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.exam.model.ExamRoomSharing;
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     * 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(ExamPeriodPlacement)}. <br>
024     * <br>
025     * 
026     * @version ExamTT 1.2 (Examination Timetabling)<br>
027     *          Copyright (C) 2008 - 2010 Tomas Muller<br>
028     *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
029     *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
030     * <br>
031     *          This library is free software; you can redistribute it and/or modify
032     *          it under the terms of the GNU Lesser General Public License as
033     *          published by the Free Software Foundation; either version 3 of the
034     *          License, or (at your option) any later version. <br>
035     * <br>
036     *          This library is distributed in the hope that it will be useful, but
037     *          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. <br>
040     * <br>
041     *          You should have received a copy of the GNU Lesser General Public
042     *          License along with this library; if not see
043     *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
044     */
045    public class ExamTimeMove implements NeighbourSelection<Exam,ExamPlacement> {
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        @Override
062        public void init(Solver<Exam,ExamPlacement> solver) {}
063        
064        /**
065         * Select an exam randomly,
066         * select an available period randomly (if it is not assigned), 
067         * use rooms if possible, select rooms using {@link Exam#findBestAvailableRooms(ExamPeriodPlacement)} if not (exam is unassigned, a room is not available or used).
068         */
069        @Override
070        public Neighbour<Exam,ExamPlacement> selectNeighbour(Solution<Exam,ExamPlacement> solution) {
071            ExamModel model = (ExamModel)solution.getModel();
072            ExamRoomSharing sharing = model.getRoomSharing();
073            Exam exam = ToolBox.random(model.variables());
074            ExamPlacement placement = exam.getAssignment();
075            int px = ToolBox.random(exam.getPeriodPlacements().size());
076            for (int p=0;p<exam.getPeriodPlacements().size();p++) {
077                ExamPeriodPlacement period = exam.getPeriodPlacements().get((p+px)%exam.getPeriodPlacements().size());
078                if (placement!=null && placement.getPeriod().equals(period)) continue;
079                if (iCheckStudentConflicts && exam.countStudentConflicts(period)>0) continue;
080                if (iCheckDistributionConstraints && !exam.checkDistributionConstraints(period)) continue;
081                if (placement!=null) {
082                    boolean ok = true;
083                    if (sharing != null && placement.getRoomPlacements().size() == 1) {
084                        ExamRoomPlacement room = placement.getRoomPlacements().iterator().next();
085                        ok = room.isAvailable(period.getPeriod()) && !sharing.inConflict(exam, room.getRoom().getPlacements(period.getPeriod()), room.getRoom());
086                    } else {
087                        for (Iterator<ExamRoomPlacement> i=placement.getRoomPlacements().iterator();i.hasNext();) {
088                            ExamRoomPlacement room = i.next();
089                            if (!room.isAvailable(period.getPeriod()) || !room.getRoom().getPlacements(period.getPeriod()).isEmpty()) {
090                                ok = false; break;
091                            }
092                        }
093                    }
094                    if (ok)
095                        return new ExamSimpleNeighbour(new ExamPlacement(exam, period, placement.getRoomPlacements()));
096                }
097                Set<ExamRoomPlacement> rooms = exam.findBestAvailableRooms(period);
098                if (rooms==null) continue;
099                return new ExamSimpleNeighbour(new ExamPlacement(exam, period, rooms));
100            }
101            return null;
102        }
103    }