001package org.cpsolver.studentsct.heuristics; 002 003import java.util.ArrayList; 004import java.util.List; 005 006import org.cpsolver.ifs.heuristics.NeighbourSelection; 007import org.cpsolver.ifs.model.Neighbour; 008import org.cpsolver.ifs.solution.Solution; 009import org.cpsolver.ifs.solver.Solver; 010import org.cpsolver.ifs.util.DataProperties; 011import org.cpsolver.studentsct.StudentSectioningModel; 012import org.cpsolver.studentsct.model.Enrollment; 013import org.cpsolver.studentsct.model.Request; 014import org.cpsolver.studentsct.model.Student; 015 016 017/** 018 * Two-phase (Batch) student sectioning neighbour selection. It is based on 019 * {@link StudentSctNeighbourSelection}, however in the first round, only real 020 * students are sectioned. All dummy students are removed from the problem 021 * during initialization of this neighbour selection, they are returned into the 022 * problem after the first round of {@link StudentSctNeighbourSelection}. 023 * 024 * <br> 025 * <br> 026 * 027 * @version StudentSct 1.3 (Student Sectioning)<br> 028 * Copyright (C) 2007 - 2014 Tomáš Müller<br> 029 * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br> 030 * <a href="http://muller.unitime.org">http://muller.unitime.org</a><br> 031 * <br> 032 * This library is free software; you can redistribute it and/or modify 033 * it under the terms of the GNU Lesser General Public License as 034 * published by the Free Software Foundation; either version 3 of the 035 * License, or (at your option) any later version. <br> 036 * <br> 037 * This library is distributed in the hope that it will be useful, but 038 * WITHOUT ANY WARRANTY; without even the implied warranty of 039 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 040 * Lesser General Public License for more details. <br> 041 * <br> 042 * You should have received a copy of the GNU Lesser General Public 043 * License along with this library; if not see 044 * <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>. 045 */ 046 047public class TwoPhaseStudentSctNeighbourSelection extends StudentSctNeighbourSelection { 048 private int iNrRounds = 7; 049 050 public TwoPhaseStudentSctNeighbourSelection(DataProperties properties) throws Exception { 051 super(properties); 052 iNrRounds = properties.getPropertyInt("TwoPhaseSectioning.NrRoundsFirstPhase", iNrRounds); 053 } 054 055 /** Initialization -- also remove all the dummy students from the problem */ 056 @Override 057 public void init(Solver<Request, Enrollment> solver) { 058 super.init(solver); 059 if (removeDummyStudents(solver.currentSolution())) 060 registerSelection(new RestoreDummyStudents()); 061 } 062 063 List<Student> iDummyStudents = null; 064 065 private boolean removeDummyStudents(Solution<Request, Enrollment> solution) { 066 StudentSectioningModel model = (StudentSectioningModel) solution.getModel(); 067 if (model.getNrLastLikeStudents(false) == 0 || model.getNrRealStudents(false) == 0) 068 return false; 069 iDummyStudents = new ArrayList<Student>(); 070 for (Student student : new ArrayList<Student>(model.getStudents())) { 071 if (student.isDummy()) { 072 iDummyStudents.add(student); 073 model.removeStudent(student); 074 } 075 } 076 return true; 077 } 078 079 private boolean addDummyStudents(Solution<Request, Enrollment> solution) { 080 if (iDummyStudents == null || iDummyStudents.isEmpty()) 081 return false; 082 iNrRounds--; 083 if (iNrRounds > 0) 084 return false; 085 solution.restoreBest(); 086 StudentSectioningModel model = (StudentSectioningModel) solution.getModel(); 087 for (Student student : iDummyStudents) { 088 model.addStudent(student); 089 } 090 iDummyStudents = null; 091 solution.saveBest(); 092 return true; 093 } 094 095 /** 096 * Return all dummy students into the problem, executed as the last phase of 097 * the first round 098 */ 099 protected class RestoreDummyStudents implements NeighbourSelection<Request, Enrollment> { 100 public RestoreDummyStudents() { 101 } 102 103 @Override 104 public void init(Solver<Request, Enrollment> solver) { 105 } 106 107 /** Return all (removed) dummy students into the problem */ 108 @Override 109 public Neighbour<Request, Enrollment> selectNeighbour(Solution<Request, Enrollment> solution) { 110 addDummyStudents(solution); 111 return null; 112 } 113 } 114}