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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.
*/
/**
* Created by IntelliJ IDEA.
* User: Jean-Guillaume Fages
* Date: 03/10/11
* Time: 19:56
*/
package org.chocosolver.solver.constraints.nary.circuit;
import gnu.trove.list.array.TIntArrayList;
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.IntEventType;
import org.chocosolver.util.ESat;
import org.chocosolver.util.tools.ArrayUtils;
import java.util.BitSet;
/**
* Subcircuit propagator (one circuit and several loops)
*
* @author Jean-Guillaume Fages
*/
public class PropSubcircuit extends Propagator {
//***********************************************************************************
// VARIABLES
//***********************************************************************************
private final int n;
private final int offset; // lower bound
private final IntVar length;
private final IStateInt[] origin;
private final IStateInt[] end;
private final IStateInt[] size;
//***********************************************************************************
// CONSTRUCTORS
//***********************************************************************************
public PropSubcircuit(IntVar[] variables, int offset, IntVar length) {
super(ArrayUtils.append(variables, new IntVar[]{length}), PropagatorPriority.UNARY, true);
n = variables.length;
this.offset = offset;
this.length = length;
origin = new IStateInt[n];
end = new IStateInt[n];
size = new IStateInt[n];
IEnvironment environment = model.getEnvironment();
for (int i = 0; i < n; i++) {
origin[i] = environment.makeInt(i);
end[i] = environment.makeInt(i);
size[i] = environment.makeInt(1);
}
}
//***********************************************************************************
// METHODS
//***********************************************************************************
@Override
public void propagate(int evtmask) throws ContradictionException {
for (int i = 0; i < n; i++) {
origin[i].set(i);
end[i].set(i);
size[i].set(1);
}
TIntArrayList fixedVar = new TIntArrayList();
for (int i = 0; i < n; i++) {
vars[i].updateBounds(offset, n - 1 + offset, this);
if (vars[i].isInstantiated() && i + offset != vars[i].getValue()) {
fixedVar.add(i);
}
}
for (int i = 0; i < fixedVar.size(); i++) {
varInstantiated(fixedVar.get(i), vars[fixedVar.get(i)].getValue() - offset);
}
}
@Override
public void propagate(int idxVarInProp, int mask) throws ContradictionException {
int next = vars[idxVarInProp].getValue();
if (idxVarInProp != next - offset) {
varInstantiated(idxVarInProp, next - offset);
}
}
/**
* var in [0,n-1] and val in [0,n-1]
*
* @param var origin
* @param val dest
* @throws ContradictionException if failure occurs
*/
private void varInstantiated(int var, int val) throws ContradictionException {
if (isPassive()) {
return;
}
int last = end[val].get(); // last in [0, n-1]
int start = origin[var].get(); // start in [0, n-1]
if (origin[val].get() != val) {
fails(); // TODO: could be more precise, for explanation purpose
}
if (end[var].get() != var) {
fails(); // TODO: could be more precise, for explanation purpose
}
if (val == start) {
length.instantiateTo(size[start].get(), this);
} else {
size[start].add(size[val].get());
if (size[start].get() == length.getUB()) {
vars[last].instantiateTo(start + offset, this);
for (int i = 0; i < n; i++) {
if (!vars[i].isInstantiated()) {
vars[i].instantiateTo(i + offset, this);
}
}
setPassive();
}
boolean isInst = false;
if (size[start].get() < length.getLB()) {
if (vars[last].removeValue(start + offset, this)) {
isInst = vars[last].isInstantiated();
}
}
origin[last].set(start);
end[start].set(last);
if (isInst) {
varInstantiated(last, vars[last].getValue() - offset);
}
}
}
@Override
public int getPropagationConditions(int vIdx) {
if(vIdx < n) {
return IntEventType.instantiation();
}else{
return IntEventType.VOID.getMask();
}
}
@Override
public ESat isEntailed() {
if (isCompletelyInstantiated() && length.isInstantiated()) {
int ct = 0;
int first = -1;
BitSet visited = new BitSet(n);
for (int i = 0; i < n; i++) {
if (vars[i].getValue() == i + offset) {
visited.set(i);
ct++;
} else if (first == -1) {
first = i;
}
}
if (length.getValue() + ct != n) {
return ESat.FALSE;
}
if (ct == n) {
return ESat.TRUE;
}
int x = first;
do {
if (visited.get(x)) {
return ESat.FALSE;
}
visited.set(x);
x = vars[x].getValue() - offset;
} while (x != first);
if (visited.cardinality() != n) {
return ESat.FALSE;
}
return ESat.TRUE;
} else {
return ESat.UNDEFINED;
}
}
}