001package org.cpsolver.coursett.heuristics;
002
003import java.util.ArrayList;
004import java.util.Collection;
005import java.util.HashMap;
006import java.util.Iterator;
007import java.util.List;
008import java.util.Map;
009import java.util.Set;
010import java.util.concurrent.locks.Lock;
011
012import org.cpsolver.coursett.model.Lecture;
013import org.cpsolver.coursett.model.Placement;
014import org.cpsolver.coursett.model.TimetableModel;
015import org.cpsolver.ifs.assignment.Assignment;
016import org.cpsolver.ifs.heuristics.StandardNeighbourSelection;
017import org.cpsolver.ifs.model.Neighbour;
018import org.cpsolver.ifs.solution.Solution;
019import org.cpsolver.ifs.solver.Solver;
020import org.cpsolver.ifs.util.DataProperties;
021import org.cpsolver.ifs.util.JProf;
022import org.cpsolver.ifs.util.ToolBox;
023
024
025/**
026 * Neighbour selection which does the standard time neighbour selection most of
027 * the time, however, the very best neighbour is selected time to time (using
028 * backtracking based search).
029 * 
030 * @see StandardNeighbourSelection
031 * @version CourseTT 1.3 (University Course Timetabling)<br>
032 *          Copyright (C) 2006 - 2014 Tomáš Müller<br>
033 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
034 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
035 * <br>
036 *          This library is free software; you can redistribute it and/or modify
037 *          it under the terms of the GNU Lesser General Public License as
038 *          published by the Free Software Foundation; either version 3 of the
039 *          License, or (at your option) any later version. <br>
040 * <br>
041 *          This library is distributed in the hope that it will be useful, but
042 *          WITHOUT ANY WARRANTY; without even the implied warranty of
043 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
044 *          Lesser General Public License for more details. <br>
045 * <br>
046 *          You should have received a copy of the GNU Lesser General Public
047 *          License along with this library; if not see
048 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
049 */
050
051public class NeighbourSelectionWithSuggestions extends StandardNeighbourSelection<Lecture, Placement> {
052    private double iSuggestionProbability = 0.1;
053    private double iSuggestionProbabilityAllAssigned = 0.5;
054    protected int iSuggestionTimeout = 500;
055    protected int iSuggestionDepth = 4;
056
057    public NeighbourSelectionWithSuggestions(DataProperties properties) throws Exception {
058        super(properties);
059        iSuggestionProbability = properties.getPropertyDouble("Neighbour.SuggestionProbability", iSuggestionProbability);
060        iSuggestionProbabilityAllAssigned = properties.getPropertyDouble("Neighbour.SuggestionProbabilityAllAssigned", iSuggestionProbabilityAllAssigned);
061        iSuggestionTimeout = properties.getPropertyInt("Neighbour.SuggestionTimeout", iSuggestionTimeout);
062        iSuggestionDepth = properties.getPropertyInt("Neighbour.SuggestionDepth", iSuggestionDepth);
063    }
064
065    public NeighbourSelectionWithSuggestions(Solver<Lecture, Placement> solver) throws Exception {
066        this(solver.getProperties());
067        init(solver);
068    }
069
070    @Override
071    public void init(Solver<Lecture, Placement> solver) {
072        super.init(solver);
073    }
074
075    @Override
076    public Neighbour<Lecture, Placement> selectNeighbour(Solution<Lecture, Placement> solution) {
077        Neighbour<Lecture, Placement> neighbour = null;
078        if (solution.getModel().unassignedVariables(solution.getAssignment()).isEmpty()) {
079            for (int d = iSuggestionDepth; d > 1; d--) {
080                if (ToolBox.random() < Math.pow(iSuggestionProbabilityAllAssigned, d - 1)) {
081                    neighbour = selectNeighbourWithSuggestions(solution, selectVariable(solution), d);
082                    break;
083                }
084            }
085        } else {
086            for (int d = iSuggestionDepth; d > 1; d--) {
087                if (ToolBox.random() < Math.pow(iSuggestionProbability, d - 1)) {
088                    neighbour = selectNeighbourWithSuggestions(solution, selectVariable(solution), d);
089                    break;
090                }
091            }
092        }
093        return (neighbour != null ? neighbour : super.selectNeighbour(solution));
094    }
095
096    public Neighbour<Lecture, Placement> selectNeighbourWithSuggestions(Solution<Lecture, Placement> solution, Lecture lecture, int depth) {
097        if (lecture == null)
098            return null;
099
100        NeighbourSelectionWithSuggestionsContext context = new NeighbourSelectionWithSuggestionsContext(solution);
101
102        Lock lock = solution.getLock().writeLock();
103        lock.lock();
104        try {
105            // System.out.println("BEFORE BT ("+lecture.getName()+"): nrAssigned="+iSolution.getModel().assignedVariables().size()+",  value="+iCmp.currentValue(iSolution));
106
107            List<Lecture> initialLectures = new ArrayList<Lecture>(1);
108            initialLectures.add(lecture);
109            backtrack(context, initialLectures, new HashMap<Lecture, Placement>(), new HashMap<Lecture, Placement>(), depth);
110
111            // System.out.println("AFTER  BT ("+lecture.getName()+"): nrAssigned="+iSolution.getModel().assignedVariables().size()+",  value="+iCmp.currentValue(iSolution));
112        } finally {
113            lock.unlock();
114        }
115
116        return context.getSuggestionNeighbour();
117    }
118
119    private boolean containsCommited(NeighbourSelectionWithSuggestionsContext context, Collection<Placement> values) {
120        if (context.getModel().hasConstantVariables()) {
121            for (Placement placement : values) {
122                Lecture lecture = placement.variable();
123                if (lecture.isCommitted())
124                    return true;
125            }
126        }
127        return false;
128    }
129
130    private void backtrack(NeighbourSelectionWithSuggestionsContext context, List<Lecture> initialLectures, Map<Lecture, Placement> resolvedLectures, HashMap<Lecture, Placement> conflictsToResolve, int depth) {
131        int nrUnassigned = conflictsToResolve.size();
132        if ((initialLectures == null || initialLectures.isEmpty()) && nrUnassigned == 0) {
133            context.setSuggestionNeighbourIfImproving(resolvedLectures);
134            return;
135        }
136        if (depth <= 0 || context.checkTimeoutReached())
137            return;
138        
139        Assignment<Lecture, Placement> assignment = context.getAssignment();
140        for (Lecture lecture: initialLectures != null && !initialLectures.isEmpty() ? initialLectures : new ArrayList<Lecture>(conflictsToResolve.keySet())) {
141            if (context.isTimeoutReached()) break;
142            if (resolvedLectures.containsKey(lecture))
143                continue;
144            List<Placement> placements = lecture.values(assignment);
145            int rnd = ToolBox.random(placements.size());
146            placements: for (int idx = 0; idx < placements.size(); idx++) {
147                Placement placement = placements.get((idx + rnd) % placements.size());
148                if (context.isTimeoutReached()) break;
149                Placement cur = assignment.getValue(lecture);
150                if (placement.equals(cur))
151                    continue;
152                if (placement.isHard(assignment))
153                    continue;
154                Set<Placement> conflicts = context.getModel().conflictValues(assignment, placement);
155                if (nrUnassigned + conflicts.size() > depth)
156                    continue;
157                if (conflicts.contains(placement))
158                    continue;
159                if (containsCommited(context, conflicts))
160                    continue;
161                for (Iterator<Placement> i = conflicts.iterator();i.hasNext();) {
162                    Placement c = i.next();
163                    if (resolvedLectures.containsKey(c.variable()))
164                        continue placements;
165                }
166                for (Iterator<Placement> i = conflicts.iterator(); i.hasNext();) {
167                    Placement c = i.next();
168                    assignment.unassign(0, c.variable());
169                }
170                assignment.assign(0, placement);
171                for (Iterator<Placement> i = conflicts.iterator(); i.hasNext();) {
172                    Placement c = i.next();
173                    conflictsToResolve.put(c.variable(), c);
174                }
175                Placement resolvedConf = conflictsToResolve.remove(lecture);
176                resolvedLectures.put(lecture, placement);
177                backtrack(context, null, resolvedLectures, conflictsToResolve, depth - 1);
178                resolvedLectures.remove(lecture);
179                if (cur == null)
180                    assignment.unassign(0, lecture);
181                else
182                    assignment.assign(0, cur);
183                for (Iterator<Placement> i = conflicts.iterator(); i.hasNext();) {
184                    Placement p = i.next();
185                    assignment.assign(0, p);
186                    conflictsToResolve.remove(p.variable());
187                }
188                if (resolvedConf != null)
189                    conflictsToResolve.put(lecture, resolvedConf);
190            }
191        }
192    }
193
194    public class SuggestionNeighbour implements Neighbour<Lecture, Placement> {
195        private double iValue = 0;
196        private List<Placement> iDifferentAssignments = null;
197
198        public SuggestionNeighbour(Map<Lecture, Placement> resolvedLectures, double value) {
199            iValue = value;
200            iDifferentAssignments = new ArrayList<Placement>(resolvedLectures.values());
201        }
202
203        @Override
204        public double value(Assignment<Lecture, Placement> assignment) {
205            return iValue;
206        }
207
208        @Override
209        public void assign(Assignment<Lecture, Placement> assignment, long iteration) {
210            // System.out.println("START ASSIGN: nrAssigned="+iSolution.getModel().assignedVariables().size()+",  value="+iCmp.currentValue(iSolution));
211            // System.out.println("  "+this);
212            for (Placement p : iDifferentAssignments)
213                assignment.unassign(iteration, p.variable());
214            for (Placement p : iDifferentAssignments)
215                assignment.assign(iteration, p);
216            // System.out.println("END ASSIGN: nrAssigned="+iSolution.getModel().assignedVariables().size()+",  value="+iCmp.currentValue(iSolution));
217        }
218
219        public int compareTo(Solution<Lecture, Placement> solution) {
220            return Double.compare(iValue, solution.getModel().getTotalValue(solution.getAssignment()));
221        }
222
223        @Override
224        public String toString() {
225            StringBuffer sb = new StringBuffer("Suggestion{value=" + iValue + ": ");
226            for (Iterator<Placement> e = iDifferentAssignments.iterator(); e.hasNext();) {
227                Placement p = e.next();
228                sb.append("\n    " + p.variable().getName() + " " + p.getName() + (e.hasNext() ? "," : ""));
229            }
230            sb.append("}");
231            return sb.toString();
232        }
233
234        @Override
235        public Map<Lecture, Placement> assignments() {
236            Map<Lecture, Placement> ret = new HashMap<Lecture, Placement>();
237            for (Placement p : iDifferentAssignments)
238                ret.put(p.variable(), p);
239            return ret;
240        }
241    }
242    
243    public class NeighbourSelectionWithSuggestionsContext {
244        private Solution<Lecture, Placement> iSolution = null;
245        private SuggestionNeighbour iSuggestionNeighbour = null;
246        private double iValue = 0;
247        private int iNrAssigned = 0;
248        private boolean iTimeoutReached = false;
249        private long iStartTime;
250        
251        public NeighbourSelectionWithSuggestionsContext(Solution<Lecture, Placement> solution) {
252            iSolution = solution;
253            iSuggestionNeighbour = null;
254            iValue = solution.getModel().getTotalValue(solution.getAssignment());
255            iNrAssigned = solution.getAssignment().nrAssignedVariables();
256            iTimeoutReached = false;
257            iStartTime = JProf.currentTimeMillis();
258        }
259
260        public SuggestionNeighbour getSuggestionNeighbour() { return iSuggestionNeighbour; }
261        
262        public boolean setSuggestionNeighbourIfImproving(Map<Lecture, Placement> assignment) {
263            if (getAssignment().nrAssignedVariables() > getNrAssigned() || (getAssignment().nrAssignedVariables() == getNrAssigned() && getValue() > getModel().getTotalValue(getAssignment()))) {
264                double value = getModel().getTotalValue(getAssignment());
265                if (getSuggestionNeighbour() == null || getSuggestionNeighbour().value(getAssignment()) >= value) {
266                    iSuggestionNeighbour = new SuggestionNeighbour(assignment, value);
267                    return true;
268                }
269            }
270            return false;
271        }
272        
273        public Solution<Lecture, Placement> getSolution() { return iSolution; }
274        public Assignment<Lecture, Placement> getAssignment() { return getSolution().getAssignment(); }
275        public TimetableModel getModel() { return (TimetableModel)getSolution().getModel(); }
276        public int getNrAssigned() { return iNrAssigned; }
277        public double getValue() { return iValue; }
278        
279        public boolean isTimeoutReached() { return iTimeoutReached; }
280        public boolean checkTimeoutReached() {
281            if (iTimeoutReached) return true;
282            if (iSuggestionTimeout > 0 && JProf.currentTimeMillis() - iStartTime > iSuggestionTimeout)
283                iTimeoutReached = true;
284            return iTimeoutReached;
285        }
286        public void setTimeoutReached(boolean timeoutReached) { iTimeoutReached = timeoutReached; }
287    }
288}