    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}