001package org.cpsolver.ifs.algorithms;
002
003import org.cpsolver.ifs.assignment.Assignment;
004import org.cpsolver.ifs.model.Model;
005import org.cpsolver.ifs.model.Neighbour;
006import org.cpsolver.ifs.model.Value;
007import org.cpsolver.ifs.model.Variable;
008import org.cpsolver.ifs.solution.Solution;
009import org.cpsolver.ifs.util.DataProperties;
010
011/**
012 * Step counting hill climber. Unlike with the ordinary hill climber, there is a bound.
013 * The bound is updated (to the value of the current solution) after a given number of
014 * moves. Based on the given mode, either all moves, only accepted moves, or only improving
015 * moves are counted. 
016 * <br>
017 * 
018 * @author  Tomáš Müller
019 * @version IFS 1.3 (Iterative Forward Search)<br>
020 *          Copyright (C) 2014 Tomáš Müller<br>
021 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
022 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
023 * <br>
024 *          This library is free software; you can redistribute it and/or modify
025 *          it under the terms of the GNU Lesser General Public License as
026 *          published by the Free Software Foundation; either version 3 of the
027 *          License, or (at your option) any later version. <br>
028 * <br>
029 *          This library is distributed in the hope that it will be useful, but
030 *          WITHOUT ANY WARRANTY; without even the implied warranty of
031 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
032 *          Lesser General Public License for more details. <br>
033 * <br>
034 *          You should have received a copy of the GNU Lesser General Public
035 *          License along with this library; if not see
036 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
037 * @param <V> Variable
038 * @param <T> Value
039 */
040public class StepCountingHillClimber<V extends Variable<V, T>, T extends Value<V, T>> extends HillClimber<V, T> {
041    public static enum Mode {
042        ALL,
043        ACCEPTED,
044        IMPROVING
045    }
046    protected int iCounterLimit = 100;
047    protected Mode iCounterMode = Mode.ACCEPTED;
048    protected Double[] iCounterLimitAdjusts = null;
049
050    /**
051     * Constructor
052     * <ul>
053     * <li>HillClimber.CounterLimit ... number of moves after which the bound is reset (defaults to 1000)
054     * <li>HillClimber.CounterMode ... counter mode (all: count all moves, accepted: count accepted moves, improving: count improving moves)
055     * </ul>
056     * @param properties solver configuration
057     */
058    public StepCountingHillClimber(DataProperties properties) {
059        super(properties);
060        iSetHCMode = false;
061        iCounterLimit = properties.getPropertyInt(getParameterBaseName() + ".CounterLimit", iCounterLimit);
062        iCounterMode = Mode.valueOf(properties.getProperty(getParameterBaseName() + ".CounterMode", iCounterMode.name()).toUpperCase());
063        iCounterLimitAdjusts = properties.getPropertyDoubleArry(getParameterBaseName() + ".CounterLimitAdjustments", null);
064    }
065
066    @Override
067    public NeighbourSearchContext createAssignmentContext(Assignment<V, T> assignment) {
068        return new StepCountingHillClimberContext();
069    }
070    
071    public class StepCountingHillClimberContext extends HillClimberContext {
072        protected Double iBound = null;
073        protected int iCounter = 0;
074
075        /**
076         * Reset the bound and the steps counter.
077         */
078        @Override
079        public void activate(Solution<V, T> solution) {
080            super.activate(solution);
081            iBound = solution.getModel().getTotalValue(solution.getAssignment());
082            iCounter = 0;
083        }
084        
085        protected int getCounterLimit(int idx) {
086            if (idx < 0 || iCounterLimitAdjusts == null || idx >= iCounterLimitAdjusts.length || iCounterLimitAdjusts[idx] == null) return iCounterLimit;
087            return (int) Math.round(iCounterLimit * iCounterLimitAdjusts[idx]);
088        }
089        
090        /**
091         * Increase iteration number, also update bound when the given number of steps is reached.
092         */
093        @Override
094        public void incIteration(Solution<V, T> solution) {
095            iIter++;
096            if (iIter % 10000 == 0) {
097                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));
098                logNeibourStatus();
099            }
100            // iProgress.setProgress(Math.round(100.0 * (iIter - iLastImprovingIter) / iMaxIdleIters));
101            if (iCounter >= getCounterLimit(solution.getAssignment().getIndex() - 1)) {
102                iBound = solution.getModel().getTotalValue(solution.getAssignment()); 
103                iCounter = 0;
104            }
105        }
106
107        /**
108         * Accept any move that does not worsen the solution (value &lt;= 0) or that is below the bound. Also increase the step counter.
109         */
110        @Override
111        protected boolean accept(Assignment<V, T> assignment, Model<V,T> model, Neighbour<V, T> neighbour, double value, boolean lazy) {
112            boolean accept = (value <= 0.0 || (lazy ? model.getTotalValue(assignment) : value + model.getTotalValue(assignment)) < iBound);
113            switch (iCounterMode) {
114                case ALL:
115                    iCounter ++;
116                    break;
117                case ACCEPTED:
118                    if (accept) iCounter ++;
119                    break;
120                case IMPROVING:
121                    if (value < 0) iCounter ++;
122                    break;
123            }
124            return accept;
125        }
126        
127        /**
128         * Stop the search when the number of idle iterations is reached and the bound is no longer decreasing
129         */
130        @Override
131        protected boolean canContinue(Solution<V, T> solution) {
132            return super.canContinue(solution) || iCounter < getCounterLimit(solution.getAssignment().getIndex() - 1) || solution.getModel().getTotalValue(solution.getAssignment()) < iBound;
133        }
134    }
135}