001 package net.sf.cpsolver.exam.neighbours;
002
003 import java.util.Iterator;
004 import java.util.Set;
005
006 import net.sf.cpsolver.exam.model.Exam;
007 import net.sf.cpsolver.exam.model.ExamModel;
008 import net.sf.cpsolver.exam.model.ExamPeriodPlacement;
009 import net.sf.cpsolver.exam.model.ExamPlacement;
010 import net.sf.cpsolver.exam.model.ExamRoomPlacement;
011 import net.sf.cpsolver.ifs.heuristics.NeighbourSelection;
012 import net.sf.cpsolver.ifs.model.Neighbour;
013 import net.sf.cpsolver.ifs.solution.Solution;
014 import net.sf.cpsolver.ifs.solver.Solver;
015 import net.sf.cpsolver.ifs.util.DataProperties;
016 import net.sf.cpsolver.ifs.util.ToolBox;
017
018 /**
019 * A new period is selected for a randomly selected exam. It tries to use the current
020 * set of rooms, if it is possible (exam is assigned, rooms are available and
021 * not used during the new period). Otherwise, rooms are selected using
022 * {@link Exam#findBestAvailableRooms(ExamPeriodPlacement)}.
023 * <br><br>
024 *
025 * @version
026 * ExamTT 1.1 (Examination Timetabling)<br>
027 * Copyright (C) 2008 Tomáš Müller<br>
028 * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
029 * Lazenska 391, 76314 Zlin, Czech Republic<br>
030 * <br>
031 * This library is free software; you can redistribute it and/or
032 * modify it under the terms of the GNU Lesser General Public
033 * License as published by the Free Software Foundation; either
034 * version 2.1 of the License, or (at your option) any later version.
035 * <br><br>
036 * This library is distributed in the hope that it will be useful,
037 * but 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.
040 * <br><br>
041 * You should have received a copy of the GNU Lesser General Public
042 * License along with this library; if not, write to the Free Software
043 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
044 */
045 public class ExamTimeMove implements NeighbourSelection {
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 public void init(Solver solver) {}
062
063 /**
064 * Select an exam randomly,
065 * select an available period randomly (if it is not assigned),
066 * use rooms if possible, select rooms using {@link Exam#findBestAvailableRooms(ExamPeriodPlacement)} if not (exam is unassigned, a room is not available or used).
067 */
068 public Neighbour selectNeighbour(Solution solution) {
069 ExamModel model = (ExamModel)solution.getModel();
070 Exam exam = (Exam)ToolBox.random(model.variables());
071 ExamPlacement placement = (ExamPlacement)exam.getAssignment();
072 int px = ToolBox.random(exam.getPeriodPlacements().size());
073 for (int p=0;p<exam.getPeriodPlacements().size();p++) {
074 ExamPeriodPlacement period = (ExamPeriodPlacement)exam.getPeriodPlacements().elementAt((p+px)%exam.getPeriodPlacements().size());
075 if (placement!=null && placement.getPeriod().equals(period)) continue;
076 if (iCheckStudentConflicts && exam.countStudentConflicts(period)>0) continue;
077 if (iCheckDistributionConstraints && !exam.checkDistributionConstraints(period)) continue;
078 if (placement!=null) {
079 boolean ok = true;
080 for (Iterator i=placement.getRoomPlacements().iterator();i.hasNext();) {
081 ExamRoomPlacement room = (ExamRoomPlacement)i.next();
082 if (!room.isAvailable(period.getPeriod()) || room.getRoom().getPlacement(period.getPeriod())!=null) {
083 ok = false; break;
084 }
085 }
086 if (ok)
087 return new ExamSimpleNeighbour(new ExamPlacement(exam, period, placement.getRoomPlacements()));
088 }
089 Set rooms = exam.findBestAvailableRooms(period);
090 if (rooms==null) continue;
091 return new ExamSimpleNeighbour(new ExamPlacement(exam, period, rooms));
092 }
093 return null;
094 }
095 }