001    package net.sf.cpsolver.coursett.constraint;
002    
003    import java.util.ArrayList;
004    import java.util.BitSet;
005    import java.util.Comparator;
006    import java.util.HashMap;
007    import java.util.HashSet;
008    import java.util.List;
009    import java.util.Set;
010    
011    import net.sf.cpsolver.coursett.Constants;
012    import net.sf.cpsolver.coursett.criteria.FlexibleConstraintCriterion;
013    import net.sf.cpsolver.coursett.model.Lecture;
014    import net.sf.cpsolver.coursett.model.Placement;
015    import net.sf.cpsolver.coursett.model.TimeLocation;
016    import net.sf.cpsolver.coursett.model.TimetableModel;
017    import net.sf.cpsolver.ifs.model.Constraint;
018    
019    /**
020     * Flexible constraint. <br>
021     * This constraint expresses relations between several classes. Provides similar
022     * functions as Group constraint. Unlike group constraint, Flexible constraint
023     * is able to parse some of its parameters from its reference field<br>
024     * 
025     * @version CourseTT 1.2 (University Course Timetabling)<br>
026     *          Copyright (C) 2013 Matej Lukac<br>
027     * <br>
028     *          This library is free software; you can redistribute it and/or modify
029     *          it under the terms of the GNU Lesser General Public License as
030     *          published by the Free Software Foundation; either version 3 of the
031     *          License, or (at your option) any later version. <br>
032     * <br>
033     *          This library is distributed in the hope that it will be useful, but
034     *          WITHOUT ANY WARRANTY; without even the implied warranty of
035     *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
036     *          Lesser General Public License for more details. <br>
037     * <br>
038     *          You should have received a copy of the GNU Lesser General Public
039     *          License along with this library; if not see
040     *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
041     */
042    public abstract class FlexibleConstraint extends Constraint<Lecture, Placement> {
043    
044        private int iPreference;
045        private boolean iIsRequired;   
046        private double iLastPreference;
047        private String iOwner;
048        
049        // Constraint type
050        protected FlexibleConstraintType iConstraintType = null;
051            
052        // A pattern the constraint was created from
053        protected String iReference = "";   
054        
055        // Determines whether the constraint is checked for every week in the semester    
056        protected List<BitSet> iWeeks = null;
057        
058        /**
059         * Flexible constraint types
060         * 
061         */
062        public static enum FlexibleConstraintType {
063            /**
064             * Given classes must be taught in a way there is a break between two blocks of classes. 
065             */
066            MAXBLOCK_BACKTOBACK("_(MaxBlock):([0-9]+):([0-9]+)_", MaxBlockFlexibleConstraint.class, "Block"),
067            /**
068             * There must be a break of a given length in a given time interval.
069             */
070            BREAK("_(Break):([0-9]+):([0-9]+):([0-9]+)_", BreakFlexibleConstraint.class, "Break"),
071            ;
072            
073            private String iPattern;
074            private Class<? extends FlexibleConstraint> iImplementation;
075            private String iName;
076            FlexibleConstraintType(String pattern, Class<? extends FlexibleConstraint> implementation, String name) {
077                iPattern = pattern; iImplementation = implementation; iName = name;
078            }
079            
080            public String getPattern() { return iPattern; }
081            
082            public String getName() { return iName; }
083    
084            public FlexibleConstraint create(Long id, String owner, String preference, String reference) throws IllegalArgumentException {
085                try {
086                    return iImplementation.getConstructor(Long.class, String.class, String.class, String.class).newInstance(id, owner, preference, reference);
087                } catch (IllegalArgumentException e) {
088                    throw e;
089                } catch (Exception e) {
090                    throw new IllegalArgumentException(e.getMessage(), e);
091                }
092            }
093        }
094    
095        @Override
096        public abstract void computeConflicts(Placement value, Set<Placement> conflicts);  
097        
098        /** 
099         * 
100         * @param conflicts conflicting placements to be unassigned
101         * @param assignments assigned placements 
102         * @return the number of violations of the constraint during days and all weeks of the semester
103         */
104        public abstract double getNrViolations(Set<Placement> conflicts, HashMap<Lecture, Placement> assignments);
105        
106        /**
107         * 
108         * @param owner identifier of distribution preference the constraint was created for
109         * @param preference time preference ("R" for required, "P" for prohibited, "-2",
110         *            "-1", "1", "2" for soft preference)   
111         * @param reference parameters of the constraint in String form            
112         */
113        public FlexibleConstraint(Long id, String owner, String preference, String reference){
114            super();                
115            iId = id;
116            iReference = reference;
117            iPreference = Constants.preference2preferenceLevel(preference);
118            iIsRequired = preference.equals(Constants.sPreferenceRequired);        
119            iOwner = owner;                
120        } 
121        
122        /**
123         * 
124         * @return i list of bitsets representing datePatterns or null if semester is whole semester is considered
125         */
126        public List<BitSet> getWeeks(){
127            if (iWeeks == null){
128                TimetableModel model = (TimetableModel) getModel();
129                iWeeks = new ArrayList<BitSet>();
130    
131                boolean checkWeeks = model.getProperties().getPropertyBoolean("FlexibleConstraint.CheckWeeks", false);
132                
133                if (checkWeeks) {
134                    // get weeks method returns bitsets representing weeks during semester
135                    iWeeks = model.getWeeks();
136                } else {
137                    // weeks are not considered, all placements are taken into consideration
138                    iWeeks.add(null);
139                } 
140            }  
141              
142            return iWeeks;
143        }
144        
145        @Override
146        public boolean isConsistent(Placement value1, Placement value2) {
147            HashMap<Lecture, Placement> assignments = new HashMap<Lecture, Placement>();
148            if (value1 != null)
149                assignments.put(value1.variable(), value1);
150            if (value2 != null)
151                assignments.put(value2.variable(), value2);
152            
153            if (getNrViolations(null, assignments) != 0) return false;
154    
155            return super.isConsistent(value1, value2);
156        }
157        
158        /**
159         * Returns placements of variables assigned to this constraint with assignment which satisfy following conditions:
160         * They must be taught in the day included in dayCode.
161         * They cannot be included in conflicts
162         * Their date pattern intersects with week
163         *  
164         * @param dayCode representation of days in week combination
165         * @param conflicts placements to be unassigned
166         * @param value placement to be assigned
167         * @param assignments placements of variables
168         * @param week bitset representing a date pattern
169         * @return placements of variables assigned to this constraint with assignment which satisfy conditions above
170         */
171        protected Set<Placement> getRelevantPlacements(int dayCode, Set<Placement> conflicts, Placement value,
172                HashMap<Lecture, Placement> assignments, BitSet week) {
173            Set<Placement> placements = new HashSet<Placement>();
174            
175            for (Lecture lecture : variables()) {
176                // lecture of the value is already assigned
177                if(value != null && lecture.equals(value.variable()))continue;
178    
179                // lecture might not have assignment if it is present in assignments
180                if (assignments != null && assignments.containsKey(lecture)) {
181                    TimeLocation t = assignments.get(lecture).getTimeLocation();
182                    if (shareWeeksAndDay(t, week, dayCode))
183                        placements.add(assignments.get(lecture));
184                    continue;
185                }
186                if (lecture.getAssignment() == null || lecture.getAssignment().getTimeLocation() == null)
187                    continue;
188                if (conflicts != null && conflicts.contains(lecture.getAssignment()))
189                    continue;
190    
191                TimeLocation t = lecture.getAssignment().getTimeLocation();
192                if (t == null || !shareWeeksAndDay(t, week, dayCode))
193                    continue;
194    
195                placements.add(lecture.getAssignment());
196            }
197    
198            if (value == null || (conflicts != null && conflicts.contains(value))) {
199                return placements;
200            } 
201            
202            if (shareWeeksAndDay(value.getTimeLocation(), week, dayCode)) placements.add(value); 
203    
204            return placements;
205        }
206        
207        /**
208         * Used to determine the daycode and week of a timelocation
209         * 
210         * @param t timelocation 
211         * @param week date pattern compared to timelocation
212         * @param dayCode days compared to timelocation
213         * @return true if TimeLocation matches the date pattern and days
214         */
215        private boolean shareWeeksAndDay(TimeLocation t, BitSet week, int dayCode){
216            boolean matchDay = (t.getDayCode() & dayCode) != 0;
217            boolean matchWeek = (week == null || t.shareWeeks(week));                
218            
219            return matchDay && matchWeek;
220        }
221        
222        /**
223         * Creates a list of blocks from a placements sorted by startSlot
224         * 
225         * @param sorted list of placements sorted by startSlot
226         * @param maxBreakBetweenBTB maximum number of free slots between BTB placements
227         * @return groups of BTB placements as a list of blocks
228         */
229        protected List<Block> mergeToBlocks(List<Placement> sorted, int maxBreakBetweenBTB){
230            List<Block> blocks = new ArrayList<Block>();
231            // add placements to blocks
232            for (int i = 0; i < sorted.size(); i++) {
233                Placement placement = sorted.get(i);
234                boolean added = false;
235                // add placement to a suitable block
236                for (int j = 0; j < blocks.size(); j++) {
237                    if (blocks.get(j).addPlacement(placement)) {
238                        added = true;
239                    }
240                }
241                // create a new block if a lecture does not fit into any block
242                if (!added) {
243                    Block block = new Block(maxBreakBetweenBTB);
244                    block.addPlacement(placement);
245                    blocks.add(block);
246                }
247            }   
248            return blocks;
249        }
250        
251        @Override
252        public boolean isHard() {
253            return iIsRequired;
254        }    
255        
256        @Override
257        public String getName() {
258            return iOwner + ": " + iConstraintType.getName();
259        }
260        
261        public FlexibleConstraintType getType(){
262            return iConstraintType;
263        }
264        
265        @Override
266        public void assigned(long iteration, Placement value) {        
267            super.assigned(iteration, value);
268            updateCriterion();        
269        }    
270    
271        public String getReference() {        
272            return iReference;
273        }
274        
275        public String getOwner() {        
276            return iOwner;
277        }   
278        
279        /**
280         * Prolog reference: "R" for required, "P" for prohibited", "-2",.."2" for
281         * preference
282         */
283        public String getPrologPreference() {
284            return Constants.preferenceLevel2preference(iPreference);
285        }
286    
287        /**
288         * Update value of FlexibleConstraintCriterion and number of violated FlexibleConstraints
289         */
290        private void updateCriterion() {
291            FlexibleConstraintCriterion pc = (FlexibleConstraintCriterion)getModel().getCriterion(FlexibleConstraintCriterion.class);
292            if (pc != null) {            
293                if (!isHard()){                
294                    pc.inc(-iLastPreference);                
295                    iLastPreference = getCurrentPreference(null, null);
296                    pc.inc(iLastPreference);  
297                }   
298            }         
299        }
300        
301        /**
302         * Return the current preference of the flexible constraint, considering conflicts and new assignments.
303         * Used to compute value for flexible constraint criterion.
304         * 
305         * @param conflicts
306         * @param assignments
307         * @return the current preference of the flexible constraint
308         */
309        public double getCurrentPreference(Set<Placement> conflicts, HashMap<Lecture, Placement> assignments){
310            double pref = getNrViolations(conflicts, assignments);
311            if(pref == 0){
312                return - Math.abs(iPreference);
313            }
314            return Math.abs(iPreference) * pref;
315        }
316    
317        @Override
318        public void unassigned(long iteration, Placement value) {
319            super.unassigned(iteration, value);
320            updateCriterion();
321        }   
322        
323        /**
324         * A block is a list of placements sorted by startSlot, which are BTB.
325         * maxSlotsBetweenBackToBack determines the number of free slots between two BTB placements
326         *
327         */
328        public class Block {
329            
330            // start slot of the block
331            private int startSlotCurrentBlock = -1;        
332            // end slot of the block
333            private int endSlotCurrentBlock = -1;        
334            // max number of slots between classes to be considered Back-To-Back; 4 slots default      
335            private int maxSlotsBetweenBackToBack = 4;
336            // the list of placements of this block
337            private List<Placement> placements = new ArrayList<Placement>();
338            
339            public Block(int maxSlotsBetweenBTB){
340                this.maxSlotsBetweenBackToBack = maxSlotsBetweenBTB;            
341            }              
342            
343            /**
344             * Adds placement to the block and updates block's attributes.
345             * 
346             * @param placement placement to be added to the block
347             * @return true if the placement was successfully added to the block
348             */
349            public boolean addPlacement(Placement placement){   
350                if (placement == null){
351                    return false;
352                }
353                
354                TimeLocation t = placement.getTimeLocation();
355                
356                if (t == null){
357                    return false;
358                }
359                
360                // if placements is empty, the block only contains currently added placement -> set start and end
361                if (placements.isEmpty()){
362                    placements.add(placement);
363                    startSlotCurrentBlock = t.getStartSlot();
364                    endSlotCurrentBlock = t.getStartSlot() + t.getLength();
365                    return true;
366                }
367                
368                // if startSlotCurrentBlock equals placement's start slot, add placement and adjust endSlotCurrentBlock
369                if (t.getStartSlot() == startSlotCurrentBlock){
370                    placements.add(placement);
371                    int tEnd = t.getStartSlot() + t.getLength();
372                    if (tEnd > endSlotCurrentBlock){
373                        endSlotCurrentBlock = tEnd;
374                    }
375                    return true;
376                }      
377                
378                // if placement starts among endSlotCurrentBlock + modifier and startSlotCurrentBlock, add the placement
379                if (endSlotCurrentBlock + maxSlotsBetweenBackToBack >= t.getStartSlot() && t.getStartSlot() >= startSlotCurrentBlock ){
380                    placements.add(placement);
381                    int tEnd = t.getStartSlot() + t.getLength();
382                    if (tEnd > endSlotCurrentBlock){
383                        endSlotCurrentBlock = tEnd;
384                    }
385                    return true;
386                }
387                
388                return false;
389            }
390    
391            public boolean haveSameStartTime() {
392                if (!placements.isEmpty()) {
393                    int startSlot = placements.get(0).getTimeLocation().getStartSlot();
394                    for (Placement p : getPlacements()) {
395                        if (p.getTimeLocation().getStartSlot() != startSlot)
396                            return false;
397                    }
398                }
399                return true;
400            }
401            
402            public int getStartSlotCurrentBlock(){
403                return startSlotCurrentBlock;
404            }
405            
406            public int getEndSlotCurrentBlock(){
407                return endSlotCurrentBlock;
408            }
409            
410            public int getNbrPlacements(){
411                return placements.size();
412            }        
413           
414            public List<Placement> getPlacements(){
415                return placements;
416            }
417            
418            public int getLengthInSlots(){
419                return endSlotCurrentBlock - startSlotCurrentBlock;
420            }
421            
422            @Override
423            public String toString(){
424                return "[" + startSlotCurrentBlock + ", " + endSlotCurrentBlock + "]" + " PlacementsNbr: "+ getNbrPlacements();
425            }          
426        }
427        
428        /**
429         * Placement comparator: earlier placement first, shorter placement first if both start at the same time.
430         */
431        protected static class PlacementTimeComparator implements Comparator<Placement> {
432            @Override
433            public int compare(Placement p1, Placement p2) {
434                TimeLocation t1 = p1.getTimeLocation(), t2 = p2.getTimeLocation();
435                // compare by start time (earlier first)
436                if (t1.getStartSlot() < t2.getStartSlot())
437                    return -1;
438                if (t1.getStartSlot() > t2.getStartSlot())
439                    return 1;
440                // same start -> compare by length (shorter first)
441                if (t1.getLength() < t2.getLength())
442                    return -1;
443                if (t1.getLength() > t2.getLength())
444                    return 1;
445                // fallback
446                return 0;
447            }
448        }
449        
450        @Override
451        public String toString() {
452            return getName();
453        }
454    }