001package org.cpsolver.exam.neighbours;
002
003import java.util.Iterator;
004import java.util.Set;
005
006import org.cpsolver.exam.model.Exam;
007import org.cpsolver.exam.model.ExamModel;
008import org.cpsolver.exam.model.ExamPeriodPlacement;
009import org.cpsolver.exam.model.ExamPlacement;
010import org.cpsolver.exam.model.ExamRoomPlacement;
011import org.cpsolver.exam.model.ExamRoomSharing;
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 * A new period is selected for a randomly selected exam. It tries to use the
023 * current set of rooms, if it is possible (exam is assigned, rooms are
024 * available and not used during the new period). Otherwise, rooms are selected
025 * using {@link Exam#findBestAvailableRooms(Assignment, ExamPeriodPlacement)}. <br>
026 * <br>
027 * 
028 * @version ExamTT 1.3 (Examination Timetabling)<br>
029 *          Copyright (C) 2008 - 2014 Tomáš Müller<br>
030 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
031 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
032 * <br>
033 *          This library is free software; you can redistribute it and/or modify
034 *          it under the terms of the GNU Lesser General Public License as
035 *          published by the Free Software Foundation; either version 3 of the
036 *          License, or (at your option) any later version. <br>
037 * <br>
038 *          This library is distributed in the hope that it will be useful, but
039 *          WITHOUT ANY WARRANTY; without even the implied warranty of
040 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
041 *          Lesser General Public License for more details. <br>
042 * <br>
043 *          You should have received a copy of the GNU Lesser General Public
044 *          License along with this library; if not see
045 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
046 */
047public class ExamTimeMove implements NeighbourSelection<Exam,ExamPlacement> {
048    private boolean iCheckStudentConflicts = false;
049    private boolean iCheckDistributionConstraints = true;
050    
051    /**
052     * Constructor
053     * @param properties problem properties
054     */
055    public ExamTimeMove(DataProperties properties) {
056        iCheckStudentConflicts = properties.getPropertyBoolean("ExamTimeMove.CheckStudentConflicts", iCheckStudentConflicts);
057        iCheckDistributionConstraints = properties.getPropertyBoolean("ExamTimeMove.CheckDistributionConstraints", iCheckDistributionConstraints);
058    }
059    
060    /**
061     * Initialization
062     */
063    @Override
064    public void init(Solver<Exam,ExamPlacement> solver) {}
065    
066    /**
067     * Select an exam randomly,
068     * select an available period randomly (if it is not assigned), 
069     * use rooms if possible, select rooms using {@link Exam#findBestAvailableRooms(Assignment, ExamPeriodPlacement)} if not (exam is unassigned, a room is not available or used).
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        ExamRoomSharing sharing = model.getRoomSharing();
076        Exam exam = ToolBox.random(model.variables());
077        ExamPlacement placement = assignment.getValue(exam);
078        int px = ToolBox.random(exam.getPeriodPlacements().size());
079        for (int p=0;p<exam.getPeriodPlacements().size();p++) {
080            ExamPeriodPlacement period = exam.getPeriodPlacements().get((p+px)%exam.getPeriodPlacements().size());
081            if (placement!=null && placement.getPeriod().equals(period)) continue;
082            if (iCheckStudentConflicts && exam.countStudentConflicts(assignment, period)>0) continue;
083            if (iCheckDistributionConstraints && !exam.checkDistributionConstraints(assignment, period)) continue;
084            if (placement!=null) {
085                boolean ok = true;
086                if (sharing != null && placement.getRoomPlacements().size() == 1) {
087                    ExamRoomPlacement room = placement.getRoomPlacements().iterator().next();
088                    ok = room.isAvailable(period.getPeriod()) && !sharing.inConflict(exam, room.getRoom().getPlacements(assignment, period.getPeriod()), room.getRoom());
089                } else {
090                    for (Iterator<ExamRoomPlacement> i=placement.getRoomPlacements().iterator();i.hasNext();) {
091                        ExamRoomPlacement room = i.next();
092                        if (!room.isAvailable(period.getPeriod()) || !room.getRoom().getPlacements(assignment, period.getPeriod()).isEmpty()) {
093                            ok = false; break;
094                        }
095                    }
096                }
097                if (ok)
098                    return new ExamSimpleNeighbour(assignment, new ExamPlacement(exam, period, placement.getRoomPlacements()));
099            }
100            Set<ExamRoomPlacement> rooms = exam.findBestAvailableRooms(assignment, period);
101            if (rooms==null) continue;
102            return new ExamSimpleNeighbour(assignment, new ExamPlacement(exam, period, rooms));
103        }
104        return null;
105    }
106}