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// $Id: maxsize.cpp 5188 2012-08-30 00:31:31Z dub $
/*
Copyright (c) 2007-2012, Trustees of The Leland Stanford Junior University
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
Redistributions of source code must retain the above copyright notice, this
list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation
and/or other materials provided with the distribution.
Neither the name of the Stanford University nor the names of its contributors
may be used to endorse or promote products derived from this software without
specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
*/
#include "booksim.hpp"
#include <iostream>
#include "maxsize.hpp"
// shortest augmenting path:
//
// for all unmatched left nodes,
// push node onto work stack
// end
//
// for all j,
// from[j] = undefined
// end
//
// do,
//
// while( !stack.empty ),
//
// nl = stack.pop
// for each edge (nl,j),
// if ( ( lmatch[nl] != j ) && ( from[j] == undefined ) ),
// if ( rmatch[j] == undefined ),
// stop // augmenting path found
// else
// from[j] = nl
// newstack.push( rmatch[j] )
// end
// end
// end
// end
//
// stack = newstack
// end
//
//#define DEBUG_MAXSIZE
//#define PRINT_MATCHING
MaxSizeMatch::MaxSizeMatch( Module *parent, const string& name,
int inputs, int outputs ) :
DenseAllocator( parent, name, inputs, outputs )
{
_from.resize(outputs);
_s = new int [inputs];
_ns = new int [inputs];
_prio = 0;
}
MaxSizeMatch::~MaxSizeMatch( )
{
delete [] _s;
delete [] _ns;
}
void MaxSizeMatch::Allocate( )
{
// augment as many times as possible
// (this is an O(N^3) maximum-size matching algorithm)
while( _ShortestAugmenting( ) );
// next time, start at next input to ensure fairness
_prio = (_prio + 1) % _inputs;
}
bool MaxSizeMatch::_ShortestAugmenting( )
{
int i, j, jn;
int slen, nslen;
// start with empty stack
slen = 0;
// push all unassigned inputs to the stack
for ( i = 0; i < _inputs; ++i ) {
j = (i + _prio) % _inputs;
if ( _inmatch[j] == -1 ) { // start with unmatched left nodes
_s[slen++] = j;
}
}
_from.assign(_inputs, -1);
for ( int iter = 0; iter < _inputs; iter++ ) {
nslen = 0;
for ( int e = 0; e < slen; ++e ) {
i = _s[e];
for ( j = 0; j < _outputs; ++j ) {
if ( ( _request[i][j].label != -1 ) && // edge (i,j) exists
( _inmatch[i] != j ) && // (i,j) is not contained in the current matching
( _from[j] == -1 ) ) { // no shorter path to j exists
_from[j] = i; // how did we get to j?
#ifdef DEBUG_MAXSIZE
cout << " got to " << j << " from " << i << endl;
#endif
if ( _outmatch[j] == -1 ) { // j is unmatched -- augmenting path found
goto found_augmenting;
} else { // j is matched
_ns[nslen] = _outmatch[j]; // add the destination of this edge to the leaf nodes
nslen++;
#ifdef DEBUG_MAXSIZE
cout << " adding " << _outmatch[j] << endl;
#endif
}
}
}
}
// no augmenting path found yet, swap stacks
int * t = _s;
_s = _ns;
_ns = t;
slen = nslen;
}
return false; // no augmenting paths
found_augmenting:
// the augmenting path ends at node j on the right
#ifdef DEBUG_MAXSIZE
cout << "Found path: " << j << "c <- ";
#endif
i = _from[j];
_outmatch[j] = i;
#ifdef DEBUG_MAXSIZE
cout << i;
#endif
while ( _inmatch[i] != -1 ) { // loop until the end of the path
jn = _inmatch[i]; // remove previous edge (i,jn) and add (i,j)
_inmatch[i] = j;
#ifdef DEBUG_MAXSIZE
cout << " <- " << j << "c <- ";
#endif
j = jn; // add edge from (jn,in)
i = _from[j];
_outmatch[j] = i;
#ifdef DEBUG_MAXSIZE
cout << i;
#endif
}
#ifdef DEBUG_MAXSIZE
cout << endl;
#endif
_inmatch[i] = j;
#ifdef PRINT_MATCHING
cout << "left matching: ";
for ( i = 0; i < _inputs; i++ ) {
cout << _inmatch[i] << " ";
}
cout << endl;
cout << "right matching: ";
for ( i = 0; i < _outputs; i++ ) {
cout << _outmatch[i] << " ";
}
cout << endl;
#endif
return true;
}
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