    001package net.sf.cpsolver.studentsct.heuristics.selection;
    002
    003import org.apache.log4j.Logger;
    004
    005import net.sf.cpsolver.ifs.model.Neighbour;
    006import net.sf.cpsolver.ifs.solution.Solution;
    007import net.sf.cpsolver.ifs.solver.Solver;
    008import net.sf.cpsolver.ifs.util.DataProperties;
    009import net.sf.cpsolver.ifs.util.Progress;
    010import net.sf.cpsolver.studentsct.heuristics.studentord.StudentOrder;
    011import net.sf.cpsolver.studentsct.heuristics.studentord.StudentRandomOrder;
    012import net.sf.cpsolver.studentsct.model.Enrollment;
    013import net.sf.cpsolver.studentsct.model.Request;
    014import net.sf.cpsolver.studentsct.model.Student;
    015
    016/**
    017 * Resection studends with empty schedule. An extension of
    018 * {@link BranchBoundSelection}, where only students that have no enrollments (
    019 * {@link Student#nrAssignedRequests()} is zero) are resectioned.
    020 *
    021 * <br>
    022 * <br>
    023 *
    024 * @version StudentSct 1.2 (Student Sectioning)<br>
    025 *          Copyright (C) 2007 - 2010 Tomáš Müller<br>
    026 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    027 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    028 * <br>
    029 *          This library is free software; you can redistribute it and/or modify
    030 *          it under the terms of the GNU Lesser General Public License as
    031 *          published by the Free Software Foundation; either version 3 of the
    032 *          License, or (at your option) any later version. <br>
    033 * <br>
    034 *          This library is distributed in the hope that it will be useful, but
    035 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    036 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    037 *          Lesser General Public License for more details. <br>
    038 * <br>
    039 *          You should have received a copy of the GNU Lesser General Public
    040 *          License along with this library; if not see
    041 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    042 */
    043
    044public class ResectionUnassignedStudentsSelection extends BranchBoundSelection {
    045    private static Logger sLog = Logger.getLogger(ResectionUnassignedStudentsSelection.class);
    046
    047    public ResectionUnassignedStudentsSelection(DataProperties properties) {
    048        super(properties);
    049        iOrder = new StudentRandomOrder(properties);
    050        if (properties.getProperty("Neighbour.ResectionUnassignedStudentsOrder") != null) {
    051            try {
    052                iOrder = (StudentOrder) Class.forName(
    053                        properties.getProperty("Neighbour.ResectionUnassignedStudentsOrder")).getConstructor(
    054                        new Class[] { DataProperties.class }).newInstance(new Object[] { properties });
    055            } catch (Exception e) {
    056                sLog.error("Unable to set student order, reason:" + e.getMessage(), e);
    057            }
    058        }
    059    }
    060
    061    @Override
    062    public void init(Solver<Request, Enrollment> solver) {
    063        init(solver, "Resection unassigned students...");
    064    }
    065
    066    /**
    067     * Select neighbour. All students with an empty schedule are taken, one by
    068     * one in a random order. For each student a branch & bound search is
    069     * employed.
    070     */
    071    @Override
    072    public Neighbour<Request, Enrollment> selectNeighbour(Solution<Request, Enrollment> solution) {
    073        while (iStudentsEnumeration.hasNext()) {
    074            Student student = iStudentsEnumeration.next();
    075            Progress.getInstance(solution.getModel()).incProgress();
    076            if (student.nrAssignedRequests() == 0 && !student.getRequests().isEmpty()) {
    077                Neighbour<Request, Enrollment> neighbour = getSelection(student).select();
    078                if (neighbour != null)
    079                    return neighbour;
    080            }
    081        }
    082        return null;
    083    }
    084
    085}