001package net.sf.cpsolver.studentsct.heuristics; 002 003import java.util.ArrayList; 004import java.util.List; 005 006import net.sf.cpsolver.ifs.heuristics.NeighbourSelection; 007import net.sf.cpsolver.ifs.model.Neighbour; 008import net.sf.cpsolver.ifs.solution.Solution; 009import net.sf.cpsolver.ifs.solver.Solver; 010import net.sf.cpsolver.ifs.util.DataProperties; 011import net.sf.cpsolver.studentsct.StudentSectioningModel; 012import net.sf.cpsolver.studentsct.model.Enrollment; 013import net.sf.cpsolver.studentsct.model.Request; 014import net.sf.cpsolver.studentsct.model.Student; 015 016/** 017 * Two-phase (Batch) student sectioning neighbour selection. It is based on 018 * {@link StudentSctNeighbourSelection}, however in the first round, only real 019 * students are sectioned. All dummy students are removed from the problem 020 * during initialization of this neighbour selection, they are returned into the 021 * problem after the first round of {@link StudentSctNeighbourSelection}. 022 * 023 * <br> 024 * <br> 025 * 026 * @version StudentSct 1.2 (Student Sectioning)<br> 027 * Copyright (C) 2007 - 2010 Tomáš Müller<br> 028 * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br> 029 * <a href="http://muller.unitime.org">http://muller.unitime.org</a><br> 030 * <br> 031 * This library is free software; you can redistribute it and/or modify 032 * it under the terms of the GNU Lesser General Public License as 033 * published by the Free Software Foundation; either version 3 of the 034 * License, or (at your option) any later version. <br> 035 * <br> 036 * This library is distributed in the hope that it will be useful, but 037 * WITHOUT ANY WARRANTY; without even the implied warranty of 038 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 039 * Lesser General Public License for more details. <br> 040 * <br> 041 * You should have received a copy of the GNU Lesser General Public 042 * License along with this library; if not see 043 * <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>. 044 */ 045 046public class TwoPhaseStudentSctNeighbourSelection extends StudentSctNeighbourSelection { 047 private int iNrRounds = 7; 048 049 public TwoPhaseStudentSctNeighbourSelection(DataProperties properties) throws Exception { 050 super(properties); 051 iNrRounds = properties.getPropertyInt("TwoPhaseSectioning.NrRoundsFirstPhase", iNrRounds); 052 } 053 054 /** Initialization -- also remove all the dummy students from the problem */ 055 @Override 056 public void init(Solver<Request, Enrollment> solver) { 057 super.init(solver); 058 if (removeDummyStudents(solver.currentSolution())) 059 registerSelection(new RestoreDummyStudents()); 060 } 061 062 List<Student> iDummyStudents = null; 063 064 private boolean removeDummyStudents(Solution<Request, Enrollment> solution) { 065 StudentSectioningModel model = (StudentSectioningModel) solution.getModel(); 066 if (model.getNrLastLikeStudents(false) == 0 || model.getNrRealStudents(false) == 0) 067 return false; 068 iDummyStudents = new ArrayList<Student>(); 069 for (Student student : new ArrayList<Student>(model.getStudents())) { 070 if (student.isDummy()) { 071 iDummyStudents.add(student); 072 model.removeStudent(student); 073 } 074 } 075 return true; 076 } 077 078 private boolean addDummyStudents(Solution<Request, Enrollment> solution) { 079 if (iDummyStudents == null || iDummyStudents.isEmpty()) 080 return false; 081 iNrRounds--; 082 if (iNrRounds > 0) 083 return false; 084 solution.restoreBest(); 085 StudentSectioningModel model = (StudentSectioningModel) solution.getModel(); 086 for (Student student : iDummyStudents) { 087 model.addStudent(student); 088 } 089 iDummyStudents = null; 090 solution.saveBest(); 091 return true; 092 } 093 094 /** 095 * Return all dummy students into the problem, executed as the last phase of 096 * the first round 097 */ 098 protected class RestoreDummyStudents implements NeighbourSelection<Request, Enrollment> { 099 public RestoreDummyStudents() { 100 } 101 102 @Override 103 public void init(Solver<Request, Enrollment> solver) { 104 } 105 106 /** Return all (removed) dummy students into the problem */ 107 @Override 108 public Neighbour<Request, Enrollment> selectNeighbour(Solution<Request, Enrollment> solution) { 109 addDummyStudents(solution); 110 return null; 111 } 112 } 113}