001package org.cpsolver.exam.neighbours;
002
003import java.util.ArrayList;
004import java.util.List;
005import java.util.Set;
006
007import org.cpsolver.exam.model.Exam;
008import org.cpsolver.exam.model.ExamModel;
009import org.cpsolver.exam.model.ExamPeriodPlacement;
010import org.cpsolver.exam.model.ExamPlacement;
011import org.cpsolver.exam.model.ExamRoomPlacement;
012import org.cpsolver.ifs.assignment.Assignment;
013import org.cpsolver.ifs.heuristics.NeighbourSelection;
014import org.cpsolver.ifs.model.Neighbour;
015import org.cpsolver.ifs.solution.Solution;
016import org.cpsolver.ifs.solver.Solver;
017import org.cpsolver.ifs.util.DataProperties;
018import org.cpsolver.ifs.util.ToolBox;
019
020
021/**
022 * Try to swap a room between two exams. An exam is selected randomly, a
023 * different (available) room is randomly selected for the exam -- the exam is
024 * assigned into the new room (if the room is used, it tries to swap the rooms
025 * between the selected exam and the one that is using it). If an exam is
026 * assigned into two or more rooms, only one room is swapped at a time. <br>
027 * <br>
028 * 
029 * @version ExamTT 1.3 (Examination Timetabling)<br>
030 *          Copyright (C) 2008 - 2014 Tomáš Müller<br>
031 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
032 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
033 * <br>
034 *          This library is free software; you can redistribute it and/or modify
035 *          it under the terms of the GNU Lesser General Public License as
036 *          published by the Free Software Foundation; either version 3 of the
037 *          License, or (at your option) any later version. <br>
038 * <br>
039 *          This library is distributed in the hope that it will be useful, but
040 *          WITHOUT ANY WARRANTY; without even the implied warranty of
041 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
042 *          Lesser General Public License for more details. <br>
043 * <br>
044 *          You should have received a copy of the GNU Lesser General Public
045 *          License along with this library; if not see
046 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
047 */
048public class ExamRoomMove implements NeighbourSelection<Exam, ExamPlacement> {
049    private boolean iCheckStudentConflicts = false;
050    private boolean iCheckDistributionConstraints = true;
051
052    /**
053     * Constructor
054     * 
055     * @param properties
056     *            problem properties
057     */
058    public ExamRoomMove(DataProperties properties) {
059        iCheckStudentConflicts = properties.getPropertyBoolean("ExamRoomMove.CheckStudentConflicts", iCheckStudentConflicts);
060        iCheckDistributionConstraints = properties.getPropertyBoolean("ExamRoomMove.CheckDistributionConstraints", 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(Assignment, ExamPeriodPlacement)}
074     */
075    @Override
076    public Neighbour<Exam, ExamPlacement> selectNeighbour(Solution<Exam, ExamPlacement> solution) {
077        ExamModel model = (ExamModel) solution.getModel();
078        Assignment<Exam, ExamPlacement> assignment = solution.getAssignment();
079        Exam exam = ToolBox.random(model.variables());
080        if (exam.getMaxRooms() <= 0)
081            return null;
082        ExamPlacement placement = assignment.getValue(exam);
083        ExamPeriodPlacement period = (placement != null ? placement.getPeriodPlacement()
084                : (ExamPeriodPlacement) ToolBox.random(exam.getPeriodPlacements()));
085        if (iCheckStudentConflicts && placement == null && exam.countStudentConflicts(assignment, period) > 0)
086            return null;
087        if (iCheckDistributionConstraints && placement == null && !exam.checkDistributionConstraints(assignment, period))
088            return null;
089        Set<ExamRoomPlacement> rooms = (placement != null ? placement.getRoomPlacements() : exam.findBestAvailableRooms(assignment, 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(assignment, placement, current, swap);
102                if (n.canDo())
103                    return n;
104            }
105        }
106        rooms = exam.findRoomsRandom(assignment, period);
107        if (rooms == null)
108            return null;
109        return new ExamSimpleNeighbour(assignment, new ExamPlacement(exam, period, rooms));
110    }
111}