Source code

001package org.cpsolver.coursett.constraint;
002
003import java.util.ArrayList;
004import java.util.BitSet;
005import java.util.HashMap;
006import java.util.HashSet;
007import java.util.List;
008import java.util.Map;
009import java.util.Set;
010import java.util.regex.Matcher;
011import java.util.regex.Pattern;
012
013import org.cpsolver.coursett.Constants;
014import org.cpsolver.coursett.criteria.FlexibleConstraintCriterion;
015import org.cpsolver.coursett.model.Lecture;
016import org.cpsolver.coursett.model.Placement;
017import org.cpsolver.ifs.assignment.Assignment;
018import org.cpsolver.ifs.criteria.Criterion;
019import org.cpsolver.ifs.util.ToolBox;
020
021/**
022 * 
023 * The MaxDays constraint limits the number of days of week during which the given set of classes are taught.<br>
024 * It has one parameter: a maximal number of week days during which the given set of classes can be placed.<br>
025 * Reference _MaxDays:2_ translates to a maximum number of 2 days a week<br>
026 * 
027 * @version CourseTT 1.3 (University Course Timetabling)<br>
028 *          Copyright (C) 2015 Tomáš Müller<br>
029 * <br>
030 *          This library is free software; you can redistribute it and/or modify
031 *          it under the terms of the GNU Lesser General Public License as
032 *          published by the Free Software Foundation; either version 3 of the
033 *          License, or (at your option) any later version. <br>
034 * <br>
035 *          This library is distributed in the hope that it will be useful, but
036 *          WITHOUT ANY WARRANTY; without even the implied warranty of
037 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
038 *          Lesser General Public License for more details. <br>
039 * <br>
040 *          You should have received a copy of the GNU Lesser General Public
041 *          License along with this library; if not see
042 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
043 */
044public class MaxDaysFlexibleConstraint extends FlexibleConstraint {
045    private int iMaxDays;
046    
047    public MaxDaysFlexibleConstraint(Long id, String owner, String preference, String reference) {
048        super(id, owner, preference, reference);     
049
050        Matcher matcher = Pattern.compile(FlexibleConstraintType.MAX_DAYS.getPattern()).matcher(reference);
051        if (matcher.find()) {
052            iMaxDays = Integer.parseInt(matcher.group(2));
053            iConstraintType = FlexibleConstraintType.MAX_DAYS;           
054        }   
055    }
056    
057    @Override
058    public double getNrViolations(Assignment<Lecture, Placement> assignment, Set<Placement> conflicts, HashMap<Lecture, Placement> assignments) {
059        return ((MaxDaysFlexibleConstraintContext)getContext(assignment)).nrViolations(assignments, conflicts);
060    }
061
062    @Override
063    public void computeConflicts(Assignment<Lecture, Placement> assignment, Placement value, Set<Placement> conflicts) {
064        if (!isHard()) return;
065        
066        MaxDaysFlexibleConstraintContext context = (MaxDaysFlexibleConstraintContext)getContext(assignment);
067        while (context.nrDays(value, conflicts) > iMaxDays) {
068            Set<Lecture> candidates = context.candidates(value, conflicts);
069            if (candidates == null) {
070                conflicts.add(value);
071                return;
072            }
073            for (Lecture candidate: candidates) {
074                Placement conflict = assignment.getValue(candidate);
075                if (conflict != null)
076                    conflicts.add(conflict);
077            }
078        }
079    }
080    
081    @Override
082    public boolean inConflict(Assignment<Lecture, Placement> assignment, Placement value) {
083        if (!isHard()) return false;
084        return ((MaxDaysFlexibleConstraintContext)getContext(assignment)).nrDays(value, null) > iMaxDays;
085    }
086    
087    @Override
088    public FlexibleConstraintContext createAssignmentContext(Assignment<Lecture, Placement> assignment) {
089        return new MaxDaysFlexibleConstraintContext(assignment);
090    }
091    
092    public class MaxDaysFlexibleConstraintContext extends FlexibleConstraintContext {
093        private Map<BitSet, Set<Lecture>[]> iWeekDayAssignments = null;
094        private Set<Lecture> iDayAssignments[] = null;
095        
096        public MaxDaysFlexibleConstraintContext(Assignment<Lecture, Placement> assignment) {
097            super();
098            for (BitSet week: getWeeks()) {
099                Set<Lecture>[] dayAssignments = getDayAssignments(week);            
100                for (Lecture variable: variables()) {
101                    Placement value = assignment.getValue(variable);
102                    if (value != null) {
103                        for (int i = 0; i < dayAssignments.length; i++)
104                            if (hasDay(week, i, value))
105                                dayAssignments[i].add(value.variable());
106                    }
107                }
108            }
109            
110            if (!isHard()) {
111                Criterion<Lecture, Placement> criterion = getModel().getCriterion(FlexibleConstraintCriterion.class);
112                if (criterion != null) {
113                    double pref = nrViolations(null, null);
114                    if (pref == 0)
115                        iLastPreference = -Math.abs(iPreference);
116                    else 
117                        iLastPreference = Math.abs(iPreference) * pref;
118                    criterion.inc(assignment, iLastPreference);  
119                }
120            }
121        }
122        
123        protected boolean hasDay(BitSet week, int dayOfWeek, Placement value) {
124            if (value == null || value.getTimeLocation() == null) return false;
125            if (week != null && !value.getTimeLocation().getWeekCode().intersects(week)) return false;
126            return (value.getTimeLocation().getDayCode() & Constants.DAY_CODES[dayOfWeek]) != 0;
127        }
128        
129        @SuppressWarnings("unchecked")
130        protected Set<Lecture>[] getDayAssignments(BitSet week) {
131            if (week == null) {
132                if (iDayAssignments == null) {
133                    iDayAssignments = new Set[Constants.NR_DAYS];
134                    for (int i = 0; i < iDayAssignments.length; i++)
135                        iDayAssignments[i] = new HashSet<Lecture>();
136                }
137                return iDayAssignments;
138            } else {
139                if (iWeekDayAssignments == null)
140                    iWeekDayAssignments = new HashMap<BitSet, Set<Lecture>[]>();
141                Set<Lecture>[] dayAssignments = iWeekDayAssignments.get(week);
142                if (dayAssignments == null) {
143                    dayAssignments = new Set[Constants.NR_DAYS];
144                    for (int i = 0; i < dayAssignments.length; i++)
145                        dayAssignments[i] = new HashSet<Lecture>();
146                    iWeekDayAssignments.put(week, dayAssignments);
147                }
148                return dayAssignments;
149            }
150        }
151
152        @Override
153        public void assigned(Assignment<Lecture, Placement> assignment, Placement value) {
154            for (BitSet week: getWeeks()) {
155                Set<Lecture>[] dayAssignments = getDayAssignments(week);
156                for (int i = 0; i < dayAssignments.length; i++)
157                    if (hasDay(week, i, value))
158                        dayAssignments[i].add(value.variable());
159            }
160            updateCriterion(assignment);
161        }
162        
163        @Override
164        public void unassigned(Assignment<Lecture, Placement> assignment, Placement value) {
165            for (BitSet week: getWeeks()) {
166                Set<Lecture>[] dayAssignments = getDayAssignments(week);
167                for (int i = 0; i < dayAssignments.length; i++)
168                    if (hasDay(week, i, value))
169                        dayAssignments[i].remove(value.variable());
170            }
171            updateCriterion(assignment);
172        }
173        
174        public int nrDays(BitSet week, Placement value, Set<Placement> conflicts) {
175            Set<Lecture>[] dayAssignments = getDayAssignments(week);
176            int ret = 0;
177            for (int i = 0; i < dayAssignments.length; i++) {
178                int cnt = dayAssignments[i].size();
179                if (value != null) {
180                    if (hasDay(week, i, value)) cnt ++;
181                    if (dayAssignments[i].contains(value.variable())) cnt --; 
182                }
183                if (conflicts != null) {
184                    for (Placement conflict: conflicts) {
185                        if (value != null && conflict.variable().equals(value.variable())) continue;
186                        if (dayAssignments[i].contains(conflict.variable())) cnt --;
187                    }
188                }
189                if (cnt > 0) ret++;
190            }
191            return ret;
192        }
193        
194        public int nrDays(Placement value, Set<Placement> conflicts) {
195            int ret = 0; 
196            for (BitSet week: getWeeks()) {
197                int days = nrDays(week, value, conflicts);
198                if (days > ret) ret = days;
199            }
200            return ret;
201        }
202        
203        public Set<Lecture> candidates(Placement value, Set<Placement> conflicts) {
204            for (BitSet week: getWeeks()) {
205                Set<Lecture>[] dayAssignments = getDayAssignments(week);
206                int bestCnt = 0;
207                int nrDays = 0;
208                List<Integer> bestWeeks = new ArrayList<Integer>();
209                for (int i = 0; i < dayAssignments.length; i++) {
210                    if (hasDay(week, i, value)) {
211                        nrDays++;
212                        continue;
213                    }
214                    int cnt = dayAssignments[i].size();
215                    if (dayAssignments[i].contains(value.variable())) cnt --;
216                    for (Placement conflict: conflicts) {
217                        if (conflict.variable().equals(value.variable())) continue;
218                        if (dayAssignments[i].contains(conflict.variable())) cnt --;
219                    }
220                    if (cnt <= 0) continue;
221                    nrDays ++;
222                    if (bestWeeks.isEmpty() || bestCnt > cnt) {
223                        bestWeeks.clear(); bestWeeks.add(i); bestCnt = cnt;
224                    } else if (bestCnt == cnt) {
225                        bestWeeks.add(i);
226                    }
227                }
228                if (!bestWeeks.isEmpty() && nrDays > iMaxDays) return dayAssignments[ToolBox.random(bestWeeks)];
229            }
230            return null;
231        }
232        
233        public int nrViolations(BitSet week, HashMap<Lecture, Placement> assignments, Set<Placement> conflicts) {
234            Set<Lecture>[] dayAssignments = getDayAssignments(week);
235            int days = 0;
236            for (int i = 0; i < dayAssignments.length; i++) {
237                int cnt = dayAssignments[i].size();
238                if (assignments != null) {
239                    for (Map.Entry<Lecture, Placement> entry: assignments.entrySet()) {
240                        Placement assignment = entry.getValue();
241                        if (assignment != null && hasDay(week, i, assignment)) cnt ++;
242                    }
243                }
244                if (conflicts != null)
245                    for (Placement conflict: conflicts) {
246                        if (assignments != null && assignments.containsKey(conflict.variable())) continue;
247                        if (dayAssignments[i].contains(conflict.variable())) cnt --;
248                    }
249                if (cnt > 0) days ++;
250            }
251            return (days <= iMaxDays ? 0 : days - iMaxDays);
252        }
253        
254        public int nrViolations(HashMap<Lecture, Placement> assignments, Set<Placement> conflicts) {
255            int ret = 0; 
256            for (BitSet week: getWeeks()) {
257                ret += nrViolations(week, assignments, conflicts);
258            }
259            return ret;
260        }
261    }
262}