    001package org.cpsolver.ifs.extension;
    002
    003import java.util.ArrayList;
    004import java.util.HashSet;
    005import java.util.HashMap;
    006import java.util.List;
    007import java.util.Map;
    008import java.util.Set;
    009
    010import org.cpsolver.ifs.assignment.Assignment;
    011import org.cpsolver.ifs.model.Constraint;
    012import org.cpsolver.ifs.model.Value;
    013import org.cpsolver.ifs.model.Variable;
    014import org.cpsolver.ifs.solver.Solver;
    015import org.cpsolver.ifs.util.DataProperties;
    016
    017
    018/**
    019 * Computation of violated initial values (minimal perturbation problem). <br>
    020 * <br>
    021 * It is using {@link Constraint#isConsistent(Value, Value)} to find out what
    022 * initial values (of different variables) cannot be assigned when an arbitrary
    023 * value is assigned to a variable. This information is computed in advance,
    024 * before the solver is executed. It is used for better estimation of
    025 * perturbation penalty (see
    026 * {@link org.cpsolver.ifs.perturbations.PerturbationsCounter}) when a value
    027 * is to be assigned to a variable.
    028 *
    029 * @author  Tomáš Müller
    030 * @version IFS 1.3 (Iterative Forward Search)<br>
    031 *          Copyright (C) 2006 - 2014 Tomáš Müller<br>
    032 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    033 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    034 * <br>
    035 *          This library is free software; you can redistribute it and/or modify
    036 *          it under the terms of the GNU Lesser General Public License as
    037 *          published by the Free Software Foundation; either version 3 of the
    038 *          License, or (at your option) any later version. <br>
    039 * <br>
    040 *          This library is distributed in the hope that it will be useful, but
    041 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    042 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    043 *          Lesser General Public License for more details. <br>
    044 * <br>
    045 *          You should have received a copy of the GNU Lesser General Public
    046 *          License along with this library; if not see
    047 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    048 * @param <V> Variable
    049 * @param <T> Value
    050 */
    051public class ViolatedInitials<V extends Variable<V, T>, T extends Value<V, T>> extends Extension<V, T> {
    052    private static org.apache.logging.log4j.Logger sLogger = org.apache.logging.log4j.LogManager.getLogger(ViolatedInitials.class);
    053    private Map<T, Set<T>> iViolatedInitials = new HashMap<T, Set<T>>();
    054
    055    public ViolatedInitials(Solver<V, T> solver, DataProperties properties) {
    056        super(solver, properties);
    057    }
    058
    059    /** Compute the violations between any value and all other initial values
    060     * @param assignment current assignment
    061     * @return true if initialized properly
    062     **/
    063    public boolean init(Assignment<V, T> assignment) {
    064        sLogger.info("Computation of violated initials enabled.");
    065        for (V variable : getModel().variables()) {
    066            if (variable.getInitialAssignment() == null)
    067                continue;
    068            for (Constraint<V, T> constraint : variable.hardConstraints()) {
    069                for (T value : conflictValues(assignment, constraint, variable.getInitialAssignment())) {
    070                    addViolatedInitial(value, variable.getInitialAssignment());
    071                }
    072            }
    073        }
    074        return true;
    075    }
    076
    077    /** Initial values that cannot be assigned when the given value is assigned
    078     * @param value given value
    079     * @return list of initial values that cannot be assigned due to the given value
    080     *
    081     **/
    082    public Set<T> getViolatedInitials(T value) {
    083        return iViolatedInitials.get(value);
    084    }
    085
    086    private void addViolatedInitial(T value, T anotherValue) {
    087        Set<T> violations = iViolatedInitials.get(value);
    088        if (violations == null) {
    089            violations = new HashSet<T>();
    090            iViolatedInitials.put(value, violations);
    091        }
    092        violations.add(anotherValue);
    093    }
    094
    095    private List<T> conflictValues(Assignment<V, T> assignment, Constraint<V, T> constraint, T aValue) {
    096        List<T> ret = new ArrayList<T>();
    097        for (V variable : constraint.variables()) {
    098            if (variable.equals(aValue.variable()))
    099                continue;
    100            if (assignment.getValue(variable) != null)
    101                continue;
    102            for (T value : variable.values(assignment)) {
    103                if (!constraint.isConsistent(aValue, value))
    104                    ret.add(value);
    105            }
    106        }
    107        return ret;
    108    }
    109}