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.twitter.token.outputmode.jacard;
031
032import java.io.StringWriter;
033import java.util.HashSet;
034
035import org.apache.hadoop.io.LongWritable;
036import org.apache.hadoop.io.NullWritable;
037import org.apache.hadoop.io.Text;
038import org.apache.hadoop.mapreduce.Reducer;
039import org.openimaj.io.IOUtils;
040
041/**
042 * A cumulative jacard reducer designed to work as a single reducer. This reducer recieves the timeperiods
043 * in order and holds a set of words seen. Using this set the intersection and union with the current time's words can be
044 * calculated
045 * @author Sina Samangooei (ss@ecs.soton.ac.uk)
046 *
047 */
048public class CumulativeJacardReducer extends Reducer<LongWritable, Text, NullWritable, Text>{
049        private HashSet<String> seenwords;
050
051        public CumulativeJacardReducer() {
052                this.seenwords = new HashSet<String>();
053        }
054        
055        @Override
056        protected void reduce(LongWritable time, java.lang.Iterable<Text> words, org.apache.hadoop.mapreduce.Reducer<LongWritable,Text,NullWritable,Text>.Context context) throws java.io.IOException ,InterruptedException {
057                HashSet<String> unseenwords = new HashSet<String>();
058                StringWriter writer = new StringWriter();
059                
060                for (Text text : words) {
061                        unseenwords.add(text.toString());
062                }
063                long intersection = 0;
064                for (String string : unseenwords) {
065                        if(this.seenwords.contains(string)) intersection += 1;
066                        this.seenwords.add(string);
067                }
068                
069                JacardIndex index = new JacardIndex(time.get(),intersection,this.seenwords.size());
070                IOUtils.writeASCII(writer, index);
071                context.write(NullWritable.get(), new Text(writer.toString()));
072        };
073}