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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.globalcardinality;
import gnu.trove.list.array.TIntArrayList;
import gnu.trove.map.hash.TIntIntHashMap;
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.objects.setDataStructures.ISet;
import org.chocosolver.util.objects.setDataStructures.ISetIterator;
import org.chocosolver.util.objects.setDataStructures.SetFactory;
import org.chocosolver.util.tools.ArrayUtils;
/**
* Propagator for Global Cardinality Constraint (GCC) for integer variables
* Basic filter: no particular consistency but fast and with a correct checker
*
* @author Jean-Guillaume Fages
*/
public class PropFastGCC extends Propagator {
//***********************************************************************************
// VARIABLES
//***********************************************************************************
private final int n;
private final int n2;
private final int[] values;
private final ISet[] possibles;
private final ISet[] mandatories;
private final ISet valueToCompute;
private final TIntIntHashMap map;
private final TIntArrayList boundVar;
//***********************************************************************************
// CONSTRUCTORS
//***********************************************************************************
/**
* Propagator for Global Cardinality Constraint (GCC) for integer variables
* Basic filter: no particular consistency but fast and with a correct checker
*
* @param decvars array of integer variables
* @param restrictedValues array of int
* @param map mapping
* @param valueCardinalities array of integer variables
*/
public PropFastGCC(IntVar[] decvars, int[] restrictedValues, TIntIntHashMap map, IntVar[] valueCardinalities) {
super(ArrayUtils.append(decvars, valueCardinalities), PropagatorPriority.LINEAR, false);
if (restrictedValues.length != valueCardinalities.length) {
throw new UnsupportedOperationException();
}
this.values = restrictedValues;
this.n = decvars.length;
this.n2 = values.length;
this.possibles = new ISet[n2];
this.mandatories = new ISet[n2];
this.map = map;
for (int idx = 0; idx < n2; idx++) {
mandatories[idx] = SetFactory.makeBitSet(0);
possibles[idx] = SetFactory.makeBitSet(0);
}
this.valueToCompute = SetFactory.makeBitSet(0);
this.boundVar = new TIntArrayList();
for (int i = 0; i < n; i++) {
if (!vars[i].hasEnumeratedDomain()) {
boundVar.add(i);
}
}
}
//***********************************************************************************
// PROPAGATION
//***********************************************************************************
@Override
public void propagate(int evtmask) throws ContradictionException {
valueToCompute.clear();
for (int i = 0; i < n2; i++) {
mandatories[i].clear();
possibles[i].clear();
valueToCompute.add(i);
}
for (int i = 0; i < n; i++) {
IntVar v = vars[i];
int ub = v.getUB();
if (v.isInstantiated()) {
if (map.containsKey(ub)) {
int j = map.get(ub);
mandatories[j].add(i);
}
} else {
for (int k = v.getLB(); k <= ub; k = v.nextValue(k)) {
if (map.containsKey(k)) {
int j = map.get(k);
possibles[j].add(i);
}
}
}
}
while (filter()) {
ISetIterator valIt = valueToCompute.iterator();
while (valIt.hasNext()){
int i = valIt.nextInt();
ISetIterator varIt = possibles[i].iterator();
while (varIt.hasNext()){
int var = varIt.nextInt();
if (!vars[var].contains(values[i])) {
possibles[i].remove(var);
} else if (vars[var].isInstantiated()) {
possibles[i].remove(var);
mandatories[i].add(var);
}
}
}
}
}
private boolean filter() throws ContradictionException {
boolean again = false;
for (int i : valueToCompute) {
again |= vars[n + i].updateLowerBound(mandatories[i].size(), this);
again |= vars[n + i]
.updateUpperBound(mandatories[i].size() + possibles[i].size(), this);
if (vars[n + i].isInstantiated()) {
if (possibles[i].size() + mandatories[i].size() == vars[n + i].getLB()) {
ISetIterator possIt = possibles[i].iterator();
while (possIt.hasNext()) {
int j = possIt.nextInt();
mandatories[i].add(j);
again |= vars[j].instantiateTo(values[i], this);
}
possibles[i].clear();
valueToCompute.remove(i);//value[i] restriction entailed
} else if (mandatories[i].size() == vars[n + i].getUB()) {
ISetIterator possIt = possibles[i].iterator();
while (possIt.hasNext()) {
again |= vars[possIt.nextInt()].removeValue(values[i], this);
}
possibles[i].clear();
valueToCompute.remove(i);//value[i] restriction entailed
}
}
}
// manage holes in bounded variables
if (boundVar.size() > 0) {
again |= filterBounds();
}
return again;
}
private boolean filterBounds() throws ContradictionException {
boolean useful = false;
for (int i = 0; i < boundVar.size(); i++) {
int var = boundVar.get(i);
if (!vars[var].isInstantiated()) {
int lb = vars[var].getLB();
int index = -1;
if (map.containsKey(lb)) {
index = map.get(lb);
}
boolean b = index != -1 && !(possibles[index].contains(var) || mandatories[index].contains(var));
while (b) {
useful = true;
vars[var].removeValue(lb, this);
lb = vars[var].getLB();
index = -1;
if (map.containsKey(lb)) {
index = map.get(lb);
}
b = index != -1 && !(possibles[index].contains(var) || mandatories[index].contains(var));
}
int ub = vars[var].getUB();
index = -1;
if (map.containsKey(ub)) {
index = map.get(ub);
}
b = index != -1 && !(possibles[index].contains(var) || mandatories[index].contains(var));
while (b) {
useful = true;
vars[var].removeValue(ub, this);
ub = vars[var].getUB();
index = -1;
if (map.containsKey(ub)) {
index = map.get(ub);
}
b = index != -1 && !(possibles[index].contains(var) || mandatories[index].contains(var));
}
} else {
int val = vars[var].getValue();
if (map.containsKey(val)) {
int index = map.get(val);
if ((!possibles[index].contains(var) && !mandatories[index].contains(var))) {
fails(); // TODO: could be more precise, for explanation purpose
}
}
}
}
return useful;
}
//***********************************************************************************
// INFO
//***********************************************************************************
@Override
public int getPropagationConditions(int vIdx) {
if (vIdx >= n) {// cardinality variables
return IntEventType.boundAndInst();
}
return IntEventType.all();
}
@Override
public ESat isEntailed() {
int[] min = new int[n2];
int[] max = new int[n2];
int j, k, ub;
IntVar v;
for (int i = 0; i < n; i++) {
v = vars[i];
ub = v.getUB();
if (v.isInstantiated()) {
if (map.containsKey(v.getValue())) {
j = map.get(v.getValue());
min[j]++;
max[j]++;
}
} else {
for (k = v.getLB(); k <= ub; k = v.nextValue(k)) {
if (map.containsKey(k)) {
j = map.get(k);
max[j]++;
}
}
}
}
for (int i = 0; i < n2; i++) {
if (vars[n + i].getLB() > max[i] || vars[n + i].getUB() < min[i]) {
return ESat.FALSE;
}
}
for (int i = 0; i < n2; i++) {
if (!(vars[n + i].isInstantiated() && max[i] == min[i])) {
return ESat.UNDEFINED;
}
}
return ESat.TRUE;
}
@Override
public String toString() {
StringBuilder st = new StringBuilder();
st.append("PropFastGCC_(");
int i = 0;
for (; i < Math.min(4, vars.length); i++) {
st.append(vars[i].getName()).append(", ");
}
if (i < vars.length - 2) {
st.append("...,");
}
st.append(vars[vars.length - 1].getName()).append(")");
return st.toString();
}
}