org.chocosolver.solver.constraints.nary.nvalue.PropAtLeastNValues Maven / Gradle / Ivy
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Open-source constraint solver.
/*
* This file is part of choco-solver, http://choco-solver.org/
*
* Copyright (c) 2023, 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.nvalue;
import org.chocosolver.solver.constraints.Propagator;
import org.chocosolver.solver.exception.ContradictionException;
import org.chocosolver.solver.learn.ExplanationForSignedClause;
import org.chocosolver.solver.variables.IntVar;
import org.chocosolver.util.ESat;
import org.chocosolver.util.objects.setDataStructures.iterable.IntIterableRangeSet;
import java.util.stream.IntStream;
import static org.chocosolver.solver.constraints.PropagatorPriority.QUADRATIC;
import static org.chocosolver.util.tools.ArrayUtils.concat;
/**
* Propagator for the atMostNValues constraint
* The number of distinct values in the set of variables vars is at most equal to nValues
* No level of consistency but better than BC in general (for enumerated domains with holes)
*
* @author Jean-Guillaume Fages
*/
public class PropAtLeastNValues extends Propagator {
//***********************************************************************************
// VARIABLES
//***********************************************************************************
private final int[] concernedValues;
private final int n;
private final int[] mate;
//***********************************************************************************
// CONSTRUCTORS
//***********************************************************************************
/**
* Propagator for the NValues constraint
* The number of distinct values among concerned values in the set of variables vars is exactly equal to nValues
* No level of consistency for the filtering
*
* @param variables array of integer variables
* @param nValues integer variable
*/
public PropAtLeastNValues(IntVar[] variables, IntVar nValues) {
super(concat(variables, nValues), QUADRATIC, false);
n = variables.length;
this.concernedValues = model.getDomainUnion(variables);
mate = new int[concernedValues.length];
}
//***********************************************************************************
// PROPAGATION
//***********************************************************************************
@Override
public void propagate(int evtmask) throws ContradictionException {
vars[n].updateUpperBound(n, this);
int count = 0;
int countMax = 0;
for (int i = concernedValues.length - 1; i >= 0; i--) {
boolean possible = false;
boolean mandatory = false;
mate[i] = -1;
int value = concernedValues[i];
for (int v = 0; v < n; v++) {
if (vars[v].contains(value)) {
possible = true;
if (vars[v].isInstantiated()) {
mandatory = true;
mate[i] = -2;
break;
} else {
if (mate[i] == -1) {
mate[i] = v;
} else {
mate[i] = -2;
}
}
}
}
if (possible) {
countMax++;
}
if (mandatory) {
count++;
}
}
// filtering cardinality variable
vars[n].updateUpperBound(countMax, this);
// filtering decision variables
boolean again = false;
if (count < countMax && countMax == vars[n].getLB()) {
for (int i = concernedValues.length - 1; i >= 0; i--) {
if (mate[i] >= 0) {
if (vars[mate[i]].instantiateTo(concernedValues[i], this)) {
again = true;
}
}
}
if (!again) {
int nbInst = 0;
for (int i = 0; i < n; i++) {
if (vars[i].isInstantiated()) {
nbInst++;
}
}
// remove used variables when alldiff is required over uninstantiated variables
if (n - nbInst == countMax - count) {
for (int i = concernedValues.length - 1; i >= 0; i--) {
boolean mandatory = false;
int value = concernedValues[i];
for (int v = 0; v < n; v++) {
if (vars[v].isInstantiatedTo(value)) {
mandatory = true;
break;
}
}
if (mandatory) {
for (int v = 0; v < n; v++) {
if (!vars[v].isInstantiated()) {
if (vars[v].removeValue(value, this)) {
again = true;
}
}
}
}
}
}
}
}
if (count >= vars[n].getUB()) {
setPassive();
} else if (again) {
propagate(0);// fix point is required as not all possible values add a mate
}
}
//***********************************************************************************
// INFO
//***********************************************************************************
@Override
public ESat isEntailed() {
int countMin = 0;
int countMax = 0;
for (int i = concernedValues.length - 1; i >= 0; i--) {
boolean possible = false;
boolean mandatory = false;
for (int v = 0; v < n; v++) {
if (vars[v].contains(concernedValues[i])) {
possible = true;
if (vars[v].isInstantiated()) {
mandatory = true;
break;
}
}
}
if (possible) {
countMax++;
}
if (mandatory) {
countMin++;
}
}
if (countMin >= vars[n].getUB()) {
return ESat.TRUE;
}
if (countMax < vars[n].getLB()) {
return ESat.FALSE;
}
return ESat.UNDEFINED;
}
/**
* Find in the implication graph and add to the explanation all the remove value events (the real events added are inverted because only disjunctions are allowed for explanation)
*/
private void explainDiffForalliForallt(ExplanationForSignedClause e, int[] indexes) {
for (int i : indexes) {
for(int t : e.root(vars[i])){
if (!e.domain(vars[i]).contains(t)) {
vars[i].unionLit(t,e);
}
}//vars[i].unionLit(e.complement(vars[i]),e);
}
}
/**
* Find in the implication graph and add to the explanation all the remove value events except those on value t (the real events added are inverted because only disjunctions are allowed for explanation)
* @param t exception value
*/
private void explainDiffForalliForalltDifft(ExplanationForSignedClause e, int[] indexes, int t) {
for (int i : indexes) {
for(int tt : e.root(vars[i])){
if (!e.domain(vars[i]).contains(tt)&&t!=tt) {
vars[i].unionLit(tt,e);
}
}//vars[i].unionLit(e.complement(vars[i]),e);
}
}
/**
* Find in the implication graph and add in the explanation remove value t events (the real events added are inverted because only disjunctions are allowed for explanation)
* @param t value
*/
private void explainDiffForallit(ExplanationForSignedClause e, int[] indexes, int t) {
for (int i : indexes) {
if (!e.domain(vars[i]).contains(t)) {
vars[i].unionLit(t,e);
}
}
}
/**
* Find in the implication graph and add to the explanation all the instantiate events except those on value t (the real events added are inverted because only disjunctions are allowed for explanation)
* @param t exception value
*/
private void explainEquaForalliForalltDifft(ExplanationForSignedClause e, int[] indexes, int t) {
for (int i : indexes) {
for(int tt : e.root(vars[i])){
if (e.domain(vars[i]).contains(tt)&&t!=tt) {
vars[i].intersectLit(e.setDiffVal(tt),e);
}
}
}
}
/**
* Find in the implication graph and add in the explanation all instantiation events (the real events added are inverted because only disjunctions are allowed for explanation)
*/
private void explainEquaForalliForallt(ExplanationForSignedClause e, int[] indexes) {
for (int i : indexes) {
for (int t : e.root(vars[i])) {
if (e.domain(vars[i]).contains(t)) {
vars[i].intersectLit(e.setDiffVal(t), e);
}
}
}
}
/**
* Detect and explain the event at pivot variable p
* @param p pivot variable
*/
@Override
public void explain(int p, ExplanationForSignedClause e) {
IntVar pivot = e.readVar(p);
int[] X = IntStream.rangeClosed(0, vars.length - 2).filter(i->vars[i]!=pivot).toArray();
switch (e.readMask(p)) {
case 4://DECUPP
explainDiffForalliForallt(e, X);
pivot.intersectLit(IntIterableRangeSet.MIN, e.domain(pivot).max(), e);
break;
case 8://INSTANTIATE
assert e.readDom(p).size()==1;
int t = e.readDom(p).min();
explainDiffForallit(e, X, t);
explainDiffForalliForalltDifft(e, X, t);
explainEquaForalliForalltDifft(e, X, t);
vars[vars.length - 1].unionLit(e.complement(vars[vars.length - 1]),e);
IntIterableRangeSet set = e.complement(pivot);
set.add(t);
pivot.intersectLit(set, e);
break;
case 2://INCLOW
case 1://REMOVE
case 0://VOID
case 6://BOUND inclow+decup
default:
throw new UnsupportedOperationException("Unknown event type explanation");
}
}
}