    001package org.cpsolver.ifs.algorithms;
    002
    003import java.text.DecimalFormat;
    004import java.util.ArrayList;
    005import java.util.Collection;
    006import java.util.Iterator;
    007import java.util.List;
    008import java.util.Map;
    009
    010import org.apache.log4j.Logger;
    011import org.cpsolver.ifs.algorithms.neighbourhoods.HillClimberSelection;
    012import org.cpsolver.ifs.algorithms.neighbourhoods.RandomMove;
    013import org.cpsolver.ifs.algorithms.neighbourhoods.RandomSwapMove;
    014import org.cpsolver.ifs.algorithms.neighbourhoods.SuggestionMove;
    015import org.cpsolver.ifs.assignment.Assignment;
    016import org.cpsolver.ifs.assignment.context.AssignmentContext;
    017import org.cpsolver.ifs.assignment.context.NeighbourSelectionWithContext;
    018import org.cpsolver.ifs.heuristics.NeighbourSelection;
    019import org.cpsolver.ifs.model.LazyNeighbour;
    020import org.cpsolver.ifs.model.Model;
    021import org.cpsolver.ifs.model.Neighbour;
    022import org.cpsolver.ifs.model.Value;
    023import org.cpsolver.ifs.model.Variable;
    024import org.cpsolver.ifs.model.LazyNeighbour.LazyNeighbourAcceptanceCriterion;
    025import org.cpsolver.ifs.solution.Solution;
    026import org.cpsolver.ifs.solution.SolutionListener;
    027import org.cpsolver.ifs.solver.Solver;
    028import org.cpsolver.ifs.util.DataProperties;
    029import org.cpsolver.ifs.util.JProf;
    030import org.cpsolver.ifs.util.Progress;
    031import org.cpsolver.ifs.util.ToolBox;
    032
    033
    034/**
    035 * Base class for the search techniques like hill climber, great deluge, or simulated annealing.
    036 * It implements the {@link SolutionListener} and the variable neighbourhood selection.
    037 *
    038 * <br>
    039 *
    040 * @version IFS 1.3 (Iterative Forward Search)<br>
    041 *          Copyright (C) 2014 Tomáš Müller<br>
    042 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    043 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    044 * <br>
    045 *          This library is free software; you can redistribute it and/or modify
    046 *          it under the terms of the GNU Lesser General Public License as
    047 *          published by the Free Software Foundation; either version 3 of the
    048 *          License, or (at your option) any later version. <br>
    049 * <br>
    050 *          This library is distributed in the hope that it will be useful, but
    051 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    052 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    053 *          Lesser General Public License for more details. <br>
    054 * <br>
    055 *          You should have received a copy of the GNU Lesser General Public
    056 *          License along with this library; if not see
    057 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    058 * @param <V> Variable
    059 * @param <T> Value
    060 **/
    061public abstract class NeighbourSearch<V extends Variable<V, T>, T extends Value<V, T>> extends NeighbourSelectionWithContext<V, T, NeighbourSearch<V, T>.NeighbourSearchContext> implements LazyNeighbourAcceptanceCriterion<V, T>, SolutionListener<V, T> {
    062    private Logger iLog;
    063    protected DecimalFormat iDF2 = new DecimalFormat("0.00");
    064
    065    private Progress iProgress = null;
    066    protected String iPhase = null;
    067
    068    private List<NeighbourSelector<V, T>> iNeighbours = null;
    069    private boolean iRandomSelection = false;
    070    private boolean iUpdatePoints = false;
    071    private double iTotalBonus;
    072    private Solver<V, T> iSolver = null;
    073
    074    @SuppressWarnings("unchecked")
    075    public NeighbourSearch(DataProperties properties) {
    076        iPhase = getClass().getSimpleName().replaceAll("(?<=[^A-Z])([A-Z])"," $1");
    077        iLog = Logger.getLogger(getClass());
    078        iRandomSelection = properties.getPropertyBoolean(getParameterBaseName() + ".Random", iRandomSelection);
    079        iUpdatePoints = properties.getPropertyBoolean(getParameterBaseName() + ".Update", iUpdatePoints);
    080        String neighbours = properties.getProperty(getParameterBaseName() + ".Neighbours",
    081                RandomMove.class.getName() + ";" + RandomSwapMove.class.getName() + "@0.01;" + SuggestionMove.class.getName() + "@0.01");
    082        neighbours += ";" + properties.getProperty(getParameterBaseName() + ".AdditionalNeighbours", "");
    083        iNeighbours = new ArrayList<NeighbourSelector<V,T>>();
    084        for (String neighbour: neighbours.split("\\;")) {
    085            if (neighbour == null || neighbour.isEmpty()) continue;
    086            try {
    087                double bonus = 1.0;
    088                if (neighbour.indexOf('@')>=0) {
    089                    bonus = Double.parseDouble(neighbour.substring(neighbour.indexOf('@') + 1));
    090                    neighbour = neighbour.substring(0, neighbour.indexOf('@'));
    091                }
    092                Class<NeighbourSelection<V, T>> clazz = (Class<NeighbourSelection<V, T>>)Class.forName(neighbour);
    093                NeighbourSelection<V, T> selection = clazz.getConstructor(DataProperties.class).newInstance(properties);
    094                addNeighbourSelection(selection, bonus);
    095            } catch (Exception e) {
    096                iLog.error("Unable to use " + neighbour + ": " + e.getMessage());
    097            }
    098        }
    099    }
    100
    101    /**
    102     * Prints a message into the log
    103     * @param message a message to log
    104     */
    105    protected void info(String message) {
    106        iProgress.debug("[" + Thread.currentThread().getName() + "] " + iPhase + "> " + message);
    107    }
    108
    109    /**
    110     * Set search progress
    111     * @param progress between 0 and 100
    112     */
    113    protected void setProgress(long progress) {
    114        // iProgress.setProgress(progress);
    115    }
    116
    117    /**
    118     * Set search progress phase
    119     * @param phase a progress phase to set
    120     */
    121    protected void setProgressPhase(String phase) {
    122        iProgress.info("[" + Thread.currentThread().getName() + "] " + phase);
    123        // iProgress.setPhase(phase);
    124    }
    125
    126    /**
    127     * Add neighbour selection
    128     * @param ns a selection
    129     * @param bonus execution bonus (more bonus means more executions of this neighbour selection, see {@link NeighbourSelector})
    130     */
    131    protected void addNeighbourSelection(NeighbourSelection<V,T> ns, double bonus) {
    132        iNeighbours.add(new NeighbourSelector<V,T>(ns, bonus, iUpdatePoints));
    133    }
    134
    135    private double totalPoints() {
    136        if (!iUpdatePoints) return iTotalBonus;
    137        double total = 0;
    138        for (NeighbourSelector<V,T> ns: iNeighbours)
    139            total += ns.getPoints();
    140        return total;
    141    }
    142
    143    /**
    144     * Set HC mode for all the neighbour selections that support the {@link HillClimberSelection} interface.
    145     * @param hcMode true if the search is a hill climber (worsening moves are always rejected)
    146     */
    147    protected void setHCMode(boolean hcMode) {
    148        for (NeighbourSelector<V,T> s: iNeighbours) {
    149            if (s.selection() instanceof HillClimberSelection)
    150                ((HillClimberSelection)s.selection()).setHcMode(hcMode);
    151        }
    152    }
    153
    154    /**
    155     * Return list of neighbour selections
    156     * @return list of neighbour selections
    157     */
    158    protected List<? extends NeighbourSelection<V, T>> getNeighbours() {
    159        return iNeighbours;
    160    }
    161
    162    @Override
    163    public void init(Solver<V, T> solver) {
    164        super.init(solver);
    165        iProgress = Progress.getInstance(solver.currentSolution().getModel());
    166        iSolver = solver;
    167        solver.currentSolution().addSolutionListener(this);
    168        // solver.setUpdateProgress(false);
    169        for (NeighbourSelection<V, T> neighbour: iNeighbours)
    170            neighbour.init(solver);
    171        iTotalBonus = 0;
    172        for (NeighbourSelector<V,T> s: iNeighbours) {
    173            s.init(solver);
    174            iTotalBonus += s.getBonus();
    175        }
    176    }
    177
    178    /**
    179     * Generate and return next neighbour selection
    180     * @return next neighbour selection to use
    181     */
    182    protected NeighbourSelection<V,T> nextNeighbourSelection() {
    183        NeighbourSelector<V,T> ns = null;
    184        if (iRandomSelection) {
    185            ns = ToolBox.random(iNeighbours);
    186        } else {
    187            double points = (ToolBox.random() * totalPoints());
    188            for (Iterator<NeighbourSelector<V,T>> i = iNeighbours.iterator(); i.hasNext(); ) {
    189                ns = i.next();
    190                points -= (iUpdatePoints ? ns.getPoints() : ns.getBonus());
    191                if (points <= 0) break;
    192            }
    193        }
    194        return ns;
    195    }
    196
    197    /**
    198     * Log some information about neigbour selections once in a while
    199     */
    200    protected void logNeibourStatus() {
    201        if (iUpdatePoints)
    202            for (NeighbourSelector<V,T> ns: iNeighbours)
    203                iLog.info("  "+ns+" ("+iDF2.format(ns.getPoints())+" pts, "+iDF2.format(100.0*(iUpdatePoints?ns.getPoints():ns.getBonus())/totalPoints())+"%)");
    204    }
    205
    206    /**
    207     * Generate a random move
    208     * @param solution current solution
    209     * @return generated neighbour
    210     */
    211    public Neighbour<V, T> generateMove(Solution<V, T> solution) {
    212        return nextNeighbourSelection().selectNeighbour(solution);
    213    }
    214
    215    @Override
    216    public Neighbour<V, T> selectNeighbour(Solution<V, T> solution) {
    217        NeighbourSearchContext context = getContext(solution.getAssignment());
    218        context.activateIfNeeded(solution);
    219        while (context.canContinue(solution)) {
    220            if (iSolver != null && iSolver.isStop()) return null;
    221            context.incIteration(solution);
    222            Neighbour<V,T> n = generateMove(solution);
    223            if (n != null && accept(context, solution, n))
    224                return n;
    225        }
    226        context.deactivateIfNeeded(solution);
    227        return null;
    228    }
    229
    230    /**
    231     * True if the generated move is to be accepted.
    232     * @param context search context
    233     * @param solution current solution
    234     * @param neighbour a generated move
    235     * @return true if the generated move should be assigned
    236     */
    237    protected boolean accept(NeighbourSearchContext context, Solution<V, T> solution, Neighbour<V, T> neighbour) {
    238        if (neighbour instanceof LazyNeighbour) {
    239            ((LazyNeighbour<V, T>)neighbour).setAcceptanceCriterion(this);
    240            return true;
    241        }
    242        return context.accept(solution.getAssignment(), solution.getModel(), neighbour, neighbour.value(solution.getAssignment()), false);
    243    }
    244
    245    /** Accept lazy neighbour -- calling the acceptance criterion with lazy = true. */
    246    @Override
    247    public boolean accept(Assignment<V, T> assignment, LazyNeighbour<V, T> neighbour, double value) {
    248        return getContext(assignment).accept(assignment, neighbour.getModel(), neighbour, value, true);
    249    }
    250
    251    /**
    252     * Parameter base name. This can be used to distinguish between parameters of different search algorithms.
    253     * @return solver parameter base name for this search technique
    254     */
    255    public abstract String getParameterBaseName();
    256
    257    @Override
    258    public void bestSaved(Solution<V, T> solution) {
    259        getContext(solution.getAssignment()).bestSaved(solution);
    260    }
    261
    262    @Override
    263    public void solutionUpdated(Solution<V, T> solution) {
    264        getContext(solution.getAssignment()).solutionUpdated(solution);
    265    }
    266
    267    @Override
    268    public void getInfo(Solution<V, T> solution, Map<String, String> info) {
    269        getContext(solution.getAssignment()).getInfo(solution, info);
    270    }
    271
    272    @Override
    273    public void getInfo(Solution<V, T> solution, Map<String, String> info, Collection<V> variables) {
    274        getContext(solution.getAssignment()).getInfo(solution, info, variables);
    275    }
    276
    277    @Override
    278    public void bestCleared(Solution<V, T> solution) {
    279        getContext(solution.getAssignment()).bestCleared(solution);
    280    }
    281
    282    @Override
    283    public void bestRestored(Solution<V, T> solution) {
    284        getContext(solution.getAssignment()).bestRestored(solution);
    285    }
    286
    287    /**
    288     * In single solution multiple threads environments return true if the given solution is of the first thread
    289     * @param solution current solution
    290     * @return if the current thread is master (can alter bound etc.)
    291     */
    292    public boolean isMaster(Solution<V, T> solution) {
    293        return !hasContextOverride() || solution.getAssignment().getIndex() <= 1;
    294    }
    295
    296    /**
    297     * Search context
    298     */
    299    public abstract class NeighbourSearchContext implements AssignmentContext, SolutionListener<V, T> {
    300        protected long iT0 = -1;
    301        protected int iIter = 0;
    302
    303        /** Called just before the neighbourhood search is called for the first time.
    304         * @param solution current solution
    305         **/
    306        protected void activate(Solution<V, T> solution) {
    307            iT0 = JProf.currentTimeMillis();
    308            iIter = 0;
    309            setProgressPhase(iPhase + "...");
    310        }
    311
    312        private synchronized void activateIfNeeded(Solution<V, T> solution) {
    313            if (iT0 < 0) activate(solution);
    314        }
    315
    316        /** Called when the search cannot continue, just before a null neighbour is returned
    317         * @param solution current solution
    318         **/
    319        protected void deactivate(Solution<V, T> solution) {
    320            iT0 = -1;
    321        }
    322
    323        private synchronized void deactivateIfNeeded(Solution<V, T> solution) {
    324            if (isMaster(solution)) deactivate(solution);
    325        }
    326
    327        /**
    328         * Increment iteration counters etc.
    329         * @param solution current solution
    330         */
    331        protected void incIteration(Solution<V, T> solution) {
    332            iIter++;
    333        }
    334
    335        /**
    336         * Running time in milliseconds (since the last call of activate)
    337         * @return running time
    338         */
    339        protected long getTimeMillis() { return JProf.currentTimeMillis() - iT0; }
    340
    341        /**
    342         * Return false if the search is to be stopped. Null neighbour is returned when this method returns false.
    343         * @param solution current solution
    344         * @return true if can continue
    345         */
    346        protected boolean canContinue(Solution<V, T> solution) {
    347            return true;
    348        }
    349
    350        /** Acceptance criterion. If lazy, current assignment already contains the given neighbour.
    351         * @param assignment current assignment
    352         * @param model problem model
    353         * @param neighbour a generated move
    354         * @param value value of the generated move (i.e., its impact on the solution value)
    355         * @param lazy true if lazy move
    356         * @return true if the generated move is to be assigned
    357         **/
    358        protected abstract boolean accept(Assignment<V, T> assignment, Model<V, T> model, Neighbour<V, T> neighbour, double value, boolean lazy);
    359
    360        @Override
    361        public void bestSaved(Solution<V, T> solution) {
    362        }
    363
    364        @Override
    365        public void solutionUpdated(Solution<V, T> solution) {
    366        }
    367
    368        @Override
    369        public void getInfo(Solution<V, T> solution, Map<String, String> info) {
    370        }
    371
    372        @Override
    373        public void getInfo(Solution<V, T> solution, Map<String, String> info, Collection<V> variables) {
    374        }
    375
    376        @Override
    377        public void bestCleared(Solution<V, T> solution) {
    378        }
    379
    380        @Override
    381        public void bestRestored(Solution<V, T> solution) {
    382        }
    383    }
    384}