org.apache.mahout.cf.taste.hadoop.similarity.item
Class CountUsersReducer

java.lang.Object
  extended by org.apache.hadoop.mapreduce.Reducer<CountUsersKeyWritable,VarLongWritable,VarIntWritable,org.apache.hadoop.io.NullWritable>
      extended by org.apache.mahout.cf.taste.hadoop.similarity.item.CountUsersReducer

public class CountUsersReducer
extends org.apache.hadoop.mapreduce.Reducer<CountUsersKeyWritable,VarLongWritable,VarIntWritable,org.apache.hadoop.io.NullWritable>

counts all unique users, we ensure that we see userIDs sorted in ascending order via secondary sort, so we don't have to buffer all of them


Nested Class Summary
 
Nested classes/interfaces inherited from class org.apache.hadoop.mapreduce.Reducer
org.apache.hadoop.mapreduce.Reducer.Context
 
Constructor Summary
CountUsersReducer()
           
 
Method Summary
protected  void reduce(CountUsersKeyWritable key, java.lang.Iterable<VarLongWritable> userIDs, org.apache.hadoop.mapreduce.Reducer.Context context)
           
 
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

CountUsersReducer

public CountUsersReducer()
Method Detail

reduce

protected void reduce(CountUsersKeyWritable key,
                      java.lang.Iterable<VarLongWritable> userIDs,
                      org.apache.hadoop.mapreduce.Reducer.Context context)
               throws java.io.IOException,
                      java.lang.InterruptedException
Overrides:
reduce in class org.apache.hadoop.mapreduce.Reducer<CountUsersKeyWritable,VarLongWritable,VarIntWritable,org.apache.hadoop.io.NullWritable>
Throws:
java.io.IOException
java.lang.InterruptedException


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