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}