org.chocosolver.solver.constraints.nary.lex.PropLexInt Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of choco-solver Show documentation
Show all versions of choco-solver Show documentation
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.
*/
package org.chocosolver.solver.constraints.nary.lex;
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.PropagatorEventType;
import org.chocosolver.util.ESat;
import org.chocosolver.util.tools.ArrayUtils;
import java.util.Arrays;
/**
* Enforce a lexicographic ordering on one vector of integer
* variables x <_lex y with x = , and a vector of ints y = .
* ref : Global Constraints for Lexicographic Orderings (Frisch and al)
*
*
* @author Charles Prud'homme
* @since 03/05/2016
*/
public class PropLexInt extends Propagator {
private final int n; // size of both vectors
private final IStateInt alpha; // size of both vectors
private final IStateInt beta;
private boolean entailed;
private final IntVar[] x;
private final int[] y;
private final boolean strict;
public PropLexInt(IntVar[] X, int[] Y, boolean strict) {
super(ArrayUtils.append(X), PropagatorPriority.LINEAR, true);
this.x = Arrays.copyOfRange(vars, 0, X.length);
this.y = Y.clone();
this.strict = strict;
this.n = X.length;
IEnvironment environment = model.getEnvironment();
alpha = environment.makeInt(0);
beta = environment.makeInt(0);
entailed = false;
}
/**
* update this propagator with a new int vector newY
* @param newY new int vector
*/
public void updateIntVector(int[] newY){
System.arraycopy(newY, 0, y, 0, newY.length);
forcePropagationOnBacktrack();
}
@Override
public void propagate(int evtmask) throws ContradictionException {
if (PropagatorEventType.isFullPropagation(evtmask)) {
initialize();
} else {
gacLexLeq(alpha.get());
}
}
@Override
public void propagate(int vIdx, int mask) throws ContradictionException {
entailed = false;
if (vIdx < n) {
gacLexLeq(vIdx);
} else {
gacLexLeq(vIdx - n);
}
}
@Override
public ESat isEntailed() {
if (isCompletelyInstantiated()) {
for (int i = 0; i < x.length; i++) {
int xi = vars[i].getValue();
if (xi < y[i]) {
return ESat.TRUE;
} else if (xi > y[i]) {
return ESat.FALSE;
}//else xi == yi
}
if (strict) {
return ESat.FALSE;
} else {
return ESat.eval(vars[n - 1].getValue() == vars[n - 1 + n].getValue());
}
}
return ESat.UNDEFINED;
}
/////////////////////
private boolean checkLex(int i) {
if (!strict) {
if (i == n - 1) {
return x[i].getUB() <= y[i];
} else {
return x[i].getUB() < y[i];
}
} else {
return x[i].getUB() < y[i];
}
}
private void updateAlpha(int i) throws ContradictionException {
if (i == beta.get()) {
fails();
}
if (i == n) {
if (strict) {
fails();
} else {
entailed = true;
setPassive();
return;
}
}
if (!x[i].isInstantiatedTo(y[i])) {
alpha.set(i);
gacLexLeq(i);
} else {
updateAlpha(i + 1);
}
}
private void updateBeta(int i) throws ContradictionException {
if ((i + 1) == alpha.get()) {
fails();
}
if (x[i].getLB() < y[i]) {
beta.set(i + 1);
if (x[i].getUB() >= y[i]) {
gacLexLeq(i);
}
} else if (x[i].getLB() == y[i]) {
updateBeta(i - 1);
}
}
/**
* Build internal structure of the propagator, if necessary
*
* @throws ContradictionException if initialisation encounters a contradiction
*/
private void initialize() throws ContradictionException {
entailed = false;
int i = 0;
int a, b;
while (i < n && x[i].isInstantiatedTo(y[i])) {
i++;
}
if (i == n) {
if (!strict) {
entailed = true;
setPassive();
} else {
fails();
}
} else {
a = i;
if (checkLex(i)) {
setPassive();
return;
}
b = -1;
while (i != n && x[i].getLB() <= y[i]) {
if (x[i].getLB() == y[i]) {
if (b == -1) {
b = i;
}
} else {
b = -1;
}
i++;
}
if (!strict && i == n) {
b = Integer.MAX_VALUE;
}
if (b == -1) {
b = i;
}
if (a >= b) {
fails();
}
alpha.set(a);
beta.set(b);
gacLexLeq(a);
}
}
private void gacLexLeq(int i) throws ContradictionException {
int a = alpha.get();
int b = beta.get();
//Part A
if (i >= b || entailed) {
return;
}
//Part B
if (i == a && (i + 1) == b) {
x[i].updateUpperBound(y[i] - 1, this);
if(y[i] < x[i].getLB() + 1){
fails();
}
if (checkLex(i)) {
entailed = true;
setPassive();
return;
}
}
//Part C
if (i == a && (i + 1) < b) {
x[i].updateUpperBound(y[i], this);
if(y[i] < x[i].getLB()){
fails();
}
if (checkLex(i)) {
entailed = true;
setPassive();
return;
}
if (x[i].isInstantiatedTo(y[i])) {
updateAlpha(i + 1);
}
}
//Part D
if (a < i && i < b) {
if ((i == (b - 1) && x[i].getLB() == y[i]) || x[i].getLB() > y[i]) {
updateBeta(i - 1);
}
}
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder(32);
sb.append("LEX <");
int i = 0;
for (; i < Math.min(this.x.length - 1, 2); i++) {
sb.append(this.x[i]).append(", ");
}
if (i == 2 && this.x.length - 1 > 2) sb.append("..., ");
sb.append(this.x[x.length - 1]);
sb.append(">, <");
i = 0;
for (; i < Math.min(this.y.length - 1, 2); i++) {
sb.append(this.y[i]).append(", ");
}
if (i == 2 && this.y.length - 1 > 2) sb.append("..., ");
sb.append(this.y[y.length - 1]);
sb.append(">");
return sb.toString();
}
}