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/*
* vim: ts=4 sw=4 et tw=0 wm=0
*
* libvpsc - A solver for the problem of Variable Placement with
* Separation Constraints.
*
* Copyright (C) 2005-2008 Monash University
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
* See the file LICENSE.LGPL distributed with the library.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
*
* Author(s): Tim Dwyer
*/
#include <map>
#include <list>
#include <sstream>
#include <cassert>
#include <cfloat>
#include <cmath>
#include "libvpsc/constraint.h"
#include "libvpsc/variable.h"
namespace vpsc {
Constraint::Constraint(Variable *left, Variable *right, double gap, bool equality)
: left(left),
right(right),
gap(gap),
timeStamp(0),
active(false),
equality(equality),
unsatisfiable(false),
needsScaling(true),
creator(nullptr)
{
// In hindsight I think it's probably better to build the constraint DAG
// (by creating variable in/out lists) when needed, rather than in advance
//left->out.push_back(this);
//right->in.push_back(this);
}
Constraint::~Constraint() {
// see constructor: the following is just way too slow.
// Better to create a
// new DAG on demand than maintain the lists dynamically.
//Constraints::iterator i;
//for(i=left->out.begin(); i!=left->out.end(); i++) {
//if(*i==this) break;
//}
//left->out.erase(i);
//for(i=right->in.begin(); i!=right->in.end(); i++) {
//if(*i==this) break;
//}
//right->in.erase(i);
}
std::ostream& operator <<(std::ostream &os, const Constraint &c)
{
const char *type = c.equality ? "=" : "<=";
std::ostringstream lscale, rscale;
if (c.left->scale != 1)
{
lscale << c.left->scale << "*";
}
if (c.right->scale != 1)
{
rscale << c.right->scale << "*";
}
os << lscale.str() << *c.left << "+" << c.gap << type <<
rscale.str() << *c.right;
if (c.left->block && c.right->block)
{
os << "(" << c.slack() << ")" << (c.active ? "-active" : "") <<
"(lm=" << c.lm << ")";
}
else
{
os << "(vars have no position)";
}
return os;
}
#include "libvpsc/block.h"
bool CompareConstraints::operator() (
Constraint *const &l, Constraint *const &r
) const {
double const sl =
l->left->block->timeStamp > l->timeStamp
||l->left->block==l->right->block
?-DBL_MAX:l->slack();
double const sr =
r->left->block->timeStamp > r->timeStamp
||r->left->block==r->right->block
?-DBL_MAX:r->slack();
if(sl==sr) {
// arbitrary choice based on id
if(l->left->id==r->left->id) {
if(l->right->id<r->right->id) return true;
return false;
}
if(l->left->id<r->left->id) return true;
return false;
}
return sl < sr;
}
typedef std::list<std::map<Variable *, double> > VarOffsetMapList;
class EqualityConstraintSet
{
public:
EqualityConstraintSet(Variables vs)
{
for (size_t i = 0; i < vs.size(); ++i)
{
std::map<Variable *, double> varSet;
varSet[vs[i]] = 0;
variableGroups.push_back(varSet);
}
}
bool isRedundant(Variable *lhs, Variable *rhs, double sep)
{
VarOffsetMapList::iterator lhsSet = setForVar(lhs);
VarOffsetMapList::iterator rhsSet = setForVar(rhs);
COLA_ASSERT(lhsSet != variableGroups.end());
COLA_ASSERT(rhsSet != variableGroups.end());
if (lhsSet == rhsSet)
{
// Check if this is a redundant constraint.
if (fabs(((*lhsSet)[lhs] + sep) - (*rhsSet)[rhs]) < 0.0001)
{
// If so, return true.
return true;
}
}
return false;
}
void mergeSets(Variable *lhs, Variable *rhs, double sep)
{
VarOffsetMapList::iterator lhsSet = setForVar(lhs);
VarOffsetMapList::iterator rhsSet = setForVar(rhs);
if (lhsSet == rhsSet)
{
return;
}
double rhsOldOffset = (*rhsSet)[rhs];
double rhsNewOffset = (*lhsSet)[lhs] + sep;
double offset = rhsNewOffset - rhsOldOffset;
// Update offsets
for (std::map<Variable *, double>::iterator it = rhsSet->begin();
it != rhsSet->end(); ++it)
{
it->second += offset;
}
// Merge rhsSet into lhsSet
lhsSet->insert(rhsSet->begin(), rhsSet->end());
variableGroups.erase(rhsSet);
}
private:
VarOffsetMapList::iterator setForVar(Variable *var)
{
for (VarOffsetMapList::iterator it = variableGroups.begin();
it != variableGroups.end(); ++it)
{
if (it->find(var) != it->end())
{
return it;
}
}
return variableGroups.end();
}
VarOffsetMapList variableGroups;
};
Constraints constraintsRemovingRedundantEqualities(const Variables& vars,
const Constraints& constraints)
{
EqualityConstraintSet equalitySets(vars);
Constraints cs = Constraints(constraints.size());
int csSize = 0;
for (unsigned i = 0; i < constraints.size(); ++i)
{
Constraint *c = constraints[i];
if (c->equality)
{
if (!equalitySets.isRedundant(c->left, c->right, c->gap))
{
// Only add non-redundant equalities
equalitySets.mergeSets(c->left, c->right, c->gap);
cs[csSize++] = c;
}
}
else
{
// Add all non-equalities
cs[csSize++] = c;
}
}
cs.resize(csSize);
return cs;
}
}
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