Hadoop实现共同出现的单词(Word co-occurrence)

Hadoop实现共同出现的单词(Word co-occurrence)是指在一个句子中相邻的两个单词。每一个相邻的单词就是一个Co-Occurrence对。

Sample Input:

a b cc, c d d c
I Love U.
dd ee f g s sa dew ad da
So shaken as we are, so wan with care.
Find we a time for frighted peace to pant.
And breathe short-winded accents of new broil.
To be commenced in strands afar remote.
I Love U U love i.
i i i i

Sample Output:

a:b 1
a:time 1
a:we 1
accents:of 1
accents:short-winded 1
ad:da 1
ad:dew 1
afar:remote 1
afar:strands 1
and:breathe 1
are:so 1
are:we 1
as:shaken 1
as:we 1
b:cc 1
be:commenced 1
be:to 1
breathe:short-winded 1
broil:new 1
c:cc 1
c:d 2
care:with 1
commenced:in 1
d:d 1
dd:ee 1
dew:sa 1
ee:f 1
f:g 1
find:we 1
for:frighted 1
for:time 1
frighted:peace 1
g:s 1
i:i 3
i:love 3
in:strands 1
love:u 3
new:of 1
pant:to 1
peace:to 1
s:sa 1
shaken:so 1
so:wan 1
u:u 1
wan:with 1

Code:

import java.io.DataInput;
import java.io.DataOutput;
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.LongWritable;
import org.apache.hadoop.io.RawComparator;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.WritableComparator;
import org.apache.hadoop.io.WritableUtils;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
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.util.GenericOptionsParser;

public class CoOccurrence {

  public static class TextPair implements WritableComparable<TextPair> {
    private Text first;
    private Text second;
   
    public TextPair(){
     set(new Text(), new Text());
    }
    public TextPair(String left, String right) {
        set(new Text(left), new Text(right));
    }
    public TextPair(Text left, Text right) {
     set(left, right);
    }
   
    public void set(Text left, Text right){
     String l = left.toString();
     String r = right.toString();
     int cmp = l.compareTo(r);     
     if(cmp <= 0){
      this.first = left;
      this.second = right;
     }else{
      this.first = right;
      this.second = left;
     }
    }
   
    public Text getFirst() {
      return first;
    }
    public Text getSecond() {
      return second;
    }

    @Override
    public void readFields(DataInput in) throws IOException {
      first.readFields(in);
      second.readFields(in);
    }
    @Override
    public void write(DataOutput out) throws IOException {
     first.write(out);
     second.write(out);
    }
    @Override
    public int hashCode() {
      return first.hashCode() * 163 + second.hashCode();//May be some trouble here. why 163? sometimes 157
    }
    @Override
    public boolean equals(Object o) {
      if (o instanceof TextPair) {
        TextPair tp = (TextPair) o;
        return first.equals(tp.first) && second.equals(tp.second);
      }
      return false;
    }
    @Override
    public String toString(){
     return first + ":" + second;
    }
    @Override
    public int compareTo(TextPair tp) {
     int cmp = first.compareTo(tp.first);
     if(cmp != 0)
      return cmp;
     return second.compareTo(tp.second);
    }

    // A Comparator that com.pares serialized StringPair. 
    public static class Comparator extends WritableComparator {
     private static final Text.Comparator TEXT_COMPARATOR = new Text.Comparator();
     public Comparator() {
      super(TextPair.class);
     }
     @Override
     public int compare(byte[] b1, int s1, int l1, byte[] b2, int s2, int l2){
      try {
       int firstl1 = WritableUtils.decodeVIntSize(b1[s1]) + readVInt(b1, s1);
       int firstl2 = WritableUtils.decodeVIntSize(b2[s2]) + readVInt(b2, s2);
       int cmp = TEXT_COMPARATOR.compare(b1, s1, firstl1, b2, s2, firstl2);
       if(cmp != 0)
        return cmp;
       return TEXT_COMPARATOR.compare(b1, s1 + firstl1, l1 - firstl1,
                b2, s2 + firstl2, l1 - firstl2);
      }catch (IOException e) {
       throw new IllegalArgumentException(e);
      }
     }
    }//End of Comparator
    static { // register this comparator
      WritableComparator.define(TextPair.class, new Comparator());
    }

    // Compare only the first part of the pair, so that reduce is called once for each value of the first part.
    public static class FirstComparator extends WritableComparator {
     private static final Text.Comparator TEXT_COMPARATOR = new Text.Comparator();
     public FirstComparator() {
      super(TextPair.class);
     }   
     @Override
     public int compare(byte[] b1, int s1, int l1, byte[] b2, int s2, int l2){
      try {
       int firstl1 = WritableUtils.decodeVIntSize(b1[s1]) + readVInt(b1, s1);
       int firstl2 = WritableUtils.decodeVIntSize(b2[s2]) + readVInt(b2, s2);
       return TEXT_COMPARATOR.compare(b1, s1, firstl1, b2, s2, firstl2);
      }catch (IOException e) {
       throw new IllegalArgumentException(e);
      }
     }
     /*
      @Override
      public int compare(WritableComparator a, WritableComparator b) {
       if(a instanceof TextPair && b instanceof TextPair)
        return ((TextPair)a).first.compareTo(((TextPair)b).first);
       return super.compare(a, b);
      }*/
    }//End of FirstComparator   
  }//End of TextPair
 
  //Partition based on the first part of the pair.
  public static class FirstPartitioner extends Partitioner<TextPair,IntWritable>{
    @Override
    public int getPartition(TextPair key, IntWritable value, int numPartitions) {
      return Math.abs(key.getFirst().toString().indexOf(0) * 127) % numPartitions;//May be some trouble here.
    }
  }//End of FirstPartitioner

  public static class MyMapper extends Mapper<LongWritable, Text, TextPair, IntWritable> {   
    private final static IntWritable one = new IntWritable(1);
    private static Text word0 = new Text();
    private static Text word1 = new Text();
    private String pattern = "[^a-zA-Z0-9-']";

    @Override
    public void map(LongWritable inKey, Text inValue, Context context)throws IOException, InterruptedException {
     String line = inValue.toString();
     line = line.replaceAll(pattern, " ");
     line = line.toLowerCase();
     String[] str = line.split(" +");
     for(int i=0; i< str.length-1; i++)
     {
      word0.set(str[i]);
      word1.set(str[i+1]);
      TextPair pair = new TextPair(word0, word1);
      context.write(pair, one);
     }
    }
  }//End of MapClass
  public static class MyReducer extends Reducer<TextPair, IntWritable, TextPair, IntWritable> {
    private IntWritable result = new IntWritable();
   
    @Override
    public void reduce(TextPair inKey, Iterable<IntWritable> inValues, Context context) throws IOException, InterruptedException {
     int sum = 0;
        for (IntWritable val : inValues) {
          sum += val.get();
        }
        result.set(sum);
        context.write(inKey, result);
    }
  }//End of MyReducer
 
  public static void main(String[] args) throws Exception {
    Configuration conf = new Configuration();
    //conf.set("Hadoop.job.ugi", "sunguoli,cs402");
    String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
    //if (otherArgs.length != 2) {
    //  System.err.println("Usage: CoOccurrence <in> <out>");
    //  System.exit(2);
    //}
    Job job = new Job(conf, "Co-Occurrence");
    job.setJarByClass(CoOccurrence.class);
   
    job.setMapperClass(MyMapper.class);
    job.setMapOutputKeyClass(TextPair.class);
    job.setMapOutputValueClass(IntWritable.class);
   
    job.setCombinerClass(MyReducer.class);

    // group and partition by the first int in the pair
    //job.setPartitionerClass(FirstPartitioner.class);
    //job.setGroupingComparatorClass(FirstGroupingComparator.class);

    // the reduce output is Text, IntWritable
    job.setReducerClass(MyReducer.class);
    job.setOutputKeyClass(TextPair.class);
    job.setOutputValueClass(IntWritable.class);
   
    //FileInputFormat.addInputPath(job, new Path("../shakespeareinput"));
    //FileOutputFormat.setOutputPath(job, new Path("output"));
 FileInputFormat.addInputPath(job, new Path(args[0]));
    FileOutputFormat.setOutputPath(job, new Path(args[1]));
    System.exit(job.waitForCompletion(true) ? 0 : 1);
  }//End of main
}//End of CoOccurrence

更多Hadoop相关信息见Hadoop 专题页面 http://www.linuxidc.com/topicnews.aspx?tid=13