001package net.sf.cpsolver.ifs.algorithms;
002
003import net.sf.cpsolver.ifs.model.Model;
004import net.sf.cpsolver.ifs.model.Neighbour;
005import net.sf.cpsolver.ifs.model.Value;
006import net.sf.cpsolver.ifs.model.Variable;
007import net.sf.cpsolver.ifs.solution.Solution;
008import net.sf.cpsolver.ifs.util.DataProperties;
009
010/**
011 * Step counting hill climber. Unlike with the ordinary hill climber, there is a bound.
012 * The bound is updated (to the value of the current solution) after a given number of
013 * moves. Based on the given mode, either all moves, only accepted moves, or only improving
014 * moves are counted. 
015 * <br>
016 * 
017 * @version IFS 1.2 (Iterative Forward Search)<br>
018 *          Copyright (C) 2014 Tomáš Müller<br>
019 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
020 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
021 * <br>
022 *          This library is free software; you can redistribute it and/or modify
023 *          it under the terms of the GNU Lesser General Public License as
024 *          published by the Free Software Foundation; either version 3 of the
025 *          License, or (at your option) any later version. <br>
026 * <br>
027 *          This library is distributed in the hope that it will be useful, but
028 *          WITHOUT ANY WARRANTY; without even the implied warranty of
029 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
030 *          Lesser General Public License for more details. <br>
031 * <br>
032 *          You should have received a copy of the GNU Lesser General Public
033 *          License along with this library; if not see
034 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
035 */
036public class StepCountingHillClimber<V extends Variable<V, T>, T extends Value<V, T>> extends HillClimber<V, T> {
037    public static enum Mode {
038        ALL,
039        ACCEPTED,
040        IMPROVING
041    }
042    protected Double iBound = null;
043    protected int iCounter = 0;
044    protected int iCounterLimit = 100;
045    protected Mode iCounterMode = Mode.ACCEPTED;
046
047    /**
048     * Constructor
049     * <ul>
050     * <li>HillClimber.CounterLimit ... number of moves after which the bound is reset (defaults to 1000)
051     * <li>HillClimber.CounterMode ... counter mode (all: count all moves, accepted: count accepted moves, improving: count improving moves)
052     * </ul>
053     */
054    public StepCountingHillClimber(DataProperties properties, String name) {
055        super(properties);
056        iSetHCMode = false;
057    }
058    
059    /**
060     * Reset the bound and the steps counter.
061     */
062    @Override
063    public void activate(Solution<V, T> solution) {
064        super.activate(solution);
065        iBound = solution.getModel().getTotalValue();
066        iCounter = 0;
067    }
068    
069    /**
070     * Increase iteration number, also update bound when the given number of steps is reached.
071     */
072    @Override
073    public void incIteration(Solution<V, T> solution) {
074        iIter++;
075        if (iIter % 10000 == 0) {
076            iLog.info("Iter=" + (iIter / 1000)+"k, NonImpIter=" + iDF2.format((iIter-iLastImprovingIter)/1000.0)+"k, Speed="+iDF2.format(1000.0*iIter/getTimeMillis())+" it/s, Bound=" + iDF2.format(iBound));
077            logNeibourStatus();
078        }
079        iProgress.setProgress(Math.round(100.0 * (iIter - iLastImprovingIter) / iMaxIdleIters));
080        if (iCounter >= iCounterLimit) {
081            iBound = solution.getModel().getTotalValue(); 
082            iCounter = 0;
083        }
084    }
085
086    /**
087     * Accept any move that does not worsen the solution (value <= 0) or that is below the bound. Also increase the step counter.
088     */
089    @Override
090    protected boolean accept(Model<V,T> model, Neighbour<V, T> neighbour, double value, boolean lazy) {
091        boolean accept = (value <= 0.0 || (lazy ? model.getTotalValue() : value + model.getTotalValue()) < iBound);
092        switch (iCounterMode) {
093            case ALL:
094                iCounter ++;
095                break;
096            case ACCEPTED:
097                if (accept) iCounter ++;
098                break;
099            case IMPROVING:
100                if (value < 0) iCounter ++;
101                break;
102        }
103        return accept;
104    }
105    
106    /**
107     * Stop the search when the number of idle iterations is reached and the bound is no longer decreasing
108     */
109    @Override
110    protected boolean canContinue(Solution<V, T> solution) {
111        return super.canContinue(solution) || iCounter < iCounterLimit || solution.getModel().getTotalValue() < iBound;
112    }
113}