001package net.sf.cpsolver.ifs.solution;
002
003import net.sf.cpsolver.ifs.model.Value;
004import net.sf.cpsolver.ifs.model.Variable;
005import net.sf.cpsolver.ifs.util.DataProperties;
006
007/**
008 * General implementation of solution comparator. <br>
009 * <br>
010 * The solution is better than the best ever found solution when it has more
011 * variables assigned. In the case, when both solutions have the same number of
012 * assigned variables, the better solution is the one with smaller total value,
013 * i.e., the sum of {@link net.sf.cpsolver.ifs.model.Value#toDouble()} over all
014 * assigned variables.
015 * 
016 * @see Solution
017 * @see net.sf.cpsolver.ifs.solver.Solver
018 * 
019 * @version IFS 1.2 (Iterative Forward Search)<br>
020 *          Copyright (C) 2006 - 2010 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 */
038public class GeneralSolutionComparator<V extends Variable<V, T>, T extends Value<V, T>> implements
039        SolutionComparator<V, T> {
040
041    public GeneralSolutionComparator() {
042    }
043
044    /** No parameters are used so far. */
045    public GeneralSolutionComparator(DataProperties properties) {
046    }
047
048    @Override
049    public boolean isBetterThanBestSolution(Solution<V, T> currentSolution) {
050        if (currentSolution.getBestInfo() == null)
051            return true;
052        int unassigned = currentSolution.getModel().nrUnassignedVariables();
053        if (currentSolution.getModel().getBestUnassignedVariables() != unassigned)
054            return currentSolution.getModel().getBestUnassignedVariables() > unassigned;
055        return currentSolution.getModel().getTotalValue() < currentSolution.getBestValue();
056    }
057
058}