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    }