    001package net.sf.cpsolver.studentsct.heuristics;
    002
    003import net.sf.cpsolver.ifs.heuristics.RouletteWheelSelection;
    004import net.sf.cpsolver.ifs.heuristics.VariableSelection;
    005import net.sf.cpsolver.ifs.solution.Solution;
    006import net.sf.cpsolver.ifs.solver.Solver;
    007import net.sf.cpsolver.ifs.util.DataProperties;
    008import net.sf.cpsolver.studentsct.StudentSectioningModel;
    009import net.sf.cpsolver.studentsct.model.Enrollment;
    010import net.sf.cpsolver.studentsct.model.Request;
    011
    012/**
    013 * Variable ({@link Request}) selection using {@link RouletteWheelSelection}.
    014 * Unassigned request has 10 points, an assigned request has 1 point for each
    015 * section that exceeds its bound.
    016 *
    017 * <br>
    018 * <br>
    019 *
    020 * @version StudentSct 1.2 (Student Sectioning)<br>
    021 *          Copyright (C) 2007 - 2010 Tomáš Müller<br>
    022 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    023 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    024 * <br>
    025 *          This library is free software; you can redistribute it and/or modify
    026 *          it under the terms of the GNU Lesser General Public License as
    027 *          published by the Free Software Foundation; either version 3 of the
    028 *          License, or (at your option) any later version. <br>
    029 * <br>
    030 *          This library is distributed in the hope that it will be useful, but
    031 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    032 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    033 *          Lesser General Public License for more details. <br>
    034 * <br>
    035 *          You should have received a copy of the GNU Lesser General Public
    036 *          License along with this library; if not see
    037 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    038 */
    039public class RouletteWheelRequestSelection implements VariableSelection<Request, Enrollment> {
    040    RouletteWheelSelection<Request> iRoulette = null;
    041
    042    /**
    043     * Constructor
    044     *
    045     * @param properties
    046     *            configuration
    047     */
    048    public RouletteWheelRequestSelection(DataProperties properties) {
    049        super();
    050    }
    051
    052    /** Initialization */
    053    @Override
    054    public void init(Solver<Request, Enrollment> solver) {
    055
    056    }
    057
    058    /** Populate roulette wheel selection, if null or empty. */
    059    protected RouletteWheelSelection<Request> getRoulette(Solution<Request, Enrollment> solution) {
    060        if (iRoulette != null && iRoulette.hasMoreElements()) {
    061            if (iRoulette.getUsedPoints() < 0.1 * iRoulette.getTotalPoints())
    062                return iRoulette;
    063        }
    064        iRoulette = new RouletteWheelSelection<Request>();
    065        for (Request request : ((StudentSectioningModel) solution.getModel()).variables()) {
    066            double points = 0;
    067            if (request.getAssignment() == null)
    068                points += 10;
    069            else {
    070                Enrollment enrollment = request.getAssignment();
    071                if (enrollment.toDouble() > request.getBound())
    072                    points += 1;
    073            }
    074            if (points > 0)
    075                iRoulette.add(request, points);
    076        }
    077        return iRoulette;
    078    }
    079
    080    /**
    081     * Variable selection. {@link RouletteWheelSelection} is used. Unassigned
    082     * request has 10 points, an assigned request has 1 point for each section
    083     * that exceeds its bound.
    084     */
    085    @Override
    086    public Request selectVariable(Solution<Request, Enrollment> solution) {
    087        return getRoulette(solution).nextElement();
    088    }
    089}