001package org.cpsolver.coursett.constraint;
002
003import java.util.ArrayList;
004import java.util.BitSet;
005import java.util.HashSet;
006import java.util.HashMap;
007import java.util.Iterator;
008import java.util.List;
009import java.util.Set;
010
011import org.cpsolver.coursett.Constants;
012import org.cpsolver.coursett.criteria.DistributionPreferences;
013import org.cpsolver.coursett.model.Lecture;
014import org.cpsolver.coursett.model.Placement;
015import org.cpsolver.coursett.model.TimeLocation;
016import org.cpsolver.coursett.model.TimetableModel;
017import org.cpsolver.ifs.assignment.Assignment;
018import org.cpsolver.ifs.assignment.context.AssignmentConstraintContext;
019import org.cpsolver.ifs.assignment.context.ConstraintWithContext;
020import org.cpsolver.ifs.model.Constraint;
021import org.cpsolver.ifs.model.GlobalConstraint;
022import org.cpsolver.ifs.model.Model;
023import org.cpsolver.ifs.model.WeakeningConstraint;
024import org.cpsolver.ifs.util.DataProperties;
025import org.cpsolver.ifs.util.DistanceMetric;
026import org.cpsolver.ifs.util.ToolBox;
027
028
029/**
030 * Group constraint. <br>
031 * This constraint expresses relations between several classes, e.g., that two
032 * sections of the same lecture can not be taught at the same time, or that some
033 * classes have to be taught one immediately after another. It can be either
034 * hard or soft. <br>
035 * <br>
036 * Following constraints are now supported:
037 * <table border='1' summary='Related Solver Parameters'>
038 * <tr>
039 * <th>Constraint</th>
040 * <th>Comment</th>
041 * </tr>
042 * <tr>
043 * <td>SAME_TIME</td>
044 * <td>Same time: given classes have to be taught in the same hours. If the
045 * classes are of different length, the smaller one cannot start before the
046 * longer one and it cannot end after the longer one.</td>
047 * </tr>
048 * <tr>
049 * <td>SAME_DAYS</td>
050 * <td>Same days: given classes have to be taught in the same day. If the
051 * classes are of different time patterns, the days of one class have to form a
052 * subset of the days of the other class.</td>
053 * </tr>
054 * <tr>
055 * <td>BTB</td>
056 * <td>Back-to-back constraint: given classes have to be taught in the same room
057 * and they have to follow one strictly after another.</td>
058 * </tr>
059 * <tr>
060 * <td>BTB_TIME</td>
061 * <td>Back-to-back constraint: given classes have to follow one strictly after
062 * another, but they can be taught in different rooms.</td>
063 * </tr>
064 * <tr>
065 * <td>DIFF_TIME</td>
066 * <td>Different time: given classes cannot overlap in time.</td>
067 * </tr>
068 * <tr>
069 * <td>NHB(1), NHB(1.5), NHB(2), ... NHB(8)</td>
070 * <td>Number of hours between: between the given classes, the exact number of
071 * hours have to be kept.</td>
072 * </tr>
073 * <tr>
074 * <td>SAME_START</td>
075 * <td>Same starting hour: given classes have to start in the same hour.</td>
076 * </tr>
077 * <tr>
078 * <td>SAME_ROOM</td>
079 * <td>Same room: given classes have to be placed in the same room.</td>
080 * </tr>
081 * <tr>
082 * <td>NHB_GTE(1)</td>
083 * <td>Greater than or equal to 1 hour between: between the given classes, the
084 * number of hours have to be one or more.</td>
085 * </tr>
086 * <tr>
087 * <td>NHB_LT(6)</td>
088 * <td>Less than 6 hours between: between the given classes, the number of hours
089 * have to be less than six.</td>
090 * </tr>
091 * </table>
092 * 
093 * @version CourseTT 1.3 (University Course Timetabling)<br>
094 *          Copyright (C) 2006 - 2014 Tomas Muller<br>
095 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
096 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
097 * <br>
098 *          This library is free software; you can redistribute it and/or modify
099 *          it under the terms of the GNU Lesser General Public License as
100 *          published by the Free Software Foundation; either version 3 of the
101 *          License, or (at your option) any later version. <br>
102 * <br>
103 *          This library is distributed in the hope that it will be useful, but
104 *          WITHOUT ANY WARRANTY; without even the implied warranty of
105 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
106 *          Lesser General Public License for more details. <br>
107 * <br>
108 *          You should have received a copy of the GNU Lesser General Public
109 *          License along with this library; if not see
110 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
111 */
112
113public class GroupConstraint extends ConstraintWithContext<Lecture, Placement, GroupConstraint.GroupConstraintContext> {
114    private Long iConstraintId;
115    private int iPreference;
116    private ConstraintType iType;
117    private boolean iIsRequired;
118    private boolean iIsProhibited;
119    private int iDayOfWeekOffset = 0;
120    private boolean iPrecedenceConsiderDatePatterns = true;
121    private boolean iMaxNHoursADayConsiderDatePatterns = true;
122    private int iForwardCheckMaxDepth = 2;
123    private int iForwardCheckMaxDomainSize = 1000;
124    private int iNrWorkDays = 5;
125    private int iFirstWorkDay = 0;
126    
127    /**
128     * Group constraints that can be checked on pairs of classes (e.g., same room means any two classes are in the same room),
129     * only need to implement this interface.
130     */
131    public static interface PairCheck {
132        /**
133         * Check whether the constraint is satisfied for the given two assignments (required / preferred case)
134         * @param gc Calling group constraint 
135         * @param plc1 First placement
136         * @param plc2 Second placement
137         * @return true if constraint is satisfied
138         */
139        public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2);
140        /**
141         * Check whether the constraint is satisfied for the given two assignments (prohibited / discouraged case)
142         * @param gc Calling group constraint 
143         * @param plc1 First placement
144         * @param plc2 Second placement
145         * @return true if constraint is satisfied
146         */
147        public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2);
148    }
149    
150    /**
151     * Group constraints that can be checked on pairs of classes (e.g., same room means any two classes are in the same room),
152     * only need to implement this interface. Unlike {@link PairCheck}, this check is also given current assignment.
153     */
154    public static interface AssignmentPairCheck {
155        /**
156         * Check whether the constraint is satisfied for the given two assignments (required / preferred case)
157         * @param assignment current assignment
158         * @param gc Calling group constraint 
159         * @param plc1 First placement
160         * @param plc2 Second placement
161         * @return true if constraint is satisfied
162         */
163        public boolean isSatisfied(Assignment<Lecture, Placement> assignment, GroupConstraint gc, Placement plc1, Placement plc2);
164        /**
165         * Check whether the constraint is satisfied for the given two assignments (prohibited / discouraged case)
166         * @param assignment current assignment
167         * @param gc Calling group constraint 
168         * @param plc1 First placement
169         * @param plc2 Second placement
170         * @return true if constraint is satisfied
171         */
172        public boolean isViolated(Assignment<Lecture, Placement> assignment, GroupConstraint gc, Placement plc1, Placement plc2);
173    }
174    
175    /**
176     * Group constraint building blocks (individual constraints that need more than {@link PairCheck})
177     */
178    public static enum Flag {
179        /** Back-to-back constraint (sequence check) */
180        BACK_TO_BACK,
181        /** Can share room flag */
182        CAN_SHARE_ROOM,
183        /** Maximum hours a day (number of slots a day check) */
184        MAX_HRS_DAY,
185        /** Children cannot overlap */
186        CH_NOTOVERLAP;
187        /** Bit number (to combine flags) */
188        int flag() { return 1 << ordinal(); }
189    }
190    
191    /**
192     * Group constraint type.
193     */
194    public static enum ConstraintType {
195        /**
196         * Same Time: Given classes must be taught at the same time of day (independent of the actual day the classes meet).
197         * For the classes of the same length, this is the same constraint as same start. For classes of different length,
198         * the shorter one cannot start before, nor end after, the longer one.<BR>
199         * When prohibited or (strongly) discouraged: one class may not meet on any day at a time of day that overlaps with
200         * that of the other. For example, one class can not meet M 7:30 while the other meets F 7:30. Note the difference
201         * here from the different time constraint that only prohibits the actual class meetings from overlapping.
202         */
203        SAME_TIME("SAME_TIME", "Same Time", new PairCheck() {
204            @Override
205            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
206                return sameHours(plc1.getTimeLocation().getStartSlot(), plc1.getTimeLocation().getLength(),
207                        plc2.getTimeLocation().getStartSlot(), plc2.getTimeLocation().getLength());
208            }
209            @Override
210            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
211                return !(plc1.getTimeLocation().shareHours(plc2.getTimeLocation()));
212            }}),
213        /**
214         * Same Days: Given classes must be taught on the same days. In case of classes of different time patterns, a class
215         * with fewer meetings must meet on a subset of the days used by the class with more meetings. For example, if one
216         * class pattern is 3x50, all others given in the constraint can only be taught on Monday, Wednesday, or Friday.
217         * For a 2x100 class MW, MF, WF is allowed but TTh is prohibited.<BR>
218         * When prohibited or (strongly) discouraged: any pair of classes classes cannot be taught on the same days (cannot
219         *  overlap in days). For instance, if one class is MFW, the second has to be TTh.
220         */
221        SAME_DAYS("SAME_DAYS", "Same Days", new PairCheck() {
222            @Override
223            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
224                return sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray());
225            }
226            @Override
227            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
228                return !plc1.getTimeLocation().shareDays(plc2.getTimeLocation());
229            }}),
230        /**
231         * Back-To-Back &amp; Same Room: Classes must be offered in adjacent time segments and must be placed in the same room.
232         * Given classes must also be taught on the same days.<BR>
233         * When prohibited or (strongly) discouraged: classes cannot be back-to-back. There must be at least half-hour
234         * between these classes, and they must be taught on the same days and in the same room.
235         */
236        BTB("BTB", "Back-To-Back & Same Room", new PairCheck() {
237            @Override
238            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
239                return
240                    plc1.sameRooms(plc2) &&
241                    sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray());
242            }
243            @Override
244            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
245                return
246                    plc1.sameRooms(plc2) &&
247                    sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray());
248            }}, Flag.BACK_TO_BACK),
249        /**
250         * Back-To-Back: Classes must be offered in adjacent time segments but may be placed in different rooms. Given classes
251         * must also be taught on the same days.<BR>
252         * When prohibited or (strongly) discouraged: no pair of classes can be taught back-to-back. They may not overlap in time,
253         * but must be taught on the same days. This means that there must be at least half-hour between these classes. 
254         */
255        BTB_TIME("BTB_TIME", "Back-To-Back", new PairCheck() {
256            @Override
257            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
258                return sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray());
259            }
260            @Override
261            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
262                return sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray());
263            }}, Flag.BACK_TO_BACK),
264        /**
265         * Different Time: Given classes cannot overlap in time. They may be taught at the same time of day if they are on
266         * different days. For instance, MF 7:30 is compatible with TTh 7:30.<BR>
267         * When prohibited or (strongly) discouraged: every pair of classes in the constraint must overlap in time. 
268         */
269        DIFF_TIME("DIFF_TIME", "Different Time", new PairCheck() {
270            @Override
271            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
272                return !plc1.getTimeLocation().hasIntersection(plc2.getTimeLocation());
273            }
274            @Override
275            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
276                return plc1.getTimeLocation().hasIntersection(plc2.getTimeLocation());
277            }}),
278        /**
279         * 1 Hour Between: Given classes must have exactly 1 hour in between the end of one and the beginning of another.
280         * As with the <i>back-to-back time</i> constraint, given classes must be taught on the same days.<BR>
281         * When prohibited or (strongly) discouraged: classes can not have 1 hour in between. They may not overlap in time
282         * but must be taught on the same days.
283         */
284        NHB_1("NHB(1)", "1 Hour Between", 10, 12, BTB_TIME.check(), Flag.BACK_TO_BACK),
285        /**
286         * 2 Hours Between: Given classes must have exactly 2 hours in between the end of one and the beginning of another.
287         * As with the <i>back-to-back time</i> constraint, given classes must be taught on the same days.<BR>
288         * When prohibited or (strongly) discouraged: classes can not have 2 hours in between. They may not overlap in time
289         * but must be taught on the same days.
290         */
291        NHB_2("NHB(2)", "2 Hours Between", 20, 24, BTB_TIME.check(), Flag.BACK_TO_BACK),
292        /**
293         * 3 Hours Between: Given classes must have exactly 3 hours in between the end of one and the beginning of another.
294         * As with the <i>back-to-back time</i> constraint, given classes must be taught on the same days.<BR>
295         * When prohibited or (strongly) discouraged: classes can not have 3 hours in between. They may not overlap in time
296         * but must be taught on the same days.
297         */
298        NHB_3("NHB(3)", "3 Hours Between", 30, 36, BTB_TIME.check(), Flag.BACK_TO_BACK),
299        /**
300         * 4 Hours Between: Given classes must have exactly 4 hours in between the end of one and the beginning of another.
301         * As with the <i>back-to-back time</i> constraint, given classes must be taught on the same days.<BR>
302         * When prohibited or (strongly) discouraged: classes can not have 4 hours in between. They may not overlap in time
303         * but must be taught on the same days.
304         */
305        NHB_4("NHB(4)", "4 Hours Between", 40, 48, BTB_TIME.check(), Flag.BACK_TO_BACK),
306        /**
307         * 5 Hours Between: Given classes must have exactly 5 hours in between the end of one and the beginning of another.
308         * As with the <i>back-to-back time</i> constraint, given classes must be taught on the same days.<BR>
309         * When prohibited or (strongly) discouraged: classes can not have 5 hours in between. They may not overlap in time
310         * but must be taught on the same days.
311         */
312        NHB_5("NHB(5)", "5 Hours Between", 50, 60, BTB_TIME.check(), Flag.BACK_TO_BACK),
313        /**
314         * 6 Hours Between: Given classes must have exactly 6 hours in between the end of one and the beginning of another.
315         * As with the <i>back-to-back time</i> constraint, given classes must be taught on the same days.<BR>
316         * When prohibited or (strongly) discouraged: classes can not have 6 hours in between. They may not overlap in time
317         * but must be taught on the same days.
318         */
319        NHB_6("NHB(6)", "6 Hours Between", 60, 72, BTB_TIME.check(), Flag.BACK_TO_BACK),
320        /**
321         * 7 Hours Between: Given classes must have exactly 7 hours in between the end of one and the beginning of another.
322         * As with the <i>back-to-back time</i> constraint, given classes must be taught on the same days.<BR>
323         * When prohibited or (strongly) discouraged: classes can not have 7 hours in between. They may not overlap in time
324         * but must be taught on the same days.
325         */
326        NHB_7("NHB(7)", "7 Hours Between", 70, 84, BTB_TIME.check(), Flag.BACK_TO_BACK),
327        /**
328         * 8 Hours Between: Given classes must have exactly 8 hours in between the end of one and the beginning of another.
329         * As with the <i>back-to-back time</i> constraint, given classes must be taught on the same days.<BR>
330         * When prohibited or (strongly) discouraged: classes can not have 8 hours in between. They may not overlap in time
331         * but must be taught on the same days.
332         */
333        NHB_8("NHB(8)", "8 Hours Between", 80, 96, BTB_TIME.check(), Flag.BACK_TO_BACK),
334        /**
335         * Same Start Time: Given classes must start during the same half-hour period of a day (independent of the actual
336         * day the classes meet). For instance, MW 7:30 is compatible with TTh 7:30 but not with MWF 8:00.<BR>
337         * When prohibited or (strongly) discouraged: any pair of classes in the given constraint cannot start during the
338         * same half-hour period of any day of the week.
339         */
340        SAME_START("SAME_START", "Same Start Time", new PairCheck() {
341            @Override
342            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
343                return
344                    (plc1.getTimeLocation().getStartSlot() % Constants.SLOTS_PER_DAY) == 
345                    (plc2.getTimeLocation().getStartSlot() % Constants.SLOTS_PER_DAY);
346            }
347            @Override
348            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
349                return
350                    (plc1.getTimeLocation().getStartSlot() % Constants.SLOTS_PER_DAY) != 
351                    (plc2.getTimeLocation().getStartSlot() % Constants.SLOTS_PER_DAY);
352            }}),
353        /**
354         * Same Room: Given classes must be taught in the same room.<BR>
355         * When prohibited or (strongly) discouraged: any pair of classes in the constraint cannot be taught in the same room.
356         */
357        SAME_ROOM("SAME_ROOM", "Same Room", new PairCheck() {
358            @Override
359            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
360                return plc1.sameRooms(plc2);
361            }
362            @Override
363            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
364                return !plc1.sameRooms(plc2);
365            }}),
366        /**
367         * At Least 1 Hour Between: Given classes have to have 1 hour or more in between.<BR>
368         * When prohibited or (strongly) discouraged: given classes have to have less than 1 hour in between.
369         */
370        NHB_GTE_1("NHB_GTE(1)", "At Least 1 Hour Between", 6, 288, BTB_TIME.check(), Flag.BACK_TO_BACK),
371        /**
372         * Less Than 6 Hours Between: Given classes must have less than 6 hours from end of first class to the beginning of
373         * the next. Given classes must also be taught on the same days.<BR>
374         * When prohibited or (strongly) discouraged: given classes must have 6 or more hours between. This constraint does
375         * not carry over from classes taught at the end of one day to the beginning of the next.
376         */
377        NHB_LT_6("NHB_LT(6)", "Less Than 6 Hours Between", 0, 72, BTB_TIME.check(), Flag.BACK_TO_BACK),
378        /**
379         * 1.5 Hour Between: Given classes must have exactly 90 minutes in between the end of one and the beginning of another.
380         * As with the <i>back-to-back time</i> constraint, given classes must be taught on the same days.<BR>
381         * When prohibited or (strongly) discouraged: classes can not have 90 minutes in between. They may not overlap in time
382         * but must be taught on the same days.
383         */
384        NHB_1_5("NHB(1.5)", "1.5 Hour Between", 15, 18, BTB_TIME.check(), Flag.BACK_TO_BACK),
385        /**
386         * 4.5 Hours Between: Given classes must have exactly 4.5 hours in between the end of one and the beginning of another.
387         * As with the <i>back-to-back time</i> constraint, given classes must be taught on the same days.<BR>
388         * When prohibited or (strongly) discouraged: classes can not have 4.5 hours in between. They may not overlap in time
389         * but must be taught on the same days.
390         */
391        NHB_4_5("NHB(4.5)", "4.5 Hours Between", 45, 54, BTB_TIME.check(), Flag.BACK_TO_BACK),
392        /**
393         * Same Students: Given classes are treated as they are attended by the same students, i.e., they cannot overlap in time
394         * and if they are back-to-back the assigned rooms cannot be too far (student limit is used).
395         */
396        SAME_STUDENTS("SAME_STUDENTS", "Same Students", new PairCheck() {
397            @Override
398            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
399                return !JenrlConstraint.isInConflict(plc1, plc2, ((TimetableModel)gc.getModel()).getDistanceMetric());
400            }
401            @Override
402            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
403                return true;
404            }}),
405        /**
406         * Same Instructor: Given classes are treated as they are taught by the same instructor, i.e., they cannot overlap in time
407         * and if they are back-to-back the assigned rooms cannot be too far (instructor limit is used).<BR>
408         * If the constraint is required and the classes are back-to-back, discouraged and strongly discouraged distances between
409         * assigned rooms are also considered.
410         */
411        SAME_INSTR("SAME_INSTR", "Same Instructor", new PairCheck() {
412            @Override
413            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
414                TimeLocation t1 = plc1.getTimeLocation(), t2 = plc2.getTimeLocation();
415                if (t1.shareDays(t2) && t1.shareWeeks(t2)) {
416                    if (t1.shareHours(t2)) return false; // overlap
417                    DistanceMetric m = ((TimetableModel)gc.getModel()).getDistanceMetric();
418                    if ((t1.getStartSlot() + t1.getLength() == t2.getStartSlot() || t2.getStartSlot() + t2.getLength() == t1.getStartSlot())) {
419                        if (Placement.getDistanceInMeters(m, plc1, plc2) > m.getInstructorProhibitedLimit())
420                            return false;
421                    } else if (m.doComputeDistanceConflictsBetweenNonBTBClasses()) {
422                        if (t1.getStartSlot() + t1.getLength() < t2.getStartSlot() && 
423                            Placement.getDistanceInMinutes(m, plc1, plc2) > t1.getBreakTime() + Constants.SLOT_LENGTH_MIN * (t2.getStartSlot() - t1.getStartSlot() - t1.getLength()))
424                            return false;
425                        if (t2.getStartSlot() + t2.getLength() < t1.getStartSlot() &&
426                            Placement.getDistanceInMinutes(m, plc1, plc2) > t2.getBreakTime() + Constants.SLOT_LENGTH_MIN * (t1.getStartSlot() - t2.getStartSlot() - t2.getLength()))
427                            return false;
428                    }
429                }
430                return true;
431            }
432            @Override
433            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
434                return true;
435            }}),
436        /**
437         * Can Share Room: Given classes can share the room (use the room in the same time) if the room is big enough.
438         */
439        CAN_SHARE_ROOM("CAN_SHARE_ROOM", "Can Share Room", Flag.CAN_SHARE_ROOM),
440        /**
441         * Precedence: Given classes have to be taught in the given order (the first meeting of the first class has to end before
442         * the first meeting of the second class etc.)<BR>
443         * When prohibited or (strongly) discouraged: classes have to be taught in the order reverse to the given one.
444         */
445        PRECEDENCE("PRECEDENCE", "Precedence", new PairCheck() {
446            @Override
447            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
448                return gc.isPrecedence(plc1, plc2, true, true);
449            }
450            @Override
451            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
452                return gc.isPrecedence(plc1, plc2, false, true);
453            }}),
454        /**
455         * Back-To-Back Day: Classes must be offered on adjacent days and may be placed in different rooms.<BR>
456         * When prohibited or (strongly) discouraged: classes can not be taught on adjacent days. They also can not be taught
457         * on the same days. This means that there must be at least one day between these classes.
458         */
459        BTB_DAY("BTB_DAY", "Back-To-Back Day", new PairCheck() {
460            @Override
461            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
462                return
463                    !sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray()) &&
464                    gc.isBackToBackDays(plc1.getTimeLocation(), plc2.getTimeLocation());
465            }
466            @Override
467            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
468                return
469                    !sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray()) &&
470                    !gc.isBackToBackDays(plc1.getTimeLocation(), plc2.getTimeLocation());
471            }}),
472        /**
473         * Meet Together: Given classes are meeting together (same as if the given classes require constraints Can Share Room,
474         * Same Room, Same Time and Same Days all together).
475         */
476        MEET_WITH("MEET_WITH", "Meet Together", new PairCheck() {
477            @Override
478            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
479                return
480                        plc1.sameRooms(plc2) &&
481                        sameHours(plc1.getTimeLocation().getStartSlot(), plc1.getTimeLocation().getLength(),
482                                plc2.getTimeLocation().getStartSlot(), plc2.getTimeLocation().getLength()) &&
483                        sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray());
484                        
485            }
486            @Override
487            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
488                return true;
489            }}, Flag.CAN_SHARE_ROOM),
490        /**
491         * More Than 1 Day Between: Given classes must have two or more days in between.<br>
492         * When prohibited or (strongly) discouraged: given classes must be offered on adjacent days or with at most one day in between.
493         */
494        NDB_GT_1("NDB_GT_1", "More Than 1 Day Between", new PairCheck() {
495            @Override
496            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
497                return
498                    !sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray()) &&
499                    gc.isNrDaysBetweenGreaterThanOne(plc1.getTimeLocation(), plc2.getTimeLocation());
500            }
501            @Override
502            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
503                return
504                    !sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray()) &&
505                    !gc.isNrDaysBetweenGreaterThanOne(plc1.getTimeLocation(), plc2.getTimeLocation());
506            }}),
507        /**
508         * Children Cannot Overlap: If parent classes do not overlap in time, children classes can not overlap in time as well.<BR>
509         * Note: This constraint only needs to be put on the parent classes. Preferred configurations are Required All Classes
510         * or Pairwise (Strongly) Preferred.
511         */
512        CH_NOTOVERLAP("CH_NOTOVERLAP", "Children Cannot Overlap", new AssignmentPairCheck() {
513            @Override
514            public boolean isSatisfied(Assignment<Lecture, Placement> assignment, GroupConstraint gc, Placement plc1, Placement plc2) {
515                return gc.isChildrenNotOverlap(assignment, plc1.variable(), plc1, plc2.variable(), plc2);
516            }
517            @Override
518            public boolean isViolated(Assignment<Lecture, Placement> assignment, GroupConstraint gc, Placement plc1, Placement plc2) {
519                return true;
520            }}),
521        /**
522         * Next Day: The second class has to be placed on the following day of the first class (if the first class is on Friday,
523         * second class have to be on Monday).<br>
524         * When prohibited or (strongly) discouraged: The second class has to be placed on the previous day of the first class
525         * (if the first class is on Monday, second class have to be on Friday).<br>
526         * Note: This constraint works only between pairs of classes.
527         */
528        FOLLOWING_DAY("FOLLOWING_DAY", "Next Day", new PairCheck() {
529            @Override
530            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
531                return gc.isFollowingDay(plc1, plc2, true);
532            }
533            @Override
534            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
535                return gc.isFollowingDay(plc1, plc2, false);
536            }}),
537        /**
538         * Two Days After: The second class has to be placed two days after the first class (Monday &rarr; Wednesday, Tuesday &rarr; 
539         * Thurday, Wednesday &rarr; Friday, Thursday &rarr; Monday, Friday &rarr; Tuesday).<br>
540         * When prohibited or (strongly) discouraged: The second class has to be placed two days before the first class (Monday &rarr;
541         * Thursday, Tuesday &rarr; Friday, Wednesday &rarr; Monday, Thursday &rarr; Tuesday, Friday &rarr; Wednesday).<br>
542         * Note: This constraint works only between pairs of classes.
543         */
544        EVERY_OTHER_DAY("EVERY_OTHER_DAY", "Two Days After", new PairCheck() {
545            @Override
546            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
547                return gc.isEveryOtherDay(plc1, plc2, true);
548            }
549            @Override
550            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
551                return gc.isEveryOtherDay(plc1, plc2, false);
552            }}),
553        /**
554          * At Most 3 Hours A Day: Classes are to be placed in a way that there is no more than three hours in any day.
555          */
556        MAX_HRS_DAY_3("MAX_HRS_DAY(3)", "At Most 3 Hours A Day", 36, null, Flag.MAX_HRS_DAY),        
557        /**
558         * At Most 4 Hours A Day: Classes are to be placed in a way that there is no more than four hours in any day.
559         */
560        MAX_HRS_DAY_4("MAX_HRS_DAY(4)", "At Most 4 Hours A Day", 48, null, Flag.MAX_HRS_DAY),        
561        /**
562          * At Most 5 Hours A Day: Classes are to be placed in a way that there is no more than five hours in any day.
563          */
564        MAX_HRS_DAY_5("MAX_HRS_DAY(5)", "At Most 5 Hours A Day", 60, null, Flag.MAX_HRS_DAY),        
565        /**
566         * At Most 6 Hours A Day: Classes are to be placed in a way that there is no more than six hours in any day.
567         */
568        MAX_HRS_DAY_6("MAX_HRS_DAY(6)", "At Most 6 Hours A Day", 72, null, Flag.MAX_HRS_DAY),
569        /**
570         * At Most 7 Hours A Day: Classes are to be placed in a way that there is no more than seven hours in any day.
571         */
572        MAX_HRS_DAY_7("MAX_HRS_DAY(7)", "At Most 7 Hours A Day", 84, null, Flag.MAX_HRS_DAY),
573        /**
574         * At Most 8 Hours A Day: Classes are to be placed in a way that there is no more than eight hours in any day.
575         */
576        MAX_HRS_DAY_8("MAX_HRS_DAY(8)", "At Most 8 Hours A Day", 96, null, Flag.MAX_HRS_DAY),
577        /**
578         * At Most 9 Hours A Day: Classes are to be placed in a way that there is no more than nine hours in any day.
579         */
580        MAX_HRS_DAY_9("MAX_HRS_DAY(9)", "At Most 9 Hours A Day", 108, null, Flag.MAX_HRS_DAY),
581        /**
582         * At Most 10 Hours A Day: Classes are to be placed in a way that there is no more than ten hours in any day.
583         */
584        MAX_HRS_DAY_10("MAX_HRS_DAY(10)", "At Most 10 Hours A Day", 120, null, Flag.MAX_HRS_DAY),
585        /**
586         * Given classes must be taught during the same weeks (i.e., must have the same date pattern).<br>
587         * When prohibited or (strongly) discouraged: any two classes must have non overlapping date patterns.
588         */
589        SAME_WEEKS("SAME_WEEKS", "Same Weeks", new PairCheck() {
590            @Override
591            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
592                return plc1.getTimeLocation().getWeekCode().equals(plc2.getTimeLocation().getWeekCode());
593            }
594            @Override
595            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
596                return !plc1.getTimeLocation().shareWeeks(plc2.getTimeLocation());
597            }}),
598        /**
599         * Classes (of different courses) are to be attended by the same students. For instance,
600         * if class A1 (of a course A) and class B1 (of a course B) are linked, a student requesting
601         * both courses must attend A1 if and only if he also attends B1. This is a student sectioning
602         * constraint that is interpreted as Same Students constraint during course timetabling.
603         */
604        LINKED_SECTIONS("LINKED_SECTIONS", "Linked Classes", SAME_STUDENTS.check()),
605        /**
606         * Back-To-Back Precedence: Given classes have to be taught in the given order, on the same days,
607         * and in adjacent time segments.
608         * When prohibited or (strongly) discouraged: Given classes have to be taught in the given order,
609         * on the same days, but cannot be back-to-back.
610         */
611        BTB_PRECEDENCE("BTB_PRECEDENCE", "Back-To-Back Precedence", new PairCheck() {
612            @Override
613            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
614                return gc.isPrecedence(plc1, plc2, true, false) && sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray());
615            }
616            @Override
617            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
618                return gc.isPrecedence(plc1, plc2, true, false) && sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray());
619            }}, Flag.BACK_TO_BACK),   
620            
621        /**
622         * Same Days-Time: Given classes must be taught at the same time of day and on the same days.
623         * It is the combination of Same Days and Same Time distribution preferences.     
624         * When prohibited or (strongly) discouraged: Any pair of classes classes cannot be taught on the same days
625         * during the same time.
626         */             
627        SAME_DAYS_TIME("SAME_D_T", "Same Days-Time", new PairCheck() {
628            @Override
629            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
630                return sameHours(plc1.getTimeLocation().getStartSlot(), plc1.getTimeLocation().getLength(),
631                        plc2.getTimeLocation().getStartSlot(), plc2.getTimeLocation().getLength()) &&
632                        sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray());
633            }
634            @Override
635            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
636                return !plc1.getTimeLocation().shareHours(plc2.getTimeLocation()) ||
637                        !plc1.getTimeLocation().shareDays(plc2.getTimeLocation());
638            }}),
639        /**
640         * Same Days-Room-Time: Given classes must be taught at the same time of day, on the same days and in the same room.
641         * It is the combination of Same Days, Same Time and Same Room distribution preferences.
642         * Note that this constraint is the same as Meet Together constraint, except it does not allow room sharing. In other words,
643         * it is only useful when these classes are taught during non-overlapping date patterns.
644         * When prohibited or (strongly) discouraged: Any pair of classes classes cannot be taught on the same days 
645         * during the same time in the same room.
646         */            
647        SAME_DAYS_ROOM_TIME("SAME_D_R_T", "Same Days-Room-Time", new PairCheck() {
648            @Override
649            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
650                return sameHours(plc1.getTimeLocation().getStartSlot(), plc1.getTimeLocation().getLength(),
651                        plc2.getTimeLocation().getStartSlot(), plc2.getTimeLocation().getLength()) &&
652                        sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray()) &&
653                        plc1.sameRooms(plc2);
654            }
655            @Override
656            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
657                return !plc1.getTimeLocation().shareHours(plc2.getTimeLocation()) ||
658                        !plc1.getTimeLocation().shareDays(plc2.getTimeLocation()) ||
659                        !plc1.sameRooms(plc2);
660            }}), 
661        /**
662         * 6 Hour Work Day: Classes are to be placed in a way that there is no more than six hours between the start of the first class and the end of the class one on any day.
663         */
664        WORKDAY_6("WORKDAY(6)", "6 Hour Work Day", 72, new PairCheck() {
665            @Override
666            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
667                TimeLocation t1 = plc1.getTimeLocation(), t2 = plc2.getTimeLocation();
668                if (t1 == null || t2 == null || !t1.shareDays(t2) || !t1.shareWeeks(t2)) return true;
669                return Math.max(t1.getStartSlot() + t1.getLength(), t2.getStartSlot() + t2.getLength()) - Math.min(t1.getStartSlot(), t2.getStartSlot()) <= gc.getType().getMax();
670            }
671            @Override
672            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) { return true; }
673            }),
674        /**
675         * 7 Hour Work Day: Classes are to be placed in a way that there is no more than seven hours between the start of the first class and the end of the class one on any day.
676         */
677        WORKDAY_7("WORKDAY(7)", "7 Hour Work Day", 84, WORKDAY_6.check()),
678        /**
679         * 8 Hour Work Day: Classes are to be placed in a way that there is no more than eight hours between the start of the first class and the end of the class one on any day.
680         */
681        WORKDAY_8("WORKDAY(8)", "8 Hour Work Day", 96, WORKDAY_6.check()),
682        /**
683         * 9 Hour Work Day: Classes are to be placed in a way that there is no more than nine hours between the start of the first class and the end of the class one on any day.
684         */
685        WORKDAY_9("WORKDAY(9)", "9 Hour Work Day", 108, WORKDAY_6.check()),
686        /**
687         * 10 Hour Work Day: Classes are to be placed in a way that there is no more than ten hours between the start of the first class and the end of the class one on any day.
688         */
689        WORKDAY_10("WORKDAY(10)", "10 Hour Work Day", 120, WORKDAY_6.check()),
690        /**
691         * 11 Hour Work Day: Classes are to be placed in a way that there is no more than eleven hours between the start of the first class and the end of the class one on any day.
692         */
693        WORKDAY_11("WORKDAY(11)", "11 Hour Work Day", 132, WORKDAY_6.check()),
694        /**
695         * 12 Hour Work Day: Classes are to be placed in a way that there is no more than twelve hours between the start of the first class and the end of the class one on any day.
696         */
697        WORKDAY_12("WORKDAY(12)", "12 Hour Work Day", 144, WORKDAY_6.check()),
698        /**
699         * Meet Together & Same Weeks: Given classes are meeting together (same as if the given classes require constraints Can Share Room,
700         * Same Room, Same Time, Same Days and Same Weeks all together).
701         */
702        MEET_WITH_WEEKS("MEET_WITH_WEEKS", "Meet Together & Same Weeks", new PairCheck() {
703            @Override
704            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
705                return
706                        plc1.sameRooms(plc2) &&
707                        sameHours(plc1.getTimeLocation().getStartSlot(), plc1.getTimeLocation().getLength(), plc2.getTimeLocation().getStartSlot(), plc2.getTimeLocation().getLength()) &&
708                        sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray()) &&
709                        plc1.getTimeLocation().getWeekCode().equals(plc2.getTimeLocation().getWeekCode());
710            }
711            @Override
712            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
713                return true;
714            }}, Flag.CAN_SHARE_ROOM),
715        ;
716        
717        String iReference, iName;
718        int iFlag = 0;
719        Flag[] iFlags = null;
720        int iMin = 0, iMax = 0;
721        PairCheck iCheck = null;
722        AssignmentPairCheck iAssignmentCheck = null;
723        ConstraintType(String reference, String name, Flag... flags) {
724            iReference = reference;
725            iName = name;
726            iFlags = flags;
727            for (Flag f: flags)
728                iFlag |= f.flag();
729        }
730        ConstraintType(String reference, String name, PairCheck check, Flag... flags) {
731            this(reference, name, flags);
732            iCheck = check;
733        }
734        ConstraintType(String reference, String name, AssignmentPairCheck check, Flag... flags) {
735            this(reference, name, flags);
736            iAssignmentCheck = check;
737        }
738        ConstraintType(String reference, String name, int limit, PairCheck check, Flag... flags) {
739            this(reference, name, check, flags);
740            iMin = iMax = limit;
741        }
742        ConstraintType(String reference, String name, int min, int max, PairCheck check, Flag... flags) {
743            this(reference, name, check, flags);
744            iMin = min;
745            iMax = max;
746        }
747        
748        /** Constraint reference
749         * @return constraint reference
750         **/
751        public String reference() { return iReference; }
752        /** Constraint name
753         * @return constraint name
754         **/
755        public String getName() { return iName; }
756        /** Minimum (gap) parameter
757         * @return minimum gap (first constraint parameter)
758         **/
759        public int getMin() { return iMin; }
760        /** Maximum (gap, hours a day) parameter 
761         * @return maximum gap (second constraint parameter) 
762         **/
763        public int getMax() { return iMax; }
764        
765        /** Flag check (true if contains given flag) 
766         * @param f a flag to check
767         * @return true if present
768         **/
769        public boolean is(Flag f) { return (iFlag & f.flag()) != 0; }
770
771        /** Constraint type from reference 
772         * @param reference constraint reference
773         * @return constraint of the reference
774         **/
775        public static ConstraintType get(String reference) {
776            for (ConstraintType t: ConstraintType.values())
777                if (t.reference().equals(reference)) return t;
778            return null;
779        }
780        
781        /** True if a required or preferred constraint is satisfied between a pair of placements 
782         * @param assignment current assignment
783         * @param gc current constraint
784         * @param plc1 first placement
785         * @param plc2 second placement
786         * @return true if the two placements are consistent with the constraint if preferred or required 
787         **/ 
788        public boolean isSatisfied(Assignment<Lecture, Placement> assignment, GroupConstraint gc, Placement plc1, Placement plc2) {
789            if (iCheck != null && !iCheck.isSatisfied(gc, plc1, plc2))
790                return false;
791            if (iAssignmentCheck != null && assignment != null && !iAssignmentCheck.isSatisfied(assignment, gc, plc1, plc2))
792                return false;
793            return true;
794        }
795        /** True if a prohibited or discouraged constraint is satisfied between a pair of placements 
796         * @param assignment current assignment
797         * @param gc current constraint
798         * @param plc1 first placement
799         * @param plc2 second placement
800         * @return true if the two placements are consistent with the constraint if discouraged or prohibited 
801         **/ 
802        public boolean isViolated(Assignment<Lecture, Placement> assignment, GroupConstraint gc, Placement plc1, Placement plc2) { 
803            if (iCheck != null && !iCheck.isViolated(gc, plc1, plc2))
804                return false;
805            if (iAssignmentCheck != null && assignment != null && !iAssignmentCheck.isViolated(assignment, gc, plc1, plc2))
806                return false;
807            return true;
808        }
809        /** Pair check */
810        private PairCheck check() { return iCheck; }
811    }
812
813    public GroupConstraint() {
814    }
815    
816    @Override
817    public void setModel(Model<Lecture, Placement> model) {
818        super.setModel(model);
819        if (model != null) {
820            DataProperties config = ((TimetableModel)model).getProperties();
821            iDayOfWeekOffset = config.getPropertyInt("DatePattern.DayOfWeekOffset", 0);
822            iPrecedenceConsiderDatePatterns = config.getPropertyBoolean("Precedence.ConsiderDatePatterns", true);
823            iForwardCheckMaxDepth = config.getPropertyInt("ForwardCheck.MaxDepth", iForwardCheckMaxDepth);
824            iForwardCheckMaxDomainSize = config.getPropertyInt("ForwardCheck.MaxDomainSize", iForwardCheckMaxDomainSize);
825            iMaxNHoursADayConsiderDatePatterns = config.getPropertyBoolean("MaxNHoursADay.ConsiderDatePatterns", iMaxNHoursADayConsiderDatePatterns);
826            iNrWorkDays = (config.getPropertyInt("General.LastWorkDay", 4) - config.getPropertyInt("General.FirstWorkDay", 0) + 1);
827            if (iNrWorkDays <= 0) iNrWorkDays += 7;
828            if (iNrWorkDays > 7) iNrWorkDays -= 7;
829            iFirstWorkDay = config.getPropertyInt("General.FirstWorkDay", 0);
830        }
831    }
832
833    @Override
834    public void addVariable(Lecture lecture) {
835        if (!variables().contains(lecture))
836            super.addVariable(lecture);
837        if (getType().is(Flag.CH_NOTOVERLAP)) {
838            if (lecture.getChildrenSubpartIds() != null) {
839                for (Long subpartId: lecture.getChildrenSubpartIds()) {
840                    for (Lecture ch : lecture.getChildren(subpartId)) {
841                        if (!variables().contains(ch))
842                            super.addVariable(ch);
843                    }
844                }
845            }
846        }
847    }
848
849    @Override
850    public void removeVariable(Lecture lecture) {
851        if (variables().contains(lecture))
852            super.removeVariable(lecture);
853        if (getType().is(Flag.CH_NOTOVERLAP)) {
854            if (lecture.getChildrenSubpartIds() != null) {
855                for (Long subpartId: lecture.getChildrenSubpartIds()) {
856                    for (Lecture ch : lecture.getChildren(subpartId)) {
857                        if (variables().contains(ch))
858                            super.removeVariable(ch);
859                    }
860                }
861            }
862        }
863    }
864
865    /**
866     * Constructor
867     * 
868     * @param id
869     *            constraint id
870     * @param type
871     *            constraString type (e.g, {@link ConstraintType#SAME_TIME})
872     * @param preference
873     *            time preference ("R" for required, "P" for prohibited, "-2",
874     *            "-1", "1", "2" for soft preference)
875     */
876    public GroupConstraint(Long id, ConstraintType type, String preference) {
877        iConstraintId = id;
878        iType = type;
879        iIsRequired = preference.equals(Constants.sPreferenceRequired);
880        iIsProhibited = preference.equals(Constants.sPreferenceProhibited);
881        iPreference = Constants.preference2preferenceLevel(preference);
882    }
883
884    /** Constraint id 
885     * @return constraint unique id
886     **/
887    public Long getConstraintId() {
888        return iConstraintId;
889    }
890
891    @Override
892    public long getId() {
893        return (iConstraintId == null ? -1 : iConstraintId.longValue());
894    }
895    
896    /** Generated unique id 
897     * @return generated unique id
898     **/
899    protected long getGeneratedId() {
900        return iId;
901    }
902
903    /** Return constraint type (e.g, {@link ConstraintType#SAME_TIME}) 
904     * @return constraint type
905     **/
906    public ConstraintType getType() {
907        return iType;
908    }
909
910    /**
911     * Set constraint type
912     * @param type constraint type
913     */
914    public void setType(ConstraintType type) {
915        iType = type;
916    }
917
918    /** Is constraint required 
919     * @return true if required
920     **/
921    public boolean isRequired() {
922        return iIsRequired;
923    }
924
925    /** Is constraint prohibited 
926     * @return true if prohibited
927     **/
928    public boolean isProhibited() {
929        return iIsProhibited;
930    }
931
932    /**
933     * Prolog reference: "R" for required, "P" for prohibited", "-2",.."2" for
934     * preference
935     * @return prolog preference
936     */
937    public String getPrologPreference() {
938        return Constants.preferenceLevel2preference(iPreference);
939    }
940
941    @Override
942    public boolean isConsistent(Placement value1, Placement value2) {
943        if (!isHard())
944            return true;
945        if (!isSatisfiedPair(null, value1, value2))
946            return false;
947        if (getType().is(Flag.BACK_TO_BACK)) {
948            HashMap<Lecture, Placement> assignments = new HashMap<Lecture, Placement>();
949            assignments.put(value1.variable(), value1);
950            assignments.put(value2.variable(), value2);
951            if (!isSatisfiedSeq(null, assignments, null))
952                return false;
953        }
954        if (getType().is(Flag.MAX_HRS_DAY)) {
955            HashMap<Lecture, Placement> assignments = new HashMap<Lecture, Placement>();
956            assignments.put(value1.variable(), value1);
957            assignments.put(value2.variable(), value2);
958            for (int dayCode: Constants.DAY_CODES) {
959                if (iMaxNHoursADayConsiderDatePatterns) {
960                    for (BitSet week: ((TimetableModel)getModel()).getWeeks()) {
961                        if (!value1.getTimeLocation().shareWeeks(week) && !value2.getTimeLocation().shareWeeks(week)) continue;
962                        if (nrSlotsADay(null, dayCode, week, assignments, null) > getType().getMax()) return false;
963                    }
964                } else {
965                    if (nrSlotsADay(null, dayCode, null, assignments, null) > getType().getMax()) return false;
966                }
967            }
968        }
969        return true;
970    }
971
972    @Override
973    public void computeConflicts(Assignment<Lecture, Placement> assignment, Placement value, Set<Placement> conflicts) {
974        computeConflicts(assignment, value, conflicts, true);
975    }
976    
977    @Override
978    public void computeConflictsNoForwardCheck(Assignment<Lecture, Placement> assignment, Placement value, Set<Placement> conflicts) {
979        computeConflicts(assignment, value, conflicts, false);
980    }
981    
982    public void computeConflicts(Assignment<Lecture, Placement> assignment, Placement value, Set<Placement> conflicts, boolean fwdCheck) {
983        if (!isHard())
984            return;
985        for (Lecture v : variables()) {
986            if (v.equals(value.variable()))
987                continue; // ignore this variable
988            Placement p = assignment.getValue(v);
989            if (p == null)
990                continue; // there is an unassigned variable -- great, still a chance to get violated
991            if (!isSatisfiedPair(assignment, p, value))
992                conflicts.add(p);
993        }
994        if (getType().is(Flag.BACK_TO_BACK)) {
995            HashMap<Lecture, Placement> assignments = new HashMap<Lecture, Placement>();
996            assignments.put(value.variable(), value);
997            if (!isSatisfiedSeq(assignment, assignments, conflicts))
998                conflicts.add(value);
999        }
1000        if (getType().is(Flag.MAX_HRS_DAY)) {
1001            HashMap<Lecture, Placement> assignments = new HashMap<Lecture, Placement>();
1002            assignments.put(value.variable(), value);
1003            for (int dayCode: Constants.DAY_CODES) {
1004                if (iMaxNHoursADayConsiderDatePatterns) {
1005                    for (BitSet week: ((TimetableModel)getModel()).getWeeks()) {
1006                        if (!value.getTimeLocation().shareWeeks(week)) continue;
1007                        if (nrSlotsADay(assignment, dayCode, week, assignments, conflicts) > getType().getMax()) {
1008                            List<Placement> adepts = new ArrayList<Placement>();
1009                            for (Lecture l: variables()) {
1010                                if (l.equals(value.variable()) || l.isConstant()) continue;
1011                                Placement p = assignment.getValue(l);
1012                                if (p == null || conflicts.contains(p) || p.getTimeLocation() == null) continue;
1013                                if ((p.getTimeLocation().getDayCode() & dayCode) == 0 || !p.getTimeLocation().shareWeeks(week)) continue;
1014                                adepts.add(p);
1015                            }
1016                            do {
1017                                if (adepts.isEmpty()) { conflicts.add(value); break; }
1018                                Placement conflict = ToolBox.random(adepts);
1019                                adepts.remove(conflict);
1020                                conflicts.add(conflict);
1021                            } while (nrSlotsADay(assignment, dayCode, week, assignments, conflicts) > getType().getMax());
1022                        }
1023                    }
1024                } else {
1025                    if (nrSlotsADay(assignment, dayCode, null, assignments, conflicts) > getType().getMax()) {
1026                        List<Placement> adepts = new ArrayList<Placement>();
1027                        for (Lecture l: variables()) {
1028                            if (l.equals(value.variable()) || l.isConstant()) continue;
1029                            Placement p = assignment.getValue(l);
1030                            if (p == null || conflicts.contains(p) || p.getTimeLocation() == null) continue;
1031                            if ((p.getTimeLocation().getDayCode() & dayCode) == 0) continue;
1032                            adepts.add(p);
1033                        }
1034                        do {
1035                            if (adepts.isEmpty()) { conflicts.add(value); break; }
1036                            Placement conflict = ToolBox.random(adepts);
1037                            adepts.remove(conflict);
1038                            conflicts.add(conflict);
1039                        } while (nrSlotsADay(assignment, dayCode, null, assignments, conflicts) > getType().getMax());
1040                    }
1041                }
1042            }
1043        }
1044        
1045        // Forward checking
1046        if (fwdCheck) forwardCheck(assignment, value, conflicts, new HashSet<GroupConstraint>(), iForwardCheckMaxDepth - 1);
1047    }
1048    
1049    public void forwardCheck(Assignment<Lecture, Placement> assignment, Placement value, Set<Placement> conflicts, Set<GroupConstraint> ignore, int depth) {
1050        try {
1051            if (depth < 0) return;
1052            ignore.add(this);
1053            
1054            int neededSize = value.variable().maxRoomUse();
1055            
1056            for (Lecture lecture: variables()) {
1057                if (conflicts.contains(value)) break; // already conflicting
1058
1059                if (lecture.equals(value.variable())) continue; // Skip this lecture
1060                Placement current = assignment.getValue(lecture);
1061                if (current != null) { // Has assignment, check whether it is conflicting
1062                    if (isSatisfiedPair(assignment, value, current)) {
1063                        // Increase needed size if the assignment is of the same room and overlapping in time
1064                        if (canShareRoom() && sameRoomAndOverlaps(value, current)) {
1065                            neededSize += lecture.maxRoomUse();
1066                        }
1067                        continue;
1068                    }
1069                    conflicts.add(current);
1070                }
1071                
1072                // Look for supporting assignments assignment
1073                boolean shareRoomAndOverlaps = canShareRoom();
1074                Placement support = null;
1075                int nrSupports = 0;
1076                if (lecture.nrValues() >= iForwardCheckMaxDomainSize) {
1077                    // ignore variables with large domains
1078                    return;
1079                }
1080                List<Placement> values = lecture.values(assignment);
1081                if (values.isEmpty()) {
1082                    // ignore variables with empty domain
1083                    return;
1084                }
1085                for (Placement other: values) {
1086                    if (nrSupports < 2) {
1087                        if (isSatisfiedPair(assignment, value, other)) {
1088                            if (support == null) support = other;
1089                            nrSupports ++;
1090                            if (shareRoomAndOverlaps && !sameRoomAndOverlaps(value, other))
1091                                shareRoomAndOverlaps = false;
1092                        }
1093                    } else if (shareRoomAndOverlaps && !sameRoomAndOverlaps(value, other) && isSatisfiedPair(assignment, value, other)) {
1094                        shareRoomAndOverlaps = false;
1095                    }
1096                    if (nrSupports > 1 && !shareRoomAndOverlaps)
1097                        break;
1098                }
1099                
1100                // No supporting assignment -> fail
1101                if (nrSupports == 0) {
1102                    conflicts.add(value); // other class cannot be assigned with this value
1103                    return;
1104                }
1105                // Increase needed size if all supporters are of the same room and in overlapping times
1106                if (shareRoomAndOverlaps) {
1107                    neededSize += lecture.maxRoomUse();
1108                }
1109
1110                // Only one supporter -> propagate the new assignment over other hard constraints of the lecture
1111                if (nrSupports == 1) {
1112                    for (Constraint<Lecture, Placement> other: lecture.hardConstraints()) {
1113                        if (other instanceof WeakeningConstraint) continue;
1114                        if (other instanceof GroupConstraint) {
1115                            GroupConstraint gc = (GroupConstraint)other;
1116                            if (depth > 0 && !ignore.contains(gc))
1117                                gc.forwardCheck(assignment, support, conflicts, ignore, depth - 1);
1118                        } else {
1119                            other.computeConflicts(assignment, support, conflicts);
1120                        }
1121                    }
1122                    for (GlobalConstraint<Lecture, Placement> other: getModel().globalConstraints()) {
1123                        if (other instanceof WeakeningConstraint) continue;
1124                        other.computeConflicts(assignment, support, conflicts);
1125                    }
1126
1127                    if (conflicts.contains(support))
1128                        conflicts.add(value);
1129                }
1130            }
1131            
1132            if (canShareRoom() && neededSize > value.getRoomSize()) {
1133                // room is too small to fit all meet with classes
1134                conflicts.add(value);
1135            }
1136            
1137        } finally {
1138            ignore.remove(this);
1139        }
1140    }
1141
1142    @Override
1143    public boolean inConflict(Assignment<Lecture, Placement> assignment, Placement value) {
1144        if (!isHard())
1145            return false;
1146        for (Lecture v : variables()) {
1147            if (v.equals(value.variable()))
1148                continue; // ignore this variable
1149            Placement p = assignment.getValue(v);
1150            if (p == null)
1151                continue; // there is an unassigned variable -- great, still a chance to get violated
1152            if (!isSatisfiedPair(assignment, p, value))
1153                return true;
1154        }
1155        if (getType().is(Flag.BACK_TO_BACK)) {
1156            HashMap<Lecture, Placement> assignments = new HashMap<Lecture, Placement>();
1157            assignments.put(value.variable(), value);
1158            if (!isSatisfiedSeq(assignment, assignments, null))
1159                return true;
1160        }
1161        if (getType().is(Flag.MAX_HRS_DAY)) {
1162            HashMap<Lecture, Placement> assignments = new HashMap<Lecture, Placement>();
1163            assignments.put(value.variable(), value);
1164            for (int dayCode: Constants.DAY_CODES) {
1165                if (iMaxNHoursADayConsiderDatePatterns) {
1166                    for (BitSet week: ((TimetableModel)getModel()).getWeeks()) {
1167                        if (!value.getTimeLocation().shareWeeks(week)) continue;
1168                        if (nrSlotsADay(assignment, dayCode, week, assignments, null) > getType().getMax())
1169                            return true;
1170                    }
1171                } else {
1172                    if (nrSlotsADay(assignment, dayCode, null, assignments, null) > getType().getMax()) return true;
1173                }
1174            }
1175        }
1176        
1177        if (!forwardCheck(assignment, value, new HashSet<GroupConstraint>(), iForwardCheckMaxDepth - 1)) return true;
1178        
1179        return false;
1180    }
1181    
1182    public boolean forwardCheck(Assignment<Lecture, Placement> assignment, Placement value, Set<GroupConstraint> ignore, int depth) {
1183        try {
1184            if (depth < 0) return true;
1185            ignore.add(this);
1186            
1187            int neededSize = value.variable().maxRoomUse();
1188            
1189            for (Lecture lecture: variables()) {
1190                if (lecture.equals(value.variable())) continue; // Skip this lecture
1191                Placement current = assignment.getValue(lecture);
1192                if (current != null) { // Has assignment, check whether it is conflicting
1193                    if (isSatisfiedPair(assignment, value, current)) {
1194                        // Increase needed size if the assignment is of the same room and overlapping in time
1195                        if (canShareRoom() && sameRoomAndOverlaps(value, current)) {
1196                            neededSize += lecture.maxRoomUse();
1197                        }
1198                        continue;
1199                    }
1200                    return false;
1201                }
1202                
1203                // Look for supporting assignments assignment
1204                boolean shareRoomAndOverlaps = canShareRoom();
1205                Placement support = null;
1206                int nrSupports = 0;
1207                if (lecture.nrValues() >= iForwardCheckMaxDomainSize) {
1208                    // ignore variables with large domains
1209                    return true;
1210                }
1211                List<Placement> values = lecture.values(assignment);
1212                if (values.isEmpty()) {
1213                    // ignore variables with empty domain
1214                    return true;
1215                }
1216                for (Placement other: lecture.values(assignment)) {
1217                    if (nrSupports < 2) {
1218                        if (isSatisfiedPair(assignment, value, other)) {
1219                            if (support == null) support = other;
1220                            nrSupports ++;
1221                            if (shareRoomAndOverlaps && !sameRoomAndOverlaps(value, other))
1222                                shareRoomAndOverlaps = false;
1223                        }
1224                    } else if (shareRoomAndOverlaps && !sameRoomAndOverlaps(value, other) && isSatisfiedPair(assignment, value, other)) {
1225                        shareRoomAndOverlaps = false;
1226                    }
1227                    if (nrSupports > 1 && !shareRoomAndOverlaps)
1228                        break;
1229                }
1230
1231                // No supporting assignment -> fail
1232                if (nrSupports == 0) {
1233                    return false; // other class cannot be assigned with this value
1234                }
1235                // Increase needed size if all supporters are of the same room and in overlapping times
1236                if (shareRoomAndOverlaps) {
1237                    neededSize += lecture.maxRoomUse();
1238                }
1239
1240                // Only one supporter -> propagate the new assignment over other hard constraints of the lecture
1241                if (nrSupports == 1) {
1242                    for (Constraint<Lecture, Placement> other: lecture.hardConstraints()) {
1243                        if (other instanceof WeakeningConstraint) continue;
1244                        if (other instanceof GroupConstraint) {
1245                            GroupConstraint gc = (GroupConstraint)other;
1246                            if (depth > 0 && !ignore.contains(gc) && !gc.forwardCheck(assignment, support, ignore, depth - 1)) return false;
1247                        } else {
1248                            if (other.inConflict(assignment, support)) return false;
1249                        }
1250                    }
1251                    for (GlobalConstraint<Lecture, Placement> other: getModel().globalConstraints()) {
1252                        if (other instanceof WeakeningConstraint) continue;
1253                        if (other.inConflict(assignment, support)) return false;
1254                    }
1255                }
1256            }
1257            
1258            if (canShareRoom() && neededSize > value.getRoomSize()) {
1259                // room is too small to fit all meet with classes
1260                return false;
1261            }
1262         
1263            return true;
1264        } finally {
1265            ignore.remove(this);
1266        }
1267    }
1268
1269    /** Constraint preference (0 if prohibited or required) 
1270     * @return constraint preference (if soft)
1271     **/
1272    public int getPreference() {
1273        return iPreference;
1274    }
1275
1276    /**
1277     * Current constraint preference (0 if prohibited or required, depends on
1278     * current satisfaction of the constraint)
1279     * @param assignment current assignment
1280     * @return current preference
1281     */
1282    public int getCurrentPreference(Assignment<Lecture, Placement> assignment) {
1283        if (isHard()) return 0; // no preference
1284        if (countAssignedVariables(assignment) < 2) return - Math.abs(iPreference); // not enough variable
1285        if (getType().is(Flag.MAX_HRS_DAY)) { // max hours a day
1286            int over = 0;
1287            for (int dayCode: Constants.DAY_CODES) {
1288                if (iMaxNHoursADayConsiderDatePatterns) {
1289                    for (BitSet week: ((TimetableModel)getModel()).getWeeks())
1290                        over += Math.max(0, nrSlotsADay(assignment, dayCode, week, null, null) - getType().getMax());
1291                } else {
1292                    over += Math.max(0, nrSlotsADay(assignment, dayCode, null, null, null) - getType().getMax());
1293                }
1294            }
1295            return (over > 0 ? Math.abs(iPreference) * over / 12 : - Math.abs(iPreference));
1296        }
1297        int nrViolatedPairs = 0;
1298        for (Lecture v1 : variables()) {
1299            Placement p1 = assignment.getValue(v1);
1300            if (p1 == null) continue;
1301            for (Lecture v2 : variables()) {
1302                Placement p2 = assignment.getValue(v2);
1303                if (p2 == null || v1.getId() >= v2.getId()) continue;
1304                if (!isSatisfiedPair(assignment, p1, p2)) nrViolatedPairs++;
1305            }
1306        }
1307        if (getType().is(Flag.BACK_TO_BACK)) {
1308            Set<Placement> conflicts = new HashSet<Placement>();
1309            if (isSatisfiedSeq(assignment, new HashMap<Lecture, Placement>(), conflicts))
1310                nrViolatedPairs += conflicts.size();
1311            else
1312                nrViolatedPairs = variables().size();
1313        }
1314        return (nrViolatedPairs > 0 ? Math.abs(iPreference) * nrViolatedPairs : - Math.abs(iPreference));
1315    }
1316
1317    /** Current constraint preference change (if given placement is assigned) 
1318     * @param assignment current assignment
1319     * @param placement placement that is being considered
1320     * @return change in the current preference, if assigned 
1321     **/
1322    public int getCurrentPreference(Assignment<Lecture, Placement> assignment, Placement placement) {
1323        if (isHard()) return 0; // no preference
1324        if (countAssignedVariables(assignment) + (assignment.getValue(placement.variable()) == null ? 1 : 0) < 2) return 0; // not enough variable
1325        if (getType().is(Flag.MAX_HRS_DAY)) {
1326            HashMap<Lecture, Placement> assignments = new HashMap<Lecture, Placement>();
1327            assignments.put(placement.variable(), placement);
1328            HashMap<Lecture, Placement> unassignments = new HashMap<Lecture, Placement>();
1329            unassignments.put(placement.variable(), null);
1330            int after = 0;
1331            int before = 0;
1332            for (int dayCode: Constants.DAY_CODES) {
1333                if (iMaxNHoursADayConsiderDatePatterns) {
1334                    for (BitSet week: ((TimetableModel)getModel()).getWeeks()) {
1335                        after += Math.max(0, nrSlotsADay(assignment, dayCode, week, assignments, null) - getType().getMax());
1336                        before += Math.max(0, nrSlotsADay(assignment, dayCode, week, unassignments, null) - getType().getMax());
1337                    }
1338                } else {
1339                    after += Math.max(0, nrSlotsADay(assignment, dayCode, null, assignments, null) - getType().getMax());
1340                    before += Math.max(0, nrSlotsADay(assignment, dayCode, null, unassignments, null) - getType().getMax());
1341                }
1342            }
1343            return (after > 0 ? Math.abs(iPreference) * after / 12 : - Math.abs(iPreference)) - (before > 0 ? Math.abs(iPreference) * before / 12 : - Math.abs(iPreference));
1344        }
1345        
1346        int nrViolatedPairsAfter = 0;
1347        int nrViolatedPairsBefore = 0;
1348        for (Lecture v1 : variables()) {
1349            for (Lecture v2 : variables()) {
1350                if (v1.getId() >= v2.getId()) continue;
1351                Placement p1 = (v1.equals(placement.variable()) ? null : assignment.getValue(v1));
1352                Placement p2 = (v2.equals(placement.variable()) ? null : assignment.getValue(v2));
1353                if (p1 != null && p2 != null && !isSatisfiedPair(assignment, p1, p2))
1354                    nrViolatedPairsBefore ++;
1355                if (v1.equals(placement.variable())) p1 = placement;
1356                if (v2.equals(placement.variable())) p2 = placement;
1357                if (p1 != null && p2 != null && !isSatisfiedPair(assignment, p1, p2))
1358                    nrViolatedPairsAfter ++;
1359            }
1360        }
1361        
1362        if (getType().is(Flag.BACK_TO_BACK)) {
1363            HashMap<Lecture, Placement> assignments = new HashMap<Lecture, Placement>();
1364            assignments.put(placement.variable(), placement);
1365            Set<Placement> conflicts = new HashSet<Placement>();
1366            if (isSatisfiedSeq(assignment, assignments, conflicts))
1367                nrViolatedPairsAfter += conflicts.size();
1368            else
1369                nrViolatedPairsAfter = variables().size();
1370            
1371            HashMap<Lecture, Placement> unassignments = new HashMap<Lecture, Placement>();
1372            unassignments.put(placement.variable(), null);
1373            Set<Placement> previous = new HashSet<Placement>();
1374            if (isSatisfiedSeq(assignment, unassignments, previous))
1375                nrViolatedPairsBefore += previous.size();
1376            else
1377                nrViolatedPairsBefore = variables().size();
1378        }
1379        
1380        return (nrViolatedPairsAfter > 0 ? Math.abs(iPreference) * nrViolatedPairsAfter : - Math.abs(iPreference)) -
1381                (nrViolatedPairsBefore > 0 ? Math.abs(iPreference) * nrViolatedPairsBefore : - Math.abs(iPreference));
1382    }
1383
1384    @Override
1385    public String toString() {
1386        StringBuffer sb = new StringBuffer();
1387        sb.append(getName());
1388        sb.append(" between ");
1389        for (Iterator<Lecture> e = variables().iterator(); e.hasNext();) {
1390            Lecture v = e.next();
1391            sb.append(v.getName());
1392            if (e.hasNext())
1393                sb.append(", ");
1394        }
1395        return sb.toString();
1396    }
1397
1398    @Override
1399    public boolean isHard() {
1400        return iIsRequired || iIsProhibited;
1401    }
1402
1403    @Override
1404    public String getName() {
1405        return getType().getName();
1406    }
1407
1408
1409    private boolean isPrecedence(Placement p1, Placement p2, boolean firstGoesFirst, boolean considerDatePatterns) {
1410        int ord1 = variables().indexOf(p1.variable());
1411        int ord2 = variables().indexOf(p2.variable());
1412        TimeLocation t1 = null, t2 = null;
1413        if (ord1 < ord2) {
1414            if (firstGoesFirst) {
1415                t1 = p1.getTimeLocation();
1416                t2 = p2.getTimeLocation();
1417            } else {
1418                t2 = p1.getTimeLocation();
1419                t1 = p2.getTimeLocation();
1420            }
1421        } else {
1422            if (!firstGoesFirst) {
1423                t1 = p1.getTimeLocation();
1424                t2 = p2.getTimeLocation();
1425            } else {
1426                t2 = p1.getTimeLocation();
1427                t1 = p2.getTimeLocation();
1428            }
1429        }
1430        if (considerDatePatterns && iPrecedenceConsiderDatePatterns) {
1431            boolean sameDatePattern = (t1.getDatePatternId() != null ? t1.getDatePatternId().equals(t2.getDatePatternId()) : t1.getWeekCode().equals(t2.getWeekCode()));
1432            if (!sameDatePattern) {
1433                int m1 = t1.getFirstMeeting(iDayOfWeekOffset), m2 = t2.getFirstMeeting(iDayOfWeekOffset);
1434                if (m1 != m2) return m1 < m2;
1435            }
1436        }
1437        if (iFirstWorkDay != 0) {
1438            for (int i = 0; i < Constants.DAY_CODES.length; i++) {
1439                int idx = (i + iFirstWorkDay) % 7;
1440                boolean a = (t1.getDayCode() & Constants.DAY_CODES[idx]) != 0;
1441                boolean b = (t2.getDayCode() & Constants.DAY_CODES[idx]) != 0;
1442                if (b && !a) return false; // second start first
1443                if (a && !b) return true;  // first start first
1444                if (a && b) return t1.getStartSlot() + t1.getLength() <= t2.getStartSlot(); // same day: check times
1445            }
1446        }
1447        return t1.getStartSlots().nextElement() + t1.getLength() <= t2.getStartSlots().nextElement();
1448    }
1449
1450    private boolean isBackToBackDays(TimeLocation t1, TimeLocation t2) {
1451        int f1 = -1, f2 = -1, e1 = -1, e2 = -1;
1452        for (int i = 0; i < Constants.DAY_CODES.length; i++) {
1453            int idx = (i + iFirstWorkDay) % 7;
1454            if ((t1.getDayCode() & Constants.DAY_CODES[idx]) != 0) {
1455                if (f1 < 0)
1456                    f1 = i;
1457                e1 = i;
1458            }
1459            if ((t2.getDayCode() & Constants.DAY_CODES[idx]) != 0) {
1460                if (f2 < 0)
1461                    f2 = i;
1462                e2 = i;
1463            }
1464        }
1465        return (e1 + 1 == f2) || (e2 + 1 == f1);
1466    }
1467    
1468    private boolean isNrDaysBetweenGreaterThanOne(TimeLocation t1, TimeLocation t2) {
1469        int f1 = -1, f2 = -1, e1 = -1, e2 = -1;
1470        for (int i = 0; i < Constants.DAY_CODES.length; i++) {
1471            int idx = (i + iFirstWorkDay) % 7;
1472            if ((t1.getDayCode() & Constants.DAY_CODES[idx]) != 0) {
1473                if (f1 < 0)
1474                    f1 = i;
1475                e1 = i;
1476            }
1477            if ((t2.getDayCode() & Constants.DAY_CODES[idx]) != 0) {
1478                if (f2 < 0)
1479                    f2 = i;
1480                e2 = i;
1481            }
1482        }
1483        return (e1 - f2 > 2) || (e2 - f1 > 2);
1484    }
1485
1486    private boolean isFollowingDay(Placement p1, Placement p2, boolean firstGoesFirst) {
1487        int ord1 = variables().indexOf(p1.variable());
1488        int ord2 = variables().indexOf(p2.variable());
1489        TimeLocation t1 = null, t2 = null;
1490        if (ord1 < ord2) {
1491            if (firstGoesFirst) {
1492                t1 = p1.getTimeLocation();
1493                t2 = p2.getTimeLocation();
1494            } else {
1495                t2 = p1.getTimeLocation();
1496                t1 = p2.getTimeLocation();
1497            }
1498        } else {
1499            if (!firstGoesFirst) {
1500                t1 = p1.getTimeLocation();
1501                t2 = p2.getTimeLocation();
1502            } else {
1503                t2 = p1.getTimeLocation();
1504                t1 = p2.getTimeLocation();
1505            }
1506        }
1507        int f1 = -1, f2 = -1, e1 = -1;
1508        for (int i = 0; i < Constants.DAY_CODES.length; i++) {
1509            int idx = (i + iFirstWorkDay) % 7;
1510            if ((t1.getDayCode() & Constants.DAY_CODES[idx]) != 0) {
1511                if (f1 < 0)
1512                    f1 = i;
1513                e1 = i;
1514            }
1515            if ((t2.getDayCode() & Constants.DAY_CODES[idx]) != 0) {
1516                if (f2 < 0)
1517                    f2 = i;
1518            }
1519        }
1520        return ((e1 + 1) % iNrWorkDays == f2);
1521    }
1522
1523    private boolean isEveryOtherDay(Placement p1, Placement p2, boolean firstGoesFirst) {
1524        int ord1 = variables().indexOf(p1.variable());
1525        int ord2 = variables().indexOf(p2.variable());
1526        TimeLocation t1 = null, t2 = null;
1527        if (ord1 < ord2) {
1528            if (firstGoesFirst) {
1529                t1 = p1.getTimeLocation();
1530                t2 = p2.getTimeLocation();
1531            } else {
1532                t2 = p1.getTimeLocation();
1533                t1 = p2.getTimeLocation();
1534            }
1535        } else {
1536            if (!firstGoesFirst) {
1537                t1 = p1.getTimeLocation();
1538                t2 = p2.getTimeLocation();
1539            } else {
1540                t2 = p1.getTimeLocation();
1541                t1 = p2.getTimeLocation();
1542            }
1543        }
1544        int f1 = -1, f2 = -1, e1 = -1;
1545        for (int i = 0; i < Constants.DAY_CODES.length; i++) {
1546            int idx = (i + iFirstWorkDay) % 7;
1547            if ((t1.getDayCode() & Constants.DAY_CODES[idx]) != 0) {
1548                if (f1 < 0)
1549                    f1 = i;
1550                e1 = i;
1551            }
1552            if ((t2.getDayCode() & Constants.DAY_CODES[idx]) != 0) {
1553                if (f2 < 0)
1554                    f2 = i;
1555            }
1556        }
1557        return ((e1 + 2) % iNrWorkDays == f2);
1558    }
1559
1560    private static boolean sameDays(int[] days1, int[] days2) {
1561        if (days2.length < days1.length)
1562            return sameDays(days2, days1);
1563        int i2 = 0;
1564        for (int i1 = 0; i1 < days1.length; i1++) {
1565            int d1 = days1[i1];
1566            while (true) {
1567                if (i2 == days2.length)
1568                    return false;
1569                int d2 = days2[i2];
1570                if (d1 == d2)
1571                    break;
1572                i2++;
1573                if (i2 == days2.length)
1574                    return false;
1575            }
1576            i2++;
1577        }
1578        return true;
1579    }
1580    
1581    private static boolean sameRoomAndOverlaps(Placement p1, Placement p2) {
1582        return p1.shareRooms(p2) && p1.getTimeLocation() != null && p2.getTimeLocation() != null && p1.getTimeLocation().hasIntersection(p2.getTimeLocation());
1583    }
1584
1585    private static boolean sameHours(int start1, int len1, int start2, int len2) {
1586        if (len1 > len2)
1587            return sameHours(start2, len2, start1, len1);
1588        start1 %= Constants.SLOTS_PER_DAY;
1589        start2 %= Constants.SLOTS_PER_DAY;
1590        return (start1 >= start2 && start1 + len1 <= start2 + len2);
1591    }
1592    
1593    private static boolean canFill(int totalGap, int gapMin, int gapMax, List<Integer> lengths) {
1594        if (gapMin <= totalGap && totalGap <= gapMax)
1595            return true;
1596        if (totalGap < 2 * gapMin)
1597            return false;
1598        for (int i = 0; i < lengths.size(); i++) {
1599            int length = lengths.get(i);
1600            lengths.remove(i);
1601            for (int gap = gapMin; gap <= gapMax; gap++)
1602                if (canFill(totalGap - gap - length, gapMin, gapMax, lengths))
1603                    return true;
1604            lengths.add(i, length);
1605        }
1606        return false;
1607    }
1608
1609    private boolean isSatisfiedSeq(Assignment<Lecture, Placement> assignment, HashMap<Lecture, Placement> assignments, Set<Placement> conflicts) {
1610        if (conflicts == null)
1611            return isSatisfiedSeqCheck(assignment, assignments, conflicts);
1612        else {
1613            Set<Placement> bestConflicts = isSatisfiedRecursive(assignment, 0, assignments, conflicts,
1614                    new HashSet<Placement>(), null);
1615            if (bestConflicts == null)
1616                return false;
1617            conflicts.addAll(bestConflicts);
1618            return true;
1619        }
1620    }
1621
1622    private Set<Placement> isSatisfiedRecursive(Assignment<Lecture, Placement> assignment, int idx, HashMap<Lecture, Placement> assignments,
1623            Set<Placement> conflicts, Set<Placement> newConflicts, Set<Placement> bestConflicts) {
1624        if (idx == variables().size() && newConflicts.isEmpty())
1625            return bestConflicts;
1626        if (isSatisfiedSeqCheck(assignment, assignments, conflicts)) {
1627            if (bestConflicts == null) {
1628                return new HashSet<Placement>(newConflicts);
1629            } else {
1630                int b = 0, n = 0;
1631                for (Placement value: assignments.values()) {
1632                    if (value != null && bestConflicts.contains(value)) b++;
1633                    if (value != null && newConflicts.contains(value)) n++;
1634                }
1635                if (n < b || (n == b && newConflicts.size() < bestConflicts.size()))
1636                    return new HashSet<Placement>(newConflicts);
1637            }
1638            return bestConflicts;
1639        }
1640        if (idx == variables().size())
1641            return bestConflicts;
1642        bestConflicts = isSatisfiedRecursive(assignment, idx + 1, assignments, conflicts, newConflicts,
1643                bestConflicts);
1644        Lecture lecture = variables().get(idx);
1645        //if (assignments != null && assignments.containsKey(lecture))
1646        //    return bestConflicts;
1647        Placement placement = null;
1648        if (assignments != null && assignments.containsKey(lecture))
1649            placement = assignments.get(lecture);
1650        else if (assignment != null)
1651            placement = assignment.getValue(lecture);
1652        if (placement == null)
1653            return bestConflicts;
1654        if (conflicts != null && conflicts.contains(placement))
1655            return bestConflicts;
1656        conflicts.add(placement);
1657        newConflicts.add(placement);
1658        bestConflicts = isSatisfiedRecursive(assignment, idx + 1, assignments, conflicts, newConflicts, bestConflicts);
1659        newConflicts.remove(placement);
1660        conflicts.remove(placement);
1661        return bestConflicts;
1662    }
1663
1664    private boolean isSatisfiedSeqCheck(Assignment<Lecture, Placement> assignment, HashMap<Lecture, Placement> assignments, Set<Placement> conflicts) {
1665        if (!getType().is(Flag.BACK_TO_BACK)) return true;
1666        int gapMin = getType().getMin();
1667        int gapMax = getType().getMax();
1668
1669        List<Integer> lengths = new ArrayList<Integer>();
1670
1671        Placement[] res = new Placement[Constants.SLOTS_PER_DAY];
1672        for (int i = 0; i < Constants.SLOTS_PER_DAY; i++)
1673            res[i] = null;
1674
1675        int nrLectures = 0;
1676
1677        for (Lecture lecture : variables()) {
1678            Placement placement = null;
1679            if (assignments != null && assignments.containsKey(lecture))
1680                placement = assignments.get(lecture);
1681            else if (assignment != null)
1682                placement = assignment.getValue(lecture);
1683            if (placement == null) {
1684                if (!lecture.timeLocations().isEmpty())
1685                        lengths.add(lecture.timeLocations().get(0).getLength());
1686            } else if (conflicts != null && conflicts.contains(placement)) {
1687                if (!lecture.timeLocations().isEmpty())
1688                        lengths.add(lecture.timeLocations().get(0).getLength());
1689            } else {
1690                int pos = placement.getTimeLocation().getStartSlot();
1691                int length = placement.getTimeLocation().getLength();
1692                for (int j = pos; j < pos + length; j++) {
1693                    if (res[j] != null) {
1694                        if (conflicts == null)
1695                            return false;
1696                        if (!assignments.containsKey(lecture))
1697                            conflicts.add(placement);
1698                        else if (!assignments.containsKey(res[j].variable()))
1699                            conflicts.add(res[j]);
1700                    }
1701                }
1702                for (int j = pos; j < pos + length; j++)
1703                    res[j] = placement;
1704                nrLectures++;
1705            }
1706        }
1707        if (nrLectures <= 1)
1708            return true;
1709
1710        if (iIsRequired || (!iIsProhibited && iPreference < 0)) {
1711            int i = 0;
1712            Placement p = res[i];
1713            while (p == null)
1714                p = res[++i];
1715            i = res[i].getTimeLocation().getStartSlot() + res[i].getTimeLocation().getLength();
1716            nrLectures--;
1717            while (nrLectures > 0) {
1718                int gap = 0;
1719                while (i < Constants.SLOTS_PER_DAY && res[i] == null) {
1720                    gap++;
1721                    i++;
1722                }
1723                if (i == Constants.SLOTS_PER_DAY)
1724                    break;
1725                if (!canFill(gap, gapMin, gapMax, lengths))
1726                    return false;
1727                p = res[i];
1728                i = res[i].getTimeLocation().getStartSlot() + res[i].getTimeLocation().getLength();
1729                nrLectures--;
1730            }
1731        } else if (iIsProhibited || (!iIsRequired && iPreference > 0)) {
1732            int i = 0;
1733            Placement p = res[i];
1734            while (p == null)
1735                p = res[++i];
1736            i = res[i].getTimeLocation().getStartSlot() + res[i].getTimeLocation().getLength();
1737            nrLectures--;
1738            while (nrLectures > 0) {
1739                int gap = 0;
1740                while (i < Constants.SLOTS_PER_DAY && res[i] == null) {
1741                    gap++;
1742                    i++;
1743                }
1744                if (i == Constants.SLOTS_PER_DAY)
1745                    break;
1746                if ((gapMin == 0 || !canFill(gap, 0, gapMin - 1, lengths))
1747                        && (gapMax >= Constants.SLOTS_PER_DAY || !canFill(gap, gapMax + 1, Constants.SLOTS_PER_DAY,
1748                                lengths))) {
1749                    return false;
1750                }
1751                p = res[i];
1752                i = res[i].getTimeLocation().getStartSlot() + res[i].getTimeLocation().getLength();
1753                nrLectures--;
1754            }
1755        }
1756        return true;
1757    }
1758
1759    public boolean isSatisfied(Assignment<Lecture, Placement> assignment) {
1760        if (isHard()) return true;
1761        if (countAssignedVariables(assignment) < 2) return true;
1762        if (getPreference() == 0) return true;
1763        return isHard() || countAssignedVariables(assignment) < 2 || getPreference() == 0 || getCurrentPreference(assignment) < 0;
1764    }
1765
1766    public boolean isChildrenNotOverlap(Assignment<Lecture, Placement> assignment, Lecture lec1, Placement plc1, Lecture lec2, Placement plc2) {
1767        if (lec1.getSchedulingSubpartId().equals(lec2.getSchedulingSubpartId())) {
1768            // same subpart
1769            boolean overlap = plc1.getTimeLocation().hasIntersection(plc2.getTimeLocation());
1770
1771            if (overlap && lec1.getParent() != null && variables().contains(lec1.getParent())
1772                    && lec2.getParent() != null && variables().contains(lec2.getParent())) {
1773                // children overlaps
1774                Placement p1 = assignment.getValue(lec1.getParent());
1775                Placement p2 = assignment.getValue(lec2.getParent());
1776                // parents not overlap, but children do
1777                if (p1 != null && p2 != null && !p1.getTimeLocation().hasIntersection(p2.getTimeLocation()))
1778                    return false;
1779            }
1780
1781            if (!overlap && lec1.getChildrenSubpartIds() != null && lec2.getChildrenSubpartIds() != null) {
1782                // parents not overlap
1783                for (Long subpartId: lec1.getChildrenSubpartIds()) {
1784                    for (Lecture c1 : lec1.getChildren(subpartId)) {
1785                        Placement p1 = assignment.getValue(c1);
1786                        if (p1 == null) continue;
1787                        for (Lecture c2 : lec2.getChildren(subpartId)) {
1788                            Placement p2 = assignment.getValue(c2);
1789                            if (p2 == null) continue;
1790                            if (!c1.getSchedulingSubpartId().equals(c2.getSchedulingSubpartId())) continue;
1791                            // parents not overlap, but children do
1792                            if (p1.getTimeLocation().hasIntersection(p2.getTimeLocation()))
1793                                return false;
1794                        }
1795                    }
1796                }
1797            }
1798        } else {
1799            // different subpart
1800        }
1801        return true;
1802    }
1803
1804    public boolean isSatisfiedPair(Assignment<Lecture, Placement> assignment, Placement plc1, Placement plc2) {
1805        if (iIsRequired || (!iIsProhibited && iPreference <= 0))
1806            return getType().isSatisfied(assignment, this, plc1, plc2);
1807        else if (iIsProhibited || (!iIsRequired && iPreference > 0))
1808            return getType().isViolated(assignment, this, plc1, plc2);
1809        return true;
1810    }
1811    
1812    public boolean canShareRoom() {
1813        return getType().is(Flag.CAN_SHARE_ROOM);
1814    }
1815    
1816    private int nrSlotsADay(Assignment<Lecture, Placement> assignment, int dayCode, BitSet week, HashMap<Lecture, Placement> assignments, Set<Placement> conflicts) {
1817        Set<Integer> slots = new HashSet<Integer>();
1818        for (Lecture lecture: variables()) {
1819            Placement placement = null;
1820            if (assignments != null && assignments.containsKey(lecture))
1821                placement = assignments.get(lecture);
1822            else if (assignment != null)
1823                placement = assignment.getValue(lecture);
1824            if (placement == null || placement.getTimeLocation() == null) continue;
1825            if (conflicts != null && conflicts.contains(placement)) continue;
1826            TimeLocation t = placement.getTimeLocation();
1827            if (t == null || (t.getDayCode() & dayCode) == 0 || (week != null && !t.shareWeeks(week))) continue;
1828            for (int i = 0; i < t.getLength(); i++)
1829                slots.add(i + t.getStartSlot());
1830        }
1831        return slots.size();
1832    }
1833
1834    @Override
1835    public boolean equals(Object o) {
1836        if (o == null || !(o instanceof GroupConstraint)) return false;
1837        return getGeneratedId() == ((GroupConstraint) o).getGeneratedId();
1838    }
1839    
1840    @Override
1841    public GroupConstraintContext createAssignmentContext(Assignment<Lecture, Placement> assignment) {
1842        return new GroupConstraintContext(assignment);
1843    }
1844
1845    public class GroupConstraintContext implements AssignmentConstraintContext<Lecture, Placement> {
1846        private int iLastPreference = 0;
1847        
1848        public GroupConstraintContext(Assignment<Lecture, Placement> assignment) {
1849            updateCriterion(assignment);
1850        }
1851
1852        @Override
1853        public void assigned(Assignment<Lecture, Placement> assignment, Placement value) {
1854            updateCriterion(assignment);
1855        }
1856
1857        @Override
1858        public void unassigned(Assignment<Lecture, Placement> assignment, Placement value) {
1859            updateCriterion(assignment);
1860        }
1861        
1862        private void updateCriterion(Assignment<Lecture, Placement> assignment) {
1863            if (!isHard()) {
1864                getModel().getCriterion(DistributionPreferences.class).inc(assignment, -iLastPreference);
1865                iLastPreference = getCurrentPreference(assignment) + Math.abs(iPreference);
1866                getModel().getCriterion(DistributionPreferences.class).inc(assignment, iLastPreference);
1867            }
1868        }
1869        
1870        public int getPreference() { return iLastPreference; }
1871    }
1872}