001package org.cpsolver.exam.criteria;
002
003import java.util.Collection;
004import java.util.Map;
005import java.util.Set;
006
007import org.cpsolver.exam.model.Exam;
008import org.cpsolver.exam.model.ExamModel;
009import org.cpsolver.exam.model.ExamPeriod;
010import org.cpsolver.exam.model.ExamPlacement;
011import org.cpsolver.exam.model.ExamStudent;
012import org.cpsolver.ifs.assignment.Assignment;
013import org.cpsolver.ifs.util.DataProperties;
014
015
016/**
017 * Number of back-to-back student conflicts. I.e., number of cases when
018 * an exam is attended by a student that attends some other exam at
019 * the previous {@link ExamPeriod#prev()} or following
020 * {@link ExamPeriod#next()} period. If
021 * {@link StudentBackToBackConflicts#isDayBreakBackToBack()} is false, back-to-back conflicts
022 * are only considered between consecutive periods that are of the same day.
023 * <br><br>
024 * Back-to-back student conflict weight can be set by problem property
025 * Exams.BackToBackConflictWeight, or in the input xml file,
026 * property backToBackConflictWeight.
027 * 
028 * 
029 * <br>
030 * 
031 * @version ExamTT 1.3 (Examination Timetabling)<br>
032 *          Copyright (C) 2008 - 2014 Tomáš Müller<br>
033 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
034 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
035 * <br>
036 *          This library is free software; you can redistribute it and/or modify
037 *          it under the terms of the GNU Lesser General Public License as
038 *          published by the Free Software Foundation; either version 3 of the
039 *          License, or (at your option) any later version. <br>
040 * <br>
041 *          This library is distributed in the hope that it will be useful, but
042 *          WITHOUT ANY WARRANTY; without even the implied warranty of
043 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
044 *          Lesser General Public License for more details. <br>
045 * <br>
046 *          You should have received a copy of the GNU Lesser General Public
047 *          License along with this library; if not see
048 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
049 */
050public class StudentBackToBackConflicts extends ExamCriterion {
051    private boolean iDayBreakBackToBack = false;
052    
053    @Override
054    public void configure(DataProperties properties) {   
055        super.configure(properties);
056        iDayBreakBackToBack = properties.getPropertyBoolean("Exams.IsDayBreakBackToBack", iDayBreakBackToBack);
057    }
058        
059    @Override
060    public String getWeightName() {
061        return "Exams.BackToBackConflictWeight";
062    }
063    
064    @Override
065    public String getXmlWeightName() {
066        return "backToBackConflictWeight";
067    }
068    
069    @Override
070    public double getWeightDefault(DataProperties config) {
071        return 10.0;
072    }
073
074    /**
075     * True when back-to-back student conflict is to be encountered when a
076     * student is enrolled into an exam that is on the last period of one day
077     * and another exam that is on the first period of the consecutive day. It
078     * can be set by problem property Exams.IsDayBreakBackToBack, or in the
079     * input xml file, property isDayBreakBackToBack)
080     * @return true if last exam on one day is back-to-back to the first exam of the following day
081     */
082    public boolean isDayBreakBackToBack() {
083        return iDayBreakBackToBack;
084    }
085    
086    /**
087     * True when back-to-back student conflict is to be encountered when a
088     * student is enrolled into an exam that is on the last period of one day
089     * and another exam that is on the first period of the consecutive day. It
090     * can be set by problem property Exams.IsDayBreakBackToBack, or in the
091     * input xml file, property isDayBreakBackToBack)
092     * @param dayBreakBackToBack true if last exam on one day is back-to-back to the first exam of the following day
093     * 
094     */
095    public void setDayBreakBackToBack(boolean dayBreakBackToBack) {
096        iDayBreakBackToBack = dayBreakBackToBack;
097    }
098    
099    @Override
100    public void getXmlParameters(Map<String, String> params) {
101        params.put(getXmlWeightName(), String.valueOf(getWeight()));
102        params.put("isDayBreakBackToBack", isDayBreakBackToBack() ? "true" : "false");
103    }
104    
105    @Override
106    public void setXmlParameters(Map<String, String> params) {
107        try {
108            setWeight(Double.valueOf(params.get(getXmlWeightName())));
109        } catch (NumberFormatException e) {} catch (NullPointerException e) {}
110        try {
111            setDayBreakBackToBack("true".equals(params.get("isDayBreakBackToBack")));
112        } catch (NumberFormatException e) {} catch (NullPointerException e) {}
113    }
114    
115    @Override
116    public double getValue(Assignment<Exam, ExamPlacement> assignment, ExamPlacement value, Set<ExamPlacement> conflicts) {
117        Exam exam = value.variable();
118        int penalty = 0;
119        ExamPeriod period = value.getPeriod();
120        Map<ExamStudent, Set<Exam>> prev = (period.prev() != null && (isDayBreakBackToBack() || period.prev().getDay() == period.getDay()) ? ((ExamModel)getModel()).getStudentsOfPeriod(assignment, period.prev()) : null);
121        Map<ExamStudent, Set<Exam>> next = (period.next() != null && (isDayBreakBackToBack() || period.next().getDay() == period.getDay()) ? ((ExamModel)getModel()).getStudentsOfPeriod(assignment, period.next()) : null);
122        for (ExamStudent s : exam.getStudents()) {
123            if (prev != null) {
124                Set<Exam> exams = prev.get(s);
125                if (exams != null) {
126                    int nrExams = exams.size() + (exams.contains(exam) ? -1 : 0);
127                    penalty += nrExams;
128                }
129            }
130            if (next != null) {
131                Set<Exam> exams = next.get(s);
132                if (exams != null) {
133                    int nrExams = exams.size() + (exams.contains(exam) ? -1 : 0);
134                    penalty += nrExams;
135                }
136            }
137        }
138        /*
139        for (ExamStudent s : exam.getStudents()) {
140            if (period.prev() != null) {
141                if (isDayBreakBackToBack() || period.prev().getDay() == period.getDay()) {
142                    Set<Exam> exams = s.getExams(assignment, period.prev());
143                    int nrExams = exams.size() + (exams.contains(exam) ? -1 : 0);
144                    penalty += nrExams;
145                }
146            }
147            if (period.next() != null) {
148                if (isDayBreakBackToBack() || period.next().getDay() == period.getDay()) {
149                    Set<Exam> exams = s.getExams(assignment, period.next());
150                    int nrExams = exams.size() + (exams.contains(exam) ? -1 : 0);
151                    penalty += nrExams;
152                }
153            }
154        }
155        */
156        return penalty;
157    }
158    
159    @Override
160    public double getValue(Assignment<Exam, ExamPlacement> assignment, Collection<Exam> variables) {
161        return super.getValue(assignment, variables) / 2.0;
162    }
163    
164    @Override
165    public String getName() {
166        return "Back-To-Back Conflicts";
167    }
168    
169    @Override
170    public void getInfo(Assignment<Exam, ExamPlacement> assignment, Map<String, String> info) {
171        if (getValue(assignment) != 0.0)
172            info.put(getName(), sDoubleFormat.format(getValue(assignment)));
173    }
174    
175    @Override
176    public String toString(Assignment<Exam, ExamPlacement> assignment) {
177        return "BTB:" + sDoubleFormat.format(getValue(assignment));
178    }
179}