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' summary='Related Solver Parameters'>
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 * @version StudentSct 1.3 (Student Sectioning)<br>
049 *          Copyright (C) 2007 - 2014 Tomáš Müller<br>
050 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
051 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
052 * <br>
053 *          This library is free software; you can redistribute it and/or modify
054 *          it under the terms of the GNU Lesser General Public License as
055 *          published by the Free Software Foundation; either version 3 of the
056 *          License, or (at your option) any later version. <br>
057 * <br>
058 *          This library is distributed in the hope that it will be useful, but
059 *          WITHOUT ANY WARRANTY; without even the implied warranty of
060 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
061 *          Lesser General Public License for more details. <br>
062 * <br>
063 *          You should have received a copy of the GNU Lesser General Public
064 *          License along with this library; if not see
065 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
066 */
067public class CriticalCoursesBranchAndBoundSelection extends BranchBoundSelection {
068    protected boolean iMPP = false;
069    private RequestPriority iPriority;
070    
071    public CriticalCoursesBranchAndBoundSelection(DataProperties properties, RequestPriority priority) {
072        super(properties);
073        iMPP = properties.getPropertyBoolean("General.MPP", false);
074        iTimeout = properties.getPropertyInt("Neighbour.CriticalCoursesBranchAndBoundTimeout", 10000);
075        iPriority = priority;
076        if (iOrder instanceof StudentChoiceOrder) {
077            ((StudentChoiceOrder)iOrder).setCriticalOnly(true);
078            ((StudentChoiceOrder)iOrder).setRequestPriority(iPriority);
079        }
080    }
081    
082    public CriticalCoursesBranchAndBoundSelection(DataProperties properties) {
083        this(properties, RequestPriority.Critical);
084    }
085    
086    @Override
087    public void init(Solver<Request, Enrollment> solver) {
088        init(solver, iPriority.name() + " Courses B&B" + (iFilter == null ? "" : " (" + iFilter.getName().toLowerCase() + " students)") + "...");
089    }
090    
091    @Override
092    public Neighbour<Request, Enrollment> selectNeighbour(Solution<Request, Enrollment> solution) {
093        Student student = null;
094        while ((student = nextStudent()) != null) {
095            Progress.getInstance(solution.getModel()).incProgress();
096            if (student.hasUnassignedCritical(solution.getAssignment(), iPriority)) {
097                // only consider students that have some unassigned critical course requests
098                Neighbour<Request, Enrollment> neighbour = getSelection(solution.getAssignment(), student).select();
099                if (neighbour != null) return neighbour;
100            }
101        }
102        return null;
103    }
104    
105    @Override
106    public Selection getSelection(Assignment<Request, Enrollment> assignment, Student student) {
107        return new CriticalCoursesSelection(student, assignment);
108    }
109    
110    public class CriticalCoursesSelection extends Selection {
111        
112        public CriticalCoursesSelection(Student student, Assignment<Request, Enrollment> assignment) {
113            super(student, assignment);
114        }
115        
116        public boolean isCritical(int idx) {
117            for (int i = idx; i < iStudent.getRequests().size(); i++) {
118                Request r = iStudent.getRequests().get(i);
119                if (!r.isAlternative() && iPriority.isCritical(r)) return true;
120            }
121            return false;
122        }
123        
124        @Override
125        public void backTrack(int idx) {
126            if (!isCritical(idx)) {
127                if (iMinimizePenalty) {
128                    if (getBestAssignment() == null || (getNrAssigned() > getBestNrAssigned() || (getNrAssigned() == getBestNrAssigned() && getPenalty() < getBestValue())))
129                        saveBest();
130                } else {
131                    if (getBestAssignment() == null || getValue() < getBestValue())
132                        saveBest();
133                }
134                return;
135            }
136            if (idx < iAssignment.length && !iPriority.isCritical(iStudent.getRequests().get(idx)) && (!iMPP || iStudent.getRequests().get(idx).getInitialAssignment() == null)) {
137                // not done yet && not critical && not initial >> leave unassigned
138                backTrack(idx + 1);
139            } else {
140                super.backTrack(idx);
141            }
142        }
143    }
144}