    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}