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 * @author  Tomáš Müller
025 * @version ExamTT 1.3 (Examination Timetabling)<br>
026 *          Copyright (C) 2008 - 2014 Tomáš Müller<br>
027 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
028 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
029 * <br>
030 *          This library is free software; you can redistribute it and/or modify
031 *          it under the terms of the GNU Lesser General Public License as
032 *          published by the Free Software Foundation; either version 3 of the
033 *          License, or (at your option) any later version. <br>
034 * <br>
035 *          This library is distributed in the hope that it will be useful, but
036 *          WITHOUT ANY WARRANTY; without even the implied warranty of
037 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
038 *          Lesser General Public License for more details. <br>
039 * <br>
040 *          You should have received a copy of the GNU Lesser General Public
041 *          License along with this library; if not see
042 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
043 */
044public class ExamRandomMove implements NeighbourSelection<Exam, ExamPlacement> {
045    private boolean iCheckStudentConflicts = false;
046    private boolean iCheckDistributionConstraints = true;
047
048    /**
049     * Constructor
050     * 
051     * @param properties
052     *            problem properties
053     */
054    public ExamRandomMove(DataProperties properties) {
055        iCheckStudentConflicts = properties.getPropertyBoolean("ExamRandomMove.CheckStudentConflicts", iCheckStudentConflicts);
056        iCheckDistributionConstraints = properties.getPropertyBoolean("ExamRandomMove.CheckDistributionConstraints", iCheckDistributionConstraints);
057    }
058
059    /**
060     * Initialization
061     */
062    @Override
063    public void init(Solver<Exam, ExamPlacement> solver) {
064    }
065
066    /**
067     * Select an exam randomly, select an available period randomly (from
068     * {@link Exam#getPeriodPlacements()}), select rooms using
069     * {@link Exam#findBestAvailableRooms(Assignment, ExamPeriodPlacement)}.
070     */
071    @Override
072    public Neighbour<Exam, ExamPlacement> selectNeighbour(Solution<Exam, ExamPlacement> solution) {
073        ExamModel model = (ExamModel) solution.getModel();
074        Assignment<Exam, ExamPlacement> assignment = solution.getAssignment();
075        Exam exam = ToolBox.random(model.variables());
076        int px = ToolBox.random(exam.getPeriodPlacements().size());
077        for (int p = 0; p < exam.getPeriodPlacements().size(); p++) {
078            ExamPeriodPlacement period = exam.getPeriodPlacements().get((p + px) % exam.getPeriodPlacements().size());
079            if (iCheckStudentConflicts && exam.countStudentConflicts(assignment, period) > 0)
080                continue;
081            if (iCheckDistributionConstraints && !exam.checkDistributionConstraints(assignment, period))
082                continue;
083            Set<ExamRoomPlacement> rooms = exam.findBestAvailableRooms(assignment, period);
084            if (rooms == null)
085                continue;
086            return new ExamSimpleNeighbour(assignment, new ExamPlacement(exam, period, rooms));
087        }
088        return null;
089    }
090}