    001package org.cpsolver.studentsct.heuristics;
    002
    003import org.cpsolver.ifs.heuristics.NeighbourSelection;
    004import org.cpsolver.ifs.model.Neighbour;
    005import org.cpsolver.ifs.solution.Solution;
    006import org.cpsolver.ifs.solver.Solver;
    007import org.cpsolver.ifs.util.DataProperties;
    008import org.cpsolver.ifs.util.Progress;
    009import org.cpsolver.studentsct.model.Enrollment;
    010import org.cpsolver.studentsct.model.Request;
    011
    012/**
    013 * A simple step that checks whether the best solution has improved since the last check.
    014 * If there is no improvement, restore the best solution (reset the search to start from the best
    015 * solution again). The checking is done in the seletion's initialization phase,
    016 * no neighbors are actually computed.
    017 *
    018 * @author  Tomáš Müller
    019 * @version StudentSct 1.3 (Student Sectioning)<br>
    020 *          Copyright (C) 2007 - 2014 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 RestoreBestSolution implements NeighbourSelection<Request, Enrollment> {
    039    private Double iBestValue = null;
    040
    041    public RestoreBestSolution(DataProperties config) {
    042    }
    043
    044    @Override
    045    public void init(Solver<Request, Enrollment> solver) {
    046        Progress.getInstance(solver.currentSolution().getModel()).setPhase("Restore best...", 1);
    047        if (solver.currentSolution().getBestInfo() == null) return; // no best saved yet
    048        if (iBestValue == null || iBestValue > solver.currentSolution().getBestValue()) {
    049            Progress.getInstance(solver.currentSolution().getModel()).debug("best value marked");
    050            iBestValue = solver.currentSolution().getBestValue();
    051        } else {
    052            Progress.getInstance(solver.currentSolution().getModel()).debug("best solution restored");
    053            solver.currentSolution().restoreBest();
    054        }
    055    }
    056
    057
    058    @Override
    059    public Neighbour<Request, Enrollment> selectNeighbour(Solution<Request, Enrollment> solution) {
    060        return null;
    061    }
    062
    063}