org.chocosolver.solver.constraints.graph.symmbreaking.PropIncrementalAdjacencyMatrix Maven / Gradle / Ivy
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Open-source constraint solver.
/*
* This file is part of choco-solver, http://choco-solver.org/
*
* Copyright (c) 2023, 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.symmbreaking;
import org.chocosolver.solver.constraints.Propagator;
import org.chocosolver.solver.constraints.PropagatorPriority;
import org.chocosolver.solver.exception.ContradictionException;
import org.chocosolver.solver.variables.BoolVar;
import org.chocosolver.solver.variables.DirectedGraphVar;
import org.chocosolver.solver.variables.Variable;
import org.chocosolver.solver.variables.delta.IGraphDeltaMonitor;
import org.chocosolver.solver.variables.events.GraphEventType;
import org.chocosolver.solver.variables.events.IntEventType;
import org.chocosolver.util.ESat;
import org.chocosolver.util.objects.setDataStructures.ISet;
import org.chocosolver.util.procedure.PairProcedure;
import org.chocosolver.util.tools.ArrayUtils;
import java.util.HashSet;
import java.util.Set;
/**
* @author Моклев Вячеслав
*/
public class PropIncrementalAdjacencyMatrix extends Propagator {
private final DirectedGraphVar graph;
private final IGraphDeltaMonitor gdm;
private final PairProcedure enforce;
private final PairProcedure remove;
private int n;
private final BoolVar[] t;
public PropIncrementalAdjacencyMatrix(DirectedGraphVar graphVar, BoolVar[] t) {
super(ArrayUtils.append(new Variable[]{graphVar}, t), PropagatorPriority.LINEAR, true);
graph = graphVar;
gdm = graph.monitorDelta(this);
enforce = (from, to) -> t[from + to * n].instantiateTo(1, this);
remove = (from, to) -> t[from + to * n].instantiateTo(0, this);
n = graphVar.getNbMaxNodes();
this.t = t;
}
@Override
public void propagate(int evtmask) throws ContradictionException {
// first, nonincremental propagation
propagateGraphChanged();
propagateTChanged();
// initializing incremental data-structures
gdm.startMonitoring();
}
private void propagateGraphChanged() throws ContradictionException {
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
if (t[i + j * n].isInstantiatedTo(1)) {
graph.enforceEdge(i, j, this);
}
if (t[i + j * n].isInstantiatedTo(0)) {
graph.removeEdge(i, j, this);
}
}
}
}
private void propagateTChanged() throws ContradictionException {
for (int u = 0; u < n; u++) {
for (int v : graph.getMandatorySuccessorsOf(u)) {
t[u + v * n].instantiateTo(1, this);
}
}
for (int u = 0; u < n; u++) {
Set set = new HashSet<>();
for (int v : graph.getPotentialSuccessorsOf(u)) {
set.add(v);
}
for (int v = 0; v < n; v++) {
if (!set.contains(v)) {
t[u + v * n].instantiateTo(0, this);
}
}
}
}
@Override
public void propagate(int idxVarInProp, int mask) throws ContradictionException {
// incremental propagation
if (idxVarInProp == 0) {
gdm.forEachEdge(enforce, GraphEventType.ADD_EDGE);
gdm.forEachEdge(remove, GraphEventType.REMOVE_EDGE);
} else {
propagateTChanged();
}
}
@Override
public int getPropagationConditions(int vIdx) {
if (vIdx == 0) {
return GraphEventType.ADD_EDGE.getMask() | GraphEventType.REMOVE_EDGE.getMask();
} else {
return IntEventType.boundAndInst();
}
}
@Override
public ESat isEntailed() {
for (int i = 0; i < n; i++) {
ISet children = graph.getMandatorySuccessorsOf(i);
for (int j = 0; j < n; j++) {
if (t[i + j * n].isInstantiatedTo(0) && children.contains(j)) {
return ESat.FALSE;
}
}
}
for (int i = 0; i < n; i++) {
ISet children = graph.getPotentialSuccessorsOf(i);
for (int j = 0; j < n; j++) {
if (t[i + j * n].isInstantiatedTo(1) && !children.contains(j)) {
return ESat.FALSE;
}
}
}
if (graph.isInstantiated()) {
return ESat.TRUE;
}
return ESat.UNDEFINED;
}
}