001package net.sf.cpsolver.exam.neighbours;
002
003import java.util.ArrayList;
004import java.util.HashMap;
005import java.util.HashSet;
006import java.util.List;
007import java.util.Map;
008import java.util.Set;
009
010import net.sf.cpsolver.exam.criteria.DistributionPenalty;
011import net.sf.cpsolver.exam.criteria.RoomPenalty;
012import net.sf.cpsolver.exam.criteria.RoomSizePenalty;
013import net.sf.cpsolver.exam.model.Exam;
014import net.sf.cpsolver.exam.model.ExamDistributionConstraint;
015import net.sf.cpsolver.exam.model.ExamModel;
016import net.sf.cpsolver.exam.model.ExamPeriodPlacement;
017import net.sf.cpsolver.exam.model.ExamPlacement;
018import net.sf.cpsolver.exam.model.ExamRoomPlacement;
019import net.sf.cpsolver.exam.model.ExamRoomSharing;
020import net.sf.cpsolver.ifs.heuristics.NeighbourSelection;
021import net.sf.cpsolver.ifs.model.LazySwap;
022import net.sf.cpsolver.ifs.model.Neighbour;
023import net.sf.cpsolver.ifs.solution.Solution;
024import net.sf.cpsolver.ifs.solver.Solver;
025import net.sf.cpsolver.ifs.util.DataProperties;
026import net.sf.cpsolver.ifs.util.ToolBox;
027
028/**
029 * Try to swap a period between two exams. 
030 * Two examinations are randomly selected. A new placement is generated by swapping periods of the two exams.
031 * For each exam, the best possible room placement is found. If the two exams are in the same period, it just tries
032 * to change the room assignments by looking for the best available room placement ignoring the existing room assignments
033 * of the two exams. If no conflict results from the swap the assignment is returned.
034 * The following exams of the second exam in the pair are tried for an exam swap otherwise.
035 * <br><br>
036 * 
037 * @version ExamTT 1.2 (Examination Timetabling)<br>
038 *          Copyright (C) 2013 Tomáš Müller<br>
039 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
040 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
041 * <br>
042 *          This library is free software; you can redistribute it and/or modify
043 *          it under the terms of the GNU Lesser General Public License as
044 *          published by the Free Software Foundation; either version 3 of the
045 *          License, or (at your option) any later version. <br>
046 * <br>
047 *          This library is distributed in the hope that it will be useful, but
048 *          WITHOUT ANY WARRANTY; without even the implied warranty of
049 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
050 *          Lesser General Public License for more details. <br>
051 * <br>
052 *          You should have received a copy of the GNU Lesser General Public
053 *          License along with this library; if not see
054 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
055 */
056public class ExamPeriodSwapMove implements NeighbourSelection<Exam,ExamPlacement> {
057    private boolean iCheckStudentConflicts = false;
058    private boolean iCheckDistributionConstraints = true;
059    
060    /**
061     * Constructor
062     * @param properties problem properties
063     */
064    public ExamPeriodSwapMove(DataProperties properties) {
065        iCheckStudentConflicts = properties.getPropertyBoolean("ExamPeriodSwapMove.CheckStudentConflicts", iCheckStudentConflicts);
066        iCheckDistributionConstraints = properties.getPropertyBoolean("ExamPeriodSwapMove.CheckDistributionConstraints", iCheckDistributionConstraints);
067    }
068    
069    /**
070     * Initialization
071     */
072    @Override
073    public void init(Solver<Exam,ExamPlacement> solver) {}
074
075    /**
076     * Select an exam randomly,
077     * select an available period randomly (if it is not assigned), 
078     * use rooms if possible, select rooms using {@link Exam#findBestAvailableRooms(ExamPeriodPlacement)} if not (exam is unassigned, a room is not available or used).
079     */
080    @Override
081    public Neighbour<Exam,ExamPlacement> selectNeighbour(Solution<Exam,ExamPlacement> solution) {
082        ExamModel model = (ExamModel)solution.getModel();
083        Exam x1 = ToolBox.random(model.variables());
084        if (x1.getAssignment() == null) return null;
085        int x = ToolBox.random(model.variables().size());
086        for (int v = 0; v < model.variables().size(); v++) {
087            Exam x2 = model.variables().get((v + x) % (model.variables().size()));
088            if (x1.equals(x2) || x2.getAssignment() == null) continue;
089            ExamPeriodPlacement p1 = x1.getPeriodPlacement(x2.getAssignment().getPeriod());
090            ExamPeriodPlacement p2 = x2.getPeriodPlacement(x1.getAssignment().getPeriod());
091            if (p1 == null || p2 == null) continue;
092            if (iCheckStudentConflicts && (x1.countStudentConflicts(p1) > 0 || x2.countStudentConflicts(p2) > 0)) continue;
093            if (iCheckDistributionConstraints) {
094                Map<Exam, ExamPlacement> placements = new HashMap<Exam, ExamPlacement>();
095                placements.put(x1, new ExamPlacement(x1, p1, new HashSet<ExamRoomPlacement>()));
096                placements.put(x2, new ExamPlacement(x2, p2, new HashSet<ExamRoomPlacement>()));
097                if (!checkDistributionConstraints(x1, p1, placements) || !checkDistributionConstraints(x2, p2, placements)) continue;
098            }
099            Set<ExamPlacement> conflicts = new HashSet<ExamPlacement>();
100            conflicts.add(x1.getAssignment()); conflicts.add(x2.getAssignment());
101            Map<Exam, ExamPlacement> placements = new HashMap<Exam, ExamPlacement>();
102            Set<ExamRoomPlacement> r1 = findBestAvailableRooms(x1, p1, conflicts, placements);
103            if (r1 == null) continue;
104            placements.put(x1, new ExamPlacement(x1, p1, r1));
105            Set<ExamRoomPlacement> r2 = findBestAvailableRooms(x2, p2, conflicts, placements);
106            if (r2 == null) continue;
107            return new LazySwap<Exam, ExamPlacement>(new ExamPlacement(x1, p1, r1), new ExamPlacement(x2, p2, r2));
108        }
109        return null;
110    }
111    
112    public boolean checkDistributionConstraints(Exam exam, ExamPeriodPlacement period, Map<Exam, ExamPlacement> placements) {
113        for (ExamDistributionConstraint dc : exam.getDistributionConstraints()) {
114            if (!dc.isHard())
115                continue;
116            boolean before = true;
117            for (Exam other : dc.variables()) {
118                if (other.equals(this)) {
119                    before = false;
120                    continue;
121                }
122                ExamPlacement placement = (placements.containsKey(other) ? placements.get(other) : other.getAssignment());
123                if (placement == null) continue;
124                switch (dc.getType()) {
125                    case ExamDistributionConstraint.sDistSamePeriod:
126                        if (period.getIndex() != placement.getPeriod().getIndex())
127                            return false;
128                        break;
129                    case ExamDistributionConstraint.sDistDifferentPeriod:
130                        if (period.getIndex() == placement.getPeriod().getIndex())
131                            return false;
132                        break;
133                    case ExamDistributionConstraint.sDistPrecedence:
134                        if (before) {
135                            if (period.getIndex() <= placement.getPeriod().getIndex())
136                                return false;
137                        } else {
138                            if (period.getIndex() >= placement.getPeriod().getIndex())
139                                return false;
140                        }
141                        break;
142                    case ExamDistributionConstraint.sDistPrecedenceRev:
143                        if (before) {
144                            if (period.getIndex() >= placement.getPeriod().getIndex())
145                                return false;
146                        } else {
147                            if (period.getIndex() <= placement.getPeriod().getIndex())
148                                return false;
149                        }
150                        break;
151                }
152            }
153        }
154        return true;
155    }
156    
157    public boolean checkDistributionConstraints(Exam exam, ExamRoomPlacement room, Set<ExamPlacement> conflictsToIgnore, Map<Exam, ExamPlacement> placements) {
158        for (ExamDistributionConstraint dc : exam.getDistributionConstraints()) {
159            if (!dc.isHard())
160                continue;
161            for (Exam other : dc.variables()) {
162                if (other.equals(exam)) continue;
163                ExamPlacement placement = (placements.containsKey(other) ? placements.get(other) : other.getAssignment());
164                if (placement == null || conflictsToIgnore.contains(placement)) continue;
165                switch (dc.getType()) {
166                    case ExamDistributionConstraint.sDistSameRoom:
167                        if (!placement.getRoomPlacements().contains(room))
168                            return false;
169                        break;
170                    case ExamDistributionConstraint.sDistDifferentRoom:
171                        if (placement.getRoomPlacements().contains(room))
172                            return false;
173                        break;
174                }
175            }
176        }
177        return true;
178    }
179    
180    public int getDistributionConstraintPenalty(Exam exam, ExamRoomPlacement room,  Set<ExamPlacement> conflictsToIgnore, Map<Exam, ExamPlacement> placements) {
181        int penalty = 0;
182        for (ExamDistributionConstraint dc : exam.getDistributionConstraints()) {
183            if (dc.isHard()) continue;
184            for (Exam other : dc.variables()) {
185                if (other.equals(this)) continue;
186                ExamPlacement placement = (placements.containsKey(other) ? placements.get(other) : other.getAssignment());
187                if (placement == null || conflictsToIgnore.contains(placement)) continue;
188                switch (dc.getType()) {
189                    case ExamDistributionConstraint.sDistSameRoom:
190                        if (!placement.getRoomPlacements().contains(room))
191                            penalty += dc.getWeight();
192                        break;
193                    case ExamDistributionConstraint.sDistDifferentRoom:
194                        if (placement.getRoomPlacements().contains(room))
195                            penalty += dc.getWeight();
196                        break;
197                }
198            }
199        }
200        return penalty;
201    }
202    
203    public Set<ExamRoomPlacement> findBestAvailableRooms(Exam exam, ExamPeriodPlacement period, Set<ExamPlacement> conflictsToIgnore, Map<Exam, ExamPlacement> placements) {
204        if (exam.getMaxRooms() == 0)
205            return new HashSet<ExamRoomPlacement>();
206        double sw = exam.getModel().getCriterion(RoomSizePenalty.class).getWeight();
207        double pw = exam.getModel().getCriterion(RoomPenalty.class).getWeight();
208        double cw = exam.getModel().getCriterion(DistributionPenalty.class).getWeight();
209        ExamRoomSharing sharing = ((ExamModel)exam.getModel()).getRoomSharing();
210        loop: for (int nrRooms = 1; nrRooms <= exam.getMaxRooms(); nrRooms++) {
211            HashSet<ExamRoomPlacement> rooms = new HashSet<ExamRoomPlacement>();
212            int size = 0;
213            while (rooms.size() < nrRooms && size < exam.getSize()) {
214                int minSize = (exam.getSize() - size) / (nrRooms - rooms.size());
215                ExamRoomPlacement best = null;
216                double bestWeight = 0;
217                int bestSize = 0;
218                for (ExamRoomPlacement room : exam.getRoomPlacements()) {
219                    if (!room.isAvailable(period.getPeriod())) continue;
220                    if (rooms.contains(room)) continue;
221                    
222                    List<ExamPlacement> overlaps = new ArrayList<ExamPlacement>();
223                    for (ExamPlacement overlap: room.getRoom().getPlacements(period.getPeriod()))
224                        if (!conflictsToIgnore.contains(overlap)) overlaps.add(overlap);
225                    for (ExamPlacement other: placements.values())
226                        if (other.getPeriod().equals(period.getPeriod()))
227                            for (ExamRoomPlacement r: other.getRoomPlacements())
228                                if (r.getRoom().equals(room.getRoom())) {
229                                    overlaps.add(other);
230                                    continue;
231                                }
232                    
233                    if (nrRooms == 1 && sharing != null) {
234                        if (sharing.inConflict(exam, overlaps, room.getRoom()))
235                            continue;
236                    } else {
237                        if (!overlaps.isEmpty())
238                            continue;
239                    }
240                    if (iCheckDistributionConstraints && !checkDistributionConstraints(exam, room, conflictsToIgnore, placements)) continue;
241                    int s = room.getSize(exam.hasAltSeating());
242                    if (s < minSize) break;
243                    int p = room.getPenalty(period.getPeriod());
244                    double w = pw * p + sw * (s - minSize) + cw * getDistributionConstraintPenalty(exam, room, conflictsToIgnore, placements);
245                    double d = 0;
246                    if (!rooms.isEmpty()) {
247                        for (ExamRoomPlacement r : rooms) {
248                            d += r.getDistanceInMeters(room);
249                        }
250                        w += d / rooms.size();
251                    }
252                    if (best == null || bestWeight > w) {
253                        best = room;
254                        bestSize = s;
255                        bestWeight = w;
256                    }
257                }
258                if (best == null)
259                    continue loop;
260                rooms.add(best);
261                size += bestSize;
262            }
263            if (size >= exam.getSize())
264                return rooms;
265        }
266        return null;
267    }
268}