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