001    package net.sf.cpsolver.ifs.solution;
002    
003    import net.sf.cpsolver.ifs.util.DataProperties;
004    
005    /**
006     * General implementation of solution comparator.
007     * <br><br>
008     * The solution is better than the best ever found solution when it has more variables assigned. In the case, when both
009     * solutions have the same number of assigned variables, the better solution is the one with smaller total value, i.e.,
010     * the sum of {@link net.sf.cpsolver.ifs.model.Value#toDouble()} over all assigned variables.
011     *
012     * @see Solution
013     * @see net.sf.cpsolver.ifs.solver.Solver
014     *
015     * @version
016     * IFS 1.1 (Iterative Forward Search)<br>
017     * Copyright (C) 2006 Tomáš Müller<br>
018     * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
019     * Lazenska 391, 76314 Zlin, Czech Republic<br>
020     * <br>
021     * This library is free software; you can redistribute it and/or
022     * modify it under the terms of the GNU Lesser General Public
023     * License as published by the Free Software Foundation; either
024     * version 2.1 of the License, or (at your option) any later version.
025     * <br><br>
026     * This library is distributed in the hope that it will be useful,
027     * but WITHOUT ANY WARRANTY; without even the implied warranty of
028     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
029     * Lesser General Public License for more details.
030     * <br><br>
031     * You should have received a copy of the GNU Lesser General Public
032     * License along with this library; if not, write to the Free Software
033     * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
034     */
035    public class GeneralSolutionComparator implements SolutionComparator {
036        
037        public GeneralSolutionComparator() {}
038        /** No parameters are used so far. */
039        public GeneralSolutionComparator(DataProperties properties) {
040        }
041        
042        public boolean isBetterThanBestSolution(Solution currentSolution) {
043            if (currentSolution.getBestInfo()==null) return true;
044            int unassigned = currentSolution.getModel().nrUnassignedVariables();
045            if (currentSolution.getModel().getBestUnassignedVariables()!=unassigned)
046                return currentSolution.getModel().getBestUnassignedVariables()>unassigned;
047            return currentSolution.getModel().getTotalValue()<currentSolution.getBestValue();
048        }
049        
050    }