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/**CFile****************************************************************
FileName [abcDfs.c]
SystemName [ABC: Logic synthesis and verification system.]
PackageName [Network and node package.]
Synopsis [Procedures that use depth-first search.]
Author [Alan Mishchenko]
Affiliation [UC Berkeley]
Date [Ver. 1.0. Started - June 20, 2005.]
Revision [$Id: abcDfs.c,v 1.00 2005/06/20 00:00:00 alanmi Exp $]
***********************************************************************/
#include "abc.h"
////////////////////////////////////////////////////////////////////////
/// DECLARATIONS ///
////////////////////////////////////////////////////////////////////////
static void Abc_NtkDfs_rec( Abc_Obj_t * pNode, Vec_Ptr_t * vNodes );
static void Abc_AigDfs_rec( Abc_Obj_t * pNode, Vec_Ptr_t * vNodes );
static int Abc_NtkGetLevelNum_rec( Abc_Obj_t * pNode );
static bool Abc_NtkIsAcyclic_rec( Abc_Obj_t * pNode );
////////////////////////////////////////////////////////////////////////
/// FUNCTION DEFITIONS ///
////////////////////////////////////////////////////////////////////////
/**Function*************************************************************
Synopsis [Returns the DFS ordered array of logic nodes.]
Description [Collects only the internal nodes, leaving out PIs, POs and latches.]
SideEffects []
SeeAlso []
***********************************************************************/
Vec_Ptr_t * Abc_NtkDfs( Abc_Ntk_t * pNtk )
{
Vec_Ptr_t * vNodes;
Abc_Obj_t * pNet, * pNode;
int i, fMadeComb;
// set the traversal ID
Abc_NtkIncrementTravId( pNtk );
// start the array of nodes
vNodes = Vec_PtrAlloc( 100 );
// go through the PO nodes and call for each of them
if ( Abc_NtkIsNetlist(pNtk) )
{
fMadeComb = Abc_NtkMakeComb( pNtk );
Abc_NtkForEachPo( pNtk, pNet, i )
{
if ( Abc_ObjIsCi(pNet) )
continue;
Abc_NtkDfs_rec( Abc_ObjFanin0(pNet), vNodes );
}
if ( fMadeComb ) Abc_NtkMakeSeq( pNtk );
}
else
{
Abc_NtkForEachCo( pNtk, pNode, i )
Abc_NtkDfs_rec( Abc_ObjFanin0(pNode), vNodes );
}
return vNodes;
}
/**Function*************************************************************
Synopsis [Performs DFS for one node.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
void Abc_NtkDfs_rec( Abc_Obj_t * pNode, Vec_Ptr_t * vNodes )
{
Abc_Obj_t * pFanin;
int i;
assert( !Abc_ObjIsComplement( pNode ) );
// skip the PI
if ( Abc_ObjIsPi(pNode) || Abc_ObjIsLatch(pNode) )
return;
assert( Abc_ObjIsNode( pNode ) );
// if this node is already visited, skip
if ( Abc_NodeIsTravIdCurrent( pNode ) )
return;
// mark the node as visited
Abc_NodeSetTravIdCurrent( pNode );
// visit the transitive fanin of the node
if ( Abc_NtkIsNetlist(pNode->pNtk) )
{
Abc_ObjForEachFanin( pNode, pFanin, i )
{
if ( Abc_ObjIsCi(pFanin) )
continue;
pFanin = Abc_ObjFanin0(pFanin);
Abc_NtkDfs_rec( pFanin, vNodes );
}
}
else
{
Abc_ObjForEachFanin( pNode, pFanin, i )
Abc_NtkDfs_rec( pFanin, vNodes );
}
// add the node after the fanins have been added
Vec_PtrPush( vNodes, pNode );
}
/**Function*************************************************************
Synopsis [Returns the DFS ordered array of logic nodes.]
Description [Collects only the internal nodes, leaving out PIs, POs and latches.]
SideEffects []
SeeAlso []
***********************************************************************/
Vec_Ptr_t * Abc_AigDfs( Abc_Ntk_t * pNtk )
{
Vec_Ptr_t * vNodes;
Abc_Obj_t * pNode;
int i;
assert( Abc_NtkIsAig(pNtk) );
// set the traversal ID
Abc_NtkIncrementTravId( pNtk );
// start the array of nodes
vNodes = Vec_PtrAlloc( 100 );
// go through the PO nodes and call for each of them
Abc_NtkForEachCo( pNtk, pNode, i )
Abc_AigDfs_rec( Abc_ObjFanin0(pNode), vNodes );
return vNodes;
}
/**Function*************************************************************
Synopsis [Performs DFS for one node.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
void Abc_AigDfs_rec( Abc_Obj_t * pNode, Vec_Ptr_t * vNodes )
{
Abc_Obj_t * pFanin;
int i;
assert( !Abc_ObjIsComplement( pNode ) );
// skip the PI
if ( Abc_ObjIsPi(pNode) || Abc_ObjIsLatch(pNode) )
return;
assert( Abc_ObjIsNode( pNode ) );
// if this node is already visited, skip
if ( Abc_NodeIsTravIdCurrent( pNode ) )
return;
// mark the node as visited
Abc_NodeSetTravIdCurrent( pNode );
// visit the transitive fanin of the node
Abc_ObjForEachFanin( pNode, pFanin, i )
Abc_AigDfs_rec( pFanin, vNodes );
// visit the equivalent nodes
if ( Abc_NodeIsChoice( pNode ) )
for ( pFanin = pNode->pData; pFanin; pFanin = pFanin->pData )
Abc_AigDfs_rec( pFanin, vNodes );
// add the node after the fanins have been added
Vec_PtrPush( vNodes, pNode );
}
/**Function*************************************************************
Synopsis [Computes the number of logic levels not counting PIs/POs.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Abc_NtkGetLevelNum( Abc_Ntk_t * pNtk )
{
Abc_Obj_t * pNet, * pNode, * pDriver;
unsigned LevelsMax;
int i, fMadeComb;
// set the traversal ID for this traversal
Abc_NtkIncrementTravId( pNtk );
// perform the traversal
LevelsMax = 0;
if ( Abc_NtkIsNetlist(pNtk) )
{
fMadeComb = Abc_NtkMakeComb( pNtk );
Abc_NtkForEachPo( pNtk, pNet, i )
{
if ( Abc_ObjIsCi(pNet) )
continue;
pDriver = Abc_ObjFanin0( pNet );
Abc_NtkGetLevelNum_rec( pDriver );
if ( LevelsMax < pDriver->Level )
LevelsMax = pDriver->Level;
}
if ( fMadeComb ) Abc_NtkMakeSeq( pNtk );
}
else
{
// Abc_NtkForEachCo( pNtk, pNode, i )
Abc_NtkForEachNode( pNtk, pNode, i )
{
// pDriver = Abc_ObjFanin0( pNode );
pDriver = pNode;
Abc_NtkGetLevelNum_rec( pDriver );
if ( LevelsMax < pDriver->Level )
LevelsMax = pDriver->Level;
}
}
return LevelsMax;
}
/**Function*************************************************************
Synopsis [Recursively counts the number of logic levels of one node.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Abc_NtkGetLevelNum_rec( Abc_Obj_t * pNode )
{
Abc_Obj_t * pFanin;
int i;
assert( !Abc_ObjIsComplement( pNode ) );
// skip the PI
if ( Abc_ObjIsPi(pNode) || Abc_ObjIsLatch(pNode) )
return 0;
assert( Abc_ObjIsNode( pNode ) );
// if this node is already visited, return
if ( Abc_NodeIsTravIdCurrent( pNode ) )
return pNode->Level;
// mark the node as visited
Abc_NodeSetTravIdCurrent( pNode );
// visit the transitive fanin
pNode->Level = 0;
if ( Abc_NtkIsNetlist(pNode->pNtk) )
{
Abc_ObjForEachFanin( pNode, pFanin, i )
{
if ( Abc_ObjIsCi(pFanin) )
continue;
pFanin = Abc_ObjFanin0(pFanin);
Abc_NtkGetLevelNum_rec( pFanin );
if ( pNode->Level < pFanin->Level )
pNode->Level = pFanin->Level;
}
}
else
{
Abc_ObjForEachFanin( pNode, pFanin, i )
{
Abc_NtkGetLevelNum_rec( pFanin );
if ( pNode->Level < pFanin->Level )
pNode->Level = pFanin->Level;
}
}
pNode->Level++;
return pNode->Level;
}
/**Function*************************************************************
Synopsis [Detects combinational loops.]
Description [This procedure is based on the idea suggested by Donald Chai.
As we traverse the network and visit the nodes, we need to distinquish
three types of nodes: (1) those that are visited for the first time,
(2) those that have been visited in this traversal but are currently not
on the traversal path, (3) those that have been visited and are currently
on the travesal path. When the node of type (3) is encountered, it means
that there is a combinational loop. To mark the three types of nodes,
two new values of the traversal IDs are used.]
SideEffects []
SeeAlso []
***********************************************************************/
bool Abc_NtkIsAcyclic( Abc_Ntk_t * pNtk )
{
Abc_Obj_t * pNet, * pNode;
int fAcyclic, fMadeComb, i;
// set the traversal ID for this DFS ordering
Abc_NtkIncrementTravId( pNtk );
Abc_NtkIncrementTravId( pNtk );
// pNode->TravId == pNet->nTravIds means "pNode is on the path"
// pNode->TravId == pNet->nTravIds - 1 means "pNode is visited but is not on the path"
// pNode->TravId < pNet->nTravIds - 1 means "pNode is not visited"
// traverse the network to detect cycles
fAcyclic = 1;
if ( Abc_NtkIsNetlist(pNtk) )
{
fMadeComb = Abc_NtkMakeComb( pNtk );
Abc_NtkForEachPo( pNtk, pNet, i )
{
if ( Abc_ObjIsCi(pNet) )
continue;
pNode = Abc_ObjFanin0( pNet );
if ( Abc_NodeIsTravIdPrevious(pNode) )
continue;
// traverse the output logic cone to detect the combinational loops
if ( (fAcyclic = Abc_NtkIsAcyclic_rec( pNode )) == 0 )
{ // stop as soon as the first loop is detected
fprintf( stdout, " (the output node)\n" );
break;
}
}
if ( fMadeComb ) Abc_NtkMakeSeq( pNtk );
}
else
{
Abc_NtkForEachCo( pNtk, pNode, i )
{
pNode = Abc_ObjFanin0( pNode );
if ( Abc_NodeIsTravIdPrevious(pNode) )
continue;
// traverse the output logic cone to detect the combinational loops
if ( (fAcyclic = Abc_NtkIsAcyclic_rec( pNode )) == 0 )
{ // stop as soon as the first loop is detected
fprintf( stdout, " (the output node)\n" );
break;
}
}
}
return fAcyclic;
}
/**Function*************************************************************
Synopsis [Recursively detects combinational loops.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
bool Abc_NtkIsAcyclic_rec( Abc_Obj_t * pNode )
{
Abc_Ntk_t * pNtk = pNode->pNtk;
Abc_Obj_t * pFanin;
int fAcyclic, i;
assert( !Abc_ObjIsComplement( pNode ) );
// skip the PI
if ( Abc_ObjIsPi(pNode) || Abc_ObjIsLatch(pNode) )
return 1;
assert( Abc_ObjIsNode( pNode ) );
// make sure the node is not visited
assert( !Abc_NodeIsTravIdPrevious(pNode) );
// check if the node is part of the combinational loop
if ( Abc_NodeIsTravIdCurrent(pNode) )
{
fprintf( stdout, "Network \"%s\" contains combinational loop!\n", pNtk->pName );
fprintf( stdout, "Node \"%s\" is encountered twice on the following path:\n", Abc_ObjName(pNode) );
fprintf( stdout, " %s", Abc_ObjName(pNode) );
return 0;
}
// mark this node as a node on the current path
Abc_NodeSetTravIdCurrent( pNode );
// visit the transitive fanin
if ( Abc_NtkIsNetlist(pNode->pNtk) )
{
Abc_ObjForEachFanin( pNode, pFanin, i )
{
if ( Abc_ObjIsCi(pFanin) )
continue;
pFanin = Abc_ObjFanin0(pFanin);
// make sure there is no mixing of networks
assert( pFanin->pNtk == pNode->pNtk );
// check if the fanin is visited
if ( Abc_NodeIsTravIdPrevious(pFanin) )
continue;
// traverse searching for the loop
fAcyclic = Abc_NtkIsAcyclic_rec( pFanin );
// return as soon as the loop is detected
if ( fAcyclic == 0 )
{
fprintf( stdout, " <-- %s", Abc_ObjName(pNode) );
return 0;
}
}
}
else
{
Abc_ObjForEachFanin( pNode, pFanin, i )
{
// make sure there is no mixing of networks
assert( pFanin->pNtk == pNode->pNtk );
// check if the fanin is visited
if ( Abc_NodeIsTravIdPrevious(pFanin) )
continue;
// traverse searching for the loop
fAcyclic = Abc_NtkIsAcyclic_rec( pFanin );
// return as soon as the loop is detected
if ( fAcyclic == 0 )
{
fprintf( stdout, " <-- %s", Abc_ObjName(pNode) );
return 0;
}
}
}
// mark this node as a visited node
Abc_NodeSetTravIdPrevious( pNode );
return 1;
}
////////////////////////////////////////////////////////////////////////
/// END OF FILE ///
////////////////////////////////////////////////////////////////////////
|
