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 * @author  Tomáš Müller
029 * @version CourseTT 1.3 (University Course Timetabling)<br>
030 *          Copyright (C) 2006 - 2014 Tomáš Müller<br>
031 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
032 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
033 * <br>
034 *          This library is free software; you can redistribute it and/or modify
035 *          it under the terms of the GNU Lesser General Public License as
036 *          published by the Free Software Foundation; either version 3 of the
037 *          License, or (at your option) any later version. <br>
038 * <br>
039 *          This library is distributed in the hope that it will be useful, but
040 *          WITHOUT ANY WARRANTY; without even the implied warranty of
041 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
042 *          Lesser General Public License for more details. <br>
043 * <br>
044 *          You should have received a copy of the GNU Lesser General Public
045 *          License along with this library; if not see
046 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
047 */
048public class StudentMinimizeScheduleHoles extends StudentConflict {
049    
050    /**
051     * Time distance between two placements in hours. The classes must be on the same days and weeks,
052     * but not overlapping in time. If the two classes are taught on multiple days during the week, the
053     * distance is also multiplied by the number of shared days of week.
054     * @param p1 first placement
055     * @param p2 second placement
056     * @return distance between the two classes in hours
057     */
058    public static double btbDistance(Placement p1, Placement p2) {
059        if (p1 == null || p2 == null) return 0.0;
060        return btbDistance(p1.getTimeLocation(), p2.getTimeLocation());
061    }
062    
063    private static double btbDistance(TimeLocation t1, TimeLocation t2) {
064        if (!t1.shareDays(t2) || !t1.shareWeeks(t2) || t1.shareHours(t2)) return 0.0;
065        int s1 = t1.getStartSlot(), e1 = s1 + t1.getLength();
066        int s2 = t2.getStartSlot(), e2 = s2 + t2.getLength();
067        if (e1 < s2) {
068            return t1.nrSharedDays(t2) * (s2 - e1) / 12.0;
069        } else if (e2 < s1) {
070            return t1.nrSharedDays(t2) * (s1 - e2) / 12.0;
071        }
072        return 0.0;        
073    }
074    
075    @Override
076    public boolean inConflict(Placement p1, Placement p2) {
077        return btbDistance(p1, p2) > 0.0;
078    }
079    
080    @Override
081    protected double jointEnrollment(JenrlConstraint jenrl, Placement p1, Placement p2) {
082        return btbDistance(p1, p2) * jenrl.jenrl();
083    }
084    
085    @Override
086    protected double jointEnrollment(JenrlConstraint jenrl) {
087        double max = 0;
088        for (TimeLocation t1: jenrl.first().timeLocations())
089            for (TimeLocation t2: jenrl.second().timeLocations()) {
090                double distance = btbDistance(t1, t2);
091                if (distance > max) max = distance;
092            }
093        return max;
094    }
095    
096    @Override
097    public boolean isApplicable(Lecture l1, Lecture l2) {
098        return l1 != null && l2 != null && !ignore(l1, l2) && applicable(l1, l2);
099    }
100    
101    @Override
102    public void incJenrl(Assignment<Lecture, Placement> assignment, JenrlConstraint jenrl, double studentWeight, Double conflictPriority, Student student) {
103        if (isApplicable(student, jenrl.first(), jenrl.second()))
104            inc(assignment, studentWeight * btbDistance(assignment.getValue(jenrl.first()), assignment.getValue(jenrl.second())));
105    }
106    
107    @Override
108    public double getWeightDefault(DataProperties config) {
109        return config.getPropertyDouble("Comparator.MinimizeStudentScheduleHolesWeight", 0.05 * config.getPropertyDouble("Comparator.StudentConflictWeight", 1.0));
110    }
111    
112    @Override
113    public String getPlacementSelectionWeightName() {
114        return "Placement.MinimizeStudentScheduleHolesWeight";
115    }
116
117    @Override
118    public void getInfo(Assignment<Lecture, Placement> assignment, Map<String, String> info) {
119        super.getInfo(assignment, info);
120        double total = 0;
121        for (JenrlConstraint jenrl: ((TimetableModel)getModel()).getJenrlConstraints()) {
122            if (!jenrl.isToBeIgnored())
123                total += jenrl.jenrl();
124        }
125        info.put("Student class distance", sDoubleFormat.format(60.0 * getValue(assignment) / total) + " minutes");
126    }
127    
128    @Override
129    public void getInfo(Assignment<Lecture, Placement> assignment, Map<String, String> info, Collection<Lecture> variables) {
130        super.getInfo(assignment, info, variables);
131        Set<JenrlConstraint> jenrls = new HashSet<JenrlConstraint>();
132        double distance = 0;
133        double total = 0;
134        for (Lecture lecture: variables) {
135            for (JenrlConstraint jenrl: lecture.jenrlConstraints())
136                if (jenrls.add(jenrl) && !jenrl.isToBeIgnored()) {
137                    distance += jenrl.jenrl() * btbDistance(assignment.getValue(jenrl.first()), assignment.getValue(jenrl.second()));
138                    total += jenrl.jenrl();
139                }
140        }
141        info.put("Student class distance", sDoubleFormat.format(60.0 * distance / total) + " minutes");
142    }
143
144}