    001package org.cpsolver.studentsct.heuristics;
    002
    003import org.cpsolver.ifs.heuristics.RouletteWheelSelection;
    004import org.cpsolver.ifs.heuristics.VariableSelection;
    005import org.cpsolver.ifs.solution.Solution;
    006import org.cpsolver.ifs.solver.Solver;
    007import org.cpsolver.ifs.util.DataProperties;
    008import org.cpsolver.studentsct.StudentSectioningModel;
    009import org.cpsolver.studentsct.model.Enrollment;
    010import org.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 * @author  Tomáš Müller
    021 * @version StudentSct 1.3 (Student Sectioning)<br>
    022 *          Copyright (C) 2007 - 2014 Tomáš Müller<br>
    023 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    024 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    025 * <br>
    026 *          This library is free software; you can redistribute it and/or modify
    027 *          it under the terms of the GNU Lesser General Public License as
    028 *          published by the Free Software Foundation; either version 3 of the
    029 *          License, or (at your option) any later version. <br>
    030 * <br>
    031 *          This library is distributed in the hope that it will be useful, but
    032 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    033 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    034 *          Lesser General Public License for more details. <br>
    035 * <br>
    036 *          You should have received a copy of the GNU Lesser General Public
    037 *          License along with this library; if not see
    038 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    039 */
    040public class RouletteWheelRequestSelection implements VariableSelection<Request, Enrollment> {
    041    RouletteWheelSelection<Request> iRoulette = null;
    042
    043    /**
    044     * Constructor
    045     *
    046     * @param properties
    047     *            configuration
    048     */
    049    public RouletteWheelRequestSelection(DataProperties properties) {
    050        super();
    051    }
    052
    053    /** Initialization */
    054    @Override
    055    public void init(Solver<Request, Enrollment> solver) {
    056
    057    }
    058
    059    /** Populate roulette wheel selection, if null or empty.
    060     * @param solution current solution
    061     * @return selection
    062     **/
    063    protected RouletteWheelSelection<Request> getRoulette(Solution<Request, Enrollment> solution) {
    064        if (iRoulette != null && iRoulette.hasMoreElements()) {
    065            if (iRoulette.getUsedPoints() < 0.1 * iRoulette.getTotalPoints())
    066                return iRoulette;
    067        }
    068        iRoulette = new RouletteWheelSelection<Request>();
    069        for (Request request : ((StudentSectioningModel) solution.getModel()).variables()) {
    070            double points = 0;
    071            if (solution.getAssignment().getValue(request) == null)
    072                points += 10;
    073            else {
    074                Enrollment enrollment = solution.getAssignment().getValue(request);
    075                if (enrollment.toDouble(solution.getAssignment()) > request.getBound())
    076                    points += 1;
    077            }
    078            if (points > 0)
    079                iRoulette.add(request, points);
    080        }
    081        return iRoulette;
    082    }
    083
    084    /**
    085     * Variable selection. {@link RouletteWheelSelection} is used. Unassigned
    086     * request has 10 points, an assigned request has 1 point for each section
    087     * that exceeds its bound.
    088     */
    089    @Override
    090    public synchronized Request selectVariable(Solution<Request, Enrollment> solution) {
    091        return getRoulette(solution).nextElement();
    092    }
    093}