001package net.sf.cpsolver.exam.neighbours;
002
003import java.util.Set;
004
005import net.sf.cpsolver.exam.model.Exam;
006import net.sf.cpsolver.exam.model.ExamModel;
007import net.sf.cpsolver.exam.model.ExamPeriodPlacement;
008import net.sf.cpsolver.exam.model.ExamPlacement;
009import net.sf.cpsolver.exam.model.ExamRoomPlacement;
010import net.sf.cpsolver.ifs.heuristics.NeighbourSelection;
011import net.sf.cpsolver.ifs.model.Neighbour;
012import net.sf.cpsolver.ifs.solution.Solution;
013import net.sf.cpsolver.ifs.solver.Solver;
014import net.sf.cpsolver.ifs.util.DataProperties;
015import net.sf.cpsolver.ifs.util.ToolBox;
016
017/**
018 * A period is selected randomly for a randomly selected exam. Rooms are
019 * computed using {@link Exam#findBestAvailableRooms(ExamPeriodPlacement)}. <br>
020 * <br>
021 * 
022 * @version ExamTT 1.2 (Examination Timetabling)<br>
023 *          Copyright (C) 2008 - 2010 Tomáš Müller<br>
024 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
025 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
026 * <br>
027 *          This library is free software; you can redistribute it and/or modify
028 *          it under the terms of the GNU Lesser General Public License as
029 *          published by the Free Software Foundation; either version 3 of the
030 *          License, or (at your option) any later version. <br>
031 * <br>
032 *          This library is distributed in the hope that it will be useful, but
033 *          WITHOUT ANY WARRANTY; without even the implied warranty of
034 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
035 *          Lesser General Public License for more details. <br>
036 * <br>
037 *          You should have received a copy of the GNU Lesser General Public
038 *          License along with this library; if not see
039 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
040 */
041public class ExamRandomMove implements NeighbourSelection<Exam, ExamPlacement> {
042    private boolean iCheckStudentConflicts = false;
043    private boolean iCheckDistributionConstraints = true;
044
045    /**
046     * Constructor
047     * 
048     * @param properties
049     *            problem properties
050     */
051    public ExamRandomMove(DataProperties properties) {
052        iCheckStudentConflicts = properties.getPropertyBoolean("ExamRandomMove.CheckStudentConflicts",
053                iCheckStudentConflicts);
054        iCheckDistributionConstraints = properties.getPropertyBoolean("ExamRandomMove.CheckDistributionConstraints",
055                iCheckDistributionConstraints);
056    }
057
058    /**
059     * Initialization
060     */
061    @Override
062    public void init(Solver<Exam, ExamPlacement> solver) {
063    }
064
065    /**
066     * Select an exam randomly, select an available period randomly (from
067     * {@link Exam#getPeriodPlacements()}), select rooms using
068     * {@link Exam#findBestAvailableRooms(ExamPeriodPlacement)}.
069     */
070    @Override
071    public Neighbour<Exam, ExamPlacement> selectNeighbour(Solution<Exam, ExamPlacement> solution) {
072        ExamModel model = (ExamModel) solution.getModel();
073        Exam exam = ToolBox.random(model.variables());
074        int px = ToolBox.random(exam.getPeriodPlacements().size());
075        for (int p = 0; p < exam.getPeriodPlacements().size(); p++) {
076            ExamPeriodPlacement period = exam.getPeriodPlacements().get((p + px) % exam.getPeriodPlacements().size());
077            if (iCheckStudentConflicts && exam.countStudentConflicts(period) > 0)
078                continue;
079            if (iCheckDistributionConstraints && !exam.checkDistributionConstraints(period))
080                continue;
081            Set<ExamRoomPlacement> rooms = exam.findBestAvailableRooms(period);
082            if (rooms == null)
083                continue;
084            return new ExamSimpleNeighbour(new ExamPlacement(exam, period, rooms));
085        }
086        return null;
087    }
088}