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.HashMap;
010import java.util.Iterator;
011import java.util.LinkedList;
012import java.util.List;
013import java.util.ListIterator;
014import java.util.Map;
015import java.util.concurrent.locks.Lock;
016
017import org.cpsolver.ifs.assignment.Assignment;
018import org.cpsolver.ifs.heuristics.BacktrackNeighbourSelection;
019import org.cpsolver.ifs.heuristics.NeighbourSelection;
020import org.cpsolver.ifs.model.InfoProvider;
021import org.cpsolver.ifs.model.Neighbour;
022import org.cpsolver.ifs.solution.Solution;
023import org.cpsolver.ifs.solver.Solver;
024import org.cpsolver.ifs.solver.SolverListener;
025import org.cpsolver.ifs.util.DataProperties;
026import org.cpsolver.ifs.util.Progress;
027import org.cpsolver.studentsct.StudentSectioningModel;
028import org.cpsolver.studentsct.heuristics.selection.BacktrackSelection.RequestComparator;
029import org.cpsolver.studentsct.model.CourseRequest;
030import org.cpsolver.studentsct.model.Enrollment;
031import org.cpsolver.studentsct.model.Request;
032import org.cpsolver.studentsct.model.Request.RequestPriority;
033import org.cpsolver.studentsct.model.Student.StudentPriority;
034
035/**
036 * Swap enrollments of different students of a course. This is to improve
037 * the enrollment alternativity {@link Enrollment#getPriority()} as well as
038 * selection preferences {@link Enrollment#percentSelected()}. 
039 * 
040 * <br>
041 * <br>
042 * 
043 * @version StudentSct 1.3 (Student Sectioning)<br>
044 *          Copyright (C) 2007 - 2018 Tomáš Müller<br>
045 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
046 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
047 * <br>
048 *          This library is free software; you can redistribute it and/or modify
049 *          it under the terms of the GNU Lesser General Public License as
050 *          published by the Free Software Foundation; either version 3 of the
051 *          License, or (at your option) any later version. <br>
052 * <br>
053 *          This library is distributed in the hope that it will be useful, but
054 *          WITHOUT ANY WARRANTY; without even the implied warranty of
055 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
056 *          Lesser General Public License for more details. <br>
057 * <br>
058 *          You should have received a copy of the GNU Lesser General Public
059 *          License along with this library; if not see
060 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
061 */
062
063public class StudentEnrollmentSwapSelection implements NeighbourSelection<Request, Enrollment>, InfoProvider<Request, Enrollment>, SolverListener<Request, Enrollment> {
064    private static DecimalFormat sDF = new DecimalFormat("0.00");
065    private Selection iSelection = null;
066    protected LinkedList<Request> iRequests = null;
067    
068    protected long iNbrIterations = 0;
069    protected long iTotalTime = 0;
070    protected long iNbrTimeoutReached = 0;
071    protected long iNbrNoSolution = 0;
072    protected RequestComparator iRequestComparator;
073
074    public StudentEnrollmentSwapSelection(DataProperties properties) {
075        iRequestComparator = new RequestComparator(properties);
076    }
077
078    public void init(Solver<Request, Enrollment> solver, String name) {
079        List<Request> variables = new ArrayList<Request>(solver.currentSolution().getModel().assignedVariables(solver.currentSolution().getAssignment()));
080        Collections.shuffle(variables);
081        Collections.sort(variables, iRequestComparator);
082        iRequests = new LinkedList<Request>(variables);
083        if (iSelection == null) {
084            try {
085                iSelection = new Selection(solver.getProperties());
086                iSelection.init(solver);
087            } catch (Exception e) {
088                throw new RuntimeException(e.getMessage(), e);
089            }
090        }
091        Progress.getInstance(solver.currentSolution().getModel()).setPhase(name, variables.size());
092        iNbrIterations = 0;
093        iNbrTimeoutReached = 0;
094        iNbrNoSolution = 0;
095        iTotalTime = 0;
096    }
097
098    @Override
099    public void init(Solver<Request, Enrollment> solver) {
100        init(solver, "Enrollment swaps...");
101    }
102    
103    protected synchronized Request nextRequest() {
104        return iRequests.poll();
105    }
106    
107    public synchronized void addRequest(Request request) {
108        if (iRequests != null && request != null && !request.getStudent().isDummy()) {
109            if (request.getStudent().getPriority().ordinal() < StudentPriority.Normal.ordinal() || request.getRequestPriority().ordinal() < RequestPriority.Normal.ordinal()) {
110                for (ListIterator<Request> i = iRequests.listIterator(); i.hasNext();) {
111                    Request r = i.next();
112                    if (iRequestComparator.compare(r, request) > 0) {
113                        i.previous(); // go one back
114                        i.add(request);
115                        return;
116                    }
117                }
118            }
119            iRequests.add(request);
120        }
121    }
122
123    @Override
124    public Neighbour<Request, Enrollment> selectNeighbour(Solution<Request, Enrollment> solution) {
125        Request request = null;
126        while ((request = nextRequest()) != null) {
127            Progress p = Progress.getInstance(solution.getModel()); 
128            p.incProgress();
129            if (p.getProgress() > 2.0 * p.getProgressMax()) return null;
130            if (request instanceof CourseRequest) {
131                try {
132                    Enrollment e = request.getAssignment(solution.getAssignment());
133                    if (e == null || e.getPriority() > 0 || !((CourseRequest)request).getSelectedChoices().isEmpty()) {
134                        Neighbour<Request, Enrollment> n = iSelection.selectNeighbour(solution, request);
135                        if (iSelection.getContext() != null) {
136                            iNbrIterations ++;
137                            iTotalTime += iSelection.getContext().getTime();
138                            if (iSelection.getContext().isTimeoutReached()) iNbrTimeoutReached ++;
139                            if (n == null) iNbrNoSolution ++;
140                        }
141                        if (n != null && n.value(solution.getAssignment()) <= 0.0)
142                            return n;
143                    }
144                } catch (ConcurrentModificationException e) {
145                    addRequest(request);
146                }
147            }
148        }
149        return null;
150    }
151    
152    class Selection extends BacktrackNeighbourSelection<Request, Enrollment> {
153        private int iMaxValues = 1000;
154        
155        Selection(DataProperties properties) throws Exception {
156            super(properties);
157            setTimeout(properties.getPropertyInt("Neighbour.EnrollmentSwapTimeout", 500));
158            iMaxValues = properties.getPropertyInt("Neighbour.EnrollmentSwapMaxValues", iMaxValues);
159        }
160        
161        @Override
162        protected Iterator<Enrollment> values(BacktrackNeighbourSelection<Request, Enrollment>.BacktrackNeighbourSelectionContext context, Request variable) {
163            if (variable instanceof CourseRequest) {
164                final CourseRequest request = (CourseRequest)variable;
165                final StudentSectioningModel model = (StudentSectioningModel)context.getModel();
166                final Assignment<Request, Enrollment> assignment = context.getAssignment();
167                List<Enrollment> values = null;
168                Enrollment current = request.getAssignment(context.getAssignment());
169                if (!request.getSelectedChoices().isEmpty() && current != null && current.getPriority() == 0) {
170                    values = request.getSelectedEnrollments(assignment, false);
171                } else {
172                    values = (iMaxValues > 0 ? request.computeRandomEnrollments(assignment, iMaxValues) : request.computeEnrollments(assignment));
173                }
174                Collections.sort(values, new Comparator<Enrollment>() {
175                    private HashMap<Enrollment, Double> iValues = new HashMap<Enrollment, Double>();
176                    private Double value(Enrollment e) {
177                        Double value = iValues.get(e);
178                        if (value == null) {
179                            if (model.getStudentQuality() != null)
180                                value = model.getStudentWeights().getWeight(assignment, e, model.getStudentQuality().conflicts(e));
181                            else
182                                value = model.getStudentWeights().getWeight(assignment, e,
183                                        (model.getDistanceConflict() == null ? null : model.getDistanceConflict().conflicts(e)),
184                                        (model.getTimeOverlaps() == null ? null : model.getTimeOverlaps().conflicts(e)));
185                            iValues.put(e, value);
186                        }
187                        return value;
188                    }
189                    @Override
190                    public int compare(Enrollment e1, Enrollment e2) {
191                        if (e1.equals(assignment.getValue(request))) return -1;
192                        if (e2.equals(assignment.getValue(request))) return 1;
193                        Double v1 = value(e1), v2 = value(e2);
194                        return v1.equals(v2) ? e1.compareTo(assignment, e2) : v2.compareTo(v1);
195                    }
196                });
197                return values.iterator();
198            } else {
199                return variable.computeEnrollments(context.getAssignment()).iterator();
200            }
201        }
202        
203        @Override
204        protected void selectNeighbour(Solution<Request, Enrollment> solution, Request variable, BacktrackNeighbourSelectionContext context) {
205            iContext = context;
206            Lock lock = solution.getLock().writeLock();
207            lock.lock();
208            try {
209                exploreEnrollmentSwaps(context, variable);
210            } finally {
211                lock.unlock();
212            }
213        }
214        
215        protected void exploreEnrollmentSwaps(BacktrackNeighbourSelectionContext context, Request variable) {
216            Enrollment current = context.getAssignment().getValue(variable);
217            double currentValue = (current == null ? 0.0 : current.toDouble(context.getAssignment()));
218            for (Iterator<Enrollment> e = values(context, variable); canContinueEvaluation(context) && e.hasNext();) {
219                Enrollment value = e.next();
220                if (value.equals(current)) continue;
221                if (current != null && currentValue <= value.toDouble(context.getAssignment())) continue;
222                if (context.isTimeoutReached() || context.isMaxItersReached()) break;
223                context.incIteration();
224                if (context.getModel().inConflict(context.getAssignment(), value)) {
225                    for (Enrollment other: new ArrayList<Enrollment>(value.getCourse().getContext(context.getAssignment()).getEnrollments())) {
226                        if (other.getStudent().equals(value.getStudent()) || !other.getSections().equals(value.getSections())) continue;
227                        context.getAssignment().unassign(0, other.variable());
228                        if (!context.getModel().inConflict(context.getAssignment(), value)) {
229                            if (current != null)
230                                context.getAssignment().unassign(0, current.variable());
231                            context.getAssignment().assign(0, value);
232                            for (Iterator<Enrollment> f = values(context, other.variable()); canContinueEvaluation(context) && f.hasNext();) {
233                                Enrollment fix = f.next();
234                                if (!context.getModel().inConflict(context.getAssignment(), fix)) {
235                                    context.getAssignment().assign(0, fix);
236                                    context.saveBest(variable, other.variable());
237                                    context.getAssignment().unassign(0, fix.variable());
238                                }
239                            }
240                            if (current == null)
241                                context.getAssignment().unassign(0, variable);
242                            else
243                                context.getAssignment().assign(0, current);
244                        }
245                        context.getAssignment().assign(0, other);
246                    }
247                } else {
248                    if (current != null)
249                        context.getAssignment().unassign(0, current.variable());
250                    context.getAssignment().assign(0, value);
251                    context.saveBest(variable);
252                    if (current == null)
253                        context.getAssignment().unassign(0, variable);
254                    else
255                        context.getAssignment().assign(0, current);
256                }
257            }
258        }        
259    }
260    
261    @Override
262    public void getInfo(Assignment<Request, Enrollment> assignment, Map<String, String> info) {
263        if (iNbrIterations > 0)
264            info.put("Timing of " + getClass().getSimpleName(), sDF.format(((double)iTotalTime) / iNbrIterations) + " ms/it (" +
265                    iNbrIterations + " iterations, " +
266                    (iNbrNoSolution == 0 ? "" : sDF.format(100.0 * iNbrNoSolution / iNbrIterations) + "% no solution, ") +
267                    sDF.format(100.0 * iNbrTimeoutReached / iNbrIterations) + "% time limit of " + sDF.format(iSelection.getTimeout() / 1000.0) + " seconds reached)");
268    }
269
270    @Override
271    public void getInfo(Assignment<Request, Enrollment> assignment, Map<String, String> info, Collection<Request> variables) {
272    }
273    
274    @Override
275    public boolean variableSelected(Assignment<Request, Enrollment> assignment, long iteration, Request variable) {
276        return false;
277    }
278    @Override
279    public boolean valueSelected(Assignment<Request, Enrollment> assignment, long iteration, Request variable, Enrollment value) {
280        return false;
281    }
282    @Override
283    public boolean neighbourSelected(Assignment<Request, Enrollment> assignment, long iteration, Neighbour<Request, Enrollment> neighbour) {
284        return false;
285    }
286    @Override
287    public void neighbourFailed(Assignment<Request, Enrollment> assignment, long iteration, Neighbour<Request, Enrollment> neighbour) {
288        if (neighbour instanceof BacktrackNeighbourSelection.BackTrackNeighbour)
289            addRequest(((BacktrackNeighbourSelection<Request, Enrollment>.BackTrackNeighbour)neighbour).getAssignments().get(0).getRequest());
290    }
291}