sixdegrees.AdjacencyList.java Source code

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Here is the source code for sixdegrees.AdjacencyList.java

Source

package sixdegrees;
/**
 *  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.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

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;

import au.com.bytecode.opencsv.CSVParser;

public class AdjacencyList {

    private static final int SOURCE = 1;

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

        // Local aggregation for Map task?

        public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
            CSVParser csv = new CSVParser();

            // each record from CSV file
            String[] str = csv.parseLine(value.toString());
            String startNode = str[0];
            String adjacentNode = str[1];
            // emit from map
            context.write(new IntWritable(Integer.parseInt(startNode)),
                    new IntWritable(Integer.parseInt(adjacentNode)));
            context.write(new IntWritable(Integer.parseInt(adjacentNode)),
                    new IntWritable(Integer.parseInt(startNode)));
        }
    }

    public static class AdjacencyReducer extends Reducer<IntWritable, IntWritable, Text, Text> {

        public void reduce(IntWritable key, Iterable<IntWritable> values, Context context)
                throws IOException, InterruptedException {
            StringBuffer buf = new StringBuffer();
            buf.append(key.toString());
            buf.append(" ");

            Set<Integer> edgeSet = new HashSet<Integer>();
            for (IntWritable val : values) {
                edgeSet.add(val.get());
            }
            List<Integer> edgeList = new ArrayList<Integer>();
            edgeList.addAll(edgeSet);
            int index = 0;
            while (index < edgeList.size()) {
                if (index < edgeList.size() - 1) {
                    buf.append(edgeList.get(index).toString()).append(",");
                } else
                    buf.append(edgeList.get(index).toString());
                index++;
            }
            // distance
            buf.append(":");
            if (key.get() == SOURCE)
                buf.append("0");
            else
                buf.append("9999");
            // color      
            buf.append(":");
            if (key.get() == SOURCE)
                buf.append(Colors.GRAY);
            else
                buf.append(Colors.WHITE);
            context.write(null, new Text(buf.toString()));
        }
    }

    // custom partitioner 
    public static class CustomPartitioner extends Partitioner<IntWritable, IntWritable> {

        @Override
        // Divide into partitions based on character
        public int getPartition(IntWritable key, IntWritable value, int numReduceTasks) {
            return (key.get() % numReduceTasks);
        }

    }

    /*
      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: adjacencylist <in> <out>");
          System.exit(2);
        }
        Job job = new Job(conf, "Adjacency List");
        job.setJarByClass(AdjacencyList.class);
        job.setMapperClass(AdjacencyMapper.class);   
        job.setPartitionerClass(CustomPartitioner.class);
        job.setReducerClass(AdjacencyReducer.class);
        job.setOutputKeyClass(IntWritable.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);
      }
      */
    public void execute(String args[]) throws IOException, ClassNotFoundException, InterruptedException {
        Configuration conf = new Configuration();
        String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
        if (otherArgs.length != 2) {
            System.err.println("Usage: adjacencylist <in> <out>");
            System.exit(2);
        }
        Job job = new Job(conf, "Adjacency List");
        job.setJarByClass(AdjacencyList.class);
        job.setMapperClass(AdjacencyMapper.class);
        job.setPartitionerClass(CustomPartitioner.class);
        job.setReducerClass(AdjacencyReducer.class);
        job.setOutputKeyClass(IntWritable.class);
        job.setOutputValueClass(IntWritable.class);
        job.setNumReduceTasks(6);
        FileInputFormat.addInputPath(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1] + "0"));
        job.waitForCompletion(true);
    }
}