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}