    001package net.sf.cpsolver.exam.neighbours;
    002
    003import java.util.Iterator;
    004import java.util.Set;
    005
    006import net.sf.cpsolver.exam.model.Exam;
    007import net.sf.cpsolver.exam.model.ExamModel;
    008import net.sf.cpsolver.exam.model.ExamPeriodPlacement;
    009import net.sf.cpsolver.exam.model.ExamPlacement;
    010import net.sf.cpsolver.exam.model.ExamRoomPlacement;
    011import net.sf.cpsolver.exam.model.ExamRoomSharing;
    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 * A new period is selected for a randomly selected exam. It tries to use the
    021 * current set of rooms, if it is possible (exam is assigned, rooms are
    022 * available and not used during the new period). Otherwise, rooms are selected
    023 * using {@link Exam#findBestAvailableRooms(ExamPeriodPlacement)}. <br>
    024 * <br>
    025 *
    026 * @version ExamTT 1.2 (Examination Timetabling)<br>
    027 *          Copyright (C) 2008 - 2010 Tomáš Müller<br>
    028 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    029 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    030 * <br>
    031 *          This library is free software; you can redistribute it and/or modify
    032 *          it under the terms of the GNU Lesser General Public License as
    033 *          published by the Free Software Foundation; either version 3 of the
    034 *          License, or (at your option) any later version. <br>
    035 * <br>
    036 *          This library is distributed in the hope that it will be useful, but
    037 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    038 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    039 *          Lesser General Public License for more details. <br>
    040 * <br>
    041 *          You should have received a copy of the GNU Lesser General Public
    042 *          License along with this library; if not see
    043 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    044 */
    045public class ExamTimeMove implements NeighbourSelection<Exam,ExamPlacement> {
    046    private boolean iCheckStudentConflicts = false;
    047    private boolean iCheckDistributionConstraints = true;
    048
    049    /**
    050     * Constructor
    051     * @param properties problem properties
    052     */
    053    public ExamTimeMove(DataProperties properties) {
    054        iCheckStudentConflicts = properties.getPropertyBoolean("ExamTimeMove.CheckStudentConflicts", iCheckStudentConflicts);
    055        iCheckDistributionConstraints = properties.getPropertyBoolean("ExamTimeMove.CheckDistributionConstraints", iCheckDistributionConstraints);
    056    }
    057
    058    /**
    059     * Initialization
    060     */
    061    @Override
    062    public void init(Solver<Exam,ExamPlacement> solver) {}
    063
    064    /**
    065     * Select an exam randomly,
    066     * select an available period randomly (if it is not assigned),
    067     * use rooms if possible, select rooms using {@link Exam#findBestAvailableRooms(ExamPeriodPlacement)} if not (exam is unassigned, a room is not available or used).
    068     */
    069    @Override
    070    public Neighbour<Exam,ExamPlacement> selectNeighbour(Solution<Exam,ExamPlacement> solution) {
    071        ExamModel model = (ExamModel)solution.getModel();
    072        ExamRoomSharing sharing = model.getRoomSharing();
    073        Exam exam = ToolBox.random(model.variables());
    074        ExamPlacement placement = exam.getAssignment();
    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 (placement!=null && placement.getPeriod().equals(period)) continue;
    079            if (iCheckStudentConflicts && exam.countStudentConflicts(period)>0) continue;
    080            if (iCheckDistributionConstraints && !exam.checkDistributionConstraints(period)) continue;
    081            if (placement!=null) {
    082                boolean ok = true;
    083                if (sharing != null && placement.getRoomPlacements().size() == 1) {
    084                    ExamRoomPlacement room = placement.getRoomPlacements().iterator().next();
    085                    ok = room.isAvailable(period.getPeriod()) && !sharing.inConflict(exam, room.getRoom().getPlacements(period.getPeriod()), room.getRoom());
    086                } else {
    087                    for (Iterator<ExamRoomPlacement> i=placement.getRoomPlacements().iterator();i.hasNext();) {
    088                        ExamRoomPlacement room = i.next();
    089                        if (!room.isAvailable(period.getPeriod()) || !room.getRoom().getPlacements(period.getPeriod()).isEmpty()) {
    090                            ok = false; break;
    091                        }
    092                    }
    093                }
    094                if (ok)
    095                    return new ExamSimpleNeighbour(new ExamPlacement(exam, period, placement.getRoomPlacements()));
    096            }
    097            Set<ExamRoomPlacement> rooms = exam.findBestAvailableRooms(period);
    098            if (rooms==null) continue;
    099            return new ExamSimpleNeighbour(new ExamPlacement(exam, period, rooms));
    100        }
    101        return null;
    102    }
    103}