
+        Counter += (Vec_IntEntry(vValues, i) != (int)pObj->pCopy);
+    if ( Counter > 0 )
+        printf( "%d outputs (out of %d) have a value mismatch.\n", Counter, Abc_NtkPoNum(pNtkCone) );
+    return 1;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Transfer latch initial values to pCopy.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Abc_NtkRetimeTranferToCopy( Abc_Ntk_t * pNtk )
+{
+    Abc_Obj_t * pObj;
+    int i;
+    Abc_NtkForEachObj( pNtk, pObj, i )
+        if ( Abc_ObjIsLatch(pObj) )
+            pObj->pCopy = (void *)Abc_LatchIsInit1(pObj);
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Transfer latch initial values from pCopy.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Abc_NtkRetimeTranferFromCopy( Abc_Ntk_t * pNtk )
+{
+    Abc_Obj_t * pObj;
+    int i;
+    Abc_NtkForEachObj( pNtk, pObj, i )
+        if ( Abc_ObjIsLatch(pObj) )
+            pObj->pData = (void *)(pObj->pCopy? ABC_INIT_ONE : ABC_INIT_ZERO);
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Transfer latch initial values to pCopy.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Vec_Int_t * Abc_NtkRetimeCollectLatchValues( Abc_Ntk_t * pNtk )
+{
+    Vec_Int_t * vValues;
+    Abc_Obj_t * pObj;
+    int i;
+    vValues = Vec_IntAlloc( Abc_NtkLatchNum(pNtk) );
+    Abc_NtkForEachObj( pNtk, pObj, i )
+        if ( Abc_ObjIsLatch(pObj) )
+            Vec_IntPush( vValues, Abc_LatchIsInit1(pObj) );
+    return vValues;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Transfer latch initial values from pCopy.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Abc_NtkRetimeInsertLatchValues( Abc_Ntk_t * pNtk, Vec_Int_t * vValues )
+{
+    Abc_Obj_t * pObj;
+    int i, Counter = 0;
+    Abc_NtkForEachObj( pNtk, pObj, i )
+        if ( Abc_ObjIsLatch(pObj) )
+            pObj->pCopy = (void *)Counter++;
+    Abc_NtkForEachObj( pNtk, pObj, i )
+        if ( Abc_ObjIsLatch(pObj) )
+            pObj->pData = (void *)(vValues? (Vec_IntEntry(vValues,(int)pObj->pCopy)? ABC_INIT_ONE : ABC_INIT_ZERO) : ABC_INIT_DC);
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Transfer latch initial values to pCopy.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Abc_Ntk_t * Abc_NtkRetimeBackwardInitialStart( Abc_Ntk_t * pNtk )
+{
+    Abc_Ntk_t * pNtkNew;
+    Abc_Obj_t * pObj;
+    int i;
+    // create the network used for the initial state computation
+    pNtkNew = Abc_NtkAlloc( ABC_NTK_LOGIC, ABC_FUNC_SOP, 1 );
+    // create POs corresponding to the initial values
+    Abc_NtkForEachObj( pNtk, pObj, i )
+        if ( Abc_ObjIsLatch(pObj) )
+            pObj->pCopy = Abc_NtkCreatePo(pNtkNew);
+    return pNtkNew;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Transfer latch initial values to pCopy.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Abc_NtkRetimeBackwardInitialFinish( Abc_Ntk_t * pNtk, Abc_Ntk_t * pNtkNew, Vec_Int_t * vValuesOld, int fVerbose )
+{
+    Vec_Int_t * vValuesNew;
+    Abc_Obj_t * pObj;
+    int i;
+    // create PIs corresponding to the initial values
+    Abc_NtkForEachObj( pNtk, pObj, i )
+        if ( Abc_ObjIsLatch(pObj) )
+            Abc_ObjAddFanin( pObj->pCopy, Abc_NtkCreatePi(pNtkNew) );
+    pObj = Abc_NtkPo(pNtkNew, 0);
+    // assign dummy node names
+    Abc_NtkAddDummyPiNames( pNtkNew );
+    Abc_NtkAddDummyPoNames( pNtkNew );
+    // check the network
+    if ( !Abc_NtkCheck( pNtkNew ) )
+        fprintf( stdout, "Abc_NtkRetimeBackwardInitialFinish(): Network check has failed.\n" );
+    // derive new initial values
+    vValuesNew = Abc_NtkRetimeInitialValues( pNtkNew, vValuesOld, fVerbose );
+    // insert new initial values
+    Abc_NtkRetimeInsertLatchValues( pNtk, vValuesNew );
+    if ( vValuesNew ) Vec_IntFree( vValuesNew );
+}
+
+
+/**Function*************************************************************
+
+  Synopsis    [Cycles the circuit to create a new initial state.]
+
+  Description [Simulates the circuit with random input for the given 
+  number of timeframes to get a better initial state.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Abc_NtkCycleInitStateSop( Abc_Ntk_t * pNtk, int nFrames, int fVerbose )
+{
+    Vec_Ptr_t * vNodes;
+    Abc_Obj_t * pObj;
+    int i, f;
+    assert( Abc_NtkIsSopLogic(pNtk) );
+    srand( 0x12341234 );
+    // initialize the values
+    Abc_NtkForEachPi( pNtk, pObj, i )
+        pObj->pCopy = (void *)(rand() & 1);
+    Abc_NtkForEachLatch( pNtk, pObj, i )
+        pObj->pCopy = (void *)Abc_LatchIsInit1(pObj);
+    // simulate for the given number of timeframes
+    vNodes = Abc_NtkDfs( pNtk, 0 );
+    for ( f = 0; f < nFrames; f++ )
+    {
+        // simulate internal nodes
+        Vec_PtrForEachEntry( vNodes, pObj, i )
+            pObj->pCopy = (void *)Abc_ObjSopSimulate( pObj );
+        // bring the results to the COs
+        Abc_NtkForEachCo( pNtk, pObj, i )
+            pObj->pCopy = Abc_ObjFanin0(pObj)->pCopy;
+        // assign PI values
+        Abc_NtkForEachPi( pNtk, pObj, i )
+            pObj->pCopy = (void *)(rand() & 1);
+        // transfer the latch values
+        Abc_NtkForEachLatch( pNtk, pObj, i )
+            Abc_ObjFanout0(pObj)->pCopy = Abc_ObjFanin0(pObj)->pCopy;
+    }
+    Vec_PtrFree( vNodes );
+    // set the final values
+    Abc_NtkForEachLatch( pNtk, pObj, i )
+        pObj->pData = (void *)(Abc_ObjFanout0(pObj)->pCopy ? ABC_INIT_ONE : ABC_INIT_ZERO);
 }
 
 ////////////////////////////////////////////////////////////////////////
diff --git a/src/opt/ret/retInt.h b/src/opt/ret/retInt.h
index 2cb465fa..9b3aa00a 100644
--- a/src/opt/ret/retInt.h
+++ b/src/opt/ret/retInt.h
@@ -44,20 +44,28 @@
 ////////////////////////////////////////////////////////////////////////
 
 /*=== retArea.c ========================================================*/
-extern int         Abc_NtkRetimeMinArea( Abc_Ntk_t * pNtk, int fVerbose );
-/*=== retBwd.c ========================================================*/
-extern int         Abc_NtkRetimeBackward( Abc_Ntk_t * pNtk, int fVerbose );
+extern int         Abc_NtkRetimeMinArea( Abc_Ntk_t * pNtk, int fForwardOnly, int fBackwardOnly, int fVerbose );
 /*=== retCore.c ========================================================*/
-extern int         Abc_NtkRetime( Abc_Ntk_t * pNtk, int Mode, int fVerbose );
+extern int         Abc_NtkRetime( Abc_Ntk_t * pNtk, int Mode, int fForwardOnly, int fBackwardOnly, int fVerbose );
 /*=== retDelay.c ========================================================*/
-extern int         Abc_NtkRetimeMinDelay( Abc_Ntk_t * pNtk, int fVerbose );
+extern int         Abc_NtkRetimeMinDelay( Abc_Ntk_t * pNtk, Abc_Ntk_t * pNtkCopy, int nIterLimit, int fForward, int fVerbose );
+/*=== retDirect.c ========================================================*/
+extern int         Abc_NtkRetimeIncremental( Abc_Ntk_t * pNtk, int fForward, int fMinDelay, int fVerbose );
+extern void        Abc_NtkRetimeShareLatches( Abc_Ntk_t * pNtk );
+extern int         Abc_NtkRetimeNodeIsEnabled( Abc_Obj_t * pObj, int fForward );
+extern void        Abc_NtkRetimeNode( Abc_Obj_t * pObj, int fForward, int fInitial );
 /*=== retFlow.c ========================================================*/
 extern void        Abc_NtkMaxFlowTest( Abc_Ntk_t * pNtk );
 extern Vec_Ptr_t * Abc_NtkMaxFlow( Abc_Ntk_t * pNtk, int fForward, int fVerbose );
-/*=== retFwd.c ========================================================*/
-extern int         Abc_NtkRetimeForward( Abc_Ntk_t * pNtk, int fVerbose );
 /*=== retInit.c ========================================================*/
-extern void        Abc_NtkRetimeInitialValues( Abc_Ntk_t * pNtk, Abc_Ntk_t * pNtkMiter, int fVerbose );
+extern Vec_Int_t * Abc_NtkRetimeInitialValues( Abc_Ntk_t * pNtkSat, Vec_Int_t * vValues, int fVerbose );
+extern int         Abc_ObjSopSimulate( Abc_Obj_t * pObj );
+extern void        Abc_NtkRetimeTranferToCopy( Abc_Ntk_t * pNtk );
+extern void        Abc_NtkRetimeTranferFromCopy( Abc_Ntk_t * pNtk );
+extern Vec_Int_t * Abc_NtkRetimeCollectLatchValues( Abc_Ntk_t * pNtk );
+extern void        Abc_NtkRetimeInsertLatchValues( Abc_Ntk_t * pNtk, Vec_Int_t * vValues );
+extern Abc_Ntk_t * Abc_NtkRetimeBackwardInitialStart( Abc_Ntk_t * pNtk );
+extern void        Abc_NtkRetimeBackwardInitialFinish( Abc_Ntk_t * pNtk, Abc_Ntk_t * pNtkNew, Vec_Int_t * vValuesOld, int fVerbose );
 
 #endif