    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}