    001package org.cpsolver.ifs.heuristics;
    002
    003import java.util.ArrayList;
    004import java.util.HashMap;
    005import java.util.List;
    006import java.util.Map;
    007
    008import org.apache.log4j.Logger;
    009import org.cpsolver.ifs.model.InfoProvider;
    010import org.cpsolver.ifs.model.Neighbour;
    011import org.cpsolver.ifs.model.Value;
    012import org.cpsolver.ifs.model.Variable;
    013import org.cpsolver.ifs.solution.Solution;
    014import org.cpsolver.ifs.solver.Solver;
    015import org.cpsolver.ifs.util.DataProperties;
    016import org.cpsolver.ifs.util.Progress;
    017
    018/**
    019 * A round robin neighbour selection. Two or more {@link NeighbourSelection}
    020 * needs to be registered within the selection. This selection criterion takes
    021 * the registered neighbour selections one by one and performs
    022 * {@link NeighbourSelection#init(Solver)} and then it is using
    023 * {@link NeighbourSelection#selectNeighbour(Solution)} to select a neighbour.
    024 * When null is returned by the underlaying selection, next registered neighbour
    025 * selection is initialized and used for the following selection(s). If the last
    026 * registered selection returns null, the selection is returned to the first
    027 * registered neighbour selection (it is initialized before used again).
    028 *
    029 * <br>
    030 * <br>
    031 *
    032 * @version StudentSct 1.3 (Student Sectioning)<br>
    033 *          Copyright (C) 2007 - 2014 Tomáš Müller<br>
    034 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    035 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    036 * <br>
    037 *          This library is free software; you can redistribute it and/or modify
    038 *          it under the terms of the GNU Lesser General Public License as
    039 *          published by the Free Software Foundation; either version 3 of the
    040 *          License, or (at your option) any later version. <br>
    041 * <br>
    042 *          This library is distributed in the hope that it will be useful, but
    043 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    044 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    045 *          Lesser General Public License for more details. <br>
    046 * <br>
    047 *          You should have received a copy of the GNU Lesser General Public
    048 *          License along with this library; if not see
    049 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    050 *
    051 * @param <V> Variable
    052 * @param <T> Value
    053 */
    054public class RoundRobinNeighbourSelection<V extends Variable<V, T>, T extends Value<V, T>> extends StandardNeighbourSelection<V, T> {
    055    protected static Logger sLogger = Logger.getLogger(RoundRobinNeighbourSelection.class);
    056    private int iSelectionIdx = -1;
    057    private List<NeighbourSelection<V, T>> iSelections = new ArrayList<NeighbourSelection<V, T>>();
    058    protected Solver<V, T> iSolver = null;
    059
    060    /**
    061     * Constructor
    062     *
    063     * @param properties
    064     *            configuration
    065     * @throws Exception thrown when initialization fails
    066     */
    067    public RoundRobinNeighbourSelection(DataProperties properties) throws Exception {
    068        super(properties);
    069    }
    070
    071    /** Register a neighbour selection
    072     * @param selection a neighbour selection to include in the selection
    073     **/
    074    public void registerSelection(NeighbourSelection<V, T> selection) {
    075        iSelections.add(selection);
    076    }
    077
    078    /** Initialization */
    079    @Override
    080    public void init(Solver<V, T> solver) {
    081        super.init(solver);
    082        iSolver = solver;
    083    }
    084
    085    /**
    086     * Select neighbour. A first registered selections is initialized and used
    087     * until it returns null, then the second registered selections is
    088     * initialized and used and vice versa.
    089     */
    090    @Override
    091    public Neighbour<V, T> selectNeighbour(Solution<V, T> solution) {
    092        int nrChanges = 0;
    093        while (nrChanges <= iSelections.size()) {
    094            int selectionIndex = getSelectionIndex();
    095            NeighbourSelection<V, T> selection = iSelections.get(selectionIndex % iSelections.size());
    096            Neighbour<V, T> neighbour = selection.selectNeighbour(solution);
    097            if (neighbour != null)
    098                return neighbour;
    099            changeSelection(selectionIndex);
    100            nrChanges ++;
    101        }
    102        return null;
    103    }
    104
    105    public int getSelectionIndex() {
    106        if (iSelectionIdx == -1) changeSelection(-1);
    107        iSolver.currentSolution().getLock().readLock().lock();
    108        try {
    109            return iSelectionIdx;
    110        } finally {
    111            iSolver.currentSolution().getLock().readLock().unlock();
    112        }
    113    }
    114
    115    /** Change selection
    116     * @param selectionIndex current selection index
    117     **/
    118    @SuppressWarnings("unchecked")
    119    public void changeSelection(int selectionIndex) {
    120        iSolver.currentSolution().getLock().writeLock().lock();
    121        try {
    122            Progress progress = Progress.getInstance(iSolver.currentSolution().getModel());
    123            int newSelectionIndex = 1 + selectionIndex;
    124            if (newSelectionIndex <= iSelectionIdx) return; // already changed
    125            if (selectionIndex == -1 && iSelectionIdx >= 0) return; // already changed
    126            iSelectionIdx = newSelectionIndex;
    127            if (selectionIndex >= 0) {
    128                try {
    129                    NeighbourSelection<V, T> selection = iSelections.get(selectionIndex % iSelections.size());
    130                    if (selection instanceof InfoProvider) {
    131                        Map<String, String> info = new HashMap<String, String>();
    132                        ((InfoProvider<V, T>)selection).getInfo(iSolver.currentSolution().getAssignment(), info);
    133                        if (!info.isEmpty())
    134                            for (Map.Entry<String, String> e: info.entrySet())
    135                                progress.debug(e.getKey() + ": " + e.getValue());
    136                    }
    137                } catch (Exception e) {}
    138            }
    139            sLogger.info("Phase changed to " + ((newSelectionIndex % iSelections.size()) + 1));
    140            progress.debug(iSolver.currentSolution().toString());
    141            if (iSolver.currentSolution().getBestInfo() == null || iSolver.getSolutionComparator().isBetterThanBestSolution(iSolver.currentSolution()))
    142                iSolver.currentSolution().saveBest();
    143            iSelections.get(iSelectionIdx % iSelections.size()).init(iSolver);
    144        } finally {
    145            iSolver.currentSolution().getLock().writeLock().unlock();
    146        }
    147    }
    148
    149    public NeighbourSelection<V, T> getSelection() {
    150        return iSelections.get(getSelectionIndex() % iSelections.size());
    151    }
    152}