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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.sat;
import org.chocosolver.solver.ICause;
import org.chocosolver.solver.exception.ContradictionException;
import org.chocosolver.solver.variables.BoolVar;
import org.chocosolver.solver.variables.IntVar;
import org.chocosolver.solver.variables.SetVar;
import org.chocosolver.solver.variables.Variable;
import org.chocosolver.util.ESat;
import java.util.Objects;
import static org.chocosolver.sat.MiniSat.sgn;
import static org.chocosolver.sat.MiniSat.var;
/**
*
* This abstract class makes possible to maintain relationships between a CP variable
* and a SAT variable.
*
*
* That is, it turns an event on a variable from constraint programming side
* to an event on a variable in SAT side ({@link MiniSat}).
*
* On the other side, it turns an event on a variable from SAT side
* to an event on a variable in CP side.
*
*
* @author Charles Prud'homme
* @since 29/03/2021
*/
public interface Literalizer {
/**
* Set the SAT variable
*/
void svar(int svar);
/**
* @return this SAT variable
*/
int svar();
/**
* @return this CP variable
*/
Variable cvar();
/**
* @return {@code true} if this will fix its literal
*/
boolean canReact();
/**
* Turns an event into a literal and returns it.
*
* @return the literal to enqueue in SAT
*/
int toLit();
/**
* Turns an event from SAT side (in the form of a literal) to an event in CP side.
* Actually, it is expected that the event is directly applied, that's why a contradiction may be thrown.
*
* @param lit the literal
* @param cause cause (for CP propagation purpose)
* @return {@code true} if the CP variable has been modified
* @throws ContradictionException if the conversion leads to a failure
*/
boolean toEvent(int lit, ICause cause) throws ContradictionException;
boolean check(boolean sign);
class BoolLit implements Literalizer {
public final BoolVar cpVar;
public int satVar;
public BoolLit(BoolVar cpVar) {
this.cpVar = cpVar;
this.satVar = -1;
}
@Override
public void svar(int svar) {
if (satVar == -1) {
this.satVar = svar;
} else {
throw new UnsupportedOperationException("Overriding Literalizer's satVar is forbidden");
}
}
@Override
public int svar() {
return satVar;
}
@Override
public Variable cvar() {
return cpVar;
}
@Override
public boolean canReact() {
return cpVar.isInstantiated();
}
@Override
public int toLit() {
return MiniSat.makeLiteral(satVar, cpVar.getValue() != 0);
}
@Override
public boolean toEvent(int lit, ICause cause) throws ContradictionException {
assert satVar == var(lit);
return cpVar.instantiateTo(sgn(lit) ? 1 : 0, cause);
}
/**
* @return {@code true} if this relationship holds
*/
@Override
public boolean check(boolean sign) {
return cpVar.getBooleanValue().equals(ESat.eval(sign));
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (!(o instanceof BoolLit)) return false;
BoolLit boolLit = (BoolLit) o;
return cpVar.equals(boolLit.cpVar);
}
@Override
public int hashCode() {
return Objects.hash(cpVar);
}
}
class IntEqLit implements Literalizer {
public final IntVar cpVar;
public final int val;
public int satVar;
public IntEqLit(IntVar cpVar, int val) {
this.cpVar = cpVar;
this.val = val;
this.satVar = -1;
}
@Override
public void svar(int svar) {
if (satVar == -1) {
this.satVar = svar;
} else {
throw new UnsupportedOperationException("Overriding Literalizer's satVar is forbidden");
}
}
@Override
public int svar() {
return satVar;
}
@Override
public Variable cvar() {
return cpVar;
}
@Override
public boolean canReact() {
return cpVar.isInstantiated() || !cpVar.contains(val);
}
@Override
public int toLit() {
return MiniSat.makeLiteral(satVar, cpVar.isInstantiatedTo(val));
}
@Override
public boolean toEvent(int lit, ICause cause) throws ContradictionException {
assert satVar == var(lit);
if (sgn(lit)) {
return cpVar.instantiateTo(val, cause);
} else {
return cpVar.removeValue(val, cause);
}
}
@Override
public boolean check(boolean sign) {
return sign ? cpVar.isInstantiatedTo(val) : !cpVar.contains(val);
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (!(o instanceof IntEqLit)) return false;
IntEqLit intEqLit = (IntEqLit) o;
return val == intEqLit.val && cpVar.equals(intEqLit.cpVar);
}
@Override
public int hashCode() {
return Objects.hash(cpVar, val);
}
}
class IntLeLit implements Literalizer {
public final IntVar cpVar;
public final int val;
public int satVar;
public IntLeLit(IntVar cpVar, int val) {
this.cpVar = cpVar;
this.val = val;
this.satVar = -1;
}
@Override
public void svar(int svar) {
if (satVar == -1) {
this.satVar = svar;
} else {
throw new UnsupportedOperationException("Overriding Literalizer's satVar is forbidden");
}
}
@Override
public int svar() {
return satVar;
}
@Override
public Variable cvar() {
return cpVar;
}
@Override
public boolean canReact() {
return cpVar.getUB() <= val || cpVar.getLB() > val;
}
@Override
public int toLit() {
return MiniSat.makeLiteral(satVar, cpVar.getUB() <= val);
}
@Override
public boolean toEvent(int lit, ICause cause) throws ContradictionException {
assert satVar == var(lit);
if (sgn(lit)) {
return cpVar.updateUpperBound(val, cause);
} else {
return cpVar.updateLowerBound(val + 1, cause);
}
}
@Override
public boolean check(boolean sign) {
return sign ? cpVar.getUB() <= val : cpVar.getLB() > val;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (!(o instanceof IntLeLit)) return false;
IntLeLit intLeLit = (IntLeLit) o;
return val == intLeLit.val && satVar == intLeLit.satVar && cpVar.equals(intLeLit.cpVar);
}
@Override
public int hashCode() {
return Objects.hash(cpVar, val);
}
}
class SetInLit implements Literalizer {
public final SetVar cpVar;
public final int val;
public int satVar;
public SetInLit(SetVar cpVar, int val) {
this.cpVar = cpVar;
this.val = val;
this.satVar = -1;
}
@Override
public void svar(int svar) {
if (satVar == -1) {
this.satVar = svar;
} else {
throw new UnsupportedOperationException("Overriding Literalizer's satVar is forbidden");
}
}
@Override
public int svar() {
return satVar;
}
@Override
public Variable cvar() {
return cpVar;
}
@Override
public boolean canReact() {
return cpVar.getLB().contains(val) || !cpVar.getUB().contains(val);
}
@Override
public int toLit() {
return MiniSat.makeLiteral(satVar, cpVar.getLB().contains(val));
}
@Override
public boolean toEvent(int lit, ICause cause) throws ContradictionException {
assert satVar == var(lit);
if (sgn(lit)) {
return cpVar.force(val, cause);
} else {
return cpVar.remove(val, cause);
}
}
@Override
public boolean check(boolean sign) {
return sign ? cpVar.getLB().contains(val) : !cpVar.getUB().contains(val);
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (!(o instanceof SetInLit)) return false;
SetInLit setInLit = (SetInLit) o;
return val == setInLit.val && cpVar.equals(setInLit.cpVar);
}
@Override
public int hashCode() {
return Objects.hash(cpVar, val);
}
}
}