001package net.sf.cpsolver.coursett.neighbourhoods;
002
003import java.util.ArrayList;
004import java.util.HashMap;
005import java.util.List;
006import java.util.Map;
007import java.util.Set;
008
009import net.sf.cpsolver.coursett.model.Lecture;
010import net.sf.cpsolver.coursett.model.Placement;
011import net.sf.cpsolver.coursett.model.RoomLocation;
012import net.sf.cpsolver.coursett.model.TimetableModel;
013import net.sf.cpsolver.ifs.algorithms.neighbourhoods.RandomSwapMove;
014import net.sf.cpsolver.ifs.model.Neighbour;
015import net.sf.cpsolver.ifs.model.SimpleNeighbour;
016import net.sf.cpsolver.ifs.solution.Solution;
017import net.sf.cpsolver.ifs.solver.Solver;
018import net.sf.cpsolver.ifs.util.DataProperties;
019import net.sf.cpsolver.ifs.util.JProf;
020import net.sf.cpsolver.ifs.util.ToolBox;
021
022/**
023 * Try to assign a class with a new room. A class is selected randomly, a
024 * different room is randomly selected for the class -- the class is
025 * assigned into the new room. If the room is used or there is some other conflict, 
026 * it tries to resolve these conflicts by assigning conflicting classes to other
027 * rooms as well.
028 * <br>
029 * 
030 * @version IFS 1.2 (Iterative Forward Search)<br>
031 *          Copyright (C) 2014 Tomáš Müller<br>
032 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
033 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
034 * <br>
035 *          This library is free software; you can redistribute it and/or modify
036 *          it under the terms of the GNU Lesser General Public License as
037 *          published by the Free Software Foundation; either version 3 of the
038 *          License, or (at your option) any later version. <br>
039 * <br>
040 *          This library is distributed in the hope that it will be useful, but
041 *          WITHOUT ANY WARRANTY; without even the implied warranty of
042 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
043 *          Lesser General Public License for more details. <br>
044 * <br>
045 *          You should have received a copy of the GNU Lesser General Public
046 *          License along with this library; if not see
047 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
048 */
049public class RoomSwap extends RandomSwapMove<Lecture, Placement> {
050
051    public RoomSwap(DataProperties config) {
052        super(config);
053    }
054
055    @Override
056    public void init(Solver<Lecture, Placement> solver) {
057    }
058
059    @Override
060    public Neighbour<Lecture, Placement> selectNeighbour(Solution<Lecture, Placement> solution) {
061        TimetableModel model = (TimetableModel)solution.getModel();
062        double total = model.getTotalValue();
063        int varIdx = ToolBox.random(model.variables().size());
064        for (int i = 0; i < model.variables().size(); i++) {
065            Lecture lecture = model.variables().get((i + varIdx) % model.variables().size());
066            Placement old = lecture.getAssignment();
067            if (old == null || old.getNrRooms() != 1) continue;
068
069            List<RoomLocation> values = lecture.roomLocations();
070            if (values.isEmpty()) continue;
071
072            int attempts = 0;
073            int valIdx = ToolBox.random(values.size());
074            long startTime = JProf.currentTimeMillis();
075            for (int j = 0; j < values.size(); j++) {
076                RoomLocation room = values.get((j + valIdx) % values.size());
077                if (room.getPreference() > 50) continue;
078                if (room.equals(old.getRoomLocation())) continue;
079                
080                Placement placement = new Placement(lecture, old.getTimeLocation(), room);
081                if (!placement.isValid()) continue;
082                
083                Set<Placement> conflicts = model.conflictValues(placement);
084                if (conflicts.contains(placement)) continue;
085                if (conflicts.isEmpty()) {
086                    SimpleNeighbour<Lecture, Placement> n = new SimpleNeighbour<Lecture, Placement>(lecture, placement);
087                    if (!iHC || n.value() <= 0) return n;
088                    else continue;
089                }
090                
091                Map<Lecture, Placement> assignments = new HashMap<Lecture, Placement>();
092                assignments.put(lecture, placement);
093                
094                for (Placement conflict: conflicts)
095                    conflict.variable().unassign(solution.getIteration());
096                lecture.assign(solution.getIteration(), placement);
097                
098                Double v = resolve(solution, total, startTime, assignments, new ArrayList<Placement>(conflicts), 0);
099                if (!conflicts.isEmpty())
100                    attempts ++;
101                
102                lecture.unassign(solution.getIteration());
103                for (Placement conflict: conflicts)
104                    conflict.variable().assign(solution.getIteration(), conflict);
105                lecture.assign(solution.getIteration(), old);
106                
107                if (v != null) 
108                    return new SwapNeighbour(assignments.values(), v);
109                
110                if (attempts >= iMaxAttempts) break;
111            }
112        }
113        return null;
114    }
115    
116    
117    @Override
118    public Double resolve(Solution<Lecture, Placement> solution, double total, long startTime, Map<Lecture, Placement> assignments, List<Placement> conflicts, int index) {
119        if (index == conflicts.size()) return solution.getModel().getTotalValue() - total;
120        Placement conflict = conflicts.get(index);
121        Lecture variable = conflict.variable();
122        
123        if (conflict.getNrRooms() != 1) return null;
124
125        List<RoomLocation> values = variable.roomLocations();
126        if (values.isEmpty()) return null;
127        
128        int valIdx = ToolBox.random(values.size());
129        int attempts = 0;
130        for (int i = 0; i < values.size(); i++) {
131            RoomLocation room = values.get((i + valIdx) % values.size());
132            if (room.getPreference() > 50) continue;
133            if (room.equals(conflict.getRoomLocation())) continue;
134            
135            Placement value = new Placement(variable, conflict.getTimeLocation(), room);
136            if (!value.isValid() || solution.getModel().inConflict(value)) continue;
137            
138            variable.assign(solution.getIteration(), value);
139            Double v = resolve(solution, total, startTime, assignments, conflicts, 1 + index);
140            variable.unassign(solution.getIteration());
141            attempts ++;
142            
143            if (v != null && (!iHC || v <= 0)) {
144                assignments.put(variable, value);
145                return v;
146            }
147            if (attempts >= iMaxAttempts || isTimeLimitReached(startTime)) break;
148        }
149            
150        return null;
151    }
152}