001package org.cpsolver.studentsct.heuristics.selection;
002
003import org.cpsolver.ifs.assignment.Assignment;
004import org.cpsolver.ifs.model.Neighbour;
005import org.cpsolver.ifs.solution.Solution;
006import org.cpsolver.ifs.solver.Solver;
007import org.cpsolver.ifs.util.DataProperties;
008import org.cpsolver.ifs.util.Progress;
009import org.cpsolver.studentsct.heuristics.studentord.StudentChoiceOrder;
010import org.cpsolver.studentsct.model.CourseRequest;
011import org.cpsolver.studentsct.model.Enrollment;
012import org.cpsolver.studentsct.model.Request;
013import org.cpsolver.studentsct.model.Student;
014import org.cpsolver.studentsct.model.Request.RequestPriority;
015
016/**
017 * This selection is very much like {@link BranchBoundSelection}, but only critical
018 * course requests are assigned (see {@link CourseRequest#isCritical()}.
019 * Students that do not have any unassigned critical courses are skipped.
020 * 
021 * <br>
022 * <br>
023 * Parameters: <br>
024 * <table border='1'><caption>Related Solver Parameters</caption>
025 * <tr>
026 * <th>Parameter</th>
027 * <th>Type</th>
028 * <th>Comment</th>
029 * </tr>
030 * <tr>
031 * <td>Neighbour.CriticalCoursesBranchAndBoundTimeout</td>
032 * <td>{@link Integer}</td>
033 * <td>Timeout for each neighbour selection (in milliseconds).</td>
034 * </tr>
035 * <tr>
036 * <td>Neighbour.BranchAndBoundMinimizePenalty</td>
037 * <td>{@link Boolean}</td>
038 * <td>If true, section penalties (instead of section values) are minimized:
039 * overall penalty is minimized together with the maximization of the number of
040 * assigned requests and minimization of distance conflicts -- this variant is
041 * to better mimic the case when students can choose their sections (section
042 * times).</td>
043 * </tr>
044 * </table>
045 * <br>
046 * <br>
047 * 
048 * @author  Tomáš Müller
049 * @version StudentSct 1.3 (Student Sectioning)<br>
050 *          Copyright (C) 2007 - 2014 Tomáš Müller<br>
051 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
052 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
053 * <br>
054 *          This library is free software; you can redistribute it and/or modify
055 *          it under the terms of the GNU Lesser General Public License as
056 *          published by the Free Software Foundation; either version 3 of the
057 *          License, or (at your option) any later version. <br>
058 * <br>
059 *          This library is distributed in the hope that it will be useful, but
060 *          WITHOUT ANY WARRANTY; without even the implied warranty of
061 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
062 *          Lesser General Public License for more details. <br>
063 * <br>
064 *          You should have received a copy of the GNU Lesser General Public
065 *          License along with this library; if not see
066 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
067 */
068public class CriticalCoursesBranchAndBoundSelection extends BranchBoundSelection {
069    protected boolean iMPP = false;
070    private RequestPriority iPriority;
071    
072    public CriticalCoursesBranchAndBoundSelection(DataProperties properties, RequestPriority priority) {
073        super(properties);
074        iMPP = properties.getPropertyBoolean("General.MPP", false);
075        iTimeout = properties.getPropertyInt("Neighbour.CriticalCoursesBranchAndBoundTimeout", 10000);
076        iPriority = priority;
077        if (iOrder instanceof StudentChoiceOrder) {
078            ((StudentChoiceOrder)iOrder).setCriticalOnly(true);
079            ((StudentChoiceOrder)iOrder).setRequestPriority(iPriority);
080        }
081    }
082    
083    public CriticalCoursesBranchAndBoundSelection(DataProperties properties) {
084        this(properties, RequestPriority.Critical);
085    }
086    
087    @Override
088    public void init(Solver<Request, Enrollment> solver) {
089        init(solver, iPriority.name() + " Courses B&B" + (iFilter == null ? "" : " (" + iFilter.getName().toLowerCase() + " students)") + "...");
090    }
091    
092    @Override
093    public Neighbour<Request, Enrollment> selectNeighbour(Solution<Request, Enrollment> solution) {
094        Student student = null;
095        while ((student = nextStudent()) != null) {
096            Progress.getInstance(solution.getModel()).incProgress();
097            if (student.hasUnassignedCritical(solution.getAssignment(), iPriority)) {
098                // only consider students that have some unassigned critical course requests
099                Neighbour<Request, Enrollment> neighbour = getSelection(solution.getAssignment(), student).select();
100                if (neighbour != null) return neighbour;
101            }
102        }
103        return null;
104    }
105    
106    @Override
107    public Selection getSelection(Assignment<Request, Enrollment> assignment, Student student) {
108        return new CriticalCoursesSelection(student, assignment);
109    }
110    
111    public class CriticalCoursesSelection extends Selection {
112        
113        public CriticalCoursesSelection(Student student, Assignment<Request, Enrollment> assignment) {
114            super(student, assignment);
115        }
116        
117        public boolean isCritical(int idx) {
118            for (int i = idx; i < iStudent.getRequests().size(); i++) {
119                Request r = iStudent.getRequests().get(i);
120                if (!r.isAlternative() && iPriority.isCritical(r)) return true;
121            }
122            return false;
123        }
124        
125        @Override
126        public void backTrack(int idx) {
127            if (!isCritical(idx)) {
128                if (iMinimizePenalty) {
129                    if (getBestAssignment() == null || (getNrAssigned() > getBestNrAssigned() || (getNrAssigned() == getBestNrAssigned() && getPenalty() < getBestValue())))
130                        saveBest();
131                } else {
132                    if (getBestAssignment() == null || getValue() < getBestValue())
133                        saveBest();
134                }
135                return;
136            }
137            if (idx < iAssignment.length && !iPriority.isCritical(iStudent.getRequests().get(idx)) && (!iMPP || iStudent.getRequests().get(idx).getInitialAssignment() == null)) {
138                // not done yet && not critical && not initial >> leave unassigned
139                backTrack(idx + 1);
140            } else {
141                super.backTrack(idx);
142            }
143        }
144    }
145}