001 package net.sf.cpsolver.studentsct.heuristics.selection;
002
003 import org.apache.log4j.Logger;
004
005 import net.sf.cpsolver.ifs.model.Neighbour;
006 import net.sf.cpsolver.ifs.solution.Solution;
007 import net.sf.cpsolver.ifs.solver.Solver;
008 import net.sf.cpsolver.ifs.util.DataProperties;
009 import net.sf.cpsolver.ifs.util.Progress;
010 import net.sf.cpsolver.studentsct.heuristics.studentord.StudentOrder;
011 import net.sf.cpsolver.studentsct.heuristics.studentord.StudentRandomOrder;
012 import net.sf.cpsolver.studentsct.model.Student;
013
014 /**
015 * Resection studends with empty schedule.
016 * An extension of {@link BranchBoundSelection}, where only students that have
017 * no enrollments ({@link Student#nrAssignedRequests()} is zero) are
018 * resectioned.
019 *
020 * <br><br>
021 *
022 * @version
023 * StudentSct 1.1 (Student Sectioning)<br>
024 * Copyright (C) 2007 Tomáš Müller<br>
025 * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
026 * Lazenska 391, 76314 Zlin, Czech Republic<br>
027 * <br>
028 * This library is free software; you can redistribute it and/or
029 * modify it under the terms of the GNU Lesser General Public
030 * License as published by the Free Software Foundation; either
031 * version 2.1 of the License, or (at your option) any later version.
032 * <br><br>
033 * This library is distributed in the hope that it will be useful,
034 * but WITHOUT ANY WARRANTY; without even the implied warranty of
035 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
036 * Lesser General Public License for more details.
037 * <br><br>
038 * You should have received a copy of the GNU Lesser General Public
039 * License along with this library; if not, write to the Free Software
040 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
041 */
042
043 public class ResectionUnassignedStudentsSelection extends BranchBoundSelection {
044 private static Logger sLog = Logger.getLogger(ResectionUnassignedStudentsSelection.class);
045
046 public ResectionUnassignedStudentsSelection(DataProperties properties) {
047 super(properties);
048 iOrder = new StudentRandomOrder(properties);
049 if (properties.getProperty("Neighbour.ResectionUnassignedStudentsOrder")!=null) {
050 try {
051 iOrder = (StudentOrder)Class.forName(properties.getProperty("Neighbour.ResectionUnassignedStudentsOrder")).
052 getConstructor(new Class[] {DataProperties.class}).
053 newInstance(new Object[] {properties});
054 } catch (Exception e) {
055 sLog.error("Unable to set student order, reason:"+e.getMessage(),e);
056 }
057 }
058 }
059
060 public void init(Solver solver) {
061 init(solver, "Resection unassigned students...");
062 }
063
064 /**
065 * Select neighbour. All students with an empty schedule are taken,
066 * one by one in a random order. For each student a branch & bound search is employed.
067 */
068 public Neighbour selectNeighbour(Solution solution) {
069 while (iStudentsEnumeration.hasMoreElements()) {
070 Student student = (Student)iStudentsEnumeration.nextElement();
071 Progress.getInstance(solution.getModel()).incProgress();
072 if (student.nrAssignedRequests()==0 && !student.getRequests().isEmpty()) {
073 Neighbour neighbour = getSelection(student).select();
074 if (neighbour!=null) return neighbour;
075 }
076 }
077 return null;
078 }
079
080 }