    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 * @version StudentSct 1.3 (Student Sectioning)<br>
    019 *          Copyright (C) 2007 - 2014 Tomáš Müller<br>
    020 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    021 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    022 * <br>
    023 *          This library is free software; you can redistribute it and/or modify
    024 *          it under the terms of the GNU Lesser General Public License as
    025 *          published by the Free Software Foundation; either version 3 of the
    026 *          License, or (at your option) any later version. <br>
    027 * <br>
    028 *          This library is distributed in the hope that it will be useful, but
    029 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    030 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    031 *          Lesser General Public License for more details. <br>
    032 * <br>
    033 *          You should have received a copy of the GNU Lesser General Public
    034 *          License along with this library; if not see
    035 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    036 */
    037public class RestoreBestSolution implements NeighbourSelection<Request, Enrollment> {
    038    private Double iBestValue = null;
    039
    040    public RestoreBestSolution(DataProperties config) {
    041    }
    042
    043    @Override
    044    public void init(Solver<Request, Enrollment> solver) {
    045        Progress.getInstance(solver.currentSolution().getModel()).setPhase("Restore best...", 1);
    046        if (solver.currentSolution().getBestInfo() == null) return; // no best saved yet
    047        if (iBestValue == null || iBestValue > solver.currentSolution().getBestValue()) {
    048            Progress.getInstance(solver.currentSolution().getModel()).debug("best value marked");
    049            iBestValue = solver.currentSolution().getBestValue();
    050        } else {
    051            Progress.getInstance(solver.currentSolution().getModel()).debug("best solution restored");
    052            solver.currentSolution().restoreBest();
    053        }
    054    }
    055
    056
    057    @Override
    058    public Neighbour<Request, Enrollment> selectNeighbour(Solution<Request, Enrollment> solution) {
    059        return null;
    060    }
    061
    062}