    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 for minimal perturbation
    010 * problem. <br>
    011 * <br>
    012 * The solution is better than the best ever found solution when it has more
    013 * variables assigned. In the case, when both solutions have the same number of
    014 * assigned variables, the one with smaller number of perturbations (i.e.,
    015 * variables assigned to non-initial values) is selected. When all solution have
    016 * the same number of assigned variables and number of perturbations, better
    017 * solution is the one with smaller total value, i.e., the sum of
    018 * {@link org.cpsolver.ifs.model.Value#toDouble(Assignment)} over all assigned
    019 * variables.
    020 *
    021 * @see Solution
    022 * @see org.cpsolver.ifs.solver.Solver
    023 *
    024 * @version IFS 1.3 (Iterative Forward Search)<br>
    025 *          Copyright (C) 2006 - 2014 Tomáš Müller<br>
    026 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    027 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    028 * <br>
    029 *          This library is free software; you can redistribute it and/or modify
    030 *          it under the terms of the GNU Lesser General Public License as
    031 *          published by the Free Software Foundation; either version 3 of the
    032 *          License, or (at your option) any later version. <br>
    033 * <br>
    034 *          This library is distributed in the hope that it will be useful, but
    035 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    036 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    037 *          Lesser General Public License for more details. <br>
    038 * <br>
    039 *          You should have received a copy of the GNU Lesser General Public
    040 *          License along with this library; if not see
    041 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    042 *
    043 * @param <V> Variable
    044 * @param <T> Value
    045 */
    046public class MPPSolutionComparator<V extends Variable<V, T>, T extends Value<V, T>> implements SolutionComparator<V, T> {
    047
    048    public MPPSolutionComparator() {
    049    }
    050
    051    /** No parameters are used so far.
    052     * @param properties solver configuration
    053     **/
    054    public MPPSolutionComparator(DataProperties properties) {
    055    }
    056
    057    @Override
    058    public boolean isBetterThanBestSolution(Solution<V, T> currentSolution) {
    059        if (currentSolution.getBestInfo() == null)
    060            return true;
    061        int unassigned = currentSolution.getAssignment().nrUnassignedVariables(currentSolution.getModel());
    062        if (currentSolution.getModel().getBestUnassignedVariables() != unassigned)
    063            return currentSolution.getModel().getBestUnassignedVariables() > unassigned;
    064        int pert = currentSolution.getModel().perturbVariables(currentSolution.getAssignment()).size();
    065        if (currentSolution.getModel().getBestPerturbations() != pert)
    066            return currentSolution.getModel().getBestPerturbations() > pert;
    067        return currentSolution.getModel().getTotalValue(currentSolution.getAssignment()) < currentSolution.getModel().getBestValue();
    068    }
    069
    070}