001package net.sf.cpsolver.studentsct.heuristics.studentord;
002
003import java.util.ArrayList;
004import java.util.Collections;
005import java.util.Comparator;
006import java.util.HashSet;
007import java.util.HashMap;
008import java.util.List;
009
010import net.sf.cpsolver.ifs.util.DataProperties;
011import net.sf.cpsolver.studentsct.model.Config;
012import net.sf.cpsolver.studentsct.model.Course;
013import net.sf.cpsolver.studentsct.model.CourseRequest;
014import net.sf.cpsolver.studentsct.model.Request;
015import net.sf.cpsolver.studentsct.model.Section;
016import net.sf.cpsolver.studentsct.model.Student;
017import net.sf.cpsolver.studentsct.model.Subpart;
018
019/**
020 * Return the given set of students in an order of average number of choices of
021 * each student (students with more choices first).
022 * 
023 * @version StudentSct 1.2 (Student Sectioning)<br>
024 *          Copyright (C) 2007 - 2010 Tomáš Müller<br>
025 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
026 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
027 * <br>
028 *          This library is free software; you can redistribute it and/or modify
029 *          it under the terms of the GNU Lesser General Public License as
030 *          published by the Free Software Foundation; either version 3 of the
031 *          License, or (at your option) any later version. <br>
032 * <br>
033 *          This library is distributed in the hope that it will be useful, but
034 *          WITHOUT ANY WARRANTY; without even the implied warranty of
035 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
036 *          Lesser General Public License for more details. <br>
037 * <br>
038 *          You should have received a copy of the GNU Lesser General Public
039 *          License along with this library; if not see
040 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
041 */
042public class StudentChoiceOrder implements StudentOrder, Comparator<Student> {
043    private boolean iReverse = false;
044    private boolean iFast = true;
045    private HashMap<Config, Integer> iCache = new HashMap<Config, Integer>();
046
047    public StudentChoiceOrder(DataProperties config) {
048        iReverse = config.getPropertyBoolean("StudentChoiceOrder.Reverse", iReverse);
049        iFast = config.getPropertyBoolean("StudentChoiceOrder.Fast", iFast);
050    }
051
052    /** Is order reversed */
053    public boolean isReverse() {
054        return iReverse;
055    }
056
057    /** Set reverse order */
058    public void setReverse(boolean reverse) {
059        iReverse = reverse;
060    }
061
062    /** Order the given list of students */
063    @Override
064    public List<Student> order(List<Student> students) {
065        List<Student> ret = new ArrayList<Student>(students);
066        Collections.sort(ret, this);
067        return ret;
068    }
069
070    @Override
071    public int compare(Student s1, Student s2) {
072        try {
073            int cmp = -Double.compare(avgNrChoices(s1), avgNrChoices(s2));
074            if (cmp != 0)
075                return (iReverse ? -1 : 1) * cmp;
076        } catch (Exception e) {
077            e.printStackTrace();
078        }
079        return (iReverse ? -1 : 1) * Double.compare(s1.getId(), s2.getId());
080    }
081
082    private int nrChoices(Config config, int idx, HashSet<Section> sections) {
083        if (iFast) {
084            int nrChoices = 1;
085            for (Subpart subpart: config.getSubparts()) {
086                if (subpart.getChildren().isEmpty())
087                    nrChoices *= subpart.getSections().size();
088            }
089            return nrChoices;
090        }
091        if (config.getSubparts().size() == idx) {
092            return 1;
093        } else {
094            Subpart subpart = config.getSubparts().get(idx);
095            int choicesThisSubpart = 0;
096            for (Section section : subpart.getSections()) {
097                if (section.getParent() != null && !sections.contains(section.getParent()))
098                    continue;
099                if (section.isOverlapping(sections))
100                    continue;
101                sections.add(section);
102                choicesThisSubpart += nrChoices(config, idx + 1, sections);
103                sections.remove(section);
104            }
105            return choicesThisSubpart;
106        }
107    }
108    
109    /** Average number of choices for each student */
110    public double avgNrChoices(Student student) {
111        int nrRequests = 0;
112        int nrChoices = 0;
113        for (Request request : student.getRequests()) {
114            if (request instanceof CourseRequest) {
115                CourseRequest cr = (CourseRequest) request;
116                for (Course course : cr.getCourses()) {
117                    for (Config config : course.getOffering().getConfigs()) {
118                        Integer nrChoicesThisCfg = iCache.get(config);
119                        if (nrChoicesThisCfg == null) {
120                            nrChoicesThisCfg = new Integer(nrChoices(config, 0, new HashSet<Section>()));
121                            iCache.put(config, nrChoicesThisCfg);
122                        }
123                        nrChoices += nrChoicesThisCfg.intValue();
124                    }
125                }
126                nrRequests++;
127            }
128        }
129        return (nrRequests == 0 ? 0.0 : ((double) nrChoices) / nrRequests);
130    }
131}