001    package net.sf.cpsolver.coursett.constraint;
002    
003    import java.util.ArrayList;
004    import java.util.HashSet;
005    import java.util.HashMap;
006    import java.util.Iterator;
007    import java.util.List;
008    import java.util.Set;
009    
010    import net.sf.cpsolver.coursett.Constants;
011    import net.sf.cpsolver.coursett.criteria.DistributionPreferences;
012    import net.sf.cpsolver.coursett.model.Lecture;
013    import net.sf.cpsolver.coursett.model.Placement;
014    import net.sf.cpsolver.coursett.model.TimeLocation;
015    import net.sf.cpsolver.coursett.model.TimetableModel;
016    import net.sf.cpsolver.ifs.model.Constraint;
017    import net.sf.cpsolver.ifs.model.GlobalConstraint;
018    import net.sf.cpsolver.ifs.model.Model;
019    import net.sf.cpsolver.ifs.model.WeakeningConstraint;
020    import net.sf.cpsolver.ifs.util.DataProperties;
021    import net.sf.cpsolver.ifs.util.DistanceMetric;
022    import net.sf.cpsolver.ifs.util.ToolBox;
023    
024    /**
025     * Group constraint. <br>
026     * This constraint expresses relations between several classes, e.g., that two
027     * sections of the same lecture can not be taught at the same time, or that some
028     * classes have to be taught one immediately after another. It can be either
029     * hard or soft. <br>
030     * <br>
031     * Following constraints are now supported:
032     * <table border='1'>
033     * <tr>
034     * <th>Constraint</th>
035     * <th>Comment</th>
036     * </tr>
037     * <tr>
038     * <td>SAME_TIME</td>
039     * <td>Same time: given classes have to be taught in the same hours. If the
040     * classes are of different length, the smaller one cannot start before the
041     * longer one and it cannot end after the longer one.</td>
042     * </tr>
043     * <tr>
044     * <td>SAME_DAYS</td>
045     * <td>Same days: given classes have to be taught in the same day. If the
046     * classes are of different time patterns, the days of one class have to form a
047     * subset of the days of the other class.</td>
048     * </tr>
049     * <tr>
050     * <td>BTB</td>
051     * <td>Back-to-back constraint: given classes have to be taught in the same room
052     * and they have to follow one strictly after another.</td>
053     * </tr>
054     * <tr>
055     * <td>BTB_TIME</td>
056     * <td>Back-to-back constraint: given classes have to follow one strictly after
057     * another, but they can be taught in different rooms.</td>
058     * </tr>
059     * <tr>
060     * <td>DIFF_TIME</td>
061     * <td>Different time: given classes cannot overlap in time.</td>
062     * </tr>
063     * <tr>
064     * <td>NHB(1), NHB(1.5), NHB(2), ... NHB(8)</td>
065     * <td>Number of hours between: between the given classes, the exact number of
066     * hours have to be kept.</td>
067     * </tr>
068     * <tr>
069     * <td>SAME_START</td>
070     * <td>Same starting hour: given classes have to start in the same hour.</td>
071     * </tr>
072     * <tr>
073     * <td>SAME_ROOM</td>
074     * <td>Same room: given classes have to be placed in the same room.</td>
075     * </tr>
076     * <tr>
077     * <td>NHB_GTE(1)</td>
078     * <td>Greater than or equal to 1 hour between: between the given classes, the
079     * number of hours have to be one or more.</td>
080     * </tr>
081     * <tr>
082     * <td>NHB_LT(6)</td>
083     * <td>Less than 6 hours between: between the given classes, the number of hours
084     * have to be less than six.</td>
085     * </tr>
086     * </table>
087     * 
088     * @version CourseTT 1.2 (University Course Timetabling)<br>
089     *          Copyright (C) 2006 - 2010 Tomas Muller<br>
090     *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
091     *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
092     * <br>
093     *          This library is free software; you can redistribute it and/or modify
094     *          it under the terms of the GNU Lesser General Public License as
095     *          published by the Free Software Foundation; either version 3 of the
096     *          License, or (at your option) any later version. <br>
097     * <br>
098     *          This library is distributed in the hope that it will be useful, but
099     *          WITHOUT ANY WARRANTY; without even the implied warranty of
100     *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
101     *          Lesser General Public License for more details. <br>
102     * <br>
103     *          You should have received a copy of the GNU Lesser General Public
104     *          License along with this library; if not see
105     *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
106     */
107    
108    public class GroupConstraint extends Constraint<Lecture, Placement> {
109        private Long iId;
110        private int iPreference;
111        private ConstraintType iType;
112        private boolean iIsRequired;
113        private boolean iIsProhibited;
114        private int iLastPreference = 0;
115        private int iDayOfWeekOffset = 0;
116        private boolean iPrecedenceConsiderDatePatterns = true;
117        
118        /**
119         * Group constraints that can be checked on pairs of classes (e.g., same room means any two classes are in the same room),
120         * only need to implement this interface.
121         */
122        public static interface PairCheck {
123            /**
124             * Check whether the constraint is satisfied for the given two assignments (required / preferred case)
125             * @param gc Calling group constraint 
126             * @param plc1 First placement
127             * @param plc2 Second placement
128             * @return true if constraint is satisfied
129             */
130            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2);
131            /**
132             * Check whether the constraint is satisfied for the given two assignments (prohibited / discouraged case)
133             * @param gc Calling group constraint 
134             * @param plc1 First placement
135             * @param plc2 Second placement
136             * @return true if constraint is satisfied
137             */
138            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2);
139        }
140        
141        /**
142         * Group constraint building blocks (individual constraints that need more than {@link PairCheck})
143         */
144        public static enum Flag {
145            /** Back-to-back constraint (sequence check) */
146            BACK_TO_BACK,
147            /** Can share room flag */
148            CAN_SHARE_ROOM,
149            /** Maximum hours a day (number of slots a day check) */
150            MAX_HRS_DAY,
151            /** Children cannot overlap */
152            CH_NOTOVERLAP;
153            /** Bit number (to combine flags) */
154            int flag() { return 1 << ordinal(); }
155        }
156        
157        /**
158         * Group constraint type.
159         */
160        public static enum ConstraintType {
161            /**
162             * Same Time: Given classes must be taught at the same time of day (independent of the actual day the classes meet).
163             * For the classes of the same length, this is the same constraint as same start. For classes of different length,
164             * the shorter one cannot start before, nor end after, the longer one.<BR>
165             * When prohibited or (strongly) discouraged: one class may not meet on any day at a time of day that overlaps with
166             * that of the other. For example, one class can not meet M 7:30 while the other meets F 7:30. Note the difference
167             * here from the different time constraint that only prohibits the actual class meetings from overlapping.
168             */
169            SAME_TIME("SAME_TIME", "Same Time", new PairCheck() {
170                @Override
171                public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
172                    return sameHours(plc1.getTimeLocation().getStartSlot(), plc1.getTimeLocation().getLength(),
173                            plc2.getTimeLocation().getStartSlot(), plc2.getTimeLocation().getLength());
174                }
175                @Override
176                public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
177                    return !(plc1.getTimeLocation().shareHours(plc2.getTimeLocation()));
178                }}),
179            /**
180             * Same Days: Given classes must be taught on the same days. In case of classes of different time patterns, a class
181             * with fewer meetings must meet on a subset of the days used by the class with more meetings. For example, if one
182             * class pattern is 3x50, all others given in the constraint can only be taught on Monday, Wednesday, or Friday.
183             * For a 2x100 class MW, MF, WF is allowed but TTh is prohibited.<BR>
184             * When prohibited or (strongly) discouraged: any pair of classes classes cannot be taught on the same days (cannot
185             *  overlap in days). For instance, if one class is MFW, the second has to be TTh.
186             */
187            SAME_DAYS("SAME_DAYS", "Same Days", new PairCheck() {
188                @Override
189                public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
190                    return sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray());
191                }
192                @Override
193                public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
194                    return !plc1.getTimeLocation().shareDays(plc2.getTimeLocation());
195                }}),
196            /**
197             * Back-To-Back & Same Room: Classes must be offered in adjacent time segments and must be placed in the same room.
198             * Given classes must also be taught on the same days.<BR>
199             * When prohibited or (strongly) discouraged: classes cannot be back-to-back. There must be at least half-hour
200             * between these classes, and they must be taught on the same days and in the same room.
201             */
202            BTB("BTB", "Back-To-Back & Same Room", new PairCheck() {
203                @Override
204                public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
205                    return
206                        plc1.sameRooms(plc2) &&
207                        sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray());
208                }
209                @Override
210                public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
211                    return
212                        plc1.sameRooms(plc2) &&
213                        sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray());
214                }}, Flag.BACK_TO_BACK),
215            /**
216             * Back-To-Back: Classes must be offered in adjacent time segments but may be placed in different rooms. Given classes
217             * must also be taught on the same days.<BR>
218             * When prohibited or (strongly) discouraged: no pair of classes can be taught back-to-back. They may not overlap in time,
219             * but must be taught on the same days. This means that there must be at least half-hour between these classes. 
220             */
221            BTB_TIME("BTB_TIME", "Back-To-Back", 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 sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray());
229                }}, Flag.BACK_TO_BACK),
230            /**
231             * Different Time: Given classes cannot overlap in time. They may be taught at the same time of day if they are on
232             * different days. For instance, MF 7:30 is compatible with TTh 7:30.<BR>
233             * When prohibited or (strongly) discouraged: every pair of classes in the constraint must overlap in time. 
234             */
235            DIFF_TIME("DIFF_TIME", "Different Time", new PairCheck() {
236                @Override
237                public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
238                    return !plc1.getTimeLocation().hasIntersection(plc2.getTimeLocation());
239                }
240                @Override
241                public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
242                    return plc1.getTimeLocation().hasIntersection(plc2.getTimeLocation());
243                }}),
244            /**
245             * 1 Hour Between: Given classes must have exactly 1 hour in between the end of one and the beginning of another.
246             * As with the <i>back-to-back time</i> constraint, given classes must be taught on the same days.<BR>
247             * When prohibited or (strongly) discouraged: classes can not have 1 hour in between. They may not overlap in time
248             * but must be taught on the same days.
249             */
250            NHB_1("NHB(1)", "1 Hour Between", 10, 12, BTB_TIME.check(), Flag.BACK_TO_BACK),
251            /**
252             * 2 Hours Between: Given classes must have exactly 2 hours in between the end of one and the beginning of another.
253             * As with the <i>back-to-back time</i> constraint, given classes must be taught on the same days.<BR>
254             * When prohibited or (strongly) discouraged: classes can not have 2 hours in between. They may not overlap in time
255             * but must be taught on the same days.
256             */
257            NHB_2("NHB(2)", "2 Hours Between", 20, 24, BTB_TIME.check(), Flag.BACK_TO_BACK),
258            /**
259             * 3 Hours Between: Given classes must have exactly 3 hours in between the end of one and the beginning of another.
260             * As with the <i>back-to-back time</i> constraint, given classes must be taught on the same days.<BR>
261             * When prohibited or (strongly) discouraged: classes can not have 3 hours in between. They may not overlap in time
262             * but must be taught on the same days.
263             */
264            NHB_3("NHB(3)", "3 Hours Between", 30, 36, BTB_TIME.check(), Flag.BACK_TO_BACK),
265            /**
266             * 4 Hours Between: Given classes must have exactly 4 hours in between the end of one and the beginning of another.
267             * As with the <i>back-to-back time</i> constraint, given classes must be taught on the same days.<BR>
268             * When prohibited or (strongly) discouraged: classes can not have 4 hours in between. They may not overlap in time
269             * but must be taught on the same days.
270             */
271            NHB_4("NHB(4)", "4 Hours Between", 40, 48, BTB_TIME.check(), Flag.BACK_TO_BACK),
272            /**
273             * 5 Hours Between: Given classes must have exactly 5 hours in between the end of one and the beginning of another.
274             * As with the <i>back-to-back time</i> constraint, given classes must be taught on the same days.<BR>
275             * When prohibited or (strongly) discouraged: classes can not have 5 hours in between. They may not overlap in time
276             * but must be taught on the same days.
277             */
278            NHB_5("NHB(5)", "5 Hours Between", 50, 60, BTB_TIME.check(), Flag.BACK_TO_BACK),
279            /**
280             * 6 Hours Between: Given classes must have exactly 6 hours in between the end of one and the beginning of another.
281             * As with the <i>back-to-back time</i> constraint, given classes must be taught on the same days.<BR>
282             * When prohibited or (strongly) discouraged: classes can not have 6 hours in between. They may not overlap in time
283             * but must be taught on the same days.
284             */
285            NHB_6("NHB(6)", "6 Hours Between", 60, 72, BTB_TIME.check(), Flag.BACK_TO_BACK),
286            /**
287             * 7 Hours Between: Given classes must have exactly 7 hours in between the end of one and the beginning of another.
288             * As with the <i>back-to-back time</i> constraint, given classes must be taught on the same days.<BR>
289             * When prohibited or (strongly) discouraged: classes can not have 7 hours in between. They may not overlap in time
290             * but must be taught on the same days.
291             */
292            NHB_7("NHB(7)", "7 Hours Between", 70, 84, BTB_TIME.check(), Flag.BACK_TO_BACK),
293            /**
294             * 8 Hours Between: Given classes must have exactly 8 hours in between the end of one and the beginning of another.
295             * As with the <i>back-to-back time</i> constraint, given classes must be taught on the same days.<BR>
296             * When prohibited or (strongly) discouraged: classes can not have 8 hours in between. They may not overlap in time
297             * but must be taught on the same days.
298             */
299            NHB_8("NHB(8)", "8 Hours Between", 80, 96, BTB_TIME.check(), Flag.BACK_TO_BACK),
300            /**
301             * Same Start Time: Given classes must start during the same half-hour period of a day (independent of the actual
302             * day the classes meet). For instance, MW 7:30 is compatible with TTh 7:30 but not with MWF 8:00.<BR>
303             * When prohibited or (strongly) discouraged: any pair of classes in the given constraint cannot start during the
304             * same half-hour period of any day of the week.
305             */
306            SAME_START("SAME_START", "Same Start Time", new PairCheck() {
307                @Override
308                public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
309                    return
310                        (plc1.getTimeLocation().getStartSlot() % Constants.SLOTS_PER_DAY) == 
311                        (plc2.getTimeLocation().getStartSlot() % Constants.SLOTS_PER_DAY);
312                }
313                @Override
314                public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
315                    return
316                        (plc1.getTimeLocation().getStartSlot() % Constants.SLOTS_PER_DAY) != 
317                        (plc2.getTimeLocation().getStartSlot() % Constants.SLOTS_PER_DAY);
318                }}),
319            /**
320             * Same Room: Given classes must be taught in the same room.<BR>
321             * When prohibited or (strongly) discouraged: any pair of classes in the constraint cannot be taught in the same room.
322             */
323            SAME_ROOM("SAME_ROOM", "Same Room", new PairCheck() {
324                @Override
325                public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
326                    return plc1.sameRooms(plc2);
327                }
328                @Override
329                public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
330                    return !plc1.sameRooms(plc2);
331                }}),
332            /**
333             * At Least 1 Hour Between: Given classes have to have 1 hour or more in between.<BR>
334             * When prohibited or (strongly) discouraged: given classes have to have less than 1 hour in between.
335             */
336            NHB_GTE_1("NHB_GTE(1)", "At Least 1 Hour Between", 6, 288, BTB_TIME.check(), Flag.BACK_TO_BACK),
337            /**
338             * Less Than 6 Hours Between: Given classes must have less than 6 hours from end of first class to the beginning of
339             * the next. Given classes must also be taught on the same days.<BR>
340             * When prohibited or (strongly) discouraged: given classes must have 6 or more hours between. This constraint does
341             * not carry over from classes taught at the end of one day to the beginning of the next.
342             */
343            NHB_LT_6("NHB_LT(6)", "Less Than 6 Hours Between", 0, 72, BTB_TIME.check(), Flag.BACK_TO_BACK),
344            /**
345             * 1.5 Hour Between: Given classes must have exactly 90 minutes in between the end of one and the beginning of another.
346             * As with the <i>back-to-back time</i> constraint, given classes must be taught on the same days.<BR>
347             * When prohibited or (strongly) discouraged: classes can not have 90 minutes in between. They may not overlap in time
348             * but must be taught on the same days.
349             */
350            NHB_1_5("NHB(1.5)", "1.5 Hour Between", 15, 18, BTB_TIME.check(), Flag.BACK_TO_BACK),
351            /**
352             * 4.5 Hours Between: Given classes must have exactly 4.5 hours in between the end of one and the beginning of another.
353             * As with the <i>back-to-back time</i> constraint, given classes must be taught on the same days.<BR>
354             * When prohibited or (strongly) discouraged: classes can not have 4.5 hours in between. They may not overlap in time
355             * but must be taught on the same days.
356             */
357            NHB_4_5("NHB(4.5)", "4.5 Hours Between", 45, 54, BTB_TIME.check(), Flag.BACK_TO_BACK),
358            /**
359             * Same Students: Given classes are treated as they are attended by the same students, i.e., they cannot overlap in time
360             * and if they are back-to-back the assigned rooms cannot be too far (student limit is used).
361             */
362            SAME_STUDENTS("SAME_STUDENTS", "Same Students", new PairCheck() {
363                @Override
364                public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
365                    return !JenrlConstraint.isInConflict(plc1, plc2, ((TimetableModel)gc.getModel()).getDistanceMetric());
366                }
367                @Override
368                public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
369                    return true;
370                }}),
371            /**
372             * Same Instructor: Given classes are treated as they are taught by the same instructor, i.e., they cannot overlap in time
373             * and if they are back-to-back the assigned rooms cannot be too far (instructor limit is used).<BR>
374             * If the constraint is required and the classes are back-to-back, discouraged and strongly discouraged distances between
375             * assigned rooms are also considered.
376             */
377            SAME_INSTR("SAME_INSTR", "Same Instructor", new PairCheck() {
378                @Override
379                public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
380                    TimeLocation t1 = plc1.getTimeLocation(), t2 = plc2.getTimeLocation();
381                    if (t1.shareDays(t2) && t1.shareWeeks(t2)) {
382                        if (t1.shareHours(t2)) return false; // overlap
383                        DistanceMetric m = ((TimetableModel)gc.getModel()).getDistanceMetric();
384                        if ((t1.getStartSlot() + t1.getLength() == t2.getStartSlot() || t2.getStartSlot() + t2.getLength() == t1.getStartSlot())) {
385                            if (Placement.getDistanceInMeters(m, plc1, plc2) > m.getInstructorProhibitedLimit())
386                                return false;
387                        } else if (m.doComputeDistanceConflictsBetweenNonBTBClasses()) {
388                            if (t1.getStartSlot() + t1.getLength() < t2.getStartSlot() && 
389                                Placement.getDistanceInMinutes(m, plc1, plc2) > t1.getBreakTime() + Constants.SLOT_LENGTH_MIN * (t2.getStartSlot() - t1.getStartSlot() - t1.getLength()))
390                                return false;
391                            if (t2.getStartSlot() + t2.getLength() < t1.getStartSlot() &&
392                                Placement.getDistanceInMinutes(m, plc1, plc2) > t2.getBreakTime() + Constants.SLOT_LENGTH_MIN * (t1.getStartSlot() - t2.getStartSlot() - t2.getLength()))
393                                return false;
394                        }
395                    }
396                    return true;
397                }
398                @Override
399                public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
400                    return true;
401                }}),
402            /**
403             * Can Share Room: Given classes can share the room (use the room in the same time) if the room is big enough.
404             */
405            CAN_SHARE_ROOM("CAN_SHARE_ROOM", "Can Share Room", null, Flag.CAN_SHARE_ROOM),
406            /**
407             * Precedence: Given classes have to be taught in the given order (the first meeting of the first class has to end before
408             * the first meeting of the second class etc.)<BR>
409             * When prohibited or (strongly) discouraged: classes have to be taught in the order reverse to the given one.
410             */
411            PRECEDENCE("PRECEDENCE", "Precedence", new PairCheck() {
412                @Override
413                public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
414                    return gc.isPrecedence(plc1, plc2, true, true);
415                }
416                @Override
417                public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
418                    return gc.isPrecedence(plc1, plc2, false, true);
419                }}),
420            /**
421             * Back-To-Back Day: Classes must be offered on adjacent days and may be placed in different rooms.<BR>
422             * When prohibited or (strongly) discouraged: classes can not be taught on adjacent days. They also can not be taught
423             * on the same days. This means that there must be at least one day between these classes.
424             */
425            BTB_DAY("BTB_DAY", "Back-To-Back Day", new PairCheck() {
426                @Override
427                public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
428                    return
429                        !sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray()) &&
430                        isBackToBackDays(plc1.getTimeLocation(), plc2.getTimeLocation());
431                }
432                @Override
433                public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
434                    return
435                        !sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray()) &&
436                        !isBackToBackDays(plc1.getTimeLocation(), plc2.getTimeLocation());
437                }}),
438            /**
439             * Meet Together: Given classes are meeting together (same as if the given classes require constraints Can Share Room,
440             * Same Room, Same Time and Same Days all together).
441             */
442            MEET_WITH("MEET_WITH", "Meet Together", new PairCheck() {
443                @Override
444                public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
445                    return
446                            plc1.sameRooms(plc2) &&
447                            sameHours(plc1.getTimeLocation().getStartSlot(), plc1.getTimeLocation().getLength(),
448                                    plc2.getTimeLocation().getStartSlot(), plc2.getTimeLocation().getLength()) &&
449                            sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray());
450                            
451                }
452                @Override
453                public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
454                    return true;
455                }}, Flag.CAN_SHARE_ROOM),
456            /**
457             * More Than 1 Day Between: Given classes must have two or more days in between.<br>
458             * When prohibited or (strongly) discouraged: given classes must be offered on adjacent days or with at most one day in between.
459             */
460            NDB_GT_1("NDB_GT_1", "More Than 1 Day Between", new PairCheck() {
461                @Override
462                public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
463                    return
464                        !sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray()) &&
465                        isNrDaysBetweenGreaterThanOne(plc1.getTimeLocation(), plc2.getTimeLocation());
466                }
467                @Override
468                public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
469                    return
470                        !sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray()) &&
471                        !isNrDaysBetweenGreaterThanOne(plc1.getTimeLocation(), plc2.getTimeLocation());
472                }}),
473            /**
474             * Children Cannot Overlap: If parent classes do not overlap in time, children classes can not overlap in time as well.<BR>
475             * Note: This constraint only needs to be put on the parent classes. Preferred configurations are Required All Classes
476             * or Pairwise (Strongly) Preferred.
477             */
478            CH_NOTOVERLAP("CH_NOTOVERLAP", "Children Cannot Overlap", new PairCheck() {
479                @Override
480                public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
481                    return gc.isChildrenNotOverlap(plc1.variable(), plc1, plc2.variable(), plc2);
482                }
483                @Override
484                public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
485                    return true;
486                }}),
487            /**
488             * Next Day: The second class has to be placed on the following day of the first class (if the first class is on Friday,
489             * second class have to be on Monday).<br>
490             * When prohibited or (strongly) discouraged: The second class has to be placed on the previous day of the first class
491             * (if the first class is on Monday, second class have to be on Friday).<br>
492             * Note: This constraint works only between pairs of classes.
493             */
494            FOLLOWING_DAY("FOLLOWING_DAY", "Next Day", new PairCheck() {
495                @Override
496                public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
497                    return gc.isFollowingDay(plc1, plc2, true);
498                }
499                @Override
500                public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
501                    return gc.isFollowingDay(plc1, plc2, false);
502                }}),
503            /**
504             * Two Days After: The second class has to be placed two days after the first class (Monday &rarr; Wednesday, Tuesday &rarr; 
505             * Thurday, Wednesday &rarr; Friday, Thursday &rarr; Monday, Friday &rarr; Tuesday).<br>
506             * When prohibited or (strongly) discouraged: The second class has to be placed two days before the first class (Monday &rarr;
507             * Thursday, Tuesday &rarr; Friday, Wednesday &rarr; Monday, Thursday &rarr; Tuesday, Friday &rarr; Wednesday).<br>
508             * Note: This constraint works only between pairs of classes.
509             */
510            EVERY_OTHER_DAY("EVERY_OTHER_DAY", "Two Days After", new PairCheck() {
511                @Override
512                public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
513                    return gc.isEveryOtherDay(plc1, plc2, true);
514                }
515                @Override
516                public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
517                    return gc.isEveryOtherDay(plc1, plc2, false);
518                }}),
519            /**
520              * 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.
521              */
522            MAX_HRS_DAY_5("MAX_HRS_DAY(5)", "At Most 5 Hours A Day", 60, null, Flag.MAX_HRS_DAY),        
523            /**
524             * 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.
525             */
526            MAX_HRS_DAY_6("MAX_HRS_DAY(6)", "At Most 6 Hours A Day", 72, null, Flag.MAX_HRS_DAY),
527            /**
528             * 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.
529             */
530            MAX_HRS_DAY_7("MAX_HRS_DAY(7)", "At Most 7 Hours A Day", 84, null, Flag.MAX_HRS_DAY),
531            /**
532             * 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.
533             */
534            MAX_HRS_DAY_8("MAX_HRS_DAY(8)", "At Most 8 Hours A Day", 96, null, Flag.MAX_HRS_DAY),
535            /**
536             * Given classes must be taught during the same weeks (i.e., must have the same date pattern).<br>
537             * When prohibited or (strongly) discouraged: any two classes must have non overlapping date patterns.
538             */
539            SAME_WEEKS("SAME_WEEKS", "Same Weeks", new PairCheck() {
540                @Override
541                public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
542                    return plc1.getTimeLocation().getWeekCode().equals(plc2.getTimeLocation().getWeekCode());
543                }
544                @Override
545                public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
546                    return !plc1.getTimeLocation().shareWeeks(plc2.getTimeLocation());
547                }}),
548            /**
549             * Classes (of different courses) are to be attended by the same students. For instance,
550             * if class A1 (of a course A) and class B1 (of a course B) are linked, a student requesting
551             * both courses must attend A1 if and only if he also attends B1. This is a student sectioning
552             * constraint that is interpreted as Same Students constraint during course timetabling.
553             */
554            LINKED_SECTIONS("LINKED_SECTIONS", "Linked Classes", SAME_STUDENTS.check()),
555            /**
556             * Back-To-Back Precedence: Given classes have to be taught in the given order, on the same days,
557             * and in adjacent time segments.
558             * When prohibited or (strongly) discouraged: Given classes have to be taught in the given order,
559             * on the same days, but cannot be back-to-back.
560             */
561            BTB_PRECEDENCE("BTB_PRECEDENCE", "Back-To-Back Precedence", new PairCheck() {
562                @Override
563                public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
564                    return gc.isPrecedence(plc1, plc2, true, false) && sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray());
565                }
566                @Override
567                public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
568                    return gc.isPrecedence(plc1, plc2, true, false) && sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray());
569                }}, Flag.BACK_TO_BACK),   
570                
571            /**
572             * Same Days-Time: Given classes must be taught at the same time of day and on the same days.
573             * It is the combination of Same Days and Same Time distribution preferences.     
574             * When prohibited or (strongly) discouraged: Any pair of classes classes cannot be taught on the same days
575             * during the same time.
576             */             
577            SAME_DAYS_TIME("SAME_D_T", "Same Days-Time", new PairCheck() {
578                @Override
579                public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
580                    return sameHours(plc1.getTimeLocation().getStartSlot(), plc1.getTimeLocation().getLength(),
581                            plc2.getTimeLocation().getStartSlot(), plc2.getTimeLocation().getLength()) &&
582                            sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray());
583                }
584                @Override
585                public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
586                    return !plc1.getTimeLocation().shareHours(plc2.getTimeLocation()) ||
587                            !plc1.getTimeLocation().shareDays(plc2.getTimeLocation());
588                }}),
589            /**
590             * Same Days-Room-Time: Given classes must be taught at the same time of day, on the same days and in the same room.
591             * It is the combination of Same Days, Same Time and Same Room distribution preferences.
592             * Note that this constraint is the same as Meet Together constraint, except it does not allow room sharing. In other words,
593             * it is only useful when these classes are taught during non-overlapping date patterns.
594             * When prohibited or (strongly) discouraged: Any pair of classes classes cannot be taught on the same days 
595             * during the same time in the same room.
596             */            
597            SAME_DAYS_ROOM_TIME("SAME_D_R_T", "Same Days-Room-Time", new PairCheck() {
598                @Override
599                public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) {
600                    return sameHours(plc1.getTimeLocation().getStartSlot(), plc1.getTimeLocation().getLength(),
601                            plc2.getTimeLocation().getStartSlot(), plc2.getTimeLocation().getLength()) &&
602                            sameDays(plc1.getTimeLocation().getDaysArray(), plc2.getTimeLocation().getDaysArray()) &&
603                            plc1.sameRooms(plc2);
604                }
605                @Override
606                public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) {
607                    return !plc1.getTimeLocation().shareHours(plc2.getTimeLocation()) ||
608                            !plc1.getTimeLocation().shareDays(plc2.getTimeLocation()) ||
609                            !plc1.sameRooms(plc2);
610                }}), 
611            ;
612            
613            String iReference, iName;
614            int iFlag = 0;
615            Flag[] iFlags = null;
616            int iMin = 0, iMax = 0;
617            PairCheck iCheck = null;
618            ConstraintType(String reference, String name, PairCheck check, Flag... flags) {
619                iReference = reference;
620                iName = name;
621                iCheck = check;
622                iFlags = flags;
623                for (Flag f: flags)
624                    iFlag |= f.flag();
625            }
626            ConstraintType(String reference, String name, int limit, PairCheck check, Flag... flags) {
627                this(reference, name, check, flags);
628                iMin = iMax = limit;
629            }
630            ConstraintType(String reference, String name, int min, int max, PairCheck check, Flag... flags) {
631                this(reference, name, check, flags);
632                iMin = min;
633                iMax = max;
634            }
635            
636            /** Constraint reference */
637            public String reference() { return iReference; }
638            /** Constraint name */
639            public String getName() { return iName; }
640            /** Minimum (gap) parameter */
641            public int getMin() { return iMin; }
642            /** Maximum (gap, hours a day) parameter */
643            public int getMax() { return iMax; }
644            
645            /** Flag check (true if contains given flag) */
646            public boolean is(Flag f) { return (iFlag & f.flag()) != 0; }
647    
648            /** Constraint type from reference */
649            public static ConstraintType get(String reference) {
650                for (ConstraintType t: ConstraintType.values())
651                    if (t.reference().equals(reference)) return t;
652                return null;
653            }
654            
655            /** True if a required or preferred constraint is satisfied between a pair of placements */ 
656            public boolean isSatisfied(GroupConstraint gc, Placement plc1, Placement plc2) { return (iCheck == null ? true : iCheck.isSatisfied(gc, plc1, plc2)); }
657            /** True if a prohibited or discouraged constraint is satisfied between a pair of placements */ 
658            public boolean isViolated(GroupConstraint gc, Placement plc1, Placement plc2) { return (iCheck == null ? true : iCheck.isViolated(gc, plc1, plc2)); }
659            /** Pair check */
660            private PairCheck check() { return iCheck; }
661        }
662    
663        public GroupConstraint() {
664        }
665        
666        @Override
667        public void setModel(Model<Lecture, Placement> model) {
668            super.setModel(model);
669            if (model != null) {
670                DataProperties config = ((TimetableModel)model).getProperties();
671                iDayOfWeekOffset = config.getPropertyInt("DatePattern.DayOfWeekOffset", 0);
672                iPrecedenceConsiderDatePatterns = config.getPropertyBoolean("Precedence.ConsiderDatePatterns", true);
673            }
674        }
675    
676        @Override
677        public void addVariable(Lecture lecture) {
678            if (!variables().contains(lecture))
679                super.addVariable(lecture);
680            if (getType().is(Flag.CH_NOTOVERLAP)) {
681                if (lecture.getChildrenSubpartIds() != null) {
682                    for (Long subpartId: lecture.getChildrenSubpartIds()) {
683                        for (Lecture ch : lecture.getChildren(subpartId)) {
684                            if (!variables().contains(ch))
685                                super.addVariable(ch);
686                        }
687                    }
688                }
689            }
690        }
691    
692        @Override
693        public void removeVariable(Lecture lecture) {
694            if (variables().contains(lecture))
695                super.removeVariable(lecture);
696            if (getType().is(Flag.CH_NOTOVERLAP)) {
697                if (lecture.getChildrenSubpartIds() != null) {
698                    for (Long subpartId: lecture.getChildrenSubpartIds()) {
699                        for (Lecture ch : lecture.getChildren(subpartId)) {
700                            if (variables().contains(ch))
701                                super.removeVariable(ch);
702                        }
703                    }
704                }
705            }
706        }
707    
708        /**
709         * Constructor
710         * 
711         * @param id
712         *            constraint id
713         * @param type
714         *            constraString type (e.g, {@link ConstraintType#SAME_TIME})
715         * @param preference
716         *            time preference ("R" for required, "P" for prohibited, "-2",
717         *            "-1", "1", "2" for soft preference)
718         */
719        public GroupConstraint(Long id, ConstraintType type, String preference) {
720            iId = id;
721            iType = type;
722            iIsRequired = preference.equals(Constants.sPreferenceRequired);
723            iIsProhibited = preference.equals(Constants.sPreferenceProhibited);
724            iPreference = Constants.preference2preferenceLevel(preference);
725        }
726    
727        /** Constraint id */
728        public Long getConstraintId() {
729            return iId;
730        }
731    
732        @Override
733        public long getId() {
734            return (iId == null ? -1 : iId.longValue());
735        }
736    
737        /** ConstraString type (e.g, {@link ConstraintType#SAME_TIME}) */
738        public ConstraintType getType() {
739            return iType;
740        }
741    
742        public void setType(ConstraintType type) {
743            iType = type;
744        }
745    
746        /** Is constraint required */
747        public boolean isRequired() {
748            return iIsRequired;
749        }
750    
751        /** Is constraint prohibited */
752        public boolean isProhibited() {
753            return iIsProhibited;
754        }
755    
756        /**
757         * Prolog reference: "R" for required, "P" for prohibited", "-2",.."2" for
758         * preference
759         */
760        public String getPrologPreference() {
761            return Constants.preferenceLevel2preference(iPreference);
762        }
763    
764        @Override
765        public boolean isConsistent(Placement value1, Placement value2) {
766            if (!isHard())
767                return true;
768            if (!isSatisfiedPair(value1, value2))
769                return false;
770            if (getType().is(Flag.BACK_TO_BACK)) {
771                HashMap<Lecture, Placement> assignments = new HashMap<Lecture, Placement>();
772                assignments.put(value1.variable(), value1);
773                assignments.put(value2.variable(), value2);
774                if (!isSatisfiedSeq(assignments, false, null))
775                    return false;
776            }
777            if (getType().is(Flag.MAX_HRS_DAY)) {
778                HashMap<Lecture, Placement> assignments = new HashMap<Lecture, Placement>();
779                assignments.put(value1.variable(), value1);
780                assignments.put(value2.variable(), value2);
781                for (int dayCode: Constants.DAY_CODES) {
782                    if (nrSlotsADay(dayCode, assignments, null) > getType().getMax())
783                        return false;
784                }
785            }
786            return true;
787        }
788    
789        @Override
790        public void computeConflicts(Placement value, Set<Placement> conflicts) {
791            if (!isHard())
792                return;
793            for (Lecture v : variables()) {
794                if (v.equals(value.variable()))
795                    continue; // ignore this variable
796                if (v.getAssignment() == null)
797                    continue; // there is an unassigned variable -- great, still a
798                              // chance to get violated
799                if (!isSatisfiedPair(v.getAssignment(), value))
800                    conflicts.add(v.getAssignment());
801            }
802            if (getType().is(Flag.BACK_TO_BACK)) {
803                HashMap<Lecture, Placement> assignments = new HashMap<Lecture, Placement>();
804                assignments.put(value.variable(), value);
805                if (!isSatisfiedSeq(assignments, true, conflicts))
806                    conflicts.add(value);
807            }
808            if (getType().is(Flag.MAX_HRS_DAY)) {
809                HashMap<Lecture, Placement> assignments = new HashMap<Lecture, Placement>();
810                assignments.put(value.variable(), value);
811                for (int dayCode: Constants.DAY_CODES) {
812                    if (nrSlotsADay(dayCode, assignments, conflicts) > getType().getMax()) {
813                        List<Placement> adepts = new ArrayList<Placement>();
814                        for (Lecture lecture: assignedVariables()) {
815                            if (conflicts.contains(lecture.getAssignment()) || lecture.equals(value.variable())) continue;
816                            if (lecture.getAssignment().getTimeLocation() == null) continue;
817                            if ((lecture.getAssignment().getTimeLocation().getDayCode() & dayCode) == 0) continue;
818                            adepts.add(lecture.getAssignment());
819                        }
820                        do {
821                            Placement conflict = ToolBox.random(adepts);
822                            adepts.remove(conflict);
823                            conflicts.add(conflict);
824                        } while (!adepts.isEmpty() && nrSlotsADay(dayCode, assignments, conflicts) > getType().getMax());
825                    }
826                }
827            }
828            
829            if (iType == ConstraintType.MEET_WITH && !conflicts.contains(value)) {
830                // Check the room size
831                int neededSize = 0;
832                for (Lecture lecture: variables())
833                    neededSize += lecture.maxRoomUse();
834                if (neededSize > value.getRoomSize()) {
835                    conflicts.add(value); // room is too small to fit all meet with classes
836                    return;
837                }
838                for (Lecture lecture: variables()) {
839                    if (lecture.equals(value.variable())) continue; // Skip this lecture
840                    if (lecture.getAssignment() != null) { // Has assignment, check whether it is conflicting
841                        Placement other = lecture.getAssignment();
842                        if (other.sameRooms(value) && sameHours(value.getTimeLocation(), other.getTimeLocation()) &&
843                            sameDays(value.getTimeLocation(), other.getTimeLocation()))
844                            continue;
845                        conflicts.add(lecture.getAssignment());
846                    }
847                    // Look for a matching assignment
848                    List<Placement> sameAssignments = new ArrayList<Placement>();
849                    for (Placement other: lecture.values()) {
850                        if (other.sameRooms(value) && sameHours(value.getTimeLocation(), other.getTimeLocation()) &&
851                                sameDays(value.getTimeLocation(), other.getTimeLocation())) {
852                            sameAssignments.add(other);
853                        }
854                    }
855                    // No matching assignment -> fail
856                    if (sameAssignments.isEmpty()) {
857                        conflicts.add(value); // other meet with class cannot be assigned with this value
858                        return;
859                    }
860                    // Propagate the new assignment over other hard constraints of the lecture
861                    if (sameAssignments.size() == 1) {
862                        Placement sameAssignment = sameAssignments.get(0);
863                        for (Constraint<Lecture, Placement> other: lecture.hardConstraints()) {
864                            if (other.equals(this)) continue;
865                            if (other instanceof GroupConstraint && ((GroupConstraint)other).getType() == ConstraintType.MEET_WITH) continue;
866                            if (other instanceof WeakeningConstraint) continue;
867                            other.computeConflicts(sameAssignment, conflicts);
868                            if (conflicts.contains(value)) return;
869                            if (conflicts.contains(sameAssignment)) {
870                                conflicts.add(value); return;
871                            }
872                        }
873                        for (GlobalConstraint<Lecture, Placement> other: getModel().globalConstraints()) {
874                            if (other instanceof WeakeningConstraint) continue;
875                            other.computeConflicts(sameAssignment, conflicts);
876                            if (conflicts.contains(value)) return;
877                            if (conflicts.contains(sameAssignment)) {
878                                conflicts.add(value); return;
879                            }
880                        }   
881                    }
882                }
883            }
884        }
885    
886        @Override
887        public boolean inConflict(Placement value) {
888            if (!isHard())
889                return false;
890            for (Lecture v : variables()) {
891                if (v.equals(value.variable()))
892                    continue; // ignore this variable
893                if (v.getAssignment() == null)
894                    continue; // there is an unassigned variable -- great, still a
895                              // chance to get violated
896                if (!isSatisfiedPair(v.getAssignment(), value))
897                    return true;
898            }
899            if (getType().is(Flag.BACK_TO_BACK)) {
900                HashMap<Lecture, Placement> assignments = new HashMap<Lecture, Placement>();
901                assignments.put(value.variable(), value);
902                if (!isSatisfiedSeq(assignments, true, null))
903                    return true;
904            }
905            if (getType().is(Flag.MAX_HRS_DAY)) {
906                HashMap<Lecture, Placement> assignments = new HashMap<Lecture, Placement>();
907                assignments.put(value.variable(), value);
908                for (int dayCode: Constants.DAY_CODES) {
909                    if (nrSlotsADay(dayCode, assignments, null) > getType().getMax())
910                        return true;
911                }
912            }
913            return false;
914        }
915    
916        /** Constraint preference (0 if prohibited or reqired) */
917        public int getPreference() {
918            return iPreference;
919        }
920    
921        /**
922         * Current constraint preference (0 if prohibited or reqired, depends on
923         * current satisfaction of the constraint)
924         */
925        public int getCurrentPreference() {
926            if (isHard()) return 0; // no preference
927            if (countAssignedVariables() < 2) return 0; // not enough variable
928            if (getType().is(Flag.MAX_HRS_DAY)) { // max hours a day
929                int over = 0;
930                for (int dayCode: Constants.DAY_CODES)
931                    over += Math.max(0, nrSlotsADay(dayCode, null, null) - getType().getMax());
932                return (over > 0 ? Math.abs(iPreference) * over / 12 : - Math.abs(iPreference));
933            }
934            int nrViolatedPairs = 0;
935            for (Lecture v1 : variables()) {
936                if (v1.getAssignment() == null) continue;
937                for (Lecture v2 : variables()) {
938                    if (v2.getAssignment() == null || v1.getId() >= v2.getId()) continue;
939                    if (!isSatisfiedPair(v1.getAssignment(), v2.getAssignment())) nrViolatedPairs++;
940                }
941            }
942            if (getType().is(Flag.BACK_TO_BACK)) {
943                Set<Placement> conflicts = new HashSet<Placement>();
944                if (isSatisfiedSeq(new HashMap<Lecture, Placement>(), true, conflicts))
945                    nrViolatedPairs += conflicts.size();
946                else
947                    nrViolatedPairs = variables().size();
948            }
949            return (nrViolatedPairs > 0 ? Math.abs(iPreference) * nrViolatedPairs : - Math.abs(iPreference));
950        }
951    
952        /** Current constraint preference (if given placement is assigned) */
953        public int getCurrentPreference(Placement placement) {
954            if (getType().is(Flag.MAX_HRS_DAY)) {
955                if (placement.getTimeLocation() == null) return 0;
956                HashMap<Lecture, Placement> assignments = new HashMap<Lecture, Placement>();
957                assignments.put(placement.variable(), placement);
958                int over = 0;
959                for (int dayCode: Constants.DAY_CODES)
960                    if ((placement.getTimeLocation().getDayCode() & dayCode) != 0)
961                        over += Math.min(Math.max(0, nrSlotsADay(dayCode, assignments, null) - getType().getMax()), placement.getTimeLocation().getLength());
962                return (over > 0 ? Math.abs(iPreference) * over / 12 : - Math.abs(iPreference));
963            }
964            int nrViolatedPairs = 0;
965            for (Lecture v1 : variables()) {
966                if (v1.getAssignment() == null || v1.equals(placement.variable())) continue;
967                if (!isSatisfiedPair(v1.getAssignment(), placement)) nrViolatedPairs++;
968            }
969            if (getType().is(Flag.BACK_TO_BACK)) {
970                HashMap<Lecture, Placement> assignment = new HashMap<Lecture, Placement>();
971                assignment.put(placement.variable(), placement);
972                Set<Placement> conflicts = new HashSet<Placement>();
973                if (isSatisfiedSeq(assignment, true, conflicts))
974                    nrViolatedPairs += conflicts.size();
975                else
976                    nrViolatedPairs = variables().size();
977            }
978            return (nrViolatedPairs > 0 ? Math.abs(iPreference) * nrViolatedPairs : - Math.abs(iPreference));
979        }
980    
981        @Override
982        public void unassigned(long iteration, Placement value) {
983            super.unassigned(iteration, value);
984            if (iIsRequired || iIsProhibited)
985                return;
986            getModel().getCriterion(DistributionPreferences.class).inc(-iLastPreference);
987            iLastPreference = Math.min(0, getCurrentPreference());
988            getModel().getCriterion(DistributionPreferences.class).inc(iLastPreference);
989        }
990    
991        @Override
992        public void assigned(long iteration, Placement value) {
993            super.assigned(iteration, value);
994            if (iIsRequired || iIsProhibited)
995                return;
996            getModel().getCriterion(DistributionPreferences.class).inc(-iLastPreference);
997            iLastPreference = Math.min(0, getCurrentPreference());
998            getModel().getCriterion(DistributionPreferences.class).inc(iLastPreference);
999        }
1000    
1001        @Override
1002        public String toString() {
1003            StringBuffer sb = new StringBuffer();
1004            sb.append(getName());
1005            sb.append(" between ");
1006            for (Iterator<Lecture> e = variables().iterator(); e.hasNext();) {
1007                Lecture v = e.next();
1008                sb.append(v.getName());
1009                if (e.hasNext())
1010                    sb.append(", ");
1011            }
1012            return sb.toString();
1013        }
1014    
1015        @Override
1016        public boolean isHard() {
1017            return iIsRequired || iIsProhibited;
1018        }
1019    
1020        @Override
1021        public String getName() {
1022            return getType().getName();
1023        }
1024    
1025    
1026        private boolean isPrecedence(Placement p1, Placement p2, boolean firstGoesFirst, boolean considerDatePatterns) {
1027            int ord1 = variables().indexOf(p1.variable());
1028            int ord2 = variables().indexOf(p2.variable());
1029            TimeLocation t1 = null, t2 = null;
1030            if (ord1 < ord2) {
1031                if (firstGoesFirst) {
1032                    t1 = p1.getTimeLocation();
1033                    t2 = p2.getTimeLocation();
1034                } else {
1035                    t2 = p1.getTimeLocation();
1036                    t1 = p2.getTimeLocation();
1037                }
1038            } else {
1039                if (!firstGoesFirst) {
1040                    t1 = p1.getTimeLocation();
1041                    t2 = p2.getTimeLocation();
1042                } else {
1043                    t2 = p1.getTimeLocation();
1044                    t1 = p2.getTimeLocation();
1045                }
1046            }
1047            if (considerDatePatterns && iPrecedenceConsiderDatePatterns) {
1048                boolean sameDatePattern = (t1.getDatePatternId() != null ? t1.getDatePatternId().equals(t2.getDatePatternId()) : t1.getWeekCode().equals(t2.getWeekCode()));
1049                if (!sameDatePattern) {
1050                    int m1 = getFirstMeeting(t1), m2 = getFirstMeeting(t2);
1051                    if (m1 != m2) return m1 < m2;
1052                }
1053            }
1054            return t1.getStartSlots().nextElement() + t1.getLength() <= t2.getStartSlots().nextElement();
1055        }
1056        
1057        private int getFirstMeeting(TimeLocation time) {
1058            int idx = -1;
1059            while ((idx = time.getWeekCode().nextSetBit(1 + idx)) >= 0) {
1060                int dow = (idx + iDayOfWeekOffset) % 7;
1061                if ((time.getDayCode() & Constants.DAY_CODES[dow]) != 0) break;
1062            }
1063            return idx;
1064        }
1065    
1066        private static boolean isBackToBackDays(TimeLocation t1, TimeLocation t2) {
1067            int f1 = -1, f2 = -1, e1 = -1, e2 = -1;
1068            for (int i = 0; i < Constants.DAY_CODES.length; i++) {
1069                if ((t1.getDayCode() & Constants.DAY_CODES[i]) != 0) {
1070                    if (f1 < 0)
1071                        f1 = i;
1072                    e1 = i;
1073                }
1074                if ((t2.getDayCode() & Constants.DAY_CODES[i]) != 0) {
1075                    if (f2 < 0)
1076                        f2 = i;
1077                    e2 = i;
1078                }
1079            }
1080            return (e1 + 1 == f2) || (e2 + 1 == f1);
1081        }
1082        
1083        private static boolean isNrDaysBetweenGreaterThanOne(TimeLocation t1, TimeLocation t2) {
1084            int f1 = -1, f2 = -1, e1 = -1, e2 = -1;
1085            for (int i = 0; i < Constants.DAY_CODES.length; i++) {
1086                if ((t1.getDayCode() & Constants.DAY_CODES[i]) != 0) {
1087                    if (f1 < 0)
1088                        f1 = i;
1089                    e1 = i;
1090                }
1091                if ((t2.getDayCode() & Constants.DAY_CODES[i]) != 0) {
1092                    if (f2 < 0)
1093                        f2 = i;
1094                    e2 = i;
1095                }
1096            }
1097            return (e1 - f2 > 2) || (e2 - f1 > 2);
1098        }
1099    
1100        private boolean isFollowingDay(Placement p1, Placement p2, boolean firstGoesFirst) {
1101            int ord1 = variables().indexOf(p1.variable());
1102            int ord2 = variables().indexOf(p2.variable());
1103            TimeLocation t1 = null, t2 = null;
1104            if (ord1 < ord2) {
1105                if (firstGoesFirst) {
1106                    t1 = p1.getTimeLocation();
1107                    t2 = p2.getTimeLocation();
1108                } else {
1109                    t2 = p1.getTimeLocation();
1110                    t1 = p2.getTimeLocation();
1111                }
1112            } else {
1113                if (!firstGoesFirst) {
1114                    t1 = p1.getTimeLocation();
1115                    t2 = p2.getTimeLocation();
1116                } else {
1117                    t2 = p1.getTimeLocation();
1118                    t1 = p2.getTimeLocation();
1119                }
1120            }
1121            int f1 = -1, f2 = -1, e1 = -1;
1122            for (int i = 0; i < Constants.DAY_CODES.length; i++) {
1123                if ((t1.getDayCode() & Constants.DAY_CODES[i]) != 0) {
1124                    if (f1 < 0)
1125                        f1 = i;
1126                    e1 = i;
1127                }
1128                if ((t2.getDayCode() & Constants.DAY_CODES[i]) != 0) {
1129                    if (f2 < 0)
1130                        f2 = i;
1131                }
1132            }
1133            return ((e1 + 1) % Constants.NR_DAYS_WEEK == f2);
1134        }
1135    
1136        private boolean isEveryOtherDay(Placement p1, Placement p2, boolean firstGoesFirst) {
1137            int ord1 = variables().indexOf(p1.variable());
1138            int ord2 = variables().indexOf(p2.variable());
1139            TimeLocation t1 = null, t2 = null;
1140            if (ord1 < ord2) {
1141                if (firstGoesFirst) {
1142                    t1 = p1.getTimeLocation();
1143                    t2 = p2.getTimeLocation();
1144                } else {
1145                    t2 = p1.getTimeLocation();
1146                    t1 = p2.getTimeLocation();
1147                }
1148            } else {
1149                if (!firstGoesFirst) {
1150                    t1 = p1.getTimeLocation();
1151                    t2 = p2.getTimeLocation();
1152                } else {
1153                    t2 = p1.getTimeLocation();
1154                    t1 = p2.getTimeLocation();
1155                }
1156            }
1157            int f1 = -1, f2 = -1, e1 = -1;
1158            for (int i = 0; i < Constants.DAY_CODES.length; i++) {
1159                if ((t1.getDayCode() & Constants.DAY_CODES[i]) != 0) {
1160                    if (f1 < 0)
1161                        f1 = i;
1162                    e1 = i;
1163                }
1164                if ((t2.getDayCode() & Constants.DAY_CODES[i]) != 0) {
1165                    if (f2 < 0)
1166                        f2 = i;
1167                }
1168            }
1169            return ((e1 + 2) % Constants.NR_DAYS_WEEK == f2);
1170        }
1171    
1172        private static boolean sameDays(int[] days1, int[] days2) {
1173            if (days2.length < days1.length)
1174                return sameDays(days2, days1);
1175            int i2 = 0;
1176            for (int i1 = 0; i1 < days1.length; i1++) {
1177                int d1 = days1[i1];
1178                while (true) {
1179                    if (i2 == days2.length)
1180                        return false;
1181                    int d2 = days2[i2];
1182                    if (d1 == d2)
1183                        break;
1184                    i2++;
1185                    if (i2 == days2.length)
1186                        return false;
1187                }
1188                i2++;
1189            }
1190            return true;
1191        }
1192        
1193        private static boolean sameDays(TimeLocation t1, TimeLocation t2) {
1194            if (t1 == null || t2 == null) return false;
1195            return sameDays(t1.getDaysArray(), t2.getDaysArray());
1196        }
1197    
1198        private static boolean sameHours(int start1, int len1, int start2, int len2) {
1199            if (len1 > len2)
1200                return sameHours(start2, len2, start1, len1);
1201            start1 %= Constants.SLOTS_PER_DAY;
1202            start2 %= Constants.SLOTS_PER_DAY;
1203            return (start1 >= start2 && start1 + len1 <= start2 + len2);
1204        }
1205        
1206        private static boolean sameHours(TimeLocation t1, TimeLocation t2) {
1207            if (t1 == null || t2 == null) return false;
1208            return sameHours(t1.getStartSlot(), t1.getLength(), t2.getStartSlot(), t2.getLength());
1209        }
1210    
1211        private static boolean canFill(int totalGap, int gapMin, int gapMax, List<Integer> lengths) {
1212            if (gapMin <= totalGap && totalGap <= gapMax)
1213                return true;
1214            if (totalGap < 2 * gapMin)
1215                return false;
1216            for (int i = 0; i < lengths.size(); i++) {
1217                int length = lengths.get(i);
1218                lengths.remove(i);
1219                for (int gap = gapMin; gap <= gapMax; gap++)
1220                    if (canFill(totalGap - gap - length, gapMin, gapMax, lengths))
1221                        return true;
1222                lengths.add(i, length);
1223            }
1224            return false;
1225        }
1226    
1227        private boolean isSatisfiedSeq(HashMap<Lecture, Placement> assignments, boolean considerCurrentAssignments,
1228                Set<Placement> conflicts) {
1229            if (conflicts == null)
1230                return isSatisfiedSeqCheck(assignments, considerCurrentAssignments, conflicts);
1231            else {
1232                Set<Placement> bestConflicts = isSatisfiedRecursive(0, assignments, considerCurrentAssignments, conflicts,
1233                        new HashSet<Placement>(), null);
1234                if (bestConflicts == null)
1235                    return false;
1236                conflicts.addAll(bestConflicts);
1237                return true;
1238            }
1239        }
1240    
1241        private Set<Placement> isSatisfiedRecursive(int idx, HashMap<Lecture, Placement> assignments,
1242                boolean considerCurrentAssignments, Set<Placement> conflicts, Set<Placement> newConflicts,
1243                Set<Placement> bestConflicts) {
1244            if (idx == variables().size() && newConflicts.isEmpty())
1245                return bestConflicts;
1246            if (isSatisfiedSeqCheck(assignments, considerCurrentAssignments, conflicts)) {
1247                if (bestConflicts == null || bestConflicts.size() > newConflicts.size())
1248                    return new HashSet<Placement>(newConflicts);
1249                return bestConflicts;
1250            }
1251            if (idx == variables().size())
1252                return bestConflicts;
1253            bestConflicts = isSatisfiedRecursive(idx + 1, assignments, considerCurrentAssignments, conflicts, newConflicts,
1254                    bestConflicts);
1255            Lecture lecture = variables().get(idx);
1256            if (assignments != null && assignments.containsKey(lecture))
1257                return bestConflicts;
1258            Placement placement = (assignments == null ? null : assignments.get(lecture));
1259            if (placement == null && considerCurrentAssignments)
1260                placement = lecture.getAssignment();
1261            if (placement == null)
1262                return bestConflicts;
1263            if (conflicts != null && conflicts.contains(placement))
1264                return bestConflicts;
1265            conflicts.add(placement);
1266            newConflicts.add(placement);
1267            bestConflicts = isSatisfiedRecursive(idx + 1, assignments, considerCurrentAssignments, conflicts, newConflicts,
1268                    bestConflicts);
1269            newConflicts.remove(placement);
1270            conflicts.remove(placement);
1271            return bestConflicts;
1272        }
1273    
1274        private boolean isSatisfiedSeqCheck(HashMap<Lecture, Placement> assignments, boolean considerCurrentAssignments,
1275                Set<Placement> conflicts) {
1276            if (!getType().is(Flag.BACK_TO_BACK)) return true;
1277            int gapMin = getType().getMin();
1278            int gapMax = getType().getMax();
1279    
1280            List<Integer> lengths = new ArrayList<Integer>();
1281    
1282            Placement[] res = new Placement[Constants.SLOTS_PER_DAY];
1283            for (int i = 0; i < Constants.SLOTS_PER_DAY; i++)
1284                res[i] = null;
1285    
1286            int nrLectures = 0;
1287    
1288            for (Lecture lecture : variables()) {
1289                Placement placement = (assignments == null ? null : assignments.get(lecture));
1290                if (placement == null && considerCurrentAssignments)
1291                    placement = lecture.getAssignment();
1292                if (placement == null) {
1293                    lengths.add(lecture.timeLocations().get(0).getLength());
1294                } else if (conflicts != null && conflicts.contains(placement)) {
1295                    lengths.add(lecture.timeLocations().get(0).getLength());
1296                } else {
1297                    int pos = placement.getTimeLocation().getStartSlot();
1298                    int length = placement.getTimeLocation().getLength();
1299                    for (int j = pos; j < pos + length; j++) {
1300                        if (res[j] != null) {
1301                            if (conflicts == null)
1302                                return false;
1303                            if (!assignments.containsKey(lecture))
1304                                conflicts.add(placement);
1305                            else if (!assignments.containsKey(res[j].variable()))
1306                                conflicts.add(res[j]);
1307                        }
1308                    }
1309                    for (int j = pos; j < pos + length; j++)
1310                        res[j] = placement;
1311                    nrLectures++;
1312                }
1313            }
1314            if (nrLectures <= 1)
1315                return true;
1316    
1317            if (iIsRequired || (!iIsProhibited && iPreference < 0)) {
1318                int i = 0;
1319                Placement p = res[i];
1320                while (p == null)
1321                    p = res[++i];
1322                i += res[i].getTimeLocation().getLength();
1323                nrLectures--;
1324                while (nrLectures > 0) {
1325                    int gap = 0;
1326                    while (i < Constants.SLOTS_PER_DAY && res[i] == null) {
1327                        gap++;
1328                        i++;
1329                    }
1330                    if (i == Constants.SLOTS_PER_DAY)
1331                        break;
1332                    if (!canFill(gap, gapMin, gapMax, lengths))
1333                        return false;
1334                    p = res[i];
1335                    i += res[i].getTimeLocation().getLength();
1336                    nrLectures--;
1337                }
1338            } else if (iIsProhibited || (!iIsRequired && iPreference > 0)) {
1339                int i = 0;
1340                Placement p = res[i];
1341                while (p == null)
1342                    p = res[++i];
1343                i += res[i].getTimeLocation().getLength();
1344                nrLectures--;
1345                while (nrLectures > 0) {
1346                    int gap = 0;
1347                    while (i < Constants.SLOTS_PER_DAY && res[i] == null) {
1348                        gap++;
1349                        i++;
1350                    }
1351                    if (i == Constants.SLOTS_PER_DAY)
1352                        break;
1353                    if ((gapMin == 0 || !canFill(gap, 0, gapMin - 1, lengths))
1354                            && (gapMax >= Constants.SLOTS_PER_DAY || !canFill(gap, gapMax + 1, Constants.SLOTS_PER_DAY,
1355                                    lengths))) {
1356                        return false;
1357                    }
1358                    p = res[i];
1359                    i += res[i].getTimeLocation().getLength();
1360                    nrLectures--;
1361                }
1362            }
1363            return true;
1364        }
1365    
1366        public boolean isSatisfied() {
1367            if (isHard()) return true;
1368            if (countAssignedVariables() < 2) return true;
1369            if (getPreference() == 0) return true;
1370            return isHard() || countAssignedVariables() < 2 || getPreference() == 0 || getCurrentPreference() < 0;
1371        }
1372    
1373        public boolean isChildrenNotOverlap(Lecture lec1, Placement plc1, Lecture lec2, Placement plc2) {
1374            if (lec1.getSchedulingSubpartId().equals(lec2.getSchedulingSubpartId())) {
1375                // same subpart
1376                boolean overlap = plc1.getTimeLocation().hasIntersection(plc2.getTimeLocation());
1377    
1378                if (overlap && lec1.getParent() != null && variables().contains(lec1.getParent())
1379                        && lec2.getParent() != null && variables().contains(lec2.getParent())) {
1380                    // children overlaps
1381                    Placement p1 = lec1.getParent().getAssignment();
1382                    Placement p2 = lec2.getParent().getAssignment();
1383                    // parents not overlap, but children do
1384                    if (p1 != null && p2 != null && !p1.getTimeLocation().hasIntersection(p2.getTimeLocation()))
1385                        return false;
1386                }
1387    
1388                if (!overlap && lec1.getChildrenSubpartIds() != null && lec2.getChildrenSubpartIds() != null) {
1389                    // parents not overlap
1390                    for (Long subpartId: lec1.getChildrenSubpartIds()) {
1391                        for (Lecture c1 : lec1.getChildren(subpartId)) {
1392                            if (c1.getAssignment() == null)
1393                                continue;
1394                            for (Lecture c2 : lec2.getChildren(subpartId)) {
1395                                if (c2.getAssignment() == null)
1396                                    continue;
1397                                if (!c1.getSchedulingSubpartId().equals(c2.getSchedulingSubpartId()))
1398                                    continue;
1399                                Placement p1 = c1.getAssignment();
1400                                Placement p2 = c2.getAssignment();
1401                                // parents not overlap, but children do
1402                                if (p1.getTimeLocation().hasIntersection(p2.getTimeLocation()))
1403                                    return false;
1404                            }
1405                        }
1406                    }
1407                }
1408            } else {
1409                // different subpart
1410            }
1411            return true;
1412        }
1413    
1414        public boolean isSatisfiedPair(Placement plc1, Placement plc2) {
1415            if (iIsRequired || (!iIsProhibited && iPreference <= 0))
1416                return getType().isSatisfied(this, plc1, plc2);
1417            else if (iIsProhibited || (!iIsRequired && iPreference > 0))
1418                return getType().isViolated(this, plc1, plc2);
1419            return true;
1420        }
1421        
1422        public boolean canShareRoom() {
1423            return getType().is(Flag.CAN_SHARE_ROOM);
1424        }
1425        
1426        private int nrSlotsADay(int dayCode, HashMap<Lecture, Placement> assignments, Set<Placement> conflicts) {
1427            Set<Integer> slots = new HashSet<Integer>();
1428            for (Lecture lecture: variables()) {
1429                Placement placement = (assignments == null ? null : assignments.get(lecture));
1430                if (placement == null) {
1431                    placement = lecture.getAssignment();
1432                    if (conflicts != null && conflicts.contains(placement)) continue;
1433                }
1434                if (placement == null || placement.getTimeLocation() == null) continue;
1435                TimeLocation t = placement.getTimeLocation();
1436                if (t == null || (t.getDayCode() & dayCode) == 0) continue;
1437                for (int i = 0; i < t.getLength(); i++)
1438                    slots.add(i + t.getStartSlot());
1439            }
1440            return slots.size();
1441        }
1442    
1443        
1444    }