001 package net.sf.cpsolver.studentsct.heuristics;
002
003 import java.util.Enumeration;
004
005 import net.sf.cpsolver.ifs.heuristics.RouletteWheelSelection;
006 import net.sf.cpsolver.ifs.heuristics.VariableSelection;
007 import net.sf.cpsolver.ifs.model.Variable;
008 import net.sf.cpsolver.ifs.solution.Solution;
009 import net.sf.cpsolver.ifs.solver.Solver;
010 import net.sf.cpsolver.ifs.util.DataProperties;
011 import net.sf.cpsolver.studentsct.model.Enrollment;
012 import net.sf.cpsolver.studentsct.model.Request;
013
014 /**
015 * Variable ({@link Request}) selection using {@link RouletteWheelSelection}.
016 * Unassigned request has 10 points, an assigned request has 1 point for
017 * each section that exceeds its bound.
018 *
019 * <br><br>
020 *
021 * @version
022 * StudentSct 1.1 (Student Sectioning)<br>
023 * Copyright (C) 2007 Tomáš Müller<br>
024 * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
025 * Lazenska 391, 76314 Zlin, Czech Republic<br>
026 * <br>
027 * This library is free software; you can redistribute it and/or
028 * modify it under the terms of the GNU Lesser General Public
029 * License as published by the Free Software Foundation; either
030 * version 2.1 of the License, or (at your option) any later version.
031 * <br><br>
032 * This library is distributed in the hope that it will be useful,
033 * but WITHOUT ANY WARRANTY; without even the implied warranty of
034 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
035 * Lesser General Public License for more details.
036 * <br><br>
037 * You should have received a copy of the GNU Lesser General Public
038 * License along with this library; if not, write to the Free Software
039 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
040 */
041 public class RouletteWheelRequestSelection implements VariableSelection {
042 RouletteWheelSelection iRoulette = null;
043
044 /**
045 * Constructor
046 * @param properties configuration
047 */
048 public RouletteWheelRequestSelection(DataProperties properties) {
049 super();
050 }
051
052 /** Initialization */
053 public void init(Solver solver) {
054
055 }
056
057 /** Populate roulette wheel selection, if null or empty. */
058 protected RouletteWheelSelection getRoulette(Solution solution) {
059 if (iRoulette!=null && iRoulette.hasMoreElements()) {
060 if (iRoulette.getUsedPoints()<0.1*iRoulette.getTotalPoints()) return iRoulette;
061 }
062 iRoulette = new RouletteWheelSelection();
063 for (Enumeration e=solution.getModel().variables().elements();e.hasMoreElements();) {
064 Request request = (Request)e.nextElement();
065 double points = 0;
066 if (request.getAssignment()==null)
067 points +=10;
068 else {
069 Enrollment enrollment = (Enrollment)request.getAssignment();
070 if (enrollment.toDouble()>request.getBound())
071 points +=1;
072 }
073 if (points>0)
074 iRoulette.add(request, points);
075 }
076 return iRoulette;
077 }
078
079 /**
080 * Variable selection. {@link RouletteWheelSelection} is used.
081 * Unassigned request has 10 points, an assigned request has 1 point for
082 * each section that exceeds its bound.
083 */
084 public Variable selectVariable(Solution solution) {
085 return (Variable)getRoulette(solution).nextElement();
086 }
087 }