001package org.cpsolver.ifs.solution;
002
003import org.cpsolver.ifs.model.Value;
004import org.cpsolver.ifs.model.Variable;
005
006/**
007 * IFS solution comparator. <br>
008 * <br>
009 * The solution comparator compares two solutions: the current solution and the
010 * best solution found. This comparison can be based on several criteria. For
011 * example, it can lexicographically order solutions according to the number of
012 * unassigned variables (smaller number is better) and the number of violated
013 * soft constraints.
014 * 
015 * @see Solution
016 * @see org.cpsolver.ifs.solver.Solver
017 * 
018 * @author  Tomáš Müller
019 * @version IFS 1.3 (Iterative Forward Search)<br>
020 *          Copyright (C) 2006 - 2014 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 * 
038 * @param <V> Variable
039 * @param <T> Value
040 */
041public interface SolutionComparator<V extends Variable<V, T>, T extends Value<V, T>> {
042    /**
043     * Compares two solutions. Returns true if the given solution is better than
044     * its best ever found solution (see {@link Solution#saveBest()} and
045     * {@link Solution#restoreBest()}).
046     * 
047     * @param currentSolution
048     *            given solution
049     * @return true if the given solution is better than the best ever found
050     *         solution
051     */
052    public boolean isBetterThanBestSolution(Solution<V, T> currentSolution);
053}