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.hadoop.tools.fastkmeans;
031
032import java.io.IOException;
033
034import org.apache.hadoop.io.BytesWritable;
035import org.apache.hadoop.io.IntWritable;
036import org.apache.hadoop.io.Text;
037import org.apache.hadoop.mapreduce.Mapper;
038import org.apache.hadoop.mapreduce.Reducer;
039import org.openimaj.tools.clusterquantiser.FileType;
040
041/**
042 * Map-Reduce (random) feature selection
043 * 
044 * @author Sina Samangooei (ss@ecs.soton.ac.uk)
045 * 
046 */
047public class FeatureSelect {
048        static final String FILETYPE_KEY = "clusterquantiser.FileType";
049        static final String NFEATURE_KEY = "fastkmeans.nfeatures";
050
051        /**
052         * Mapper
053         * 
054         * @author Sina Samangooei (ss@ecs.soton.ac.uk)
055         * 
056         */
057        public static class Map extends Mapper<Text, BytesWritable, IntWritable, BytesWritable>
058        {
059                private int nfeatures = -1;
060                private static FileType fileType = null;
061                private IndexedByteArrayPriorityQueue queue;
062
063                @Override
064                protected void setup(Mapper<Text, BytesWritable, IntWritable, BytesWritable>.Context context) throws IOException,
065                                InterruptedException
066                {
067                        if (fileType == null) {
068                                fileType = FileType.valueOf(context.getConfiguration().get(FILETYPE_KEY));
069                        }
070                        if (nfeatures == -1) {
071                                nfeatures = Integer.parseInt(context.getConfiguration().get(NFEATURE_KEY));
072                        }
073
074                        queue = new IndexedByteArrayPriorityQueue(nfeatures);
075                }
076
077                @Override
078                public void map(Text key, BytesWritable value, Context context) throws IOException, InterruptedException {
079                        final byte[] validBytes = new byte[value.getLength()];
080                        System.arraycopy(value.getBytes(), 0, validBytes, 0, validBytes.length);
081                        final IndexedByteArray indexedItem = new IndexedByteArray(validBytes);
082                        queue.insert(indexedItem);
083                }
084
085                @Override
086                protected void cleanup(Context context) throws IOException, InterruptedException {
087                        while (this.queue.size() > 0) {
088                                final IndexedByteArray item = this.queue.pop();
089                                context.write(new IntWritable(item.index), new BytesWritable(item.array));
090                        }
091                }
092        }
093
094        /**
095         * Reducer
096         * 
097         * @author Sina Samangooei (ss@ecs.soton.ac.uk)
098         * 
099         */
100        public static class Reduce extends Reducer<IntWritable, BytesWritable, IntWritable, BytesWritable> {
101                private int nfeatures = -1;
102                private int seen = 0;
103
104                @Override
105                protected void setup(Context context) throws IOException, InterruptedException {
106                        if (nfeatures == -1) {
107                                nfeatures = Integer.parseInt(context.getConfiguration().getStrings(NFEATURE_KEY)[0]);
108                        }
109                }
110
111                @Override
112                public void reduce(IntWritable key, Iterable<BytesWritable> values, Context context) throws IOException,
113                                InterruptedException
114                {
115                        if (seen >= nfeatures) {
116                                return;
117                        }
118                        for (final BytesWritable val : values) {
119                                context.write(new IntWritable(seen), val);
120                                seen++;
121                                if (seen >= nfeatures) {
122                                        return;
123                                }
124                        }
125                }
126        }
127
128}