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Open-source constraint solver.
/*
* 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.nary.count;
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 org.chocosolver.util.tools.ArrayUtils;
import static java.lang.Integer.MAX_VALUE;
import static java.lang.Math.max;
import static java.lang.Math.min;
/**
* Define a COUNT constraint setting size{forall v in lvars | v = occval} = occVar
* assumes the occVar variable to be the last of the variables of the constraint:
* vars = [lvars | occVar]
* Arc Consistent algorithm
* with lvars = list of variables for which the occurrence of occval in their domain is constrained
*
*
* @author Jean-Guillaume Fages
*/
public class PropCountVar extends Propagator {
//***********************************************************************************
// VARIABLES
//***********************************************************************************
private final int n;
private final IntVar val;
private final IntVar card;
//***********************************************************************************
// CONSTRUCTORS
//***********************************************************************************
/**
* Propagator for Count Constraint for integer variables
* Performs Arc Consistency
*
* @param decvars an array of integer variables
* @param restrictedValue integer variable
* @param valueCardinality integer variable
*/
public PropCountVar(IntVar[] decvars, IntVar restrictedValue, IntVar valueCardinality) {
super(ArrayUtils.concat(decvars, valueCardinality, restrictedValue), PropagatorPriority.QUADRATIC, false);
this.n = decvars.length;
this.card = this.vars[n];
this.val = this.vars[n + 1];
}
@Override
public String toString() {
StringBuilder st = new StringBuilder();
st.append("PropCountVar_(");
int i = 0;
for (; i < Math.min(4, vars.length-1); i++) {
st.append(vars[i].getName()).append(", ");
}
if (i < vars.length - 2) {
st.append("..., ");
}
st.append(vars[vars.length - 1].getName());
st.append(", value=").append(val.getName());
st.append(", cardinality=").append(card.getName());
return st.toString();
}
//***********************************************************************************
// PROPAGATION
//***********************************************************************************
@Override
public void propagate(int evtmask) throws ContradictionException {
int minCard = MAX_VALUE / 10;
int maxCard = -minCard;
int cardLB = card.getLB();
int cardUB = card.getUB();
for (int value = val.getLB(); value <= val.getUB(); value = val.nextValue(value)) {
int min = 0;
int max = 0;
for (int i = 0; i < n; i++) {
IntVar v = vars[i];
if (v.contains(value)) {
max++;
if (v.isInstantiated()) {
min++;
}
}
}
if (cardLB > max || cardUB < min) {
val.removeValue(value, this);
} else {
minCard = min(minCard, min);
maxCard = max(maxCard, max);
}
}
card.updateBounds(minCard, maxCard, this);
if (val.isInstantiated() && card.isInstantiated()) {
int nb = card.getValue();
int value = val.getValue();
if (maxCard == nb) {
for (int i = 0; i < n; i++) {
if (vars[i].contains(value)) {
vars[i].instantiateTo(value, this);
}
}
setPassive();
} else if (minCard == nb) {
int nbInst = 0; // security
for (int i = 0; i < n; i++) {
if (vars[i].contains(value)) {
if (vars[i].isInstantiated()) {
nbInst++;
} else {
vars[i].removeValue(value, this);
}
}
}
card.instantiateTo(nbInst, this);
}
}
}
//***********************************************************************************
// INFO
//***********************************************************************************
@Override
public int getPropagationConditions(int vIdx) {
if (vIdx == vars.length - 2) {// cardinality variables
return IntEventType.boundAndInst();
}
return IntEventType.all();
}
@Override
public ESat isEntailed() {
boolean support = false;
boolean instSupport = false;
for (int value = val.getLB(); value <= val.getUB(); value = val.nextValue(value)) {
int min = 0;
int max = 0;
for (int i = 0; i < n; i++) {
IntVar v = vars[i];
if (v.contains(value)) {
max++;
if (v.isInstantiated()) {
min++;
}
}
}
if (card.getLB() <= max && card.getUB() >= min) {
support = true;
if (min == max) {
instSupport = true;
}
}
}
if (!support) {
return ESat.FALSE;
}
if (val.isInstantiated() && instSupport && card.isInstantiated()) {
return ESat.TRUE;
}
return ESat.UNDEFINED;
}
}