    001package org.cpsolver.ifs.algorithms.neighbourhoods;
    002
    003import java.util.List;
    004
    005import org.cpsolver.ifs.assignment.Assignment;
    006import org.cpsolver.ifs.heuristics.NeighbourSelection;
    007import org.cpsolver.ifs.model.Model;
    008import org.cpsolver.ifs.model.Neighbour;
    009import org.cpsolver.ifs.model.SimpleNeighbour;
    010import org.cpsolver.ifs.model.Value;
    011import org.cpsolver.ifs.model.Variable;
    012import org.cpsolver.ifs.solution.Solution;
    013import org.cpsolver.ifs.solver.Solver;
    014import org.cpsolver.ifs.util.DataProperties;
    015import org.cpsolver.ifs.util.ToolBox;
    016
    017
    018/**
    019 * Try to assign a variable with a new value. A variable is selected randomly, a
    020 * different (available) value is randomly selected for the variable -- the variable is
    021 * assigned with the new value if there is no conflict.
    022 * <br>
    023 *
    024 * @author  Tomáš Müller
    025 * @version IFS 1.3 (Iterative Forward Search)<br>
    026 *          Copyright (C) 2014 Tomáš Müller<br>
    027 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    028 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    029 * <br>
    030 *          This library is free software; you can redistribute it and/or modify
    031 *          it under the terms of the GNU Lesser General Public License as
    032 *          published by the Free Software Foundation; either version 3 of the
    033 *          License, or (at your option) any later version. <br>
    034 * <br>
    035 *          This library is distributed in the hope that it will be useful, but
    036 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    037 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    038 *          Lesser General Public License for more details. <br>
    039 * <br>
    040 *          You should have received a copy of the GNU Lesser General Public
    041 *          License along with this library; if not see
    042 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    043 * @param <V> Variable
    044 * @param <T> Value
    045 */
    046public class RandomMove<V extends Variable<V, T>, T extends Value<V, T>> implements NeighbourSelection<V, T>, HillClimberSelection {
    047    protected boolean iHC = false;
    048
    049    public RandomMove(DataProperties config) {
    050    }
    051
    052    @Override
    053    public void setHcMode(boolean hcMode) {
    054        iHC = hcMode;
    055    }
    056
    057    @Override
    058    public void init(Solver<V, T> solver) {
    059    }
    060
    061    @Override
    062    public Neighbour<V, T> selectNeighbour(Solution<V, T> solution) {
    063        Model<V, T> model = solution.getModel();
    064        Assignment<V, T> assignment = solution.getAssignment();
    065        int varIdx = ToolBox.random(model.variables().size());
    066        for (int i = 0; i < model.variables().size(); i++) {
    067            V variable = model.variables().get((i + varIdx) % model.variables().size());
    068            List<T> values = variable.values(solution.getAssignment());
    069            if (values.isEmpty()) continue;
    070            int valIdx = ToolBox.random(values.size());
    071            for (int j = 0; j < values.size(); j++) {
    072                T value = values.get((j + valIdx) % values.size());
    073                if (!model.inConflict(assignment, value)) {
    074                    SimpleNeighbour<V, T> n = new SimpleNeighbour<V, T>(variable, value);
    075                    if (!iHC || n.value(assignment) <= 0) return n;
    076                }
    077            }
    078        }
    079        return null;
    080    }
    081}