001package org.cpsolver.studentsct.heuristics.selection; 002 003import java.text.DecimalFormat; 004import java.util.ArrayList; 005import java.util.Collection; 006import java.util.Collections; 007import java.util.Comparator; 008import java.util.ConcurrentModificationException; 009import java.util.LinkedList; 010import java.util.List; 011import java.util.ListIterator; 012import java.util.Map; 013 014import org.cpsolver.ifs.assignment.Assignment; 015import org.cpsolver.ifs.heuristics.BacktrackNeighbourSelection; 016import org.cpsolver.ifs.heuristics.NeighbourSelection; 017import org.cpsolver.ifs.model.InfoProvider; 018import org.cpsolver.ifs.model.Neighbour; 019import org.cpsolver.ifs.solution.Solution; 020import org.cpsolver.ifs.solver.Solver; 021import org.cpsolver.ifs.solver.SolverListener; 022import org.cpsolver.ifs.util.DataProperties; 023import org.cpsolver.ifs.util.Progress; 024import org.cpsolver.studentsct.filter.StudentFilter; 025import org.cpsolver.studentsct.heuristics.RandomizedBacktrackNeighbourSelection; 026import org.cpsolver.studentsct.model.CourseRequest; 027import org.cpsolver.studentsct.model.Enrollment; 028import org.cpsolver.studentsct.model.FreeTimeRequest; 029import org.cpsolver.studentsct.model.Request; 030import org.cpsolver.studentsct.model.Request.RequestPriority; 031import org.cpsolver.studentsct.model.Student.StudentPriority; 032 033 034/** 035 * Use backtrack neighbour selection. For all unassigned variables (in a random 036 * order), {@link RandomizedBacktrackNeighbourSelection} is being used. 037 * 038 * <br> 039 * <br> 040 * 041 * @version StudentSct 1.3 (Student Sectioning)<br> 042 * Copyright (C) 2007 - 2014 Tomas Muller<br> 043 * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br> 044 * <a href="http://muller.unitime.org">http://muller.unitime.org</a><br> 045 * <br> 046 * This library is free software; you can redistribute it and/or modify 047 * it under the terms of the GNU Lesser General Public License as 048 * published by the Free Software Foundation; either version 3 of the 049 * License, or (at your option) any later version. <br> 050 * <br> 051 * This library is distributed in the hope that it will be useful, but 052 * WITHOUT ANY WARRANTY; without even the implied warranty of 053 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 054 * Lesser General Public License for more details. <br> 055 * <br> 056 * You should have received a copy of the GNU Lesser General Public 057 * License along with this library; if not see 058 * <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>. 059 */ 060 061public class BacktrackSelection implements NeighbourSelection<Request, Enrollment>, InfoProvider<Request, Enrollment>, SolverListener<Request, Enrollment> { 062 private static DecimalFormat sDF = new DecimalFormat("0.00"); 063 protected RandomizedBacktrackNeighbourSelection iRBtNSel = null; 064 protected LinkedList<Request> iRequests = null; 065 protected boolean iIncludeAssignedRequests = false; 066 067 protected long iNbrIterations = 0; 068 protected long iTotalTime = 0; 069 protected long iNbrTimeoutReached = 0; 070 protected long iNbrNoSolution = 0; 071 protected StudentFilter iFilter = null; 072 protected RequestComparator iRequestComparator = null; 073 074 public BacktrackSelection(DataProperties properties) { 075 iIncludeAssignedRequests = properties.getPropertyBoolean("Neighbour.IncludeAssignedRequests", iIncludeAssignedRequests); 076 iRequestComparator = new RequestComparator(properties); 077 } 078 079 public void init(Solver<Request, Enrollment> solver, String name) { 080 List<Request> variables = new ArrayList<Request>(iIncludeAssignedRequests ? solver.currentSolution().getModel().variables() : solver.currentSolution().getModel().unassignedVariables(solver.currentSolution().getAssignment())); 081 Collections.shuffle(variables); 082 Collections.sort(variables, iRequestComparator); 083 iRequests = new LinkedList<Request>(variables); 084 if (iRBtNSel == null) { 085 try { 086 iRBtNSel = new RandomizedBacktrackNeighbourSelection(solver.getProperties()); 087 iRBtNSel.init(solver); 088 } catch (Exception e) { 089 throw new RuntimeException(e.getMessage(), e); 090 } 091 } 092 Progress.getInstance(solver.currentSolution().getModel()).setPhase(name, variables.size()); 093 } 094 095 @Override 096 public void init(Solver<Request, Enrollment> solver) { 097 init(solver, "Backtracking" + (iFilter == null ? "" : " (" + iFilter.getName().toLowerCase() + " students)") + "..."); 098 099 iNbrIterations = 0; 100 iNbrTimeoutReached = 0; 101 iNbrNoSolution = 0; 102 iTotalTime = 0; 103 } 104 105 protected synchronized Request nextRequest() { 106 while (true) { 107 Request request = iRequests.poll(); 108 if (request == null) return null; 109 if (iFilter == null || iFilter.accept(request.getStudent())) return request; 110 } 111 } 112 113 public synchronized void addRequest(Request request) { 114 if (iRequests != null && request != null && !request.getStudent().isDummy()) { 115 if (request.getStudent().getPriority().ordinal() < StudentPriority.Normal.ordinal() || request.getRequestPriority().ordinal() < RequestPriority.Normal.ordinal()) { 116 for (ListIterator<Request> i = iRequests.listIterator(); i.hasNext();) { 117 Request r = i.next(); 118 if (iRequestComparator.compare(r, request) > 0) { 119 i.previous(); // go one back 120 i.add(request); 121 return; 122 } 123 } 124 } 125 iRequests.add(request); 126 } 127 } 128 129 @Override 130 public Neighbour<Request, Enrollment> selectNeighbour(Solution<Request, Enrollment> solution) { 131 Request request = null; 132 while ((request = nextRequest()) != null) { 133 Progress.getInstance(solution.getModel()).incProgress(); 134 Enrollment e = request.getAssignment(solution.getAssignment()); 135 if (e != null && request instanceof FreeTimeRequest) continue; 136 if (e != null && e.getPriority() == 0 && ((CourseRequest)request).getSelectedChoices().isEmpty()) continue; 137 for (int i = 0; i < 5; i++) { 138 try { 139 Neighbour<Request, Enrollment> n = iRBtNSel.selectNeighbour(solution, request); 140 if (iRBtNSel.getContext() != null) { 141 iNbrIterations ++; 142 iTotalTime += iRBtNSel.getContext().getTime(); 143 if (iRBtNSel.getContext().isTimeoutReached()) iNbrTimeoutReached ++; 144 if (n == null) iNbrNoSolution ++; 145 } 146 if (n != null && n.value(solution.getAssignment()) <= 0.0) 147 return n; 148 break; 149 } catch (ConcurrentModificationException ex) {} 150 } 151 } 152 return null; 153 } 154 155 @Override 156 public void getInfo(Assignment<Request, Enrollment> assignment, Map<String, String> info) { 157 if (iNbrIterations > 0) 158 info.put("Timing of " + getClass().getSimpleName(), sDF.format(((double)iTotalTime) / iNbrIterations) + " ms/it (" + 159 iNbrIterations + " iterations, " + 160 (iNbrNoSolution == 0 ? "" : sDF.format(100.0 * iNbrNoSolution / iNbrIterations) + "% no solution, ") + 161 sDF.format(100.0 * iNbrTimeoutReached / iNbrIterations) + "% time limit of " + sDF.format(iRBtNSel.getTimeout() / 1000.0) + " seconds reached)"); 162 } 163 164 @Override 165 public void getInfo(Assignment<Request, Enrollment> assignment, Map<String, String> info, Collection<Request> variables) { 166 } 167 168 /** 169 * Only consider students meeting the given filter. 170 */ 171 public StudentFilter getFilter() { return iFilter; } 172 173 /** 174 * Only consider students meeting the given filter. 175 */ 176 public BacktrackSelection withFilter(StudentFilter filter) { iFilter = filter; return this; } 177 178 @Override 179 public boolean variableSelected(Assignment<Request, Enrollment> assignment, long iteration, Request variable) { 180 return false; 181 } 182 @Override 183 public boolean valueSelected(Assignment<Request, Enrollment> assignment, long iteration, Request variable, Enrollment value) { 184 return false; 185 } 186 @Override 187 public boolean neighbourSelected(Assignment<Request, Enrollment> assignment, long iteration, Neighbour<Request, Enrollment> neighbour) { 188 return false; 189 } 190 @Override 191 public void neighbourFailed(Assignment<Request, Enrollment> assignment, long iteration, Neighbour<Request, Enrollment> neighbour) { 192 if (neighbour instanceof BacktrackNeighbourSelection.BackTrackNeighbour) 193 addRequest(((BacktrackNeighbourSelection<Request, Enrollment>.BackTrackNeighbour)neighbour).getAssignments().get(0).getRequest()); 194 } 195 196 public static class RequestComparator implements Comparator<Request> { 197 protected boolean iPreferPriorityStudents = true; 198 protected RequestComparator(DataProperties properties) { 199 iPreferPriorityStudents = properties.getPropertyBoolean("Sectioning.PriorityStudentsFirstSelection.AllIn", true); 200 } 201 202 @Override 203 public int compare(Request r1, Request r2) { 204 if (iPreferPriorityStudents) { 205 if (r1.getStudent().getPriority() != r2.getStudent().getPriority()) 206 return r1.getStudent().getPriority().compareTo(r2.getStudent().getPriority()); 207 if (r1.getRequestPriority() != r2.getRequestPriority()) 208 return r1.getRequestPriority().compareTo(r2.getRequestPriority()); 209 } else { 210 if (r1.getRequestPriority() != r2.getRequestPriority()) 211 return r1.getRequestPriority().compareTo(r2.getRequestPriority()); 212 if (r1.getRequestPriority() != r2.getRequestPriority()) 213 return r1.getStudent().getPriority().compareTo(r2.getStudent().getPriority()); 214 } 215 if (r1.isAlternative() != r2.isAlternative()) 216 return r2.isAlternative() ? -1 : 1; 217 if (r1.getPriority() != r2.getPriority()) 218 return r1.getPriority() < r2.getPriority() ? -1 : 1; 219 return 0; 220 } 221 } 222}