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 * @author  Tomáš Müller
023 * @version IFS 1.3 (Iterative Forward Search)<br>
024 *          Copyright (C) 2006 - 2014 Tomáš Müller<br>
025 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
026 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
027 * <br>
028 *          This library is free software; you can redistribute it and/or modify
029 *          it under the terms of the GNU Lesser General Public License as
030 *          published by the Free Software Foundation; either version 3 of the
031 *          License, or (at your option) any later version. <br>
032 * <br>
033 *          This library is distributed in the hope that it will be useful, but
034 *          WITHOUT ANY WARRANTY; without even the implied warranty of
035 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
036 *          Lesser General Public License for more details. <br>
037 * <br>
038 *          You should have received a copy of the GNU Lesser General Public
039 *          License along with this library; if not see
040 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
041 * @param <V> Variable
042 * @param <T> Value
043 */
044public class SearchIntensification<V extends Variable<V, T>, T extends Value<V, T>> extends ExtensionWithContext<V, T, SearchIntensification<V, T>.Context> implements SolutionListener<V, T> {
045    private static org.apache.logging.log4j.Logger sLogger = org.apache.logging.log4j.LogManager.getLogger(SearchIntensification.class);
046    private long iInitialIterationLimit = 100;
047    private ConflictStatistics<V, T> iCBS = null;
048    private int iResetInterval = 5;
049    private int iMux = 2;
050    private int iMuxInterval = 2;
051
052    public SearchIntensification(Solver<V, T> solver, DataProperties properties) {
053        super(solver, properties);
054        iInitialIterationLimit = properties.getPropertyLong("SearchIntensification.IterationLimit", iInitialIterationLimit);
055        iResetInterval = properties.getPropertyInt("SearchIntensification.ResetInterval", iResetInterval);
056        iMuxInterval = properties.getPropertyInt("SearchIntensification.MultiplyInterval", iMuxInterval);
057        iMux = properties.getPropertyInt("SearchIntensification.Multiply", iMux);
058    }
059
060    @Override
061    public boolean init(Solver<V, T> solver) {
062        if (iResetInterval > 0) {
063            for (Extension<V, T> ex : solver.getExtensions()) {
064                if (ConflictStatistics.class.isInstance(ex)) {
065                    iCBS = (ConflictStatistics<V, T>) ex;
066                    break;
067                }
068            }
069        }
070        return super.init(solver);
071    }
072
073    @Override
074    public void register(Model<V, T> model) {
075        super.register(model);
076        getSolver().currentSolution().addSolutionListener(this);
077    }
078
079    @Override
080    public void unregister(Model<V, T> model) {
081        super.unregister(model);
082        getSolver().currentSolution().removeSolutionListener(this);
083    }
084
085    @Override
086    public void afterAssigned(Assignment<V, T> assignment, long iteration, T value) {
087        getContext(assignment).afterAssigned(assignment, iteration, value);
088    }
089
090    @Override
091    public void bestSaved(Solution<V, T> solution) {
092        Context context = getContext(solution.getAssignment());
093        context.bestSaved(solution);
094    }
095
096    @Override
097    public void solutionUpdated(Solution<V, T> solution) {
098    }
099
100    @Override
101    public void bestCleared(Solution<V, T> solution) {
102    }
103
104    @Override
105    public void bestRestored(Solution<V, T> solution) {
106    }
107
108    @Override
109    public void getInfo(Solution<V, T> solution, Map<String, String> info) {
110    }
111
112    @Override
113    public void getInfo(Solution<V, T> solution, Map<String, String> info, Collection<V> variables) {
114    }
115    
116    /**
117     * Assignment context
118     */
119    public class Context implements AssignmentContext {
120        private int iResetCounter = 0;
121        private int iMuxCounter = 0;
122        private long iLastReturn = 0;
123        private long iIterationLimit = 100;
124        
125        public Context(Assignment<V, T> assignment) {
126            iIterationLimit = iInitialIterationLimit;
127        }
128        
129        public void afterAssigned(Assignment<V, T> assignment, long iteration, T value) {
130            if (iIterationLimit > 0 && iteration > 0) {
131                Solution<V, T> solution = getSolver().currentSolution();
132                if (solution.getBestIteration() < 0 || !solution.isBestComplete())
133                    return;
134                long bestIt = Math.max(solution.getBestIteration(), iLastReturn);
135                long currIt = solution.getIteration();
136                if (currIt - bestIt > iIterationLimit) {
137                    iLastReturn = currIt;
138                    iResetCounter++;
139                    iMuxCounter++;
140                    sLogger.debug("Going back to the best known solution...");
141                    solution.restoreBest();
142                    sLogger.debug("Reset counter set to " + iResetCounter);
143                    if (iMuxInterval > 0 && (iMuxCounter % iMuxInterval) == 0) {
144                        iIterationLimit *= iMux;
145                        sLogger.debug("Iteration limit increased to " + iIterationLimit);
146                    }
147                    if (iCBS != null && iResetInterval > 0 && (iResetCounter % iResetInterval) == 0) {
148                        sLogger.debug("Reseting CBS...");
149                        iCBS.reset();
150                    }
151                }
152            }
153        }
154
155        public void bestSaved(Solution<V, T> solution) {
156            if (iResetCounter > 0)
157                sLogger.debug("Reset counter set to zero.");
158            iResetCounter = 0;
159            iMuxCounter = 0;
160            iIterationLimit = iInitialIterationLimit;
161        }
162    }
163
164    @Override
165    public Context createAssignmentContext(Assignment<V, T> assignment) {
166        return new Context(assignment);
167    }
168}