001/**
002 * Copyright (C) 2007 - 2016, Jens Lehmann
003 *
004 * This file is part of DL-Learner.
005 *
006 * DL-Learner is free software; you can redistribute it and/or modify
007 * it under the terms of the GNU General Public License as published by
008 * the Free Software Foundation; either version 3 of the License, or
009 * (at your option) any later version.
010 *
011 * DL-Learner is distributed in the hope that it will be useful,
012 * but WITHOUT ANY WARRANTY; without even the implied warranty of
013 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
014 * GNU General Public License for more details.
015 *
016 * You should have received a copy of the GNU General Public License
017 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
018 */
019package org.dllearner.algorithms.el;
020
021import com.google.common.collect.ComparisonChain;
022import org.dllearner.core.ComponentAnn;
023import org.dllearner.core.ComponentInitException;
024
025/**
026 * A stable comparator for search tree nodes. Stable means that the order
027 * of nodes will not change during the run of the learning algorithm. In
028 * this implementation, this is ensured by using only covered examples
029 * and tree size as criteria.
030 * 
031 * @author Jens Lehmann
032 *
033 */
034@ComponentAnn(name = "Stable Heuristic", shortName = "el_heuristic", version = 0.1)
035public class StableHeuristic implements ELHeuristic {
036
037        private final ELDescriptionTreeComparator cmp = new ELDescriptionTreeComparator();
038        
039        @Override
040        public int compare(SearchTreeNode o1, SearchTreeNode o2) {
041                return ComparisonChain.start()
042                                .compare(o1.getScore().getAccuracy(), o2.getScore().getAccuracy())
043                                .compare(o2.getDescriptionTree().size, o1.getDescriptionTree().size)
044                                .compare(o1.getDescriptionTree(), o2.getDescriptionTree(), cmp)
045                                .result();
046        }
047
048        /* (non-Javadoc)
049         * @see org.dllearner.core.Component#init()
050         */
051        @Override
052        public void init() throws ComponentInitException {}
053
054        @Override
055        public double getNodeScore(SearchTreeNode node) {
056                return node.getScore().getAccuracy();
057        }
058}