pegasus.mapreduce.cc

Class Finalization.LargeStarReducer

java.lang.Object

org.apache.hadoop.mapreduce.Reducer<org.apache.hadoop.io.IntWritable,LongPairWritable,org.apache.hadoop.io.LongWritable,org.apache.hadoop.io.LongWritable>

pegasus.mapreduce.cc.Finalization.LargeStarReducer

Enclosing class:

Finalization

public static class Finalization.LargeStarReducer
extends org.apache.hadoop.mapreduce.Reducer<org.apache.hadoop.io.IntWritable,LongPairWritable,org.apache.hadoop.io.LongWritable,org.apache.hadoop.io.LongWritable>

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.hadoop.mapreduce.Reducer

org.apache.hadoop.mapreduce.Reducer.Context

Constructor Summary

Constructors

Constructor and Description
LargeStarReducer()

Method Summary

Modifier and Type	Method and Description
long	find(long x) the find function of the union-find algorithm.
protected void	reduce(org.apache.hadoop.io.IntWritable key, java.lang.Iterable<LongPairWritable> values, org.apache.hadoop.mapreduce.Reducer.Context context) the reduce function.
void	union(long x, long y) the union function of the union-find algorithm.

Methods inherited from class org.apache.hadoop.mapreduce.Reducer

cleanup, run, setup

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

LargeStarReducer

public LargeStarReducer()

Method Detail

reduce

protected void reduce(org.apache.hadoop.io.IntWritable key,
                      java.lang.Iterable<LongPairWritable> values,
                      org.apache.hadoop.mapreduce.Reducer.Context context)
               throws java.io.IOException,
                      java.lang.InterruptedException

the reduce function. It find connected components in a partition.

Overrides:

reduce in class org.apache.hadoop.mapreduce.Reducer<org.apache.hadoop.io.IntWritable,LongPairWritable,org.apache.hadoop.io.LongWritable,org.apache.hadoop.io.LongWritable>

Parameters:

key - the partition number. not used.

values - edges

context - of hadoop

Throws:

java.io.IOException - by hadoop

java.lang.InterruptedException - by hadoop

find

public long find(long x)

the find function of the union-find algorithm. parent table is updated as a side effect

Parameters:

x - node to process

Returns:

component id (smallest node reachable to node x)

union

public void union(long x,
                  long y)

the union function of the union-find algorithm. It updates parent table to union the two

Parameters:

x - a node

y - another node