    001package net.sf.cpsolver.exam.neighbours;
    002
    003import java.util.ArrayList;
    004import java.util.List;
    005import java.util.Set;
    006
    007import net.sf.cpsolver.exam.model.Exam;
    008import net.sf.cpsolver.exam.model.ExamModel;
    009import net.sf.cpsolver.exam.model.ExamPeriodPlacement;
    010import net.sf.cpsolver.exam.model.ExamPlacement;
    011import net.sf.cpsolver.exam.model.ExamRoomPlacement;
    012import net.sf.cpsolver.ifs.heuristics.NeighbourSelection;
    013import net.sf.cpsolver.ifs.model.Neighbour;
    014import net.sf.cpsolver.ifs.solution.Solution;
    015import net.sf.cpsolver.ifs.solver.Solver;
    016import net.sf.cpsolver.ifs.util.DataProperties;
    017import net.sf.cpsolver.ifs.util.ToolBox;
    018
    019/**
    020 * Try to swap a room between two exams. An exam is selected randomly, a
    021 * different (available) room is randomly selected for the exam -- the exam is
    022 * assigned into the new room (if the room is used, it tries to swap the rooms
    023 * between the selected exam and the one that is using it). If an exam is
    024 * assigned into two or more rooms, only one room is swapped at a time. <br>
    025 * <br>
    026 *
    027 * @version ExamTT 1.2 (Examination Timetabling)<br>
    028 *          Copyright (C) 2008 - 2010 Tomáš Müller<br>
    029 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    030 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    031 * <br>
    032 *          This library is free software; you can redistribute it and/or modify
    033 *          it under the terms of the GNU Lesser General Public License as
    034 *          published by the Free Software Foundation; either version 3 of the
    035 *          License, or (at your option) any later version. <br>
    036 * <br>
    037 *          This library is distributed in the hope that it will be useful, but
    038 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    039 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    040 *          Lesser General Public License for more details. <br>
    041 * <br>
    042 *          You should have received a copy of the GNU Lesser General Public
    043 *          License along with this library; if not see
    044 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    045 */
    046public class ExamRoomMove implements NeighbourSelection<Exam, ExamPlacement> {
    047    private boolean iCheckStudentConflicts = false;
    048    private boolean iCheckDistributionConstraints = true;
    049
    050    /**
    051     * Constructor
    052     *
    053     * @param properties
    054     *            problem properties
    055     */
    056    public ExamRoomMove(DataProperties properties) {
    057        iCheckStudentConflicts = properties.getPropertyBoolean("ExamRoomMove.CheckStudentConflicts",
    058                iCheckStudentConflicts);
    059        iCheckDistributionConstraints = properties.getPropertyBoolean("ExamRoomMove.CheckDistributionConstraints",
    060                iCheckDistributionConstraints);
    061    }
    062
    063    /**
    064     * Initialization
    065     */
    066    @Override
    067    public void init(Solver<Exam, ExamPlacement> solver) {
    068    }
    069
    070    /**
    071     * Select an exam randomly, select an available period randomly (if it is
    072     * not assigned, from {@link Exam#getPeriodPlacements()}), select rooms
    073     * using {@link Exam#findRoomsRandom(ExamPeriodPlacement)}
    074     */
    075    @Override
    076    public Neighbour<Exam, ExamPlacement> selectNeighbour(Solution<Exam, ExamPlacement> solution) {
    077        ExamModel model = (ExamModel) solution.getModel();
    078        Exam exam = ToolBox.random(model.variables());
    079        if (exam.getMaxRooms() <= 0)
    080            return null;
    081        ExamPlacement placement = exam.getAssignment();
    082        ExamPeriodPlacement period = (placement != null ? placement.getPeriodPlacement()
    083                : (ExamPeriodPlacement) ToolBox.random(exam.getPeriodPlacements()));
    084        if (iCheckStudentConflicts && placement == null && exam.countStudentConflicts(period) > 0)
    085            return null;
    086        if (iCheckDistributionConstraints && placement == null && !exam.checkDistributionConstraints(period))
    087            return null;
    088        Set<ExamRoomPlacement> rooms = (placement != null ? placement.getRoomPlacements() : exam
    089                .findBestAvailableRooms(period));
    090        if (rooms == null || rooms.isEmpty())
    091            return null;
    092        if (placement == null)
    093            placement = new ExamPlacement(exam, period, rooms);
    094        List<ExamRoomPlacement> roomVect = new ArrayList<ExamRoomPlacement>(rooms);
    095        int rx = ToolBox.random(roomVect.size());
    096        for (int r = 0; r < roomVect.size(); r++) {
    097            ExamRoomPlacement current = roomVect.get((r + rx) % roomVect.size());
    098            int mx = ToolBox.random(exam.getRoomPlacements().size());
    099            for (int m = 0; m < exam.getRoomPlacements().size(); m++) {
    100                ExamRoomPlacement swap = exam.getRoomPlacements().get((m + mx) % exam.getRoomPlacements().size());
    101                ExamRoomSwapNeighbour n = new ExamRoomSwapNeighbour(placement, current, swap);
    102                if (n.canDo())
    103                    return n;
    104            }
    105        }
    106        rooms = exam.findRoomsRandom(period);
    107        if (rooms == null)
    108            return null;
    109        return new ExamSimpleNeighbour(new ExamPlacement(exam, period, rooms));
    110    }
    111}