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

java.lang.Object
  extended by org.apache.hadoop.mapreduce.Reducer<VarLongWritable,VarLongWritable,VarLongWritable,VectorWritable>
      extended by 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
static class ToUserVectorsReducer.Counters
           
 
Nested classes/interfaces inherited from class org.apache.hadoop.mapreduce.Reducer
org.apache.hadoop.mapreduce.Reducer.Context
 
Field Summary
static String MIN_PREFERENCES_PER_USER
           
 
Constructor Summary
ToUserVectorsReducer()
           
 
Method Summary
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


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