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)))
Constructor and Description |
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AggregateAndRecommendReducer() |
Modifier and Type | Method and Description |
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protected void |
reduce(VarLongWritable userID,
Iterable<PrefAndSimilarityColumnWritable> values,
org.apache.hadoop.mapreduce.Reducer.Context context) |
protected void |
setup(org.apache.hadoop.mapreduce.Reducer.Context context) |
protected void setup(org.apache.hadoop.mapreduce.Reducer.Context context) throws IOException
setup
in class org.apache.hadoop.mapreduce.Reducer<VarLongWritable,PrefAndSimilarityColumnWritable,VarLongWritable,RecommendedItemsWritable>
IOException
protected void reduce(VarLongWritable userID, Iterable<PrefAndSimilarityColumnWritable> values, org.apache.hadoop.mapreduce.Reducer.Context context) throws IOException, InterruptedException
reduce
in class org.apache.hadoop.mapreduce.Reducer<VarLongWritable,PrefAndSimilarityColumnWritable,VarLongWritable,RecommendedItemsWritable>
IOException
InterruptedException
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