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}