001/**
002 * Copyright (c) 2011, The University of Southampton and the individual contributors.
003 * All rights reserved.
004 *
005 * Redistribution and use in source and binary forms, with or without modification,
006 * are permitted provided that the following conditions are met:
007 *
008 *   *  Redistributions of source code must retain the above copyright notice,
009 *      this list of conditions and the following disclaimer.
010 *
011 *   *  Redistributions in binary form must reproduce the above copyright notice,
012 *      this list of conditions and the following disclaimer in the documentation
013 *      and/or other materials provided with the distribution.
014 *
015 *   *  Neither the name of the University of Southampton nor the names of its
016 *      contributors may be used to endorse or promote products derived from this
017 *      software without specific prior written permission.
018 *
019 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
020 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
021 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
022 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
023 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
024 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
025 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
026 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
027 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
028 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029 */
030package org.openimaj.ml.clustering.spectral;
031
032import java.io.File;
033import java.io.IOException;
034
035import org.apache.log4j.Logger;
036import org.openimaj.io.IOUtils;
037
038import ch.akuhn.matrix.SparseMatrix;
039import ch.akuhn.matrix.eigenvalues.Eigenvalues;
040
041/**
042 * {@link DoubleSpectralClustering} extention which knows how to write and read its eigenvectors to disk
043 * and therefore not regenerate them when calling the underlying {@link PreparedSpectralClustering} 
044 * 
045 * @author Sina Samangooei (ss@ecs.soton.ac.uk)
046 *
047 */
048public class CachedDoubleSpectralClustering extends DoubleSpectralClustering{
049        private final static Logger logger = Logger.getLogger(CachedDoubleSpectralClustering.class);
050        private File cache;
051
052        /**
053         * @param cache location to cache the eigenvectors
054         * @param conf
055         * cluster the eigen vectors
056         */
057        public CachedDoubleSpectralClustering(File cache, SpectralClusteringConf<double[]> conf) {
058                super(conf);
059                this.cache = cache;
060        }
061        
062        protected Eigenvalues spectralCluster(SparseMatrix data) {
063                Eigenvalues eig = null;
064                if(cache.exists()){
065                        logger.debug("Loading eigenvectors from cache");
066                        try {
067                                eig = IOUtils.readFromFile(cache);
068                        } catch (IOException e) {
069                                throw new RuntimeException(e);
070                        }
071                }
072                else{                   
073                        // Compute the laplacian of the graph
074                        logger.debug("Cache empty, recreating eigenvectors");
075                        final SparseMatrix laplacian = laplacian(data);
076                        eig = laplacianEigenVectors(laplacian);
077                        try {
078                                logger.debug("Writing eigenvectors to cache");
079                                IOUtils.writeToFile(eig, cache);
080                        } catch (IOException e) {
081                                throw new RuntimeException(e);
082                        }
083                }
084                
085                return eig;
086        }
087        
088}