org.chocosolver.solver.constraints.binary.PropEqualX_Y Maven / Gradle / Ivy
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/*
* This file is part of choco-solver, http://choco-solver.org/
*
* Copyright (c) 2019, IMT Atlantique. All rights reserved.
*
* Licensed under the BSD 4-clause license.
*
* See LICENSE file in the project root for full license information.
*/
package org.chocosolver.solver.constraints.binary;
import org.chocosolver.solver.constraints.Propagator;
import org.chocosolver.solver.constraints.PropagatorPriority;
import org.chocosolver.solver.exception.ContradictionException;
import org.chocosolver.solver.learn.ExplanationForSignedClause;
import org.chocosolver.solver.learn.Implications;
import org.chocosolver.solver.variables.IntVar;
import org.chocosolver.solver.variables.delta.IIntDeltaMonitor;
import org.chocosolver.solver.variables.events.IntEventType;
import org.chocosolver.util.ESat;
import org.chocosolver.util.objects.ValueSortedMap;
import org.chocosolver.util.objects.setDataStructures.iterable.IntIterableRangeSet;
import org.chocosolver.util.procedure.IntProcedure;
import org.chocosolver.util.tools.ArrayUtils;
/**
* X = Y
*
* Ensures Arc-Consistency
*
*
* @author Charles Prud'homme, Jean-Guillaume Fages
* @since 1 oct. 2010
*/
public final class PropEqualX_Y extends Propagator {
private IntVar x, y;
// enumerated domains
private boolean bothEnumerated;
private IIntDeltaMonitor[] idms;
private IntProcedure rem_proc;
private int indexToFilter;
public PropEqualX_Y(IntVar x, IntVar y) {
super(ArrayUtils.toArray(x, y), PropagatorPriority.BINARY, true);
this.x = vars[0];
this.y = vars[1];
if (x.hasEnumeratedDomain() && y.hasEnumeratedDomain()) {
bothEnumerated = true;
idms = new IIntDeltaMonitor[2];
idms[0] = vars[0].monitorDelta(this);
idms[1] = vars[1].monitorDelta(this);
rem_proc = i -> vars[indexToFilter].removeValue(i, this);
}
}
@Override
public int getPropagationConditions(int vIdx) {
if (vars[0].hasEnumeratedDomain() && vars[1].hasEnumeratedDomain())
return IntEventType.all();
else
return IntEventType.boundAndInst();
}
@SuppressWarnings("StatementWithEmptyBody")
private void updateBounds() throws ContradictionException {
while (x.updateLowerBound(y.getLB(), this) | y.updateLowerBound(x.getLB(), this)) ;
while (x.updateUpperBound(y.getUB(), this) | y.updateUpperBound(x.getUB(), this)) ;
}
@Override
public void propagate(int evtmask) throws ContradictionException {
updateBounds();
// ensure that, in case of enumerated domains, holes are also propagated
if (bothEnumerated) {
int ub = x.getUB();
for (int val = x.getLB(); val <= ub; val = x.nextValue(val)) {
if (!(y.contains(val))) {
x.removeValue(val, this);
}
}
ub = y.getUB();
for (int val = y.getLB(); val <= ub; val = y.nextValue(val)) {
if (!(x.contains(val))) {
y.removeValue(val, this);
}
}
idms[0].unfreeze();
idms[1].unfreeze();
}
if (x.isInstantiated()) {
assert (y.isInstantiated());
// no more test should be done on the value,
// filtering algo ensures that both are assigned to the same value
setPassive();
}
}
@Override
public void propagate(int varIdx, int mask) throws ContradictionException {
updateBounds();
if (x.isInstantiated()) {
assert (y.isInstantiated());
setPassive();
} else if (bothEnumerated) {
indexToFilter = 1 - varIdx;
idms[varIdx].freeze();
idms[varIdx].forEachRemVal(rem_proc);
idms[varIdx].unfreeze();
}
}
@Override
public ESat isEntailed() {
if ((x.getUB() < y.getLB()) ||
(x.getLB() > y.getUB()) ||
x.hasEnumeratedDomain() && y.hasEnumeratedDomain() && !match()
)
return ESat.FALSE;
else if (x.isInstantiated() &&
y.isInstantiated() &&
(x.getValue() == y.getValue()))
return ESat.TRUE;
else
return ESat.UNDEFINED;
}
private boolean match() {
int lb = x.getLB();
int ub = x.getUB();
for (; lb <= ub; lb = x.nextValue(lb)) {
if (y.contains(lb)) return true;
}
return false;
}
/**
* @implSpec
* Premise: x = y
*
* Two cases here, either a) x was filtered from y, or b) y was filtered from x.
* Both cases are explained the same way, just swap the variables.
*
*
* Consider Dy = dom(y), Dx = dom(x) before propagation, Dx'= dom(x) after propagation.
*
* ( y ∈ Dy ∧ x &isn; Dx ) → x ∈ Dx'
*
* Note that, due to premise, Dy = Dx', so:
*
* ( y ∉ Dy ∨ x ∈ Dy )
*
*
*
*
*/
@Override
public void explain(ExplanationForSignedClause explanation,
ValueSortedMap front,
Implications ig, int p) {
IntIterableRangeSet set0, set1, set2;
boolean isPivot;
if(isPivot = (ig.getIntVarAt(p) == vars[0])) { // case a. (see javadoc)
set1 = explanation.getComplementSet(vars[1]);
set0 = explanation.getRootSet(vars[0]);
set2 = explanation.getSet(vars[1]);
set0.retainAll(set2);
explanation.returnSet(set2);
}else { // case b. (see javadoc)
assert ig.getIntVarAt(p) == vars[1];
set0 = explanation.getComplementSet(vars[0]);
set1 = explanation.getRootSet(vars[1]);
set2 = explanation.getSet(vars[0]);
set1.retainAll(set2);
explanation.returnSet(set2);
}
explanation.addLiteral(vars[0], set0, isPivot);
explanation.addLiteral(vars[1], set1, !isPivot);
}
@Override
public String toString() {
return "prop(" + vars[0].getName() + ".EQ." + vars[1].getName() + ")";
}
}