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A graph module for Choco Solver.
/*
* Copyright (c) 1999-2014, Ecole des Mines de Nantes
* All rights reserved.
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of the Ecole des Mines de Nantes nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE REGENTS AND CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/**
* Created by IntelliJ IDEA.
* User: Jean-Guillaume Fages
* Date: 03/10/11
* Time: 19:56
*/
package org.chocosolver.graphsolver.cstrs.cost.trees;
import org.chocosolver.graphsolver.variables.GraphEventType;
import org.chocosolver.graphsolver.variables.IUndirectedGraphVar;
import org.chocosolver.graphsolver.variables.delta.IGraphDeltaMonitor;
import org.chocosolver.memory.IEnvironment;
import org.chocosolver.memory.IStateInt;
import org.chocosolver.solver.constraints.Propagator;
import org.chocosolver.solver.constraints.PropagatorPriority;
import org.chocosolver.solver.exception.ContradictionException;
import org.chocosolver.util.ESat;
import org.chocosolver.util.objects.setDataStructures.ISet;
import org.chocosolver.util.procedure.PairProcedure;
import java.util.BitSet;
/**
* Simple NoSubtour applied to (undirected) tree/forest
*/
public class PropTreeNoSubtour extends Propagator {
//***********************************************************************************
// VARIABLES
//***********************************************************************************
private IUndirectedGraphVar g;
private IGraphDeltaMonitor gdm;
private int n;
private PairProcedure arcEnforced;
private IStateInt[] color, size;
// list
private int[] fifo;
private int[] mate;
private BitSet in;
//***********************************************************************************
// CONSTRUCTORS
//***********************************************************************************
/**
* Ensures that graph has no cycle
* runs in O(n) per instantiation event
*
* @param graph
*/
public PropTreeNoSubtour(IUndirectedGraphVar graph) {
super(new IUndirectedGraphVar[]{graph}, PropagatorPriority.LINEAR, true);
g = graph;
gdm = g.monitorDelta(this);
this.n = g.getNbMaxNodes();
arcEnforced = new EnfArc();
fifo = new int[n];
mate = new int[n];
in = new BitSet(n);
color = new IStateInt[n];
size = new IStateInt[n];
IEnvironment environment = graph.getEnvironment();
for (int i = 0; i < n; i++) {
color[i] = environment.makeInt(i);
size[i] = environment.makeInt(1);
}
}
//***********************************************************************************
// METHODS
//***********************************************************************************
@Override
public void propagate(int evtmask) throws ContradictionException {
for (int i = 0; i < n; i++) {
color[i].set(i);
size[i].set(1);
mate[i] = -1;
}
ISet nei;
for (int i = 0; i < n; i++) {
nei = g.getMandNeighOf(i);
for (int j : nei) {
if (i < j) {
enforce(i, j);
}
}
}
gdm.unfreeze();
}
@Override
public void propagate(int idxVarInProp, int mask) throws ContradictionException {
gdm.freeze();
gdm.forEachArc(arcEnforced, GraphEventType.ADD_ARC);
gdm.unfreeze();
}
@Override
public int getPropagationConditions(int vIdx) {
return GraphEventType.ADD_ARC.getMask();
}
@Override
public ESat isEntailed() {
return ESat.TRUE; //not implemented
}
private void enforce(int i, int j) throws ContradictionException {
if (size[color[i].get()].get() > size[color[j].get()].get()) {
enforce(j, i);
return;
}
if (i == j) {
throw new UnsupportedOperationException();
}
int ci = color[i].get();
int cj = color[j].get();
if (ci == cj) {
fails();
}
int idxFirst = 0;
int idxLast = 0;
in.clear();
in.set(i);
fifo[idxLast++] = i;
int x, ck;
mate[i] = j;
while (idxFirst < idxLast) {
x = fifo[idxFirst++];
for (int k : g.getPotNeighOf(x)) {
if (k != mate[x]) {
ck = color[k].get();
if (ck == cj) {
g.removeArc(x, k, this);
} else {
if (ck == ci && !in.get(k)) {
in.set(k);
fifo[idxLast++] = k;
mate[k] = x;
}
}
}
}
color[x].set(cj);
}
size[cj].add(size[ci].get());
}
//***********************************************************************************
// PROCEDURES
//***********************************************************************************
private class EnfArc implements PairProcedure {
@Override
public void execute(int i, int j) throws ContradictionException {
enforce(i, j);
}
}
}