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Open-source constraint solver.
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/*
* This file is part of choco-solver, http://choco-solver.org/
*
* Copyright (c) 2024, 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.variables.IntVar;
import org.chocosolver.util.ESat;
import org.chocosolver.util.objects.setDataStructures.iterable.IntIterableBitSet;
import org.chocosolver.util.tools.MathUtils;
/**
* Scale propagator : ensures x * y = z
* With y a constant greater than one
* Ensures AC
*
*
* @author Jean-Guillaume Fages
* @since 08/04/2014
*/
public class PropScale extends Propagator {
protected static final int MAX = Integer.MAX_VALUE - 1, MIN = Integer.MIN_VALUE + 1;
private final IntVar X, Z;
private final int Y;
private final boolean enumerated;
private final IntIterableBitSet values;
/**
* Scale propagator : ensures x * y = z
*
* @param x an integer variable
* @param y a constant (should be >1)
* @param z an integer variable
*/
public PropScale(IntVar x, int y, IntVar z) {
super(new IntVar[]{x, z}, PropagatorPriority.BINARY, false);
this.X = vars[0];
this.Z = vars[1];
this.Y = y;
assert y > 1;
this.enumerated = X.hasEnumeratedDomain() && Z.hasEnumeratedDomain();
this.values = enumerated?new IntIterableBitSet():null;
}
@Override
public final void propagate(int evtmask) throws ContradictionException {
X.updateBounds(MathUtils.divCeil(Z.getLB(), Y), MathUtils.divFloor(Z.getUB(), Y), this);
boolean hasChanged;
hasChanged = Z.updateBounds(X.getLB() * Y, X.getUB() * Y, this);
if (enumerated) {
int ub = X.getUB();
for (int v = X.getLB(); v <= ub; v = X.nextValue(v)) {
if (!Z.contains(v * Y)) {
X.removeValue(v, this);
}
}
int v = Z.getLB();
this.values.clear();
this.values.setOffset(v);
ub = Z.getUB();
for (; v <= ub; v = Z.nextValue(v)) {
if ((v / Y) * Y != v || !X.contains(v / Y)) {
this.values.add(v);
}
}
Z.removeValues(values, this);
} else if (hasChanged && Z.hasEnumeratedDomain()) {
if (Z.getLB() > X.getLB() * Y || Z.getUB() < X.getUB() * Y) {
propagate(evtmask);
}
}
}
@Override
public final ESat isEntailed() {
if (X.getUB() * Y < Z.getLB() || X.getLB() * Y > Z.getUB()) {
return ESat.FALSE;
}
if (X.isInstantiated() && Z.isInstantiated()) {
return ESat.TRUE;
}
return ESat.UNDEFINED;
}
}