    001package net.sf.cpsolver.ifs.algorithms.neighbourhoods;
    002
    003import java.util.List;
    004
    005import net.sf.cpsolver.ifs.heuristics.NeighbourSelection;
    006import net.sf.cpsolver.ifs.model.Model;
    007import net.sf.cpsolver.ifs.model.Neighbour;
    008import net.sf.cpsolver.ifs.model.SimpleNeighbour;
    009import net.sf.cpsolver.ifs.model.Value;
    010import net.sf.cpsolver.ifs.model.Variable;
    011import net.sf.cpsolver.ifs.solution.Solution;
    012import net.sf.cpsolver.ifs.solver.Solver;
    013import net.sf.cpsolver.ifs.util.DataProperties;
    014import net.sf.cpsolver.ifs.util.ToolBox;
    015
    016/**
    017 * Try to assign a variable with a new value. A variable is selected randomly, a
    018 * different (available) value is randomly selected for the variable -- the variable is
    019 * assigned with the new value if there is no conflict.
    020 * <br>
    021 *
    022 * @version IFS 1.2 (Iterative Forward Search)<br>
    023 *          Copyright (C) 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 */
    041public class RandomMove<V extends Variable<V, T>, T extends Value<V, T>> implements NeighbourSelection<V, T>, HillClimberSelection {
    042    protected boolean iHC = false;
    043
    044    public RandomMove(DataProperties config) {
    045    }
    046
    047    @Override
    048    public void setHcMode(boolean hcMode) {
    049        iHC = hcMode;
    050    }
    051
    052    @Override
    053    public void init(Solver<V, T> solver) {
    054    }
    055
    056    @Override
    057    public Neighbour<V, T> selectNeighbour(Solution<V, T> solution) {
    058        Model<V, T> model = solution.getModel();
    059        int varIdx = ToolBox.random(model.variables().size());
    060        for (int i = 0; i < model.variables().size(); i++) {
    061            V variable = model.variables().get((i + varIdx) % model.variables().size());
    062            List<T> values = variable.values();
    063            if (values.isEmpty()) continue;
    064            int valIdx = ToolBox.random(values.size());
    065            for (int j = 0; j < values.size(); j++) {
    066                T value = values.get((j + valIdx) % values.size());
    067                if (!model.inConflict(value)) {
    068                    SimpleNeighbour<V, T> n = new SimpleNeighbour<V, T>(variable, value);
    069                    if (!iHC || n.value() <= 0) return n;
    070                }
    071            }
    072        }
    073        return null;
    074    }
    075}