org.chocosolver.solver.constraints.graph.basic.PropNbNodes Maven / Gradle / Ivy
/*
* This file is part of choco-solver, http://choco-solver.org/
*
* Copyright (c) 2022, 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.graph.basic;
import org.chocosolver.solver.variables.events.GraphEventType;
import org.chocosolver.solver.variables.GraphVar;
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.solver.variables.Variable;
import org.chocosolver.solver.variables.events.IntEventType;
import org.chocosolver.util.ESat;
import org.chocosolver.util.objects.setDataStructures.ISet;
/**
* Propagator that ensures that k nodes belong to the final graph
*
* @author Jean-Guillaume Fages
*/
public class PropNbNodes extends Propagator {
//***********************************************************************************
// VARIABLES
//***********************************************************************************
private final GraphVar g;
private final IntVar k;
//***********************************************************************************
// CONSTRUCTORS
//***********************************************************************************
public PropNbNodes(GraphVar graph, IntVar k) {
super(new Variable[]{graph, k}, PropagatorPriority.LINEAR, false);
this.g = graph;
this.k = k;
}
//***********************************************************************************
// PROPAGATIONS
//***********************************************************************************
@Override
public void propagate(int evtmask) throws ContradictionException {
int env = g.getPotentialNodes().size();
int ker = g.getMandatoryNodes().size();
k.updateLowerBound(ker, this);
k.updateUpperBound(env, this);
if (ker == env) {
setPassive();
} else if (k.isInstantiated()) {
int v = k.getValue();
ISet envNodes = g.getPotentialNodes();
if (v == env) {
for (int i : envNodes) {
g.enforceNode(i, this);
}
setPassive();
} else if (v == ker) {
ISet kerNodes = g.getMandatoryNodes();
for (int i : envNodes) {
if (!kerNodes.contains(i)) {
g.removeNode(i, this);
}
}
setPassive();
}
}
}
//***********************************************************************************
// INFO
//***********************************************************************************
@Override
public int getPropagationConditions(int vIdx) {
if (vIdx == 0) {
return GraphEventType.REMOVE_NODE.getMask() + GraphEventType.ADD_NODE.getMask();
} else {
return IntEventType.boundAndInst();
}
}
@Override
public ESat isEntailed() {
int env = g.getPotentialNodes().size();
int ker = g.getMandatoryNodes().size();
if (env < k.getLB() || ker > k.getUB()) {
return ESat.FALSE;
}
if (env == ker) {
return ESat.TRUE;
}
return ESat.UNDEFINED;
}
}
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