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}