001 package net.sf.cpsolver.exam.neighbours;
002
003 import java.util.Set;
004
005 import net.sf.cpsolver.exam.model.Exam;
006 import net.sf.cpsolver.exam.model.ExamModel;
007 import net.sf.cpsolver.exam.model.ExamPeriodPlacement;
008 import net.sf.cpsolver.exam.model.ExamPlacement;
009 import net.sf.cpsolver.exam.model.ExamRoomPlacement;
010 import net.sf.cpsolver.ifs.heuristics.NeighbourSelection;
011 import net.sf.cpsolver.ifs.model.Neighbour;
012 import net.sf.cpsolver.ifs.solution.Solution;
013 import net.sf.cpsolver.ifs.solver.Solver;
014 import net.sf.cpsolver.ifs.util.DataProperties;
015 import net.sf.cpsolver.ifs.util.ToolBox;
016
017 /**
018 * A period is selected randomly for a randomly selected exam. Rooms are
019 * computed using {@link Exam#findBestAvailableRooms(ExamPeriodPlacement)}. <br>
020 * <br>
021 *
022 * @version ExamTT 1.2 (Examination Timetabling)<br>
023 * Copyright (C) 2008 - 2010 Tomas Muller<br>
024 * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
025 * <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
026 * <br>
027 * This library is free software; you can redistribute it and/or modify
028 * it under the terms of the GNU Lesser General Public License as
029 * published by the Free Software Foundation; either version 3 of the
030 * License, or (at your option) any later version. <br>
031 * <br>
032 * This library is distributed in the hope that it will be useful, but
033 * WITHOUT ANY WARRANTY; without even the implied warranty of
034 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
035 * Lesser General Public License for more details. <br>
036 * <br>
037 * You should have received a copy of the GNU Lesser General Public
038 * License along with this library; if not see
039 * <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
040 */
041 public class ExamRandomMove implements NeighbourSelection<Exam, ExamPlacement> {
042 private boolean iCheckStudentConflicts = false;
043 private boolean iCheckDistributionConstraints = true;
044
045 /**
046 * Constructor
047 *
048 * @param properties
049 * problem properties
050 */
051 public ExamRandomMove(DataProperties properties) {
052 iCheckStudentConflicts = properties.getPropertyBoolean("ExamRandomMove.CheckStudentConflicts",
053 iCheckStudentConflicts);
054 iCheckDistributionConstraints = properties.getPropertyBoolean("ExamRandomMove.CheckDistributionConstraints",
055 iCheckDistributionConstraints);
056 }
057
058 /**
059 * Initialization
060 */
061 @Override
062 public void init(Solver<Exam, ExamPlacement> solver) {
063 }
064
065 /**
066 * Select an exam randomly, select an available period randomly (from
067 * {@link Exam#getPeriodPlacements()}), select rooms using
068 * {@link Exam#findBestAvailableRooms(ExamPeriodPlacement)}.
069 */
070 @Override
071 public Neighbour<Exam, ExamPlacement> selectNeighbour(Solution<Exam, ExamPlacement> solution) {
072 ExamModel model = (ExamModel) solution.getModel();
073 Exam exam = ToolBox.random(model.variables());
074 int px = ToolBox.random(exam.getPeriodPlacements().size());
075 for (int p = 0; p < exam.getPeriodPlacements().size(); p++) {
076 ExamPeriodPlacement period = exam.getPeriodPlacements().get((p + px) % exam.getPeriodPlacements().size());
077 if (iCheckStudentConflicts && exam.countStudentConflicts(period) > 0)
078 continue;
079 if (iCheckDistributionConstraints && !exam.checkDistributionConstraints(period))
080 continue;
081 Set<ExamRoomPlacement> rooms = exam.findBestAvailableRooms(period);
082 if (rooms == null)
083 continue;
084 return new ExamSimpleNeighbour(new ExamPlacement(exam, period, rooms));
085 }
086 return null;
087 }
088 }