    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 * @author  Tomáš Müller
    025 * @version IFS 1.3 (Iterative Forward Search)<br>
    026 *          Copyright (C) 2006 - 2014 Tomáš Müller<br>
    027 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    028 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    029 * <br>
    030 *          This library is free software; you can redistribute it and/or modify
    031 *          it under the terms of the GNU Lesser General Public License as
    032 *          published by the Free Software Foundation; either version 3 of the
    033 *          License, or (at your option) any later version. <br>
    034 * <br>
    035 *          This library is distributed in the hope that it will be useful, but
    036 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    037 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    038 *          Lesser General Public License for more details. <br>
    039 * <br>
    040 *          You should have received a copy of the GNU Lesser General Public
    041 *          License along with this library; if not see
    042 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    043 *
    044 * @param <V> Variable
    045 * @param <T> Value
    046 */
    047public class MPPSolutionComparator<V extends Variable<V, T>, T extends Value<V, T>> implements SolutionComparator<V, T> {
    048
    049    public MPPSolutionComparator() {
    050    }
    051
    052    /** No parameters are used so far.
    053     * @param properties solver configuration
    054     **/
    055    public MPPSolutionComparator(DataProperties properties) {
    056    }
    057
    058    @Override
    059    public boolean isBetterThanBestSolution(Solution<V, T> currentSolution) {
    060        if (currentSolution.getBestInfo() == null)
    061            return true;
    062        int unassigned = currentSolution.getAssignment().nrUnassignedVariables(currentSolution.getModel());
    063        if (currentSolution.getModel().getBestUnassignedVariables() != unassigned)
    064            return currentSolution.getModel().getBestUnassignedVariables() > unassigned;
    065        int pert = currentSolution.getModel().perturbVariables(currentSolution.getAssignment()).size();
    066        if (currentSolution.getModel().getBestPerturbations() != pert)
    067            return currentSolution.getModel().getBestPerturbations() > pert;
    068        return currentSolution.getModel().getTotalValue(currentSolution.getAssignment()) < currentSolution.getModel().getBestValue();
    069    }
    070
    071}