001package org.cpsolver.exam.neighbours;
002
003import java.util.Set;
004
005import org.cpsolver.exam.model.Exam;
006import org.cpsolver.exam.model.ExamModel;
007import org.cpsolver.exam.model.ExamPeriodPlacement;
008import org.cpsolver.exam.model.ExamPlacement;
009import org.cpsolver.exam.model.ExamRoomPlacement;
010import org.cpsolver.ifs.assignment.Assignment;
011import org.cpsolver.ifs.heuristics.NeighbourSelection;
012import org.cpsolver.ifs.model.Neighbour;
013import org.cpsolver.ifs.solution.Solution;
014import org.cpsolver.ifs.solver.Solver;
015import org.cpsolver.ifs.util.DataProperties;
016import org.cpsolver.ifs.util.ToolBox;
017
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(Assignment, ExamPeriodPlacement)}. <br>
024 * <br>
025 * 
026 * @author  Tomáš Müller
027 * @version ExamTT 1.3 (Examination Timetabling)<br>
028 *          Copyright (C) 2008 - 2014 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 ExamTimeMove implements NeighbourSelection<Exam,ExamPlacement> {
047    private boolean iCheckStudentConflicts = false;
048    private boolean iCheckDistributionConstraints = true;
049    
050    /**
051     * Constructor
052     * @param properties problem properties
053     */
054    public ExamTimeMove(DataProperties properties) {
055        iCheckStudentConflicts = properties.getPropertyBoolean("ExamTimeMove.CheckStudentConflicts", iCheckStudentConflicts);
056        iCheckDistributionConstraints = properties.getPropertyBoolean("ExamTimeMove.CheckDistributionConstraints", iCheckDistributionConstraints);
057    }
058    
059    /**
060     * Initialization
061     */
062    @Override
063    public void init(Solver<Exam,ExamPlacement> solver) {}
064    
065    /**
066     * Select an exam randomly,
067     * select an available period randomly (if it is not assigned), 
068     * use rooms if possible, select rooms using {@link Exam#findBestAvailableRooms(Assignment, ExamPeriodPlacement)} if not (exam is unassigned, a room is not available or used).
069     */
070    @Override
071    public Neighbour<Exam,ExamPlacement> selectNeighbour(Solution<Exam,ExamPlacement> solution) {
072        ExamModel model = (ExamModel)solution.getModel();
073        Assignment<Exam, ExamPlacement> assignment = solution.getAssignment();
074        Exam exam = ToolBox.random(model.variables());
075        ExamPlacement placement = assignment.getValue(exam);
076        int px = ToolBox.random(exam.getPeriodPlacements().size());
077        for (int p=0;p<exam.getPeriodPlacements().size();p++) {
078            ExamPeriodPlacement period = exam.getPeriodPlacements().get((p+px)%exam.getPeriodPlacements().size());
079            if (placement!=null && placement.getPeriod().equals(period.getPeriod())) continue;
080            if (iCheckStudentConflicts && exam.countStudentConflicts(assignment, period)>0) continue;
081            if (iCheckDistributionConstraints && !exam.checkDistributionConstraints(assignment, period)) continue;
082            if (placement!=null) {
083                boolean ok = true;
084                for (ExamRoomPlacement room: placement.getRoomPlacements())
085                    if (!room.isAvailable(period.getPeriod()) || room.getRoom().inConflict(assignment, exam, period.getPeriod())) {
086                        ok = false; break;
087                    }
088                if (ok)
089                    return new ExamSimpleNeighbour(assignment, new ExamPlacement(exam, period, placement.getRoomPlacements()));
090            }
091            Set<ExamRoomPlacement> rooms = exam.findBestAvailableRooms(assignment, period);
092            if (rooms==null) continue;
093            return new ExamSimpleNeighbour(assignment, new ExamPlacement(exam, period, rooms));
094        }
095        return null;
096    }
097}