    001package net.sf.cpsolver.ifs.solution;
    002
    003import net.sf.cpsolver.ifs.model.Value;
    004import net.sf.cpsolver.ifs.model.Variable;
    005import net.sf.cpsolver.ifs.util.DataProperties;
    006
    007/**
    008 * General implementation of solution comparator. <br>
    009 * <br>
    010 * The solution is better than the best ever found solution when it has more
    011 * variables assigned. In the case, when both solutions have the same number of
    012 * assigned variables, the better solution is the one with smaller total value,
    013 * i.e., the sum of {@link net.sf.cpsolver.ifs.model.Value#toDouble()} over all
    014 * assigned variables.
    015 *
    016 * @see Solution
    017 * @see net.sf.cpsolver.ifs.solver.Solver
    018 *
    019 * @version IFS 1.2 (Iterative Forward Search)<br>
    020 *          Copyright (C) 2006 - 2010 Tomáš Müller<br>
    021 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    022 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    023 * <br>
    024 *          This library is free software; you can redistribute it and/or modify
    025 *          it under the terms of the GNU Lesser General Public License as
    026 *          published by the Free Software Foundation; either version 3 of the
    027 *          License, or (at your option) any later version. <br>
    028 * <br>
    029 *          This library is distributed in the hope that it will be useful, but
    030 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    031 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    032 *          Lesser General Public License for more details. <br>
    033 * <br>
    034 *          You should have received a copy of the GNU Lesser General Public
    035 *          License along with this library; if not see
    036 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    037 */
    038public class GeneralSolutionComparator<V extends Variable<V, T>, T extends Value<V, T>> implements
    039        SolutionComparator<V, T> {
    040
    041    public GeneralSolutionComparator() {
    042    }
    043
    044    /** No parameters are used so far. */
    045    public GeneralSolutionComparator(DataProperties properties) {
    046    }
    047
    048    @Override
    049    public boolean isBetterThanBestSolution(Solution<V, T> currentSolution) {
    050        if (currentSolution.getBestInfo() == null)
    051            return true;
    052        int unassigned = currentSolution.getModel().nrUnassignedVariables();
    053        if (currentSolution.getModel().getBestUnassignedVariables() != unassigned)
    054            return currentSolution.getModel().getBestUnassignedVariables() > unassigned;
    055        return currentSolution.getModel().getTotalValue() < currentSolution.getBestValue();
    056    }
    057
    058}