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 * @author  Tomáš Müller
032 * @version ExamTT 1.3 (Examination Timetabling)<br>
033 *          Copyright (C) 2008 - 2014 Tomáš Müller<br>
034 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
035 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
036 * <br>
037 *          This library is free software; you can redistribute it and/or modify
038 *          it under the terms of the GNU Lesser General Public License as
039 *          published by the Free Software Foundation; either version 3 of the
040 *          License, or (at your option) any later version. <br>
041 * <br>
042 *          This library is distributed in the hope that it will be useful, but
043 *          WITHOUT ANY WARRANTY; without even the implied warranty of
044 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
045 *          Lesser General Public License for more details. <br>
046 * <br>
047 *          You should have received a copy of the GNU Lesser General Public
048 *          License along with this library; if not see
049 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
050 */
051public class StudentBackToBackConflicts extends ExamCriterion {
052    private boolean iDayBreakBackToBack = false;
053    
054    @Override
055    public void configure(DataProperties properties) {   
056        super.configure(properties);
057        iDayBreakBackToBack = properties.getPropertyBoolean("Exams.IsDayBreakBackToBack", iDayBreakBackToBack);
058    }
059        
060    @Override
061    public String getWeightName() {
062        return "Exams.BackToBackConflictWeight";
063    }
064    
065    @Override
066    public String getXmlWeightName() {
067        return "backToBackConflictWeight";
068    }
069    
070    @Override
071    public double getWeightDefault(DataProperties config) {
072        return 10.0;
073    }
074
075    /**
076     * True when back-to-back student conflict is to be encountered when a
077     * student is enrolled into an exam that is on the last period of one day
078     * and another exam that is on the first period of the consecutive day. It
079     * can be set by problem property Exams.IsDayBreakBackToBack, or in the
080     * input xml file, property isDayBreakBackToBack)
081     * @return true if last exam on one day is back-to-back to the first exam of the following day
082     */
083    public boolean isDayBreakBackToBack() {
084        return iDayBreakBackToBack;
085    }
086    
087    /**
088     * True when back-to-back student conflict is to be encountered when a
089     * student is enrolled into an exam that is on the last period of one day
090     * and another exam that is on the first period of the consecutive day. It
091     * can be set by problem property Exams.IsDayBreakBackToBack, or in the
092     * input xml file, property isDayBreakBackToBack)
093     * @param dayBreakBackToBack true if last exam on one day is back-to-back to the first exam of the following day
094     * 
095     */
096    public void setDayBreakBackToBack(boolean dayBreakBackToBack) {
097        iDayBreakBackToBack = dayBreakBackToBack;
098    }
099    
100    @Override
101    public void getXmlParameters(Map<String, String> params) {
102        params.put(getXmlWeightName(), String.valueOf(getWeight()));
103        params.put("isDayBreakBackToBack", isDayBreakBackToBack() ? "true" : "false");
104    }
105    
106    @Override
107    public void setXmlParameters(Map<String, String> params) {
108        try {
109            setWeight(Double.valueOf(params.get(getXmlWeightName())));
110        } catch (NumberFormatException e) {} catch (NullPointerException e) {}
111        try {
112            setDayBreakBackToBack("true".equals(params.get("isDayBreakBackToBack")));
113        } catch (NumberFormatException e) {} catch (NullPointerException e) {}
114    }
115    
116    @Override
117    public double getValue(Assignment<Exam, ExamPlacement> assignment, ExamPlacement value, Set<ExamPlacement> conflicts) {
118        Exam exam = value.variable();
119        int penalty = 0;
120        ExamPeriod period = value.getPeriod();
121        Map<ExamStudent, Set<Exam>> prev = (period.prev() != null && (isDayBreakBackToBack() || period.prev().getDay() == period.getDay()) ? ((ExamModel)getModel()).getStudentsOfPeriod(assignment, period.prev()) : null);
122        Map<ExamStudent, Set<Exam>> next = (period.next() != null && (isDayBreakBackToBack() || period.next().getDay() == period.getDay()) ? ((ExamModel)getModel()).getStudentsOfPeriod(assignment, period.next()) : null);
123        for (ExamStudent s : exam.getStudents()) {
124            if (prev != null) {
125                Set<Exam> exams = prev.get(s);
126                if (exams != null) {
127                    int nrExams = exams.size() + (exams.contains(exam) ? -1 : 0);
128                    penalty += nrExams;
129                }
130            }
131            if (next != null) {
132                Set<Exam> exams = next.get(s);
133                if (exams != null) {
134                    int nrExams = exams.size() + (exams.contains(exam) ? -1 : 0);
135                    penalty += nrExams;
136                }
137            }
138        }
139        /*
140        for (ExamStudent s : exam.getStudents()) {
141            if (period.prev() != null) {
142                if (isDayBreakBackToBack() || period.prev().getDay() == period.getDay()) {
143                    Set<Exam> exams = s.getExams(assignment, period.prev());
144                    int nrExams = exams.size() + (exams.contains(exam) ? -1 : 0);
145                    penalty += nrExams;
146                }
147            }
148            if (period.next() != null) {
149                if (isDayBreakBackToBack() || period.next().getDay() == period.getDay()) {
150                    Set<Exam> exams = s.getExams(assignment, period.next());
151                    int nrExams = exams.size() + (exams.contains(exam) ? -1 : 0);
152                    penalty += nrExams;
153                }
154            }
155        }
156        */
157        return penalty;
158    }
159    
160    @Override
161    public double getValue(Assignment<Exam, ExamPlacement> assignment, Collection<Exam> variables) {
162        return super.getValue(assignment, variables) / 2.0;
163    }
164    
165    @Override
166    public String getName() {
167        return "Back-To-Back Conflicts";
168    }
169    
170    @Override
171    public void getInfo(Assignment<Exam, ExamPlacement> assignment, Map<String, String> info) {
172        if (getValue(assignment) != 0.0)
173            info.put(getName(), sDoubleFormat.format(getValue(assignment)));
174    }
175    
176    @Override
177    public String toString(Assignment<Exam, ExamPlacement> assignment) {
178        return "BTB:" + sDoubleFormat.format(getValue(assignment));
179    }
180}