    001package org.cpsolver.studentsct.heuristics.selection;
    002
    003import org.apache.log4j.Logger;
    004import org.cpsolver.ifs.assignment.Assignment;
    005import org.cpsolver.ifs.model.Neighbour;
    006import org.cpsolver.ifs.solution.Solution;
    007import org.cpsolver.ifs.solver.Solver;
    008import org.cpsolver.ifs.util.DataProperties;
    009import org.cpsolver.ifs.util.Progress;
    010import org.cpsolver.studentsct.heuristics.studentord.StudentOrder;
    011import org.cpsolver.studentsct.heuristics.studentord.StudentRandomOrder;
    012import org.cpsolver.studentsct.model.Enrollment;
    013import org.cpsolver.studentsct.model.Request;
    014import org.cpsolver.studentsct.model.Student;
    015
    016
    017/**
    018 * Resection studends with empty schedule. An extension of
    019 * {@link BranchBoundSelection}, where only students that have no enrollments (
    020 * {@link Student#nrAssignedRequests(Assignment)} is zero) are resectioned.
    021 *
    022 * <br>
    023 * <br>
    024 *
    025 * @version StudentSct 1.3 (Student Sectioning)<br>
    026 *          Copyright (C) 2007 - 2014 Tomáš Müller<br>
    027 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    028 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    029 * <br>
    030 *          This library is free software; you can redistribute it and/or modify
    031 *          it under the terms of the GNU Lesser General Public License as
    032 *          published by the Free Software Foundation; either version 3 of the
    033 *          License, or (at your option) any later version. <br>
    034 * <br>
    035 *          This library is distributed in the hope that it will be useful, but
    036 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    037 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    038 *          Lesser General Public License for more details. <br>
    039 * <br>
    040 *          You should have received a copy of the GNU Lesser General Public
    041 *          License along with this library; if not see
    042 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    043 */
    044
    045public class ResectionUnassignedStudentsSelection extends BranchBoundSelection {
    046    private static Logger sLog = Logger.getLogger(ResectionUnassignedStudentsSelection.class);
    047
    048    public ResectionUnassignedStudentsSelection(DataProperties properties) {
    049        super(properties);
    050        iOrder = new StudentRandomOrder(properties);
    051        if (properties.getProperty("Neighbour.ResectionUnassignedStudentsOrder") != null) {
    052            try {
    053                iOrder = (StudentOrder) Class.forName(
    054                        properties.getProperty("Neighbour.ResectionUnassignedStudentsOrder")).getConstructor(
    055                        new Class[] { DataProperties.class }).newInstance(new Object[] { properties });
    056            } catch (Exception e) {
    057                sLog.error("Unable to set student order, reason:" + e.getMessage(), e);
    058            }
    059        }
    060    }
    061
    062    @Override
    063    public void init(Solver<Request, Enrollment> solver) {
    064        init(solver, "Resection unassigned students...");
    065    }
    066
    067    /**
    068     * Select neighbour. All students with an empty schedule are taken, one by
    069     * one in a random order. For each student a branch &amp; bound search is
    070     * employed.
    071     */
    072    @Override
    073    public Neighbour<Request, Enrollment> selectNeighbour(Solution<Request, Enrollment> solution) {
    074        Student student = null;
    075        while ((student = nextStudent()) != null) {
    076            Progress.getInstance(solution.getModel()).incProgress();
    077            if (student.nrAssignedRequests(solution.getAssignment()) == 0 && !student.getRequests().isEmpty()) {
    078                Neighbour<Request, Enrollment> neighbour = getSelection(solution.getAssignment(), student).select();
    079                if (neighbour != null)
    080                    return neighbour;
    081            }
    082        }
    083        return null;
    084    }
    085
    086}