    001package org.cpsolver.coursett.model;
    002
    003import org.cpsolver.ifs.assignment.Assignment;
    004import org.cpsolver.ifs.assignment.DefaultSingleAssignment;
    005import org.cpsolver.ifs.model.Constraint;
    006import org.cpsolver.ifs.model.ModelListener;
    007import org.cpsolver.ifs.solver.Solver;
    008
    009/**
    010 * On fly student sectioning. <br>
    011 * <br>
    012 * In this mode, students are resectioned after each iteration, but only between
    013 * classes that are affected by the iteration. This slows down the solver, but
    014 * it can dramatically improve results in the case when there is more stress put
    015 * on student conflicts (e.g., Woebegon College example).
    016 *
    017 * <br>
    018 * <br>
    019 * Parameters:
    020 * <table border='1'><caption>Related Solver Parameters</caption>
    021 * <tr>
    022 * <th>Parameter</th>
    023 * <th>Type</th>
    024 * <th>Comment</th>
    025 * </tr>
    026 * <tr>
    027 * <td>OnFlySectioning.Enabled</td>
    028 * <td>{@link Boolean}</td>
    029 * <td>Enable on fly sectioning (if enabled, students will be resectioned after
    030 * each iteration)</td>
    031 * </tr>
    032 * <tr>
    033 * <td>OnFlySectioning.Recursive</td>
    034 * <td>{@link Boolean}</td>
    035 * <td>Recursively resection lectures affected by a student swap</td>
    036 * </tr>
    037 * <tr>
    038 * <td>OnFlySectioning.ConfigAsWell</td>
    039 * <td>{@link Boolean}</td>
    040 * <td>Resection students between configurations as well</td>
    041 * </tr>
    042 * </table>
    043 *
    044 * @author  Tomáš Müller
    045 * @version CourseTT 1.3 (University Course Timetabling)<br>
    046 *          Copyright (C) 2006 - 2014 Tomáš Müller<br>
    047 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    048 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    049 * <br>
    050 *          This library is free software; you can redistribute it and/or modify
    051 *          it under the terms of the GNU Lesser General Public License as
    052 *          published by the Free Software Foundation; either version 3 of the
    053 *          License, or (at your option) any later version. <br>
    054 * <br>
    055 *          This library is distributed in the hope that it will be useful, but
    056 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    057 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    058 *          Lesser General Public License for more details. <br>
    059 * <br>
    060 *          You should have received a copy of the GNU Lesser General Public
    061 *          License along with this library; if not see
    062 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    063 */
    064
    065public class OnFlySectioning implements ModelListener<Lecture, Placement> {
    066    private TimetableModel iModel;
    067    private boolean iRecursive = true;
    068    private boolean iConfigAsWell = false;
    069
    070    /**
    071     * Constructor
    072     *
    073     * @param model
    074     *            timetabling model
    075     */
    076    public OnFlySectioning(TimetableModel model) {
    077        iModel = model;
    078    }
    079
    080    @Override
    081    public void variableAdded(Lecture variable) {
    082    }
    083
    084    @Override
    085    public void variableRemoved(Lecture variable) {
    086    }
    087
    088    @Override
    089    public void constraintAdded(Constraint<Lecture, Placement> constraint) {
    090    }
    091
    092    @Override
    093    public void constraintRemoved(Constraint<Lecture, Placement> constraint) {
    094    }
    095
    096    @Override
    097    public void beforeAssigned(Assignment<Lecture, Placement> assignment, long iteration, Placement value) {
    098    }
    099
    100    @Override
    101    public void beforeUnassigned(Assignment<Lecture, Placement> assignment, long iteration, Placement value) {
    102    }
    103
    104    /**
    105     * {@link FinalSectioning#resection(Assignment, Lecture, boolean, boolean)} is called
    106     * when given iteration number is greater than zero.
    107     */
    108    @Override
    109    public void afterAssigned(Assignment<Lecture, Placement> assignment, long iteration, Placement value) {
    110        if (iteration > 0 && assignment instanceof DefaultSingleAssignment)
    111            iModel.getStudentSectioning().resection(assignment, value.variable(), iRecursive, iConfigAsWell);
    112    }
    113
    114    @Override
    115    public void afterUnassigned(Assignment<Lecture, Placement> assignment, long iteration, Placement value) {
    116    }
    117
    118    /**
    119     * Initialization
    120     */
    121    @Override
    122    public boolean init(Solver<Lecture, Placement> solver) {
    123        iRecursive = solver.getProperties().getPropertyBoolean("OnFlySectioning.Recursive", true);
    124        iConfigAsWell = solver.getProperties().getPropertyBoolean("OnFlySectioning.ConfigAsWell", false);
    125        return true;
    126    }
    127}