    001package org.cpsolver.coursett.neighbourhoods;
    002
    003import java.util.ArrayList;
    004import java.util.HashMap;
    005import java.util.List;
    006import java.util.Map;
    007import java.util.Set;
    008import java.util.concurrent.locks.Lock;
    009
    010import org.cpsolver.coursett.model.Lecture;
    011import org.cpsolver.coursett.model.Placement;
    012import org.cpsolver.coursett.model.RoomLocation;
    013import org.cpsolver.coursett.model.TimeLocation;
    014import org.cpsolver.coursett.model.TimetableModel;
    015import org.cpsolver.ifs.algorithms.neighbourhoods.RandomSwapMove;
    016import org.cpsolver.ifs.assignment.Assignment;
    017import org.cpsolver.ifs.model.Neighbour;
    018import org.cpsolver.ifs.model.SimpleNeighbour;
    019import org.cpsolver.ifs.solution.Solution;
    020import org.cpsolver.ifs.solver.Solver;
    021import org.cpsolver.ifs.util.DataProperties;
    022import org.cpsolver.ifs.util.JProf;
    023import org.cpsolver.ifs.util.ToolBox;
    024
    025
    026/**
    027 * Try to assign a class with a new time. A class is selected randomly, a
    028 * different time is randomly selected for the class -- the class is
    029 * assigned into the new time. If the time is used or there is some other conflict,
    030 * it tries to resolve these conflicts by assigning conflicting classes to other
    031 * times as well.
    032 * <br>
    033 *
    034 * @version IFS 1.3 (Iterative Forward Search)<br>
    035 *          Copyright (C) 2014 Tomáš Müller<br>
    036 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    037 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    038 * <br>
    039 *          This library is free software; you can redistribute it and/or modify
    040 *          it under the terms of the GNU Lesser General Public License as
    041 *          published by the Free Software Foundation; either version 3 of the
    042 *          License, or (at your option) any later version. <br>
    043 * <br>
    044 *          This library is distributed in the hope that it will be useful, but
    045 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    046 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    047 *          Lesser General Public License for more details. <br>
    048 * <br>
    049 *          You should have received a copy of the GNU Lesser General Public
    050 *          License along with this library; if not see
    051 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    052 */
    053public class TimeSwap extends RandomSwapMove<Lecture, Placement> {
    054
    055    public TimeSwap(DataProperties config) {
    056        super(config);
    057    }
    058
    059    @Override
    060    public void init(Solver<Lecture, Placement> solver) {
    061    }
    062
    063    @Override
    064    public Neighbour<Lecture, Placement> selectNeighbour(Solution<Lecture, Placement> solution) {
    065        TimetableModel model = (TimetableModel)solution.getModel();
    066        Assignment<Lecture, Placement> assignment = solution.getAssignment();
    067        double total = model.getTotalValue(assignment);
    068        int varIdx = ToolBox.random(model.variables().size());
    069        for (int i = 0; i < model.variables().size(); i++) {
    070            Lecture lecture = model.variables().get((i + varIdx) % model.variables().size());
    071            Placement old = lecture.getAssignment(assignment);
    072            if (old == null) continue;
    073
    074            List<TimeLocation> values = lecture.timeLocations();
    075            if (values.isEmpty()) continue;
    076
    077            Lock lock = solution.getLock().writeLock();
    078            lock.lock();
    079            try {
    080                int attempts = 0;
    081                long startTime = JProf.currentTimeMillis();
    082                int valIdx = ToolBox.random(values.size());
    083                for (int j = 0; j < values.size(); j++) {
    084                    TimeLocation time = values.get((j + valIdx) % values.size());
    085                    if (time.getPreference() > 50) continue;
    086                    if (time.equals(old.getTimeLocation())) continue;
    087
    088                    Placement placement = null;
    089                    if (lecture.getNrRooms() == 0)
    090                        placement = new Placement(lecture, time, (RoomLocation) null);
    091                    else if (lecture.getNrRooms() == 1)
    092                        placement = new Placement(lecture, time, old.getRoomLocation());
    093                    else
    094                        placement = new Placement(lecture, time, old.getRoomLocations());
    095                    if (!placement.isValid()) continue;
    096
    097                    Set<Placement> conflicts = model.conflictValues(assignment, placement);
    098                    if (conflicts.contains(placement)) continue;
    099                    if (conflicts.isEmpty()) {
    100                        SimpleNeighbour<Lecture, Placement> n = new SimpleNeighbour<Lecture, Placement>(lecture, placement);
    101                        if (!iHC || n.value(assignment) <= 0) return n;
    102                        else continue;
    103                    }
    104
    105                    Map<Lecture, Placement> assignments = new HashMap<Lecture, Placement>();
    106                    assignments.put(lecture, placement);
    107
    108                    for (Placement conflict: conflicts)
    109                        assignment.unassign(solution.getIteration(), conflict.variable());
    110                    assignment.assign(solution.getIteration(), placement);
    111
    112                    Double v = resolve(solution, total, startTime, assignments, new ArrayList<Placement>(conflicts), 0);
    113                    if (!conflicts.isEmpty())
    114                        attempts ++;
    115
    116                    assignment.unassign(solution.getIteration(), lecture);
    117                    for (Placement conflict: conflicts)
    118                        assignment.assign(solution.getIteration(), conflict);
    119                    assignment.assign(solution.getIteration(), old);
    120
    121                    if (v != null)
    122                        return new SwapNeighbour(assignments.values(), v);
    123
    124                    if (attempts >= iMaxAttempts) break;
    125                }
    126            } finally {
    127                lock.unlock();
    128            }
    129        }
    130        return null;
    131    }
    132
    133
    134    @Override
    135    public Double resolve(Solution<Lecture, Placement> solution, double total, long startTime, Map<Lecture, Placement> assignments, List<Placement> conflicts, int index) {
    136        Assignment<Lecture, Placement> assignment = solution.getAssignment();
    137
    138        if (index == conflicts.size()) return solution.getModel().getTotalValue(assignment) - total;
    139        Placement conflict = conflicts.get(index);
    140        Lecture variable = conflict.variable();
    141
    142        List<TimeLocation> values = variable.timeLocations();
    143        if (values.isEmpty()) return null;
    144
    145        int valIdx = ToolBox.random(values.size());
    146        int attempts = 0;
    147        for (int i = 0; i < values.size(); i++) {
    148            TimeLocation time = values.get((i + valIdx) % values.size());
    149            if (time.getPreference() > 50) continue;
    150            if (time.equals(conflict.getTimeLocation())) continue;
    151
    152            Placement value = null;
    153            if (variable.getNrRooms() == 0)
    154                value = new Placement(variable, time, (RoomLocation) null);
    155            else if (variable.getNrRooms() == 1)
    156                value = new Placement(variable, time, conflict.getRoomLocation());
    157            else
    158                value = new Placement(variable, time, conflict.getRoomLocations());
    159            if (!value.isValid() || solution.getModel().inConflict(assignment, value)) continue;
    160
    161            assignment.assign(solution.getIteration(), value);
    162            Double v = resolve(solution, total, startTime, assignments, conflicts, 1 + index);
    163            assignment.unassign(solution.getIteration(), variable);
    164            attempts ++;
    165
    166            if (v != null && (!iHC || v <= 0)) {
    167                assignments.put(variable, value);
    168                return v;
    169            }
    170            if (attempts >= iMaxAttempts || isTimeLimitReached(startTime)) break;
    171        }
    172
    173        return null;
    174    }
    175}