Source code

001package org.cpsolver.coursett.constraint;
002
003import java.util.BitSet;
004import java.util.HashMap;
005import java.util.HashSet;
006import java.util.Map;
007import java.util.Set;
008import java.util.regex.Matcher;
009import java.util.regex.Pattern;
010
011import org.cpsolver.coursett.Constants;
012import org.cpsolver.coursett.criteria.FlexibleConstraintCriterion;
013import org.cpsolver.coursett.model.Lecture;
014import org.cpsolver.coursett.model.Placement;
015import org.cpsolver.ifs.assignment.Assignment;
016import org.cpsolver.ifs.criteria.Criterion;
017import org.cpsolver.ifs.util.ToolBox;
018
019/**
020 * 
021 * The MaxConsecutiveDays constraint limits the number of consecutive days of week during which the given set of classes are taught.<br>
022 * It has one parameter: a maximal number of consecutive days during which the given set of classes can be placed.<br>
023 * Reference _MaxConsDays:2_ translates to a maximum number of 2 consecutive days a week (so for instance, Monday & Tuesday,
024 * Tuesday & Wednesday, Wednesday & Thursday, ...)<br>
025 * 
026 * @version CourseTT 1.3 (University Course Timetabling)<br>
027 *          Copyright (C) 2022 Tomáš Müller<br>
028 * <br>
029 *          This library is free software; you can redistribute it and/or modify
030 *          it under the terms of the GNU Lesser General Public License as
031 *          published by the Free Software Foundation; either version 3 of the
032 *          License, or (at your option) any later version. <br>
033 * <br>
034 *          This library is distributed in the hope that it will be useful, but
035 *          WITHOUT ANY WARRANTY; without even the implied warranty of
036 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
037 *          Lesser General Public License for more details. <br>
038 * <br>
039 *          You should have received a copy of the GNU Lesser General Public
040 *          License along with this library; if not see
041 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
042 */
043public class MaxConsecutiveDaysFlexibleConstraint extends FlexibleConstraint {
044private int iMaxDays;
045    
046    public MaxConsecutiveDaysFlexibleConstraint(Long id, String owner, String preference, String reference) {
047        super(id, owner, preference, reference);     
048
049        Matcher matcher = Pattern.compile(FlexibleConstraintType.MAX_CONSECUTIVE_DAYS.getPattern()).matcher(reference);
050        if (matcher.find()) {
051            iMaxDays = Integer.parseInt(matcher.group(2));
052            iConstraintType = FlexibleConstraintType.MAX_CONSECUTIVE_DAYS;           
053        }
054    }
055    
056    @Override
057    public double getNrViolations(Assignment<Lecture, Placement> assignment, Set<Placement> conflicts, HashMap<Lecture, Placement> assignments) {
058        return ((MaxConsecutiveDaysFlexibleConstraintContext)getContext(assignment)).nrViolations(assignments, conflicts);
059    }
060
061    @Override
062    public void computeConflicts(Assignment<Lecture, Placement> assignment, Placement value, Set<Placement> conflicts) {
063        if (!isHard()) return;
064        
065        MaxConsecutiveDaysFlexibleConstraintContext context = (MaxConsecutiveDaysFlexibleConstraintContext)getContext(assignment);
066        while (context.nrDays(value, conflicts) > iMaxDays && !conflicts.contains(value)) {
067            Set<Lecture> candidates = context.candidates(value, conflicts);
068            if (candidates == null) {
069                conflicts.add(value);
070                return;
071            }
072            for (Lecture candidate: candidates) {
073                Placement conflict = assignment.getValue(candidate);
074                if (conflict != null)
075                    conflicts.add(conflict);
076            }
077        }
078    }
079    
080    @Override
081    public boolean inConflict(Assignment<Lecture, Placement> assignment, Placement value) {
082        if (!isHard()) return false;
083        return ((MaxConsecutiveDaysFlexibleConstraintContext)getContext(assignment)).nrDays(value, null) > iMaxDays;
084    }
085    
086    @Override
087    public FlexibleConstraintContext createAssignmentContext(Assignment<Lecture, Placement> assignment) {
088        return new MaxConsecutiveDaysFlexibleConstraintContext(assignment);
089    }
090    
091    public class MaxConsecutiveDaysFlexibleConstraintContext extends FlexibleConstraintContext {
092        private Map<BitSet, Set<Lecture>[]> iWeekDayAssignments = null;
093        private Set<Lecture> iDayAssignments[] = null;
094        
095        public MaxConsecutiveDaysFlexibleConstraintContext(Assignment<Lecture, Placement> assignment) {
096            super();
097            for (BitSet week: getWeeks()) {
098                Set<Lecture>[] dayAssignments = getDayAssignments(week);
099                for (Lecture variable: variables()) {
100                    Placement value = assignment.getValue(variable);
101                    if (value != null) {
102                        for (int i = 0; i < dayAssignments.length; i++)
103                            if (overlaps(week, i, value))
104                                dayAssignments[i].add(value.variable());
105                    }
106                }
107            }
108            if (!isHard()) {
109                Criterion<Lecture, Placement> criterion = getModel().getCriterion(FlexibleConstraintCriterion.class);
110                if (criterion != null) {
111                    double pref = nrViolations(null, null);
112                    if (pref == 0)
113                        iLastPreference = -Math.abs(iPreference);
114                    else 
115                        iLastPreference = Math.abs(iPreference) * pref;
116                    criterion.inc(assignment, iLastPreference);  
117                }
118            }
119        }
120        
121        protected boolean overlaps(BitSet week, int dayOfWeek, Placement value) {
122            if (value == null || value.getTimeLocation() == null) return false;
123            if (week != null && !value.getTimeLocation().getWeekCode().intersects(week)) return false;
124            return (value.getTimeLocation().getDayCode() & Constants.DAY_CODES[dayOfWeek]) != 0;
125        }
126        
127        @SuppressWarnings("unchecked")
128        protected Set<Lecture>[] getDayAssignments(BitSet week) {
129            if (week == null) {
130                if (iDayAssignments == null) {
131                    iDayAssignments = new Set[Constants.NR_DAYS];
132                    for (int i = 0; i < iDayAssignments.length; i++)
133                        iDayAssignments[i] = new HashSet<Lecture>();
134                }
135                return iDayAssignments;
136            } else {
137                if (iWeekDayAssignments == null)
138                    iWeekDayAssignments = new HashMap<BitSet, Set<Lecture>[]>();
139                Set<Lecture>[] dayAssignments = iWeekDayAssignments.get(week);
140                if (dayAssignments == null) {
141                    dayAssignments = new Set[Constants.NR_DAYS];
142                    for (int i = 0; i < dayAssignments.length; i++)
143                        dayAssignments[i] = new HashSet<Lecture>();
144                    iWeekDayAssignments.put(week, dayAssignments);
145                }
146                return dayAssignments;
147            }
148        }
149
150        @Override
151        public void assigned(Assignment<Lecture, Placement> assignment, Placement value) {
152            for (BitSet week: getWeeks()) {
153                Set<Lecture>[] dayAssignments = getDayAssignments(week);
154                for (int i = 0; i < dayAssignments.length; i++)
155                    if (overlaps(week, i, value))
156                        dayAssignments[i].add(value.variable());
157            }
158            updateCriterion(assignment);
159        }
160        
161        @Override
162        public void unassigned(Assignment<Lecture, Placement> assignment, Placement value) {
163            for (BitSet week: getWeeks()) {
164                Set<Lecture>[] dayAssignments = getDayAssignments(week);
165                for (int i = 0; i < dayAssignments.length; i++)
166                    if (overlaps(week, i, value))
167                        dayAssignments[i].remove(value.variable());
168            }
169            updateCriterion(assignment);
170        }
171        
172        public int nrDays(BitSet week, Placement value, Set<Placement> conflicts) {
173            Set<Lecture>[] dayAssignments = getDayAssignments(week);
174            Integer min = null, max = null;
175            for (int i = 0; i < dayAssignments.length; i++) {
176                int cnt = dayAssignments[i].size();
177                if (value != null) {
178                    if (overlaps(week, i, value)) cnt ++;
179                    if (dayAssignments[i].contains(value.variable())) cnt --; 
180                }
181                if (conflicts != null) {
182                    for (Placement conflict: conflicts) {
183                        if (value != null && conflict.variable().equals(value.variable())) continue;
184                        if (dayAssignments[i].contains(conflict.variable())) cnt --;
185                    }
186                }
187                if (cnt > 0) {
188                    if (min == null) min = i;
189                    max = i;
190                }
191            }
192            if (min == null) return 0;
193            return max - min + 1;
194        }
195        
196        public int nrDays(Placement value, Set<Placement> conflicts) {
197            int ret = 0; 
198            for (BitSet week: getWeeks()) {
199                int days = nrDays(week, value, conflicts);
200                if (days > ret) ret = days;
201            }
202            return ret;
203        }
204        
205        public Set<Lecture> candidates(Placement value, Set<Placement> conflicts) {
206            for (BitSet week: getWeeks()) {
207                Set<Lecture>[] dayAssignments = getDayAssignments(week);
208                Integer min = null, max = null;
209                Integer minThisPl = null, maxThisPl = null;
210                for (int i = 0; i < dayAssignments.length; i++) {
211                    int cnt = dayAssignments[i].size();
212                    if (overlaps(week, i, value)) {
213                        if (minThisPl == null) minThisPl = i;
214                        maxThisPl = i;
215                        cnt ++;
216                    }
217                    if (dayAssignments[i].contains(value.variable())) cnt --;
218                    for (Placement conflict: conflicts) {
219                        if (conflict.variable().equals(value.variable())) continue;
220                        if (dayAssignments[i].contains(conflict.variable())) cnt --;
221                    }
222                    if (cnt > 0) {
223                        if (min == null) min = i;
224                        max = i;
225                    }
226                }
227                if (min == null || max - min + 1 <= iMaxDays) continue;
228                if ((minThisPl == null || min < minThisPl) && (maxThisPl == null || maxThisPl < max)) {
229                    if (ToolBox.random() <= 0.5)
230                        return dayAssignments[min];
231                    else
232                        return dayAssignments[max];
233                }
234                if (minThisPl == null || min < minThisPl)
235                    return dayAssignments[min];
236                if (maxThisPl == null || maxThisPl < max)
237                    return dayAssignments[max];
238            }
239            return null;
240        }
241        
242        public int nrViolations(BitSet week, HashMap<Lecture, Placement> assignments, Set<Placement> conflicts) {
243            Set<Lecture>[] dayAssignments = getDayAssignments(week);
244            Integer min = null, max = null;
245            for (int i = 0; i < dayAssignments.length; i++) {
246                int cnt = dayAssignments[i].size();
247                if (assignments != null) {
248                    for (Map.Entry<Lecture, Placement> entry: assignments.entrySet()) {
249                        Placement assignment = entry.getValue();
250                        if (assignment != null && overlaps(week, i, assignment)) cnt ++;
251                    } 
252                }
253                if (conflicts != null) {
254                    for (Placement conflict: conflicts) {
255                        if (assignments != null && assignments.containsKey(conflict.variable())) continue;
256                        if (dayAssignments[i].contains(conflict.variable())) cnt --;
257                    }
258                }
259                if (cnt > 0) {
260                    if (min == null) min = i;
261                    max = i;
262                }
263            }
264            if (min == null) return 0;
265            return (max - min + 1 <= iMaxDays ? 0 : max - min + 1 - iMaxDays);
266        }
267        
268        public int nrViolations(HashMap<Lecture, Placement> assignments, Set<Placement> conflicts) {
269            int ret = 0; 
270            for (BitSet week: getWeeks()) {
271                ret += nrViolations(week, assignments, conflicts);
272            }
273            return ret;
274        }
275    
276    }
277}