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Open-source constraint solver.
/**
* Copyright (c) 2016, 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:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the .
* 4. Neither the name of the 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 ''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 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.solver.constraints.nary.circuit;
import gnu.trove.list.array.TIntArrayList;
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.solver.variables.IntVar;
import org.chocosolver.solver.variables.events.IntEventType;
import org.chocosolver.util.ESat;
import java.util.Arrays;
import java.util.BitSet;
/**
* Simple nocircuit contraint (from NoSubtour of Pesant or noCycle of Caseaux/Laburthe)
*
* @author Jean-Guillaume Fages
*/
public class PropNoSubtour extends Propagator {
//***********************************************************************************
// VARIABLES
//***********************************************************************************
private int n;
private int offset = 0; // lower bound
private IStateInt[] origin, end, size;
//***********************************************************************************
// CONSTRUCTORS
//***********************************************************************************
/**
* Ensures that graph has no subCircuit, with Caseaux/Laburthe/Pesant algorithm
* runs incrementally in O(1) per instantiation event
*
* @param variables array of integer variables
* @param offset offset
*/
public PropNoSubtour(IntVar[] variables, int offset) {
super(variables, PropagatorPriority.UNARY, true);
n = vars.length;
origin = new IStateInt[n];
end = new IStateInt[n];
size = new IStateInt[n];
IEnvironment environment = model.getEnvironment();
for (int i = 0; i < n; i++) {
origin[i] = environment.makeInt(i);
end[i] = environment.makeInt(i);
size[i] = environment.makeInt(1);
}
this.offset = offset;
}
//***********************************************************************************
// METHODS
//***********************************************************************************
@Override
public void propagate(int evtmask) throws ContradictionException {
TIntArrayList fixedVar = new TIntArrayList();
for (int i = 0; i < n; i++) {
vars[i].removeValue(i + offset, this);
vars[i].updateBounds(offset, n - 1 + offset, this);
if (vars[i].isInstantiated()) {
fixedVar.add(i);
}
}
for (int i = 0; i < fixedVar.size(); i++) {
varInstantiated(fixedVar.get(i), vars[fixedVar.get(i)].getValue() - offset);
}
}
@Override
public void propagate(int idxVarInProp, int mask) throws ContradictionException {
varInstantiated(idxVarInProp, vars[idxVarInProp].getValue() - offset);
}
/**
* var in [0,n-1] and val in [0,n-1]
*
* @param var origin
* @param val dest
* @throws ContradictionException
*/
private void varInstantiated(int var, int val) throws ContradictionException {
if (isPassive()) {
return;
}
int last = end[val].get(); // last in [0,n-1]
int start = origin[var].get(); // start in [0,n-1]
if (origin[val].get() != val) {
fails(); // TODO: could be more precise, for explanation purpose
}
if (end[var].get() != var) {
fails(); // TODO: could be more precise, for explanation purpose
}
if (val == start) {
if (size[start].get() != n) {
fails(); // TODO: could be more precise, for explanation purpose
}
} else {
size[start].add(size[val].get());
if (size[start].get() == n) {
vars[last].instantiateTo(start + offset, this);
setPassive();
}
boolean isInst = false;
if (size[start].get() < n) {
if (vars[last].removeValue(start + offset, this)) {
isInst = vars[last].isInstantiated();
}
}
origin[last].set(start);
end[start].set(last);
if (isInst) {
varInstantiated(last, vars[last].getValue() - offset);
}
}
}
@Override
public int getPropagationConditions(int vIdx) {
return IntEventType.instantiation();
}
@Override
public ESat isEntailed() {
for (int i = 0; i < n; i++) {
if (!vars[i].isInstantiated()) {
return ESat.UNDEFINED;
}
}
BitSet visited = new BitSet(n);
int i = 0;
int size = 0;
while (size != n) {
size++;
i = vars[i].getValue() - offset;
if (visited.get(i)) {
return ESat.FALSE;
}
visited.set(i);
}
if (i == 0) {
return ESat.TRUE;
} else {
return ESat.FALSE;
}
}
@Override
public String toString() {
return "PropNoSubTour(" + Arrays.toString(vars) + ")";
}
}