001package org.cpsolver.studentsct.heuristics.selection; 002 003import java.util.ArrayList; 004import java.util.Collections; 005import java.util.LinkedList; 006import java.util.List; 007import java.util.Queue; 008 009import org.cpsolver.ifs.assignment.Assignment; 010import org.cpsolver.ifs.heuristics.ValueSelection; 011import org.cpsolver.ifs.heuristics.VariableSelection; 012import org.cpsolver.ifs.solution.Solution; 013import org.cpsolver.ifs.solver.Solver; 014import org.cpsolver.ifs.util.DataProperties; 015import org.cpsolver.studentsct.model.Enrollment; 016import org.cpsolver.studentsct.model.Request; 017 018/** 019 * Use the standard IFS search for the unassigned critical course requests. 020 * This selection is based on {@link StandardSelection} using 021 * {@link UnassignedCriticalCourseRequestSelection} as variable selection. 022 * Unlike {@link StandardSelection}, it allows for a critical course request to be 023 * unassigned. 024 * 025 * @version StudentSct 1.3 (Student Sectioning)<br> 026 * Copyright (C) 2007 - 2014 Tomas Muller<br> 027 * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br> 028 * <a href="http://muller.unitime.org">http://muller.unitime.org</a><br> 029 * <br> 030 * This library is free software; you can redistribute it and/or modify 031 * it under the terms of the GNU Lesser General Public License as 032 * published by the Free Software Foundation; either version 3 of the 033 * License, or (at your option) any later version. <br> 034 * <br> 035 * This library is distributed in the hope that it will be useful, but 036 * WITHOUT ANY WARRANTY; without even the implied warranty of 037 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 038 * Lesser General Public License for more details. <br> 039 * <br> 040 * You should have received a copy of the GNU Lesser General Public 041 * License along with this library; if not see 042 * <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>. 043 */ 044public class CriticalStandardSelection extends StandardSelection { 045 046 public CriticalStandardSelection(DataProperties properties, ValueSelection<Request, Enrollment> valueSelection) { 047 super(properties, new UnassignedCriticalCourseRequestSelection(), valueSelection); 048 } 049 050 @Override 051 public void init(Solver<Request, Enrollment> solver) { 052 init(solver, "Ifs (critical)..."); 053 } 054 055 @Override 056 public boolean canUnassign(Enrollment enrollment, Assignment<Request, Enrollment> assignment) { 057 if (enrollment.getRequest().isMPP() && enrollment.equals(enrollment.getRequest().getInitialAssignment())) return false; 058 // Override to allow unassignment of critical course requests 059 return true; 060 } 061 062 /** 063 * Returns the unassigned critical course requests in a random order. 064 */ 065 static class UnassignedCriticalCourseRequestSelection implements VariableSelection<Request, Enrollment>{ 066 protected int iNrRounds = 0; 067 protected Queue<Request> iRequests = null; 068 069 @Override 070 public void init(Solver<Request, Enrollment> solver) { 071 iRequests = new LinkedList<Request>(); 072 iNrRounds = solver.getProperties().getPropertyInt("Neighbour.CriticalRounds", 10); 073 } 074 075 @Override 076 public Request selectVariable(Solution<Request, Enrollment> solution) { 077 return nextRequest(solution); 078 } 079 080 protected synchronized Request nextRequest(Solution<Request, Enrollment> solution) { 081 if (iRequests.isEmpty() && iNrRounds > 0) { 082 iNrRounds --; 083 List<Request> variables = new ArrayList<Request>(); 084 for (Request r: solution.getModel().unassignedVariables(solution.getAssignment())) 085 if (r.isCritical()) variables.add(r); 086 Collections.shuffle(variables); 087 iRequests.addAll(variables); 088 } 089 return iRequests.poll(); 090 } 091 } 092}