    001package org.cpsolver.ifs.solution;
    002
    003import org.cpsolver.ifs.assignment.Assignment;
    004import org.cpsolver.ifs.model.Value;
    005import org.cpsolver.ifs.model.Variable;
    006import org.cpsolver.ifs.util.DataProperties;
    007
    008/**
    009 * General implementation of solution comparator. <br>
    010 * <br>
    011 * The solution is better than the best ever found solution when it has more
    012 * variables assigned. In the case, when both solutions have the same number of
    013 * assigned variables, the better solution is the one with smaller total value,
    014 * i.e., the sum of {@link org.cpsolver.ifs.model.Value#toDouble(Assignment)} over all
    015 * assigned variables.
    016 *
    017 * @see Solution
    018 * @see org.cpsolver.ifs.solver.Solver
    019 *
    020 * @author  Tomáš Müller
    021 * @version IFS 1.3 (Iterative Forward Search)<br>
    022 *          Copyright (C) 2006 - 2014 Tomáš Müller<br>
    023 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    024 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    025 * <br>
    026 *          This library is free software; you can redistribute it and/or modify
    027 *          it under the terms of the GNU Lesser General Public License as
    028 *          published by the Free Software Foundation; either version 3 of the
    029 *          License, or (at your option) any later version. <br>
    030 * <br>
    031 *          This library is distributed in the hope that it will be useful, but
    032 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    033 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    034 *          Lesser General Public License for more details. <br>
    035 * <br>
    036 *          You should have received a copy of the GNU Lesser General Public
    037 *          License along with this library; if not see
    038 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    039 *
    040 * @param <V> Variable
    041 * @param <T> Value
    042 */
    043public class GeneralSolutionComparator<V extends Variable<V, T>, T extends Value<V, T>> implements SolutionComparator<V, T> {
    044
    045    public GeneralSolutionComparator() {
    046    }
    047
    048    /** No parameters are used so far.
    049     * @param properties solver configuration
    050     **/
    051    public GeneralSolutionComparator(DataProperties properties) {
    052    }
    053
    054    @Override
    055    public boolean isBetterThanBestSolution(Solution<V, T> currentSolution) {
    056        if (currentSolution.getBestInfo() == null)
    057            return true;
    058        int unassigned = currentSolution.getAssignment().nrUnassignedVariables(currentSolution.getModel());
    059        if (currentSolution.getModel().getBestUnassignedVariables() != unassigned)
    060            return currentSolution.getModel().getBestUnassignedVariables() > unassigned;
    061        return currentSolution.getModel().getTotalValue(currentSolution.getAssignment()) < currentSolution.getModel().getBestValue();
    062    }
    063
    064}