001package org.cpsolver.ifs.extension;
002
003import java.util.Collection;
004import java.util.Map;
005
006import org.cpsolver.ifs.assignment.Assignment;
007import org.cpsolver.ifs.assignment.context.AssignmentContext;
008import org.cpsolver.ifs.assignment.context.ExtensionWithContext;
009import org.cpsolver.ifs.model.Model;
010import org.cpsolver.ifs.model.Value;
011import org.cpsolver.ifs.model.Variable;
012import org.cpsolver.ifs.solution.Solution;
013import org.cpsolver.ifs.solution.SolutionListener;
014import org.cpsolver.ifs.solver.Solver;
015import org.cpsolver.ifs.util.DataProperties;
016
017
018/**
019 * Go back to the best known solution when no better solution is found within
020 * the given amount of iterations.
021 * 
022 * @version IFS 1.3 (Iterative Forward Search)<br>
023 *          Copyright (C) 2006 - 2014 Tomáš Müller<br>
024 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
025 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
026 * <br>
027 *          This library is free software; you can redistribute it and/or modify
028 *          it under the terms of the GNU Lesser General Public License as
029 *          published by the Free Software Foundation; either version 3 of the
030 *          License, or (at your option) any later version. <br>
031 * <br>
032 *          This library is distributed in the hope that it will be useful, but
033 *          WITHOUT ANY WARRANTY; without even the implied warranty of
034 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
035 *          Lesser General Public License for more details. <br>
036 * <br>
037 *          You should have received a copy of the GNU Lesser General Public
038 *          License along with this library; if not see
039 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
040 * @param <V> Variable
041 * @param <T> Value
042 */
043public class SearchIntensification<V extends Variable<V, T>, T extends Value<V, T>> extends ExtensionWithContext<V, T, SearchIntensification<V, T>.Context> implements SolutionListener<V, T> {
044    private static org.apache.logging.log4j.Logger sLogger = org.apache.logging.log4j.LogManager.getLogger(SearchIntensification.class);
045    private long iInitialIterationLimit = 100;
046    private ConflictStatistics<V, T> iCBS = null;
047    private int iResetInterval = 5;
048    private int iMux = 2;
049    private int iMuxInterval = 2;
050
051    public SearchIntensification(Solver<V, T> solver, DataProperties properties) {
052        super(solver, properties);
053        iInitialIterationLimit = properties.getPropertyLong("SearchIntensification.IterationLimit", iInitialIterationLimit);
054        iResetInterval = properties.getPropertyInt("SearchIntensification.ResetInterval", iResetInterval);
055        iMuxInterval = properties.getPropertyInt("SearchIntensification.MultiplyInterval", iMuxInterval);
056        iMux = properties.getPropertyInt("SearchIntensification.Multiply", iMux);
057    }
058
059    @Override
060    public boolean init(Solver<V, T> solver) {
061        if (iResetInterval > 0) {
062            for (Extension<V, T> ex : solver.getExtensions()) {
063                if (ConflictStatistics.class.isInstance(ex)) {
064                    iCBS = (ConflictStatistics<V, T>) ex;
065                    break;
066                }
067            }
068        }
069        return super.init(solver);
070    }
071
072    @Override
073    public void register(Model<V, T> model) {
074        super.register(model);
075        getSolver().currentSolution().addSolutionListener(this);
076    }
077
078    @Override
079    public void unregister(Model<V, T> model) {
080        super.unregister(model);
081        getSolver().currentSolution().removeSolutionListener(this);
082    }
083
084    @Override
085    public void afterAssigned(Assignment<V, T> assignment, long iteration, T value) {
086        getContext(assignment).afterAssigned(assignment, iteration, value);
087    }
088
089    @Override
090    public void bestSaved(Solution<V, T> solution) {
091        Context context = getContext(solution.getAssignment());
092        context.bestSaved(solution);
093    }
094
095    @Override
096    public void solutionUpdated(Solution<V, T> solution) {
097    }
098
099    @Override
100    public void bestCleared(Solution<V, T> solution) {
101    }
102
103    @Override
104    public void bestRestored(Solution<V, T> solution) {
105    }
106
107    @Override
108    public void getInfo(Solution<V, T> solution, Map<String, String> info) {
109    }
110
111    @Override
112    public void getInfo(Solution<V, T> solution, Map<String, String> info, Collection<V> variables) {
113    }
114    
115    /**
116     * Assignment context
117     */
118    public class Context implements AssignmentContext {
119        private int iResetCounter = 0;
120        private int iMuxCounter = 0;
121        private long iLastReturn = 0;
122        private long iIterationLimit = 100;
123        
124        public Context(Assignment<V, T> assignment) {
125            iIterationLimit = iInitialIterationLimit;
126        }
127        
128        public void afterAssigned(Assignment<V, T> assignment, long iteration, T value) {
129            if (iIterationLimit > 0 && iteration > 0) {
130                Solution<V, T> solution = getSolver().currentSolution();
131                if (solution.getBestIteration() < 0 || !solution.isBestComplete())
132                    return;
133                long bestIt = Math.max(solution.getBestIteration(), iLastReturn);
134                long currIt = solution.getIteration();
135                if (currIt - bestIt > iIterationLimit) {
136                    iLastReturn = currIt;
137                    iResetCounter++;
138                    iMuxCounter++;
139                    sLogger.debug("Going back to the best known solution...");
140                    solution.restoreBest();
141                    sLogger.debug("Reset counter set to " + iResetCounter);
142                    if (iMuxInterval > 0 && (iMuxCounter % iMuxInterval) == 0) {
143                        iIterationLimit *= iMux;
144                        sLogger.debug("Iteration limit increased to " + iIterationLimit);
145                    }
146                    if (iCBS != null && iResetInterval > 0 && (iResetCounter % iResetInterval) == 0) {
147                        sLogger.debug("Reseting CBS...");
148                        iCBS.reset();
149                    }
150                }
151            }
152        }
153
154        public void bestSaved(Solution<V, T> solution) {
155            if (iResetCounter > 0)
156                sLogger.debug("Reset counter set to zero.");
157            iResetCounter = 0;
158            iMuxCounter = 0;
159            iIterationLimit = iInitialIterationLimit;
160        }
161    }
162
163    @Override
164    public Context createAssignmentContext(Assignment<V, T> assignment) {
165        return new Context(assignment);
166    }
167}