    001package org.cpsolver.exam.neighbours;
    002
    003import java.util.Set;
    004
    005import org.cpsolver.exam.model.Exam;
    006import org.cpsolver.exam.model.ExamModel;
    007import org.cpsolver.exam.model.ExamPeriodPlacement;
    008import org.cpsolver.exam.model.ExamPlacement;
    009import org.cpsolver.exam.model.ExamRoomPlacement;
    010import org.cpsolver.ifs.assignment.Assignment;
    011import org.cpsolver.ifs.heuristics.NeighbourSelection;
    012import org.cpsolver.ifs.model.Neighbour;
    013import org.cpsolver.ifs.solution.Solution;
    014import org.cpsolver.ifs.solver.Solver;
    015import org.cpsolver.ifs.util.DataProperties;
    016import org.cpsolver.ifs.util.ToolBox;
    017
    018
    019/**
    020 * A period is selected randomly for a randomly selected exam. Rooms are
    021 * computed using {@link Exam#findBestAvailableRooms(Assignment, ExamPeriodPlacement)}. <br>
    022 * <br>
    023 *
    024 * @version ExamTT 1.3 (Examination Timetabling)<br>
    025 *          Copyright (C) 2008 - 2014 Tomáš Müller<br>
    026 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    027 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    028 * <br>
    029 *          This library is free software; you can redistribute it and/or modify
    030 *          it under the terms of the GNU Lesser General Public License as
    031 *          published by the Free Software Foundation; either version 3 of the
    032 *          License, or (at your option) any later version. <br>
    033 * <br>
    034 *          This library is distributed in the hope that it will be useful, but
    035 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    036 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    037 *          Lesser General Public License for more details. <br>
    038 * <br>
    039 *          You should have received a copy of the GNU Lesser General Public
    040 *          License along with this library; if not see
    041 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    042 */
    043public class ExamRandomMove implements NeighbourSelection<Exam, ExamPlacement> {
    044    private boolean iCheckStudentConflicts = false;
    045    private boolean iCheckDistributionConstraints = true;
    046
    047    /**
    048     * Constructor
    049     *
    050     * @param properties
    051     *            problem properties
    052     */
    053    public ExamRandomMove(DataProperties properties) {
    054        iCheckStudentConflicts = properties.getPropertyBoolean("ExamRandomMove.CheckStudentConflicts", iCheckStudentConflicts);
    055        iCheckDistributionConstraints = properties.getPropertyBoolean("ExamRandomMove.CheckDistributionConstraints", 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(Assignment, ExamPeriodPlacement)}.
    069     */
    070    @Override
    071    public Neighbour<Exam, ExamPlacement> selectNeighbour(Solution<Exam, ExamPlacement> solution) {
    072        ExamModel model = (ExamModel) solution.getModel();
    073        Assignment<Exam, ExamPlacement> assignment = solution.getAssignment();
    074        Exam exam = ToolBox.random(model.variables());
    075        int px = ToolBox.random(exam.getPeriodPlacements().size());
    076        for (int p = 0; p < exam.getPeriodPlacements().size(); p++) {
    077            ExamPeriodPlacement period = exam.getPeriodPlacements().get((p + px) % exam.getPeriodPlacements().size());
    078            if (iCheckStudentConflicts && exam.countStudentConflicts(assignment, period) > 0)
    079                continue;
    080            if (iCheckDistributionConstraints && !exam.checkDistributionConstraints(assignment, period))
    081                continue;
    082            Set<ExamRoomPlacement> rooms = exam.findBestAvailableRooms(assignment, period);
    083            if (rooms == null)
    084                continue;
    085            return new ExamSimpleNeighbour(assignment, new ExamPlacement(exam, period, rooms));
    086        }
    087        return null;
    088    }
    089}