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    }