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Open-source constraint solver.
/*
* This file is part of choco-solver, http://choco-solver.org/
*
* Copyright (c) 2020, 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.variables.view;
import org.chocosolver.solver.ICause;
import org.chocosolver.solver.exception.ContradictionException;
import org.chocosolver.solver.learn.ExplanationForSignedClause;
import org.chocosolver.solver.learn.Implications;
import org.chocosolver.solver.variables.IntVar;
import org.chocosolver.solver.variables.events.IntEventType;
import org.chocosolver.util.ESat;
import org.chocosolver.util.objects.ValueSortedMap;
import org.chocosolver.util.objects.setDataStructures.iterable.IntIterableRangeSet;
/**
* declare an BoolVar based on X and C, such as (X <= C) is reified by this.
Based on "Views
* and Iterators for Generic Constraint Implementations"
C. Shulte and G. Tack.
Eleventh
* International Conference on Principles and Practice of Constraint Programming
*
* @author Charles Prud'homme
* @since 04/02/11
*/
public final class LeqView extends IntBoolView {
/**
* A boolean view based on var such that var ≤ cste
*
* @param var an integer variable
* @param cste an int
*/
public LeqView(final IntVar var, final int cste) {
super(var, "≤", cste);
}
@Override
public ESat getBooleanValue() {
if (var.getUB() <= cste) {
return ESat.TRUE;
} else if (var.getLB() > cste) {
return ESat.FALSE;
}
return ESat.UNDEFINED;
}
@Override
public boolean instantiateTo(int value, ICause cause) throws ContradictionException {
assert cause != null;
boolean done = false;
if (!this.contains(value)) {
model.getSolver().getEventObserver().instantiateTo(this, value, cause, getLB(), getUB());
this.contradiction(this, MSG_EMPTY);
} else if (!isInstantiated()) {
model.getSolver().getEventObserver().instantiateTo(this, value, cause, getLB(), getUB());
notifyPropagators(IntEventType.INSTANTIATE, cause);
this.fixed.set(true);
if (reactOnRemoval) {
delta.add(1 - value, cause);
}
if (value == 1) {
done = var.updateUpperBound(cste, this);
} else {
done = var.updateLowerBound(cste + 1, this);
}
}
return done;
}
@Override
public int getDomainSize() {
return isInstantiated()?1:2;
}
@Override
public boolean isInstantiated() {
if (var.getUB() <= cste) {
return true;
} else return var.getLB() > cste;
}
@Override
public boolean contains(int value) {
if (value == 0) {
return cste < var.getUB();
} else if (value == 1) {
return var.getLB() <= cste;
}
return false;
}
@Override
public boolean isInstantiatedTo(int value) {
if (value == 0) {
return cste < var.getLB();
} else if (value == 1) {
return var.getUB() <= cste;
}
return false;
}
@Override
public int getLB() {
if (cste < var.getUB()) {
return 0;
}
return 1;
}
@Override
public int getUB() {
if (var.getLB() <= cste) {
return 1;
}
return 0;
}
@Override
public int nextValue(int v) {
if (v < 0 && contains(0)) {
return 0;
}
return v <= 0 && contains(1) ? 1 : Integer.MAX_VALUE;
}
@Override
public int nextValueOut(int v) {
int lb = 0, ub = 1;
if (var.getLB() > cste) {
ub = 0;
} else if (cste >= var.getUB()) {
lb = 1;
}
if (lb - 1 <= v && v <= ub) {
return ub + 1;
} else {
return v + 1;
}
}
@Override
public int previousValue(int v) {
if (v > 1 && contains(1)) {
return 1;
}
return v >= 1 && contains(0) ? 0 : Integer.MIN_VALUE;
}
@Override
public int previousValueOut(int v) {
int lb = 0, ub = 1;
if (var.getLB() > cste) {
ub = 0;
} else if (cste >= var.getUB()) {
lb = 1;
}
if (lb <= v && v <= ub + 1) {
return lb - 1;
} else {
return v - 1;
}
}
@Override
public void justifyEvent(IntEventType mask, int one, int two, int three) {
if (this.isInstantiated()) return;
switch (mask) {
case DECUPP:
if (one <= cste) {
model.getSolver().getEventObserver().instantiateTo(this, 1, this, 0, 1);
}
break;
case INCLOW:
if (cste < one) {
model.getSolver().getEventObserver().instantiateTo(this, 0, this, 0, 1);
}
break;
case REMOVE:
if(var.getUB() == one && var.previousValue(one) <= cste){
model.getSolver().getEventObserver().instantiateTo(this, 1, this, 0, 1);
}else if(var.getLB() == one && var.nextValue(one) > cste){
model.getSolver().getEventObserver().instantiateTo(this, 0, this, 0, 1);
}
break;
case INSTANTIATE:
if (one <= cste) {
model.getSolver().getEventObserver().instantiateTo(this, 1, this, 0, 1);
} else {
model.getSolver().getEventObserver().instantiateTo(this, 0, this, 0, 1);
}
break;
}
}
@Override
public void explain(ExplanationForSignedClause explanation, ValueSortedMap front, Implications ig, int p) {
IntVar pivot = ig.getIntVarAt(p);
int value = getValue();
if (value == 1) { // b is true and X < c holds
if (pivot == this) { // b is the pivot
explanation.addLiteral(this, explanation.getFreeSet(1), true);
IntIterableRangeSet dom0 = explanation.getComplementSet(var);
dom0.retainBetween(cste + 1, IntIterableRangeSet.MAX);
explanation.addLiteral(var,dom0, false);
} else /*if (pivot == var)*/ { // x is the pivot
explanation.addLiteral(this, explanation.getFreeSet(0), false);
IntIterableRangeSet dom0 = explanation.getRootSet(var);
dom0.retainBetween(IntIterableRangeSet.MIN, cste);
explanation.addLiteral(var, dom0, true);
}
} else if (value == 0) {
if (pivot == this) { // b is the pivot
explanation.addLiteral(this, explanation.getFreeSet(0), true);
IntIterableRangeSet dom0 = explanation.getComplementSet(var);
dom0.retainBetween(IntIterableRangeSet.MIN, cste);
explanation.addLiteral(var, dom0, false);
} else /*if (pivot == vars[0])*/ { // x is the pivot, case e. in javadoc
explanation.addLiteral(this, explanation.getFreeSet(1), false);
IntIterableRangeSet dom0 = explanation.getRootSet(var);
dom0.retainBetween(cste + 1, IntIterableRangeSet.MAX);
explanation.addLiteral(var, dom0, true);
}
}
}
}