SiCombiner.java Source code

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Here is the source code for SiCombiner.java

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/**
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

import java.io.IOException;
import java.util.StringTokenizer;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Partitioner;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;

public class SiCombiner {

    public static class TokenizerMapper extends Mapper<Object, Text, Text, IntWritable> {

        private final static IntWritable one = new IntWritable(1);
        private Text word = new Text();

        public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
            StringTokenizer itr = new StringTokenizer(value.toString());
            while (itr.hasMoreTokens()) {
                word.set(itr.nextToken());
                // Aniket changes starts
                /* These changes are made so that the map will emit only the required
                 * word set i.e. emit only "real" words*/
                String word_new = word.toString();
                char start = word_new.charAt(0);
                if (start == 'm' || start == 'M' || start == 'n' || start == 'N' || start == 'o' || start == 'O'
                        || start == 'p' || start == 'P' || start == 'q' || start == 'Q') {
                    context.write(word, one);
                }
                // Aniket changes ends
            }
        }
    }

    public static class IntSumReducer extends Reducer<Text, IntWritable, Text, IntWritable> {
        private IntWritable result = new IntWritable();

        public void reduce(Text key, Iterable<IntWritable> values, Context context)
                throws IOException, InterruptedException {
            int sum = 0;
            for (IntWritable val : values) {
                sum += val.get();
            }
            result.set(sum);
            context.write(key, result);
        }
    }

    // Aniket changes start
    /* This is a custom partitioner This is used to send the words to required partitioner
     * So it sends all the words starting from m or M to partitioner 1
     * Sends all the words starting from n or N to partitioner 2 and so on... 
     * I am doing the % ReducerCount to see if there are less than 4 reducers available 
     * and also to avoid divide by zero error.*/
    public static class WordPartitioner extends Partitioner<Text, IntWritable> {

        @Override
        public int getPartition(Text key, IntWritable value, int ReducerCount) {
            String word = key.toString();
            char first = word.charAt(0);
            if (ReducerCount == 0)
                return 0;
            if (first == 'm' || first == 'M')
                return 0;
            if (first == 'n' || first == 'N')
                return 1 % ReducerCount;
            if (first == 'o' || first == 'O')
                return 2 % ReducerCount;
            if (first == 'p' || first == 'P')
                return 3 % ReducerCount;
            else
                return 4 % ReducerCount;

        }

    }
    // Aniket changes ends

    public static void main(String[] args) throws Exception {
        Configuration conf = new Configuration();
        String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
        if (otherArgs.length != 2) {
            System.err.println("Usage: wordcount <in> <out>");
            System.exit(2);
        }
        Job job = new Job(conf, "word count");
        job.setJarByClass(SiCombiner.class);
        job.setMapperClass(TokenizerMapper.class);
        // Aniket changes starts
        /* Here the partitioner is being called*/
        job.setPartitionerClass(WordPartitioner.class);
        // Aniket changes ends
        job.setCombinerClass(IntSumReducer.class);
        job.setReducerClass(IntSumReducer.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);
        FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
        FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
        System.exit(job.waitForCompletion(true) ? 0 : 1);
    }
}