001 package net.sf.cpsolver.ifs.extension;
002
003 import java.util.Collection;
004 import java.util.Map;
005
006 import net.sf.cpsolver.ifs.model.Model;
007 import net.sf.cpsolver.ifs.model.Value;
008 import net.sf.cpsolver.ifs.model.Variable;
009 import net.sf.cpsolver.ifs.solution.Solution;
010 import net.sf.cpsolver.ifs.solution.SolutionListener;
011 import net.sf.cpsolver.ifs.solver.Solver;
012 import net.sf.cpsolver.ifs.util.DataProperties;
013
014 /**
015 * Go back to the best known solution when no better solution is found within
016 * the given amount of iterations.
017 *
018 * @version IFS 1.2 (Iterative Forward Search)<br>
019 * Copyright (C) 2006 - 2010 Tomas Muller<br>
020 * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
021 * <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
022 * <br>
023 * This library is free software; you can redistribute it and/or modify
024 * it under the terms of the GNU Lesser General Public License as
025 * published by the Free Software Foundation; either version 3 of the
026 * License, or (at your option) any later version. <br>
027 * <br>
028 * This library is distributed in the hope that it will be useful, but
029 * WITHOUT ANY WARRANTY; without even the implied warranty of
030 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
031 * Lesser General Public License for more details. <br>
032 * <br>
033 * You should have received a copy of the GNU Lesser General Public
034 * License along with this library; if not see
035 * <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
036 */
037 public class SearchIntensification<V extends Variable<V, T>, T extends Value<V, T>> extends Extension<V, T> implements
038 SolutionListener<V, T> {
039 private static org.apache.log4j.Logger sLogger = org.apache.log4j.Logger.getLogger(SearchIntensification.class);
040 private long iInitialIterationLimit = 100;
041 private long iIterationLimit = 100;
042 private long iLastReturn = 0;
043 private ConflictStatistics<V, T> iCBS = null;
044 private int iResetInterval = 5;
045 private int iResetCounter = 0;
046 private int iMux = 2;
047 private int iMuxInterval = 2;
048 private int iMuxCounter = 0;
049
050 public SearchIntensification(Solver<V, T> solver, DataProperties properties) {
051 super(solver, properties);
052 iInitialIterationLimit = properties.getPropertyLong("SearchIntensification.IterationLimit",
053 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(long iteration, T value) {
086 if (iIterationLimit > 0 && iteration > 0) {
087 Solution<V, T> solution = getSolver().currentSolution();
088 if (solution.getBestIteration() < 0 || !solution.isBestComplete())
089 return;
090 long bestIt = Math.max(solution.getBestIteration(), iLastReturn);
091 long currIt = solution.getIteration();
092 if (currIt - bestIt > iIterationLimit) {
093 iLastReturn = currIt;
094 iResetCounter++;
095 iMuxCounter++;
096 sLogger.debug("Going back to the best known solution...");
097 solution.restoreBest();
098 sLogger.debug("Reset counter set to " + iResetCounter);
099 if (iMuxInterval > 0 && (iMuxCounter % iMuxInterval) == 0) {
100 iIterationLimit *= iMux;
101 sLogger.debug("Iteration limit increased to " + iIterationLimit);
102 }
103 if (iCBS != null && iResetInterval > 0 && (iResetCounter % iResetInterval) == 0) {
104 sLogger.debug("Reseting CBS...");
105 iCBS.reset();
106 }
107 }
108 }
109 }
110
111 @Override
112 public void bestSaved(Solution<V, T> solution) {
113 if (iResetCounter > 0)
114 sLogger.debug("Reset counter set to zero.");
115 iResetCounter = 0;
116 iMuxCounter = 0;
117 iIterationLimit = iInitialIterationLimit;
118 }
119
120 @Override
121 public void solutionUpdated(Solution<V, T> solution) {
122 }
123
124 @Override
125 public void bestCleared(Solution<V, T> solution) {
126 }
127
128 @Override
129 public void bestRestored(Solution<V, T> solution) {
130 }
131
132 @Override
133 public void getInfo(Solution<V, T> solution, Map<String, String> info) {
134 }
135
136 @Override
137 public void getInfo(Solution<V, T> solution, Map<String, String> info, Collection<V> variables) {
138 }
139 }