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From bharath v <bharathvissapragada1...@gmail.com>
Subject Implementing VectorWritable
Date Tue, 29 Dec 2009 05:29:48 GMT
Hi ,

I've implemented a simple VectorWritable class as follows


package com;

import org.apache.hadoop.*;
import org.apache.hadoop.io.*;
import java.io.*;
import java.util.Vector;


public class VectorWritable implements WritableComparable {
  private Vector<String> value = new Vector();

  public VectorWritable() {}

  public VectorWritable(Vector<String> value) { set(value); }

  public void set(Vector<String> val) { this.value = val;
  }

  public Vector<String> get() { return this.value; }

  public void readFields(DataInput in) throws IOException {
    //value = in.readInt();
  }

  public void write(DataOutput out) throws IOException {
  //  out.writeInt(value);
  }

  public boolean equals(Object o) {
    if (!(o instanceof VectorWritable))
      return false;
    VectorWritable other = (VectorWritable)o;
    return this.value.equals(other.value);
  }

  public int hashCode() {
    return value.hashCode();
  }

  public int compareTo(Object o) {
    Vector thisValue = this.value;
    Vector thatValue = ((VectorWritable)o).value;
    return (thisValue.size()<thatValue.size() ? -1 :
(thisValue.size()==thatValue.size() ? 0 : 1));
  }

  public String toString() {
    return value.toString();
  }

  public static class Comparator extends WritableComparator {
    public Comparator() {
      super(VectorWritable.class);
    }

    public int compare(byte[] b1, int s1, int l1,
                       byte[] b2, int s2, int l2) {

      int thisValue = readInt(b1, s1);
      int thatValue = readInt(b2, s2);
      return (thisValue<thatValue ? -1 : (thisValue==thatValue ? 0 : 1));
    }
  }

  static {                                        // register this
comparator
    WritableComparator.define(VectorWritable.class, new Comparator());
  }
}

The map phase is outputting correct <Text,VectorWritable> pairs .. but in
reduce phase
when I iterate over the values Iterable.. Iam getting the size of the vector
to be 0; I think there is a minor
mistake in my VectorWritable Implementation .. Can anyone point it..

Thanks

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