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.Enrollment;
013 import net.sf.cpsolver.studentsct.model.Request;
014 import 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 Tomas Muller<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
044 public 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 }