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/**CFile****************************************************************
FileName [nwkFlow.c]
SystemName [ABC: Logic synthesis and verification system.]
PackageName [Netlist representation.]
Synopsis [Max-flow/min-cut computation.]
Author [Alan Mishchenko]
Affiliation [UC Berkeley]
Date [Ver. 1.0. Started - June 20, 2005.]
Revision [$Id: nwkFlow.c,v 1.00 2005/06/20 00:00:00 alanmi Exp $]
***********************************************************************/
#include "nwk.h"
ABC_NAMESPACE_IMPL_START
/*
This code is based on the papers:
A. Hurst, A. Mishchenko, and R. Brayton, "Fast minimum-register retiming
via binary maximum-flow", Proc. FMCAD '07, pp. 181-187.
A. Hurst, A. Mishchenko, and R. Brayton, "Scalable min-area retiming
under simultaneous delay and initial state constraints". Proc. DAC'08.
*/
int DepthFwd, DepthBwd, DepthFwdMax, DepthBwdMax;
////////////////////////////////////////////////////////////////////////
/// DECLARATIONS ///
////////////////////////////////////////////////////////////////////////
// predecessors
static inline Nwk_Obj_t * Nwk_ObjPred( Nwk_Obj_t * pObj ) { return pObj->pCopy; }
static inline int Nwk_ObjSetPred( Nwk_Obj_t * pObj, Nwk_Obj_t * p ) { pObj->pCopy = p; return 1; }
// sink
static inline int Nwk_ObjIsSink( Nwk_Obj_t * pObj ) { return pObj->MarkA; }
static inline void Nwk_ObjSetSink( Nwk_Obj_t * pObj ) { pObj->MarkA = 1; }
// flow
static inline int Nwk_ObjHasFlow( Nwk_Obj_t * pObj ) { return pObj->MarkB; }
static inline void Nwk_ObjSetFlow( Nwk_Obj_t * pObj ) { pObj->MarkB = 1; }
static inline void Nwk_ObjClearFlow( Nwk_Obj_t * pObj ) { pObj->MarkB = 0; }
// representation of visited nodes
// pObj->TravId < pNtk->nTravIds-2 --- not visited
// pObj->TravId == pNtk->nTravIds-2 --- visited bot only
// pObj->TravId == pNtk->nTravIds-1 --- visited top only
// pObj->TravId == pNtk->nTravIds --- visited bot and top
static inline int Nwk_ObjVisitedBotOnly( Nwk_Obj_t * pObj )
{
return pObj->TravId == pObj->pMan->nTravIds - 2;
}
static inline int Nwk_ObjVisitedBot( Nwk_Obj_t * pObj )
{
return pObj->TravId == pObj->pMan->nTravIds - 2 || pObj->TravId == pObj->pMan->nTravIds;
}
static inline int Nwk_ObjVisitedTop( Nwk_Obj_t * pObj )
{
return pObj->TravId == pObj->pMan->nTravIds - 1 || pObj->TravId == pObj->pMan->nTravIds;
}
static inline void Nwk_ObjSetVisitedBot( Nwk_Obj_t * pObj )
{
if ( pObj->TravId < pObj->pMan->nTravIds - 2 )
pObj->TravId = pObj->pMan->nTravIds - 2;
else if ( pObj->TravId == pObj->pMan->nTravIds - 1 )
pObj->TravId = pObj->pMan->nTravIds;
else
assert( 0 );
}
static inline void Nwk_ObjSetVisitedTop( Nwk_Obj_t * pObj )
{
if ( pObj->TravId < pObj->pMan->nTravIds - 2 )
pObj->TravId = pObj->pMan->nTravIds - 1;
else if ( pObj->TravId == pObj->pMan->nTravIds - 2 )
pObj->TravId = pObj->pMan->nTravIds;
else
assert( 0 );
}
static inline Nwk_ManIncrementTravIdFlow( Nwk_Man_t * pMan )
{
Nwk_ManIncrementTravId( pMan );
Nwk_ManIncrementTravId( pMan );
Nwk_ManIncrementTravId( pMan );
}
static int Nwk_ManPushForwardTop_rec( Nwk_Obj_t * pObj, Nwk_Obj_t * pPred );
static int Nwk_ManPushForwardBot_rec( Nwk_Obj_t * pObj, Nwk_Obj_t * pPred );
static int Nwk_ManPushBackwardTop_rec( Nwk_Obj_t * pObj, Nwk_Obj_t * pPred );
static int Nwk_ManPushBackwardBot_rec( Nwk_Obj_t * pObj, Nwk_Obj_t * pPred );
////////////////////////////////////////////////////////////////////////
/// FUNCTION DEFINITIONS ///
////////////////////////////////////////////////////////////////////////
/**Function*************************************************************
Synopsis [Marks TFI of the node.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
void Nwk_ManMarkTfiCone_rec( Nwk_Obj_t * pObj )
{
Nwk_Obj_t * pNext;
int i;
if ( pObj->MarkA )
return;
pObj->MarkA = 1;
Nwk_ObjForEachFanin( pObj, pNext, i )
Nwk_ManMarkTfiCone_rec( pNext );
}
/**Function*************************************************************
Synopsis [Marks TFO of the node.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
void Nwk_ManMarkTfoCone_rec( Nwk_Obj_t * pObj )
{
Nwk_Obj_t * pNext;
int i;
if ( pObj->MarkA )
return;
pObj->MarkA = 1;
Nwk_ObjForEachFanout( pObj, pNext, i )
Nwk_ManMarkTfoCone_rec( pNext );
}
/**Function*************************************************************
Synopsis [Fast forward flow pushing.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Nwk_ManPushForwardFast_rec( Nwk_Obj_t * pObj, Nwk_Obj_t * pPred )
{
Nwk_Obj_t * pNext;
int i;
if ( Nwk_ObjIsTravIdCurrent( pObj ) )
return 0;
Nwk_ObjSetTravIdCurrent( pObj );
if ( Nwk_ObjHasFlow(pObj) )
return 0;
if ( Nwk_ObjIsSink(pObj) )
{
Nwk_ObjSetFlow(pObj);
return Nwk_ObjSetPred( pObj, pPred );
}
Nwk_ObjForEachFanout( pObj, pNext, i )
if ( Nwk_ManPushForwardFast_rec( pNext, pObj ) )
{
Nwk_ObjSetFlow(pObj);
return Nwk_ObjSetPred( pObj, pPred );
}
return 0;
}
/**Function*************************************************************
Synopsis [Fast backward flow pushing.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Nwk_ManPushBackwardFast_rec( Nwk_Obj_t * pObj, Nwk_Obj_t * pPred )
{
Nwk_Obj_t * pNext;
int i;
if ( Nwk_ObjIsTravIdCurrent( pObj ) )
return 0;
Nwk_ObjSetTravIdCurrent( pObj );
if ( Nwk_ObjHasFlow(pObj) )
return 0;
if ( Nwk_ObjIsSink(pObj) )
{
Nwk_ObjSetFlow(pObj);
return Nwk_ObjSetPred( pObj, pPred );
}
Nwk_ObjForEachFanin( pObj, pNext, i )
if ( Nwk_ManPushBackwardFast_rec( pNext, pObj ) )
{
Nwk_ObjSetFlow(pObj);
return Nwk_ObjSetPred( pObj, pPred );
}
return 0;
}
/**Function*************************************************************
Synopsis [Pushing the flow through the bottom part of the node.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Nwk_ManPushForwardBot_rec( Nwk_Obj_t * pObj, Nwk_Obj_t * pPred )
{
Nwk_Obj_t * pNext;
int i;
if ( Nwk_ObjVisitedBot(pObj) )
return 0;
Nwk_ObjSetVisitedBot(pObj);
DepthFwd++;
if ( DepthFwdMax < DepthFwd )
DepthFwdMax = DepthFwd;
// propagate through the internal edge
if ( Nwk_ObjHasFlow(pObj) )
{
if ( Nwk_ObjPred(pObj) )
if ( Nwk_ManPushForwardTop_rec( Nwk_ObjPred(pObj), Nwk_ObjPred(pObj) ) )
{
DepthFwd--;
return Nwk_ObjSetPred( pObj, pPred );
}
}
else if ( Nwk_ManPushForwardTop_rec(pObj, pObj) )
{
DepthFwd--;
Nwk_ObjSetFlow( pObj );
return Nwk_ObjSetPred( pObj, pPred );
}
// try to push through the fanins
Nwk_ObjForEachFanin( pObj, pNext, i )
if ( Nwk_ManPushForwardBot_rec( pNext, pPred ) )
{
DepthFwd--;
return 1;
}
DepthFwd--;
return 0;
}
/**Function*************************************************************
Synopsis [Pushing the flow through the top part of the node.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Nwk_ManPushForwardTop_rec( Nwk_Obj_t * pObj, Nwk_Obj_t * pPred )
{
Nwk_Obj_t * pNext;
int i;
if ( Nwk_ObjVisitedTop(pObj) )
return 0;
Nwk_ObjSetVisitedTop(pObj);
// check if this is the sink
if ( Nwk_ObjIsSink(pObj) )
return 1;
DepthFwd++;
if ( DepthFwdMax < DepthFwd )
DepthFwdMax = DepthFwd;
// try to push through the fanouts
Nwk_ObjForEachFanout( pObj, pNext, i )
if ( Nwk_ManPushForwardBot_rec( pNext, pPred ) )
{
DepthFwd--;
return 1;
}
// redirect the flow
if ( Nwk_ObjHasFlow(pObj) && !Nwk_ObjIsCi(pObj) )
if ( Nwk_ManPushForwardBot_rec( pObj, Nwk_ObjPred(pObj) ) )
{
DepthFwd--;
Nwk_ObjClearFlow( pObj );
return Nwk_ObjSetPred( pObj, NULL );
}
DepthFwd--;
return 0;
}
/**Function*************************************************************
Synopsis [Pushing the flow through the bottom part of the node.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Nwk_ManPushBackwardBot_rec( Nwk_Obj_t * pObj, Nwk_Obj_t * pPred )
{
if ( Nwk_ObjVisitedBot(pObj) )
return 0;
Nwk_ObjSetVisitedBot(pObj);
// propagate through the internal edge
if ( Nwk_ObjHasFlow(pObj) )
{
if ( Nwk_ObjPred(pObj) )
if ( Nwk_ManPushBackwardTop_rec( Nwk_ObjPred(pObj), Nwk_ObjPred(pObj) ) )
return Nwk_ObjSetPred( pObj, pPred );
}
else if ( Nwk_ManPushBackwardTop_rec(pObj, pObj) )
{
Nwk_ObjSetFlow( pObj );
return Nwk_ObjSetPred( pObj, pPred );
}
return 0;
}
/**Function*************************************************************
Synopsis [Pushing the flow through the top part of the node.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Nwk_ManPushBackwardTop_rec( Nwk_Obj_t * pObj, Nwk_Obj_t * pPred )
{
Nwk_Obj_t * pNext;
int i;
if ( Nwk_ObjVisitedTop(pObj) )
return 0;
Nwk_ObjSetVisitedTop(pObj);
// check if this is the sink
if ( Nwk_ObjIsSink(pObj) )
return 1;
// try to push through the fanins
Nwk_ObjForEachFanin( pObj, pNext, i )
if ( Nwk_ManPushBackwardBot_rec( pNext, pPred ) )
return 1;
// try to push through the fanouts
Nwk_ObjForEachFanout( pObj, pNext, i )
if ( !Nwk_ObjIsCo(pObj) && Nwk_ManPushBackwardTop_rec( pNext, pPred ) )
return 1;
// redirect the flow
if ( Nwk_ObjHasFlow(pObj) )
if ( Nwk_ObjPred(pObj) && Nwk_ManPushBackwardBot_rec( pObj, Nwk_ObjPred(pObj) ) )
{
Nwk_ObjClearFlow( pObj );
return Nwk_ObjSetPred( pObj, NULL );
}
return 0;
}
/**Function*************************************************************
Synopsis [Returns 0 if there is an unmarked path to a CI.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Nwk_ManVerifyCut_rec( Nwk_Obj_t * pObj )
{
Nwk_Obj_t * pNext;
int i;
if ( pObj->MarkA )
return 1;
if ( Nwk_ObjIsLo(pObj) )
return 0;
if ( Nwk_ObjIsTravIdCurrent( pObj ) )
return 1;
Nwk_ObjSetTravIdCurrent( pObj );
Nwk_ObjForEachFanin( pObj, pNext, i )
if ( !Nwk_ManVerifyCut_rec( pNext ) )
return 0;
return 1;
}
/**Function*************************************************************
Synopsis [Verifies the forward cut.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Nwk_ManRetimeVerifyCutForward( Nwk_Man_t * pMan, Vec_Ptr_t * vNodes )
{
Nwk_Obj_t * pObj;
int i;
// mark the nodes
Vec_PtrForEachEntry( Nwk_Obj_t *, vNodes, pObj, i )
{
assert( pObj->MarkA == 0 );
pObj->MarkA = 1;
}
// traverse from the COs
Nwk_ManIncrementTravId( pMan );
Nwk_ManForEachCo( pMan, pObj, i )
if ( !Nwk_ManVerifyCut_rec( pObj ) )
printf( "Nwk_ManRetimeVerifyCutForward(): Internal cut verification failed.\n" );
// unmark the nodes
Vec_PtrForEachEntry( Nwk_Obj_t *, vNodes, pObj, i )
pObj->MarkA = 0;
return 1;
}
/**Function*************************************************************
Synopsis [Verifies the forward cut.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Nwk_ManRetimeVerifyCutBackward( Nwk_Man_t * pMan, Vec_Ptr_t * vNodes )
{
return 1;
}
/**Function*************************************************************
Synopsis [Computes minimum cut for forward retiming.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
Vec_Ptr_t * Nwk_ManRetimeCutForward( Nwk_Man_t * pMan, int nLatches, int fVerbose )
{
Vec_Ptr_t * vNodes;
Nwk_Obj_t * pObj;
int i, RetValue, Counter = 0, Counter2 = 0;
clock_t clk = clock();
// set the sequential parameters
pMan->nLatches = nLatches;
pMan->nTruePis = Nwk_ManCiNum(pMan) - nLatches;
pMan->nTruePos = Nwk_ManCoNum(pMan) - nLatches;
// mark the COs and the TFO of PIs
Nwk_ManForEachCo( pMan, pObj, i )
pObj->MarkA = 1;
Nwk_ManForEachPiSeq( pMan, pObj, i )
Nwk_ManMarkTfoCone_rec( pObj );
// start flow computation from each LO
Nwk_ManIncrementTravIdFlow( pMan );
Nwk_ManForEachLoSeq( pMan, pObj, i )
{
if ( !Nwk_ManPushForwardFast_rec( pObj, NULL ) )
continue;
Nwk_ManIncrementTravIdFlow( pMan );
Counter++;
}
if ( fVerbose )
printf( "Forward: Max-flow = %4d -> ", Counter );
// continue flow computation from each LO
DepthFwdMax = DepthFwd = 0;
Nwk_ManIncrementTravIdFlow( pMan );
Nwk_ManForEachLoSeq( pMan, pObj, i )
{
printf( "%d ", DepthFwdMax );
if ( !Nwk_ManPushForwardBot_rec( pObj, NULL ) )
continue;
assert( DepthFwd == 0 );
Nwk_ManIncrementTravIdFlow( pMan );
Counter2++;
}
printf( "DepthMax = %d.\n", DepthFwdMax );
if ( fVerbose )
printf( "%4d. ", Counter+Counter2 );
// repeat flow computation from each LO
if ( Counter2 > 0 )
{
Nwk_ManIncrementTravIdFlow( pMan );
Nwk_ManForEachLoSeq( pMan, pObj, i )
{
RetValue = Nwk_ManPushForwardBot_rec( pObj, NULL );
assert( !RetValue );
}
}
// cut is a set of nodes whose bottom is visited but top is not visited
vNodes = Vec_PtrAlloc( Counter+Counter2 );
Counter = 0;
Nwk_ManForEachObj( pMan, pObj, i )
{
if ( Nwk_ObjVisitedBotOnly(pObj) )
{
assert( Nwk_ObjHasFlow(pObj) );
assert( !Nwk_ObjIsCo(pObj) );
Vec_PtrPush( vNodes, pObj );
Counter += Nwk_ObjIsCi(pObj);
}
}
Nwk_ManCleanMarks( pMan );
assert( Nwk_ManRetimeVerifyCutForward(pMan, vNodes) );
if ( fVerbose )
{
printf( "Min-cut = %4d. Unmoved = %4d. ", Vec_PtrSize(vNodes), Counter );
PRT( "Time", clock() - clk );
}
return vNodes;
}
/**Function*************************************************************
Synopsis [Computes minimum cut for backward retiming.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
Vec_Ptr_t * Nwk_ManRetimeCutBackward( Nwk_Man_t * pMan, int nLatches, int fVerbose )
{
Vec_Ptr_t * vNodes;
Nwk_Obj_t * pObj;
int i, RetValue, Counter = 0, Counter2 = 0;
clock_t clk = clock();
// set the sequential parameters
pMan->nLatches = nLatches;
pMan->nTruePis = Nwk_ManCiNum(pMan) - nLatches;
pMan->nTruePos = Nwk_ManCoNum(pMan) - nLatches;
// mark the CIs, the TFI of POs, and the constant nodes
Nwk_ManForEachCi( pMan, pObj, i )
pObj->MarkA = 1;
Nwk_ManForEachPoSeq( pMan, pObj, i )
Nwk_ManMarkTfiCone_rec( pObj );
Nwk_ManForEachNode( pMan, pObj, i )
if ( Nwk_ObjFaninNum(pObj) == 0 )
pObj->MarkA = 1;
// start flow computation from each LI driver
Nwk_ManIncrementTravIdFlow( pMan );
Nwk_ManForEachLiSeq( pMan, pObj, i )
{
if ( !Nwk_ManPushBackwardFast_rec( Nwk_ObjFanin0(pObj), NULL ) )
continue;
Nwk_ManIncrementTravIdFlow( pMan );
Counter++;
}
if ( fVerbose )
printf( "Backward: Max-flow = %4d -> ", Counter );
// continue flow computation from each LI driver
Nwk_ManIncrementTravIdFlow( pMan );
Nwk_ManForEachLiSeq( pMan, pObj, i )
{
if ( !Nwk_ManPushBackwardBot_rec( Nwk_ObjFanin0(pObj), NULL ) )
continue;
Nwk_ManIncrementTravIdFlow( pMan );
Counter2++;
}
if ( fVerbose )
printf( "%4d. ", Counter+Counter2 );
// repeat flow computation from each LI driver
if ( Counter2 > 0 )
{
Nwk_ManIncrementTravIdFlow( pMan );
Nwk_ManForEachLiSeq( pMan, pObj, i )
{
RetValue = Nwk_ManPushBackwardBot_rec( Nwk_ObjFanin0(pObj), NULL );
assert( !RetValue );
}
}
// cut is a set of nodes whose bottom is visited but top is not visited
vNodes = Vec_PtrAlloc( Counter+Counter2 );
Nwk_ManForEachObj( pMan, pObj, i )
{
if ( Nwk_ObjVisitedBotOnly(pObj) )
{
assert( Nwk_ObjHasFlow(pObj) );
assert( !Nwk_ObjIsCo(pObj) );
Vec_PtrPush( vNodes, pObj );
}
}
// count CO drivers
Counter = 0;
Nwk_ManForEachLiSeq( pMan, pObj, i )
if ( Nwk_ObjVisitedBotOnly( Nwk_ObjFanin0(pObj) ) )
Counter++;
Nwk_ManCleanMarks( pMan );
assert( Nwk_ManRetimeVerifyCutBackward(pMan, vNodes) );
if ( fVerbose )
{
printf( "Min-cut = %4d. Unmoved = %4d. ", Vec_PtrSize(vNodes), Counter );
PRT( "Time", clock() - clk );
}
return vNodes;
}
////////////////////////////////////////////////////////////////////////
/// END OF FILE ///
////////////////////////////////////////////////////////////////////////
ABC_NAMESPACE_IMPL_END
|
