org.apache.mahout.cf.taste.hadoop.item.ToVectorAndPrefReducer Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.mahout.cf.taste.hadoop.item;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.mahout.math.VarIntWritable;
import org.apache.mahout.math.Vector;
public final class ToVectorAndPrefReducer extends
Reducer {
private final VectorAndPrefsWritable vectorAndPrefs = new VectorAndPrefsWritable();
@Override
protected void reduce(VarIntWritable key,
Iterable values,
Context context) throws IOException, InterruptedException {
List userIDs = new ArrayList<>();
List prefValues = new ArrayList<>();
Vector similarityMatrixColumn = null;
for (VectorOrPrefWritable value : values) {
if (value.getVector() == null) {
// Then this is a user-pref value
userIDs.add(value.getUserID());
prefValues.add(value.getValue());
} else {
// Then this is the column vector
if (similarityMatrixColumn != null) {
throw new IllegalStateException("Found two similarity-matrix columns for item index " + key.get());
}
similarityMatrixColumn = value.getVector();
}
}
if (similarityMatrixColumn == null) {
return;
}
vectorAndPrefs.set(similarityMatrixColumn, userIDs, prefValues);
context.write(key, vectorAndPrefs);
}
}