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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.extension.nary;
import org.chocosolver.memory.IEnvironment;
import org.chocosolver.memory.IStateInt;
import org.chocosolver.solver.constraints.extension.Tuples;
import org.chocosolver.solver.exception.ContradictionException;
import org.chocosolver.solver.exception.SolverException;
import org.chocosolver.solver.variables.IntVar;
import org.chocosolver.solver.variables.Variable;
import org.chocosolver.solver.variables.events.PropagatorEventType;
import org.chocosolver.util.objects.setDataStructures.iterable.IntIterableBitSet;
/**
*
*
* @author Charles Prud'homme, Hadrien Cambazard
* @since 24/04/2014
*/
public class PropLargeGAC2001 extends PropLargeCSP {
// Last valid supports Last(x_i, val) = supports( (blocks(i) + val) * size )
private final IStateInt[] supports;
private final int[] blocks;
// Cardinality
private final int size;
// offsets(i) = Min(x_i)
private final int[] offsets;
// check if none of the tuple is trivially outside
//the domains and if yes use a fast valid check
//by avoiding checking the bounds
private final ValidityChecker valcheck;
private final IntIterableBitSet vrms;
private PropLargeGAC2001(IntVar[] vs, LargeRelation relation) {
super(vs, relation);
this.size = vs.length;
this.blocks = new int[size];
this.offsets = new int[size];
int nbElt = 0;
boolean allboolean = true;
for (int i = 0; i < size; i++) {
offsets[i] = vs[i].getLB();
blocks[i] = nbElt;
if ((vars[i].getTypeAndKind() & Variable.KIND) != Variable.BOOL) allboolean = false;
if (!vars[i].hasEnumeratedDomain()) {
throw new SolverException("GAC2001 can not be used with bound variables");
} else nbElt += vars[i].getUB() - vars[i].getLB() + 1;
}
this.supports = new IStateInt[nbElt * size];
IEnvironment env = vs[0].getEnvironment();
for (int i = 0; i < supports.length; i++) {
supports[i] = env.makeInt(Integer.MIN_VALUE);
}
if (allboolean)
valcheck = new FastBooleanValidityChecker(size, vars);
else
valcheck = new ValidityChecker(size, vars);
vrms = new IntIterableBitSet();
}
public PropLargeGAC2001(IntVar[] vs, Tuples tuples) {
this(vs, RelationFactory.makeLargeRelation(tuples, vs));
}
@Override
public void propagate(int evtmask) throws ContradictionException {
if (PropagatorEventType.isFullPropagation(evtmask)) {
for (int i = 0; i < vars.length; i++) {
reviseVar(i, true);
}
}
for (int i = 0; i < size; i++)
reviseVar(i, false);
}
@Override
public void propagate(int idxVarInProp, int mask) throws ContradictionException {
filter(idxVarInProp);
}
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// updates the support for all values in the domain of variable
// and remove unsupported values for variable
private void reviseVar(int indexVar, boolean fromScratch) throws ContradictionException {
int[] currentSupport;
vrms.clear();
vrms.setOffset(vars[indexVar].getLB());
int val;
for (val = vars[indexVar].getLB(); val <= vars[indexVar].getUB(); val = vars[indexVar].nextValue(val)) {
currentSupport = seekNextSupport(indexVar, val, fromScratch);
if (currentSupport != null) {
setSupport(indexVar, val, currentSupport);
} else {
vrms.add(val);
// vars[indexVar].removeVal(val, this, false);
}
}
vars[indexVar].removeValues(vrms, this);
}
// Store Last(x_i, val) = support
private void setSupport(int indexVar, int value, int[] support) {
for (int i = 0; i < vars.length; i++) {
supports[(blocks[indexVar] + value - offsets[indexVar]) * size + i].set(support[i]);
}
}
// Get Last(x_i, val)
private int[] getUBport(int indexVar, int value) {
int[] resultat = new int[size];
for (int i = 0; i < size; i++) {
resultat[i] = supports[(blocks[indexVar] + value - offsets[indexVar]) * size + i].get();
}
return resultat;
}
/**
* seek a new support for (variable, value), the smallest tuple greater than currentSupport
* the search is made through valid tuples until and allowed one is found.
*/
private int[] seekNextSupport(int indexVar, int val, boolean fromscratch) {
int[] currentSupport = new int[size];
int k = 0;
if (fromscratch) {
for (int i = 0; i < size; i++) {
if (i != indexVar)
currentSupport[i] = vars[i].getLB();
else currentSupport[i] = val;
}
if (relation.isConsistent(currentSupport)) {
return currentSupport;
}
} else {
currentSupport = getUBport(indexVar, val);
if (valcheck.isValid(currentSupport)) {
return currentSupport;
} else {
currentSupport = getFirstValidTupleFrom(currentSupport, indexVar);
if (currentSupport == null) return null;
if (relation.isConsistent(currentSupport))
return currentSupport;
}
}
while (k < vars.length) {
if (k == indexVar) k++;
if (k < vars.length) {
if (vars[k].nextValue(currentSupport[k]) == Integer.MAX_VALUE) {
currentSupport[k] = vars[k].getLB();
k++;
} else {
currentSupport[k] = vars[k].nextValue(currentSupport[k]);
if ((relation.isConsistent(currentSupport))) {
return currentSupport;
}
k = 0;
}
}
}
return null;
}
/**
* t is a consistent tuple not valid anymore, we need to go to the first valid tuple
* greater than t before searching among the valid tuples
*/
private int[] getFirstValidTupleFrom(int[] t, int indexVar) {
int k = 0;
while (k < vars.length) {
if (k == indexVar) k++;
if (k < vars.length) {
if (vars[k].nextValue(t[k]) == Integer.MAX_VALUE) {
t[k] = vars[k].getLB();
k++;
} else {
t[k] = vars[k].nextValue(t[k]);
if (valcheck.isValid(t)) {
return t;
}
k = 0;
}
}
}
return null;
}
private void filter(int idx) throws ContradictionException {
//sort variables regarding domain sizes to speedup the check !
valcheck.sortvars();
if (vars[idx].hasEnumeratedDomain()) {
for (int i = 0; i < size; i++)
if (idx != valcheck.getPosition(i))
reviseVar(valcheck.getPosition(i), false);
} else {
for (int i = 0; i < size; i++)
reviseVar(valcheck.getPosition(i), false);
}
}
}