org.apache.mahout.cf.taste.hadoop.item
Class AggregateAndRecommendReducer
java.lang.Object
org.apache.hadoop.mapreduce.Reducer<VarLongWritable,PrefAndSimilarityColumnWritable,VarLongWritable,RecommendedItemsWritable>
org.apache.mahout.cf.taste.hadoop.item.AggregateAndRecommendReducer
public final class AggregateAndRecommendReducer
- extends org.apache.hadoop.mapreduce.Reducer<VarLongWritable,PrefAndSimilarityColumnWritable,VarLongWritable,RecommendedItemsWritable>
computes prediction values for each user
u = a user
i = an item not yet rated by u
N = all items similar to i (where similarity is usually computed by pairwisely comparing the item-vectors
of the user-item matrix)
Prediction(u,i) = sum(all n from N: similarity(i,n) * rating(u,n)) / sum(all n from N: abs(similarity(i,n)))
Nested classes/interfaces inherited from class org.apache.hadoop.mapreduce.Reducer |
org.apache.hadoop.mapreduce.Reducer.Context |
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 |
AggregateAndRecommendReducer
public AggregateAndRecommendReducer()
setup
protected void setup(org.apache.hadoop.mapreduce.Reducer.Context context)
- Overrides:
setup
in class org.apache.hadoop.mapreduce.Reducer<VarLongWritable,PrefAndSimilarityColumnWritable,VarLongWritable,RecommendedItemsWritable>
reduce
protected void reduce(VarLongWritable userID,
java.lang.Iterable<PrefAndSimilarityColumnWritable> values,
org.apache.hadoop.mapreduce.Reducer.Context context)
throws java.io.IOException,
java.lang.InterruptedException
- Overrides:
reduce
in class org.apache.hadoop.mapreduce.Reducer<VarLongWritable,PrefAndSimilarityColumnWritable,VarLongWritable,RecommendedItemsWritable>
- Throws:
java.io.IOException
java.lang.InterruptedException
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