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/**CFile****************************************************************
FileName [retLvalue.c]
SystemName [ABC: Logic synthesis and verification system.]
PackageName [Retiming package.]
Synopsis [Implementation of Pan's retiming algorithm.]
Author [Alan Mishchenko]
Affiliation [UC Berkeley]
Date [Ver. 1.0. Started - Oct 31, 2006.]
Revision [$Id: retLvalue.c,v 1.00 2006/10/31 00:00:00 alanmi Exp $]
***********************************************************************/
#include "retInt.h"
////////////////////////////////////////////////////////////////////////
/// DECLARATIONS ///
////////////////////////////////////////////////////////////////////////
// node status after updating its arrival time
enum { ABC_RET_UPDATE_FAIL, ABC_RET_UPDATE_NO, ABC_RET_UPDATE_YES };
// the internal procedures
static Vec_Int_t * Abc_NtkRetimeGetLags( Abc_Ntk_t * pNtk, int nIterLimit, int fVerbose );
static int Abc_NtkRetimeUsingLags( Abc_Ntk_t * pNtk, Vec_Int_t * vLags, int fVerbose );
static int Abc_NtkRetimeSearch_rec( Abc_Ntk_t * pNtk, Vec_Ptr_t * vNodes, int FiMin, int FiMax, int nMaxIters, int fVerbose );
static int Abc_NtkRetimeForPeriod( Abc_Ntk_t * pNtk, Vec_Ptr_t * vNodes, int Fi, int nMaxIters, int fVerbose );
static int Abc_NtkRetimeNodeUpdateLValue( Abc_Obj_t * pObj, int Fi );
static Vec_Ptr_t * Abc_NtkRetimeCollect( Abc_Ntk_t * pNtk );
static inline int Abc_NodeComputeLag( int LValue, int Fi ) { return (LValue + (1<<16)*Fi)/Fi - (1<<16) - (int)(LValue % Fi == 0); }
static inline int Abc_NodeGetLValue( Abc_Obj_t * pNode ) { return (int)pNode->pCopy; }
static inline void Abc_NodeSetLValue( Abc_Obj_t * pNode, int Value ) { pNode->pCopy = (void *)Value; }
////////////////////////////////////////////////////////////////////////
/// FUNCTION DEFINITIONS ///
////////////////////////////////////////////////////////////////////////
/**Function*************************************************************
Synopsis [Implements Pan's retiming algorithm.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Abc_NtkRetimeLValue( Abc_Ntk_t * pNtk, int nIterLimit, int fVerbose )
{
Vec_Int_t * vLags;
int nLatches = Abc_NtkLatchNum(pNtk);
assert( Abc_NtkIsLogic( pNtk ) );
// get the lags
vLags = Abc_NtkRetimeGetLags( pNtk, nIterLimit, fVerbose );
// compute the retiming
// Abc_NtkRetimeUsingLags( pNtk, vLags, fVerbose );
Vec_IntFree( vLags );
// fix the COs
// Abc_NtkLogicMakeSimpleCos( pNtk, 0 );
// check for correctness
if ( !Abc_NtkCheck( pNtk ) )
fprintf( stdout, "Abc_NtkRetimeLValue(): Network check has failed.\n" );
// return the number of latches saved
return nLatches - Abc_NtkLatchNum(pNtk);
}
/**Function*************************************************************
Synopsis [Computes the retiming lags.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
Vec_Int_t * Abc_NtkRetimeGetLags( Abc_Ntk_t * pNtk, int nIterLimit, int fVerbose )
{
Vec_Int_t * vLags;
Vec_Ptr_t * vNodes;
Abc_Obj_t * pNode;
int i, FiMax, FiBest, RetValue, clk, clkIter;
char NodeLag;
// get the upper bound on the clock period
FiMax = 10 + Abc_NtkLevel(pNtk);
// make sure this clock period is feasible
vNodes = Abc_NtkRetimeCollect(pNtk);
if ( !Abc_NtkRetimeForPeriod( pNtk, vNodes, FiMax, nIterLimit, fVerbose ) )
{
Vec_PtrFree( vNodes );
printf( "Abc_NtkRetimeGetLags() error: The upper bound on the clock period cannot be computed.\n" );
return Vec_IntStart( Abc_NtkObjNumMax(pNtk) + 1 );
}
// search for the optimal clock period between 0 and nLevelMax
clk = clock();
FiBest = Abc_NtkRetimeSearch_rec( pNtk, vNodes, 0, FiMax, nIterLimit, fVerbose );
clkIter = clock() - clk;
// recompute the best l-values
RetValue = Abc_NtkRetimeForPeriod( pNtk, vNodes, FiBest, nIterLimit, fVerbose );
assert( RetValue );
Vec_PtrFree( vNodes );
// fix the problem with non-converged delays
Abc_NtkForEachNode( pNtk, pNode, i )
if ( Abc_NodeGetLValue(pNode) < -ABC_INFINITY/2 )
Abc_NodeSetLValue( pNode, 0 );
// write the retiming lags
vLags = Vec_IntStart( Abc_NtkObjNumMax(pNtk) + 1 );
Abc_NtkForEachNode( pNtk, pNode, i )
{
NodeLag = Abc_NodeComputeLag( Abc_NodeGetLValue(pNode), FiBest );
Vec_IntWriteEntry( vLags, pNode->Id, NodeLag );
}
// print the result
// if ( fVerbose )
printf( "The best clock period is %3d. (Currently, network is not modified.)\n", FiBest );
/*
// print the statistic into a file
{
FILE * pTable;
pTable = fopen( "a/ret__stats.txt", "a+" );
fprintf( pTable, "%d ", FiBest );
fclose( pTable );
}
*/
/*
printf( "lvalues and lags : " );
Abc_NtkForEachNode( pNtk, pNode, i )
printf( "%d=%d(%d) ", pNode->Id, Abc_NodeGetLValue(pNode), Abc_NodeGetLag(pNode) );
printf( "\n" );
*/
/*
{
FILE * pTable;
pTable = fopen( "a/ret_stats_pan.txt", "a+" );
fprintf( pTable, "%s ", pNtk->pName );
fprintf( pTable, "%d ", FiBest );
fprintf( pTable, "\n" );
fclose( pTable );
}
*/
return vLags;
}
/**Function*************************************************************
Synopsis [Performs binary search for the optimal clock period.]
Description [Assumes that FiMin is infeasible while FiMax is feasible.]
SideEffects []
SeeAlso []
***********************************************************************/
int Abc_NtkRetimeSearch_rec( Abc_Ntk_t * pNtk, Vec_Ptr_t * vNodes, int FiMin, int FiMax, int nMaxIters, int fVerbose )
{
int Median;
assert( FiMin < FiMax );
if ( FiMin + 1 == FiMax )
return FiMax;
Median = FiMin + (FiMax - FiMin)/2;
if ( Abc_NtkRetimeForPeriod( pNtk, vNodes, Median, nMaxIters, fVerbose ) )
return Abc_NtkRetimeSearch_rec( pNtk, vNodes, FiMin, Median, nMaxIters, fVerbose ); // Median is feasible
else
return Abc_NtkRetimeSearch_rec( pNtk, vNodes, Median, FiMax, nMaxIters, fVerbose ); // Median is infeasible
}
/**Function*************************************************************
Synopsis [Returns 1 if retiming with this clock period is feasible.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Abc_NtkRetimeForPeriod( Abc_Ntk_t * pNtk, Vec_Ptr_t * vNodes, int Fi, int nMaxIters, int fVerbose )
{
Abc_Obj_t * pObj;
int i, c, fContained, fChange, RetValue, Counter;
char * pReason = "";
// set l-values of all nodes to be minus infinity, except PIs and constants
Abc_NtkForEachObj( pNtk, pObj, i )
if ( Abc_ObjFaninNum(pObj) == 0 )
Abc_NodeSetLValue( pObj, 0 );
else
Abc_NodeSetLValue( pObj, -ABC_INFINITY );
// update all values iteratively
Counter = 0;
fContained = 1;
fChange = 1;
for ( c = 0; fContained && fChange && c < nMaxIters; c++ )
{
// go through the nodes and detect change
fChange = 0;
Vec_PtrForEachEntry( vNodes, pObj, i )
{
RetValue = Abc_NtkRetimeNodeUpdateLValue( pObj, Fi );
if ( RetValue == ABC_RET_UPDATE_FAIL )
{
fContained = 0;
break;
}
if ( RetValue == ABC_RET_UPDATE_NO )
continue;
// updating happened
fChange = 1;
Counter++;
}
}
if ( c == nMaxIters )
{
fContained = 0;
pReason = "(timeout)";
}
else
c++;
// report the results
if ( fVerbose )
{
if ( !fContained )
printf( "Period = %3d. Iterations = %3d. Updates = %10d. Infeasible %s\n", Fi, c, Counter, pReason );
else
printf( "Period = %3d. Iterations = %3d. Updates = %10d. Feasible\n", Fi, c, Counter );
}
/*
// check if any AND gates have infinite delay
Counter = 0;
Abc_NtkForEachNode( pNtk, pObj, i )
Counter += (Abc_NodeGetLValue(pObj) < -ABC_INFINITY/2);
if ( Counter > 0 )
printf( "Warning: %d internal nodes have wrong l-values!\n", Counter );
*/
return fContained;
}
/**Function*************************************************************
Synopsis [Computes the l-value of the node.]
Description [The node can be internal or a PO.]
SideEffects []
SeeAlso []
***********************************************************************/
int Abc_NtkRetimeNodeUpdateLValue( Abc_Obj_t * pObj, int Fi )
{
Abc_Obj_t * pFanin;
int lValueNew, i;
// terminals
if ( Abc_ObjFaninNum(pObj) == 0 )
return ABC_RET_UPDATE_NO;
// primary outputs
if ( Abc_ObjIsPo(pObj) )
return (Abc_NodeGetLValue(Abc_ObjFanin0(pObj)) > Fi)? ABC_RET_UPDATE_FAIL : ABC_RET_UPDATE_NO;
// other types of objects
if ( Abc_ObjIsBi(pObj) || Abc_ObjIsBo(pObj) )
lValueNew = Abc_NodeGetLValue(Abc_ObjFanin0(pObj));
else if ( Abc_ObjIsLatch(pObj) )
lValueNew = Abc_NodeGetLValue(Abc_ObjFanin0(pObj)) - Fi;
else
{
assert( Abc_ObjIsNode(pObj) );
lValueNew = -ABC_INFINITY;
Abc_ObjForEachFanin( pObj, pFanin, i )
if ( lValueNew < Abc_NodeGetLValue(pFanin) )
lValueNew = Abc_NodeGetLValue(pFanin);
lValueNew++;
}
// check if it needs to be updated
if ( lValueNew <= Abc_NodeGetLValue(pObj) )
return ABC_RET_UPDATE_NO;
// update if needed
Abc_NodeSetLValue( pObj, lValueNew );
return ABC_RET_UPDATE_YES;
}
/**Function*************************************************************
Synopsis [Implements the retiming given as a set of retiming lags.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Abc_NtkRetimeUsingLags( Abc_Ntk_t * pNtk, Vec_Int_t * vLags, int fVerbose )
{
Abc_Obj_t * pObj;
int fChanges, fForward, nTotalMoves, Lag, Counter, i;
// iterate over the nodes
nTotalMoves = 0;
do {
fChanges = 0;
Abc_NtkForEachNode( pNtk, pObj, i )
{
Lag = Vec_IntEntry( vLags, pObj->Id );
if ( !Lag )
continue;
fForward = (Lag < 0);
if ( Abc_NtkRetimeNodeIsEnabled( pObj, fForward ) )
{
Abc_NtkRetimeNode( pObj, fForward, 0 );
fChanges = 1;
nTotalMoves++;
Vec_IntAddToEntry( vLags, pObj->Id, fForward? 1 : -1 );
}
}
} while ( fChanges );
if ( fVerbose )
printf( "Total latch moves = %d.\n", nTotalMoves );
// check if there are remaining lags
Counter = 0;
Abc_NtkForEachNode( pNtk, pObj, i )
Counter += (Vec_IntEntry( vLags, pObj->Id ) != 0);
if ( Counter )
printf( "Warning! The number of nodes with unrealized lag = %d.\n", Counter );
return 1;
}
/**Function*************************************************************
Synopsis [Collect objects in the topological order from the latch inputs.]
Description [If flag fOnlyMarked is set, collects only marked nodes.
Otherwise, collects only unmarked nodes.]
SideEffects []
SeeAlso []
***********************************************************************/
void Abc_NtkRetimeCollect_rec( Abc_Obj_t * pObj, int fOnlyMarked, Vec_Ptr_t * vNodes )
{
Abc_Obj_t * pFanin;
int i;
// skip collected nodes
if ( Abc_NodeIsTravIdCurrent(pObj) )
return;
Abc_NodeSetTravIdCurrent(pObj);
// collect recursively
if ( fOnlyMarked ^ pObj->fMarkA )
return;
// visit the fanins
Abc_ObjForEachFanin( pObj, pFanin, i )
Abc_NtkRetimeCollect_rec( pFanin, fOnlyMarked, vNodes );
// collect non-trivial objects
if ( Abc_ObjFaninNum(pObj) > 0 )
Vec_PtrPush( vNodes, pObj );
}
/**Function*************************************************************
Synopsis [Collect objects in the topological order using LIs as a cut.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
Vec_Ptr_t * Abc_NtkRetimeCollect( Abc_Ntk_t * pNtk )
{
Vec_Ptr_t * vNodes;
Abc_Obj_t * pObj, * pFanin;
int i, k;
vNodes = Vec_PtrAlloc( 100 );
// mark the latch inputs
Abc_NtkForEachLatch( pNtk, pObj, i )
Abc_ObjFanin0(pObj)->fMarkA = 1;
// collect nodes in the DFS order from the marked nodes
Abc_NtkIncrementTravId(pNtk);
Abc_NtkForEachPo( pNtk, pObj, i )
Abc_NtkRetimeCollect_rec( pObj, 0, vNodes );
Abc_NtkForEachLatch( pNtk, pObj, i )
Abc_ObjForEachFanin( Abc_ObjFanin0(pObj), pFanin, k )
Abc_NtkRetimeCollect_rec( pFanin, 0, vNodes );
// collect marked nodes
Abc_NtkIncrementTravId(pNtk);
Abc_NtkForEachLatch( pNtk, pObj, i )
Abc_NtkRetimeCollect_rec( Abc_ObjFanin0(pObj), 1, vNodes );
// clean the marks
Abc_NtkForEachLatch( pNtk, pObj, i )
Abc_ObjFanin0(pObj)->fMarkA = 0;
return vNodes;
}
////////////////////////////////////////////////////////////////////////
/// END OF FILE ///
////////////////////////////////////////////////////////////////////////
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