001    package net.sf.cpsolver.exam.neighbours;
002    
003    import java.util.ArrayList;
004    import java.util.List;
005    import java.util.Set;
006    
007    import net.sf.cpsolver.exam.model.Exam;
008    import net.sf.cpsolver.exam.model.ExamModel;
009    import net.sf.cpsolver.exam.model.ExamPeriodPlacement;
010    import net.sf.cpsolver.exam.model.ExamPlacement;
011    import net.sf.cpsolver.exam.model.ExamRoomPlacement;
012    import net.sf.cpsolver.ifs.heuristics.NeighbourSelection;
013    import net.sf.cpsolver.ifs.model.Neighbour;
014    import net.sf.cpsolver.ifs.solution.Solution;
015    import net.sf.cpsolver.ifs.solver.Solver;
016    import net.sf.cpsolver.ifs.util.DataProperties;
017    import net.sf.cpsolver.ifs.util.ToolBox;
018    
019    /**
020     * Try to swap a room between two exams. An exam is selected randomly, a
021     * different (available) room is randomly selected for the exam -- the exam is
022     * assigned into the new room (if the room is used, it tries to swap the rooms
023     * between the selected exam and the one that is using it). If an exam is
024     * assigned into two or more rooms, only one room is swapped at a time. <br>
025     * <br>
026     * 
027     * @version ExamTT 1.2 (Examination Timetabling)<br>
028     *          Copyright (C) 2008 - 2010 Tomas Muller<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     */
046    public class ExamRoomMove implements NeighbourSelection<Exam, ExamPlacement> {
047        private boolean iCheckStudentConflicts = false;
048        private boolean iCheckDistributionConstraints = true;
049    
050        /**
051         * Constructor
052         * 
053         * @param properties
054         *            problem properties
055         */
056        public ExamRoomMove(DataProperties properties) {
057            iCheckStudentConflicts = properties.getPropertyBoolean("ExamRoomMove.CheckStudentConflicts",
058                    iCheckStudentConflicts);
059            iCheckDistributionConstraints = properties.getPropertyBoolean("ExamRoomMove.CheckDistributionConstraints",
060                    iCheckDistributionConstraints);
061        }
062    
063        /**
064         * Initialization
065         */
066        @Override
067        public void init(Solver<Exam, ExamPlacement> solver) {
068        }
069    
070        /**
071         * Select an exam randomly, select an available period randomly (if it is
072         * not assigned, from {@link Exam#getPeriodPlacements()}), select rooms
073         * using {@link Exam#findRoomsRandom(ExamPeriodPlacement)}
074         */
075        @Override
076        public Neighbour<Exam, ExamPlacement> selectNeighbour(Solution<Exam, ExamPlacement> solution) {
077            ExamModel model = (ExamModel) solution.getModel();
078            Exam exam = ToolBox.random(model.variables());
079            if (exam.getMaxRooms() <= 0)
080                return null;
081            ExamPlacement placement = exam.getAssignment();
082            ExamPeriodPlacement period = (placement != null ? placement.getPeriodPlacement()
083                    : (ExamPeriodPlacement) ToolBox.random(exam.getPeriodPlacements()));
084            if (iCheckStudentConflicts && placement == null && exam.countStudentConflicts(period) > 0)
085                return null;
086            if (iCheckDistributionConstraints && placement == null && !exam.checkDistributionConstraints(period))
087                return null;
088            Set<ExamRoomPlacement> rooms = (placement != null ? placement.getRoomPlacements() : exam
089                    .findBestAvailableRooms(period));
090            if (rooms == null || rooms.isEmpty())
091                return null;
092            if (placement == null)
093                placement = new ExamPlacement(exam, period, rooms);
094            List<ExamRoomPlacement> roomVect = new ArrayList<ExamRoomPlacement>(rooms);
095            int rx = ToolBox.random(roomVect.size());
096            for (int r = 0; r < roomVect.size(); r++) {
097                ExamRoomPlacement current = roomVect.get((r + rx) % roomVect.size());
098                int mx = ToolBox.random(exam.getRoomPlacements().size());
099                for (int m = 0; m < exam.getRoomPlacements().size(); m++) {
100                    ExamRoomPlacement swap = exam.getRoomPlacements().get((m + mx) % exam.getRoomPlacements().size());
101                    ExamRoomSwapNeighbour n = new ExamRoomSwapNeighbour(placement, current, swap);
102                    if (n.canDo())
103                        return n;
104                }
105            }
106            rooms = exam.findRoomsRandom(period);
107            if (rooms == null)
108                return null;
109            return new ExamSimpleNeighbour(new ExamPlacement(exam, period, rooms));
110        }
111    }