001package org.cpsolver.coursett.criteria.additional;
002
003import java.util.Collection;
004import java.util.HashSet;
005import java.util.Map;
006import java.util.Set;
007
008import org.cpsolver.coursett.constraint.JenrlConstraint;
009import org.cpsolver.coursett.criteria.StudentConflict;
010import org.cpsolver.coursett.model.Lecture;
011import org.cpsolver.coursett.model.Placement;
012import org.cpsolver.coursett.model.Student;
013import org.cpsolver.coursett.model.TimeLocation;
014import org.cpsolver.coursett.model.TimetableModel;
015import org.cpsolver.ifs.assignment.Assignment;
016import org.cpsolver.ifs.util.DataProperties;
017
018/**
019 * Naive, yet effective approach for minimizing holes in student schedule. This criterion
020 * is based on {@link StudentConflict} and it penalizes all cases where a student has
021 * two classes taught on the same day that are not back-to-back. The penalisation
022 * is based on the time distance between the two classes, computed in hours.
023 * These penalties are weighted by Comparator.MinimizeStudentScheduleHolesWeight,
024 * which defaults to 1/20 of the Comparator.StudentConflictWeight.
025 * 
026 * <br>
027 * 
028 * @version CourseTT 1.3 (University Course Timetabling)<br>
029 *          Copyright (C) 2006 - 2014 Tomáš Müller<br>
030 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
031 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
032 * <br>
033 *          This library is free software; you can redistribute it and/or modify
034 *          it under the terms of the GNU Lesser General Public License as
035 *          published by the Free Software Foundation; either version 3 of the
036 *          License, or (at your option) any later version. <br>
037 * <br>
038 *          This library is distributed in the hope that it will be useful, but
039 *          WITHOUT ANY WARRANTY; without even the implied warranty of
040 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
041 *          Lesser General Public License for more details. <br>
042 * <br>
043 *          You should have received a copy of the GNU Lesser General Public
044 *          License along with this library; if not see
045 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
046 */
047public class StudentMinimizeScheduleHoles extends StudentConflict {
048    
049    /**
050     * Time distance between two placements in hours. The classes must be on the same days and weeks,
051     * but not overlapping in time. If the two classes are taught on multiple days during the week, the
052     * distance is also multiplied by the number of shared days of week.
053     * @param p1 first placement
054     * @param p2 second placement
055     * @return distance between the two classes in hours
056     */
057    public static double btbDistance(Placement p1, Placement p2) {
058        if (p1 == null || p2 == null) return 0.0;
059        return btbDistance(p1.getTimeLocation(), p2.getTimeLocation());
060    }
061    
062    private static double btbDistance(TimeLocation t1, TimeLocation t2) {
063        if (!t1.shareDays(t2) || !t1.shareWeeks(t2) || t1.shareHours(t2)) return 0.0;
064        int s1 = t1.getStartSlot(), e1 = s1 + t1.getLength();
065        int s2 = t2.getStartSlot(), e2 = s2 + t2.getLength();
066        if (e1 < s2) {
067            return t1.nrSharedDays(t2) * (s2 - e1) / 12.0;
068        } else if (e2 < s1) {
069            return t1.nrSharedDays(t2) * (s1 - e2) / 12.0;
070        }
071        return 0.0;        
072    }
073    
074    @Override
075    public boolean inConflict(Placement p1, Placement p2) {
076        return btbDistance(p1, p2) > 0.0;
077    }
078    
079    @Override
080    protected double jointEnrollment(JenrlConstraint jenrl, Placement p1, Placement p2) {
081        return btbDistance(p1, p2) * jenrl.jenrl();
082    }
083    
084    @Override
085    protected double jointEnrollment(JenrlConstraint jenrl) {
086        double max = 0;
087        for (TimeLocation t1: jenrl.first().timeLocations())
088            for (TimeLocation t2: jenrl.second().timeLocations()) {
089                double distance = btbDistance(t1, t2);
090                if (distance > max) max = distance;
091            }
092        return max;
093    }
094    
095    @Override
096    public boolean isApplicable(Lecture l1, Lecture l2) {
097        return l1 != null && l2 != null && !ignore(l1, l2) && applicable(l1, l2);
098    }
099    
100    @Override
101    public void incJenrl(Assignment<Lecture, Placement> assignment, JenrlConstraint jenrl, double studentWeight, Double conflictPriority, Student student) {
102        if (isApplicable(student, jenrl.first(), jenrl.second()))
103            inc(assignment, studentWeight * btbDistance(assignment.getValue(jenrl.first()), assignment.getValue(jenrl.second())));
104    }
105    
106    @Override
107    public double getWeightDefault(DataProperties config) {
108        return config.getPropertyDouble("Comparator.MinimizeStudentScheduleHolesWeight", 0.05 * config.getPropertyDouble("Comparator.StudentConflictWeight", 1.0));
109    }
110    
111    @Override
112    public String getPlacementSelectionWeightName() {
113        return "Placement.MinimizeStudentScheduleHolesWeight";
114    }
115
116    @Override
117    public void getInfo(Assignment<Lecture, Placement> assignment, Map<String, String> info) {
118        super.getInfo(assignment, info);
119        double total = 0;
120        for (JenrlConstraint jenrl: ((TimetableModel)getModel()).getJenrlConstraints()) {
121            if (!jenrl.isToBeIgnored())
122                total += jenrl.jenrl();
123        }
124        info.put("Student class distance", sDoubleFormat.format(60.0 * getValue(assignment) / total) + " minutes");
125    }
126    
127    @Override
128    public void getInfo(Assignment<Lecture, Placement> assignment, Map<String, String> info, Collection<Lecture> variables) {
129        super.getInfo(assignment, info, variables);
130        Set<JenrlConstraint> jenrls = new HashSet<JenrlConstraint>();
131        double distance = 0;
132        double total = 0;
133        for (Lecture lecture: variables) {
134            for (JenrlConstraint jenrl: lecture.jenrlConstraints())
135                if (jenrls.add(jenrl) && !jenrl.isToBeIgnored()) {
136                    distance += jenrl.jenrl() * btbDistance(assignment.getValue(jenrl.first()), assignment.getValue(jenrl.second()));
137                    total += jenrl.jenrl();
138                }
139        }
140        info.put("Student class distance", sDoubleFormat.format(60.0 * distance / total) + " minutes");
141    }
142
143}