    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 for minimal perturbation
    009 * problem. <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 one with smaller number of perturbations (i.e.,
    014 * variables assigned to non-initial values) is selected. When all solution have
    015 * the same number of assigned variables and number of perturbations, better
    016 * solution is the one with smaller total value, i.e., the sum of
    017 * {@link net.sf.cpsolver.ifs.model.Value#toDouble()} over all assigned
    018 * variables.
    019 *
    020 * @see Solution
    021 * @see net.sf.cpsolver.ifs.solver.Solver
    022 *
    023 * @version IFS 1.2 (Iterative Forward Search)<br>
    024 *          Copyright (C) 2006 - 2010 Tomáš Müller<br>
    025 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    026 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    027 * <br>
    028 *          This library is free software; you can redistribute it and/or modify
    029 *          it under the terms of the GNU Lesser General Public License as
    030 *          published by the Free Software Foundation; either version 3 of the
    031 *          License, or (at your option) any later version. <br>
    032 * <br>
    033 *          This library is distributed in the hope that it will be useful, but
    034 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    035 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    036 *          Lesser General Public License for more details. <br>
    037 * <br>
    038 *          You should have received a copy of the GNU Lesser General Public
    039 *          License along with this library; if not see
    040 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    041 */
    042public class MPPSolutionComparator<V extends Variable<V, T>, T extends Value<V, T>> implements SolutionComparator<V, T> {
    043
    044    public MPPSolutionComparator() {
    045    }
    046
    047    /** No parameters are used so far. */
    048    public MPPSolutionComparator(DataProperties properties) {
    049    }
    050
    051    @Override
    052    public boolean isBetterThanBestSolution(Solution<V, T> currentSolution) {
    053        if (currentSolution.getBestInfo() == null)
    054            return true;
    055        int unassigned = currentSolution.getModel().nrUnassignedVariables();
    056        if (currentSolution.getModel().getBestUnassignedVariables() != unassigned)
    057            return currentSolution.getModel().getBestUnassignedVariables() > unassigned;
    058        int pert = currentSolution.getModel().perturbVariables().size();
    059        if (currentSolution.getModel().getBestPerturbations() != pert)
    060            return currentSolution.getModel().getBestPerturbations() > pert;
    061        return currentSolution.getModel().getTotalValue() < currentSolution.getBestValue();
    062    }
    063
    064}