/*
* 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.io.IntWritable;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.mahout.math.VarIntWritable;
import org.apache.mahout.math.Vector;
import org.apache.mahout.math.VectorWritable;
/**
* maps a row of the similarity matrix to a {@link VectorOrPrefWritable}
*
* actually a column from that matrix has to be used but as the similarity matrix is symmetric,
* we can use a row instead of having to transpose it
*/
public final class SimilarityMatrixRowWrapperMapper extends
Mapper<IntWritable,VectorWritable,VarIntWritable,VectorOrPrefWritable> {
@Override
protected void map(IntWritable key,
VectorWritable value,
Context context) throws IOException, InterruptedException {
Vector similarityMatrixRow = value.get();
/* remove self similarity */
similarityMatrixRow.set(key.get(), Double.NaN);
context.write(new VarIntWritable(key.get()), new VectorOrPrefWritable(similarityMatrixRow));
}
}