    001package net.sf.cpsolver.ifs.extension;
    002
    003import java.util.Collection;
    004import java.util.Map;
    005
    006import net.sf.cpsolver.ifs.model.Model;
    007import net.sf.cpsolver.ifs.model.Value;
    008import net.sf.cpsolver.ifs.model.Variable;
    009import net.sf.cpsolver.ifs.solution.Solution;
    010import net.sf.cpsolver.ifs.solution.SolutionListener;
    011import net.sf.cpsolver.ifs.solver.Solver;
    012import 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 Tomáš Müller<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 */
    037public 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}