/* * 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 org.apache.hadoop.mapreduce.Reducer; import org.apache.mahout.cf.taste.hadoop.EntityPrefWritable; import org.apache.mahout.cf.taste.hadoop.TasteHadoopUtils; import org.apache.mahout.math.RandomAccessSparseVector; import org.apache.mahout.math.VarLongWritable; import org.apache.mahout.math.Vector; import org.apache.mahout.math.VectorWritable; /** *
* Takes user IDs as {@link VarLongWritable} mapped to all associated item IDs and preference values, as * {@link EntityPrefWritable}s. *
* ** The same user ID mapped to a {@link 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 * {@link TasteHadoopUtils#idToIndex(long)}. The mapping is remembered for later with a combination of * {@link ItemIDIndexMapper} and {@link ItemIDIndexReducer}. *
*/ public final class ToUserVectorsReducer extends Reducer