All Downloads are FREE. Search and download functionalities are using the official Maven repository.

org.btrplace.scheduler.choco.extensions.FastIFFEq Maven / Gradle / Ivy

/*
 * Copyright  2020 The BtrPlace Authors. All rights reserved.
 * Use of this source code is governed by a LGPL-style
 * license that can be found in the LICENSE.txt file.
 */

package org.btrplace.scheduler.choco.extensions;


import org.chocosolver.solver.constraints.Constraint;
import org.chocosolver.solver.constraints.Propagator;
import org.chocosolver.solver.constraints.PropagatorPriority;
import org.chocosolver.solver.exception.ContradictionException;
import org.chocosolver.solver.variables.BoolVar;
import org.chocosolver.solver.variables.IntVar;
import org.chocosolver.solver.variables.events.IntEventType;
import org.chocosolver.util.ESat;

import java.util.Objects;

/**
 * A fast implementation for BVAR <=> VAR = CSTE
 *
 * @author Charles Prud'homme
 * @since 29/06/11
 */
public class FastIFFEq extends Constraint {

  private final BoolVar b;

  private final IntVar v;

  private final int c;
    /**
     * New constraint.
     *
     * @param b   the boolean variable.
     * @param var the variable that can be equals to c
     * @param c   the constraint
     */
    public FastIFFEq(BoolVar b, IntVar var, int c) {
        super("IFFEq", new FastIFFEqProp(b, var, c));
        this.b = b;
        this.v = var;
        this.c = c;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }
        FastIFFEq fastIFFEq = (FastIFFEq) o;
        return c == fastIFFEq.c &&
                Objects.equals(b, fastIFFEq.b) &&
                Objects.equals(v, fastIFFEq.v);
    }

    @Override
    public int hashCode() {
        return Objects.hash(b, v, c);
    }

    @Override
    public String toString() {
        return "iffeq(" + b + " <-> " + v + " = " + c + ")";
    }

    /**
     * Propagator for {@link org.btrplace.scheduler.choco.extensions.FastIFFEq}
     */
    static class FastIFFEqProp extends Propagator {

        private final int constant;

        /**
         * Default constructor.
         *
         * @param b   the boolean variable
         * @param var the integer variable
         * @param c   the constant
         */
        public FastIFFEqProp(BoolVar b, IntVar var, int c) {
            super(new IntVar[]{b, var}, PropagatorPriority.BINARY, true);
            this.constant = c;
        }

        @Override
        public int getPropagationConditions(int idx) {
            if (idx == 0) {
                return IntEventType.INSTANTIATE.getMask();
            }
            if (vars[1].hasEnumeratedDomain()) {
                return IntEventType.INSTANTIATE.getMask() + IntEventType.BOUND.getMask() + IntEventType.REMOVE.getMask();
            }
            return IntEventType.INSTANTIATE.getMask() + IntEventType.BOUND.getMask();
        }

        @Override
        public void propagate(int mask) throws ContradictionException {
            if (vars[0].isInstantiated()) {
                if (vars[0].contains(0)) {
                    if (vars[1].removeValue(constant, this))
                        setPassive();
                } else {
                    vars[1].instantiateTo(constant, this);
                }
            } else if (vars[1].isInstantiatedTo(constant)) {
                vars[0].instantiateTo(1, this);
            } else if (!vars[1].contains(constant)) {
                vars[0].instantiateTo(0, this);
                setPassive();
            }
        }

        @Override
        @SuppressWarnings("squid:S3346")
        public void propagate(int idx, int mask) throws ContradictionException {
            if (idx == 0) {
                assert IntEventType.isInstantiate(mask);
                if (vars[0].contains(0)) {
                    if (vars[1].removeValue(constant, this))
                        setPassive();
                } else {
                    vars[1].instantiateTo(constant, this);
                }
            } else {
                if (vars[1].isInstantiatedTo(constant)) {
                    vars[0].instantiateTo(1, this);
                } else if (!vars[1].contains(constant)) {
                    vars[0].instantiateTo(0, this);
                    setPassive();
                }
            }
        }

        /**
         * @return true if (b==0 && c\not\in D(x)) or (b=1 && x=c) and false if (b=1 && c\not\in D(x)) or (b==0 && x=c)
         */
        @Override
        public ESat isEntailed() {
            if (vars[0].isInstantiated()) {
                if (vars[0].contains(0)) {
                    return !vars[1].contains(constant) ? ESat.TRUE : vars[1].isInstantiated() ? ESat.FALSE : ESat.UNDEFINED;
                }
                return !vars[1].contains(constant) ? ESat.FALSE : vars[1].isInstantiated() ? ESat.TRUE : ESat.UNDEFINED;
            }
            return ESat.UNDEFINED;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) {
                return true;
            }
            if (o == null || getClass() != o.getClass()) {
                return false;
            }
            if (!super.equals(o)) {
                return false;
            }
            FastIFFEqProp that = (FastIFFEqProp) o;
            return constant == that.constant;
        }

        @Override
        public int hashCode() {
            return constant;
        }
    }

}




© 2015 - 2025 Weber Informatics LLC | Privacy Policy