org.apache.mahout.cf.taste.hadoop.item

Class ToUserVectorsReducer

java.lang.Object

org.apache.hadoop.mapreduce.Reducer<VarLongWritable,VarLongWritable,VarLongWritable,VectorWritable>

org.apache.mahout.cf.taste.hadoop.item.ToUserVectorsReducer

public final class ToUserVectorsReducer
extends org.apache.hadoop.mapreduce.Reducer<VarLongWritable,VarLongWritable,VarLongWritable,VectorWritable>

Input

Takes user IDs as VarLongWritable mapped to all associated item IDs and preference values, as EntityPrefWritables.

Output

The same user ID mapped to a RandomAccessSparseVector representation of the same item IDs and preference values. Item IDs are used as vector indexes; they are hashed into ints to work as indexes with TasteHadoopUtils.idToIndex(long). The mapping is remembered for later with a combination of ItemIDIndexMapper and ItemIDIndexReducer.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ToUserVectorsReducer.Counters

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

org.apache.hadoop.mapreduce.Reducer.Context

Field Summary

Fields

Modifier and Type	Field and Description
static String	MIN_PREFERENCES_PER_USER

Constructor Summary

Constructors

Constructor and Description
ToUserVectorsReducer()

Method Summary

Modifier and Type	Method and Description
protected void	reduce(VarLongWritable userID, Iterable<VarLongWritable> itemPrefs, org.apache.hadoop.mapreduce.Reducer.Context context)
protected void	setup(org.apache.hadoop.mapreduce.Reducer.Context ctx)

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

cleanup, run

Methods inherited from class java.lang.Object

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

Field Detail

MIN_PREFERENCES_PER_USER

public static final String MIN_PREFERENCES_PER_USER

Constructor Detail

ToUserVectorsReducer

public ToUserVectorsReducer()

Method Detail

setup

protected void setup(org.apache.hadoop.mapreduce.Reducer.Context ctx)
              throws IOException,
                     InterruptedException

Overrides:

setup in class org.apache.hadoop.mapreduce.Reducer<VarLongWritable,VarLongWritable,VarLongWritable,VectorWritable>

Throws:

IOException

InterruptedException

reduce

protected void reduce(VarLongWritable userID,
                      Iterable<VarLongWritable> itemPrefs,
                      org.apache.hadoop.mapreduce.Reducer.Context context)
               throws IOException,
                      InterruptedException

Overrides:

reduce in class org.apache.hadoop.mapreduce.Reducer<VarLongWritable,VarLongWritable,VarLongWritable,VectorWritable>

Throws:

IOException

InterruptedException