/**
* 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.common.mapreduce;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.mahout.math.RandomAccessSparseVector;
import org.apache.mahout.math.Vector;
import org.apache.mahout.math.VectorWritable;
import java.io.IOException;
import java.util.Iterator;
public class TransposeMapper extends Mapper<IntWritable,VectorWritable,IntWritable,VectorWritable> {
@Override
protected void map(IntWritable r, VectorWritable v, Context ctx) throws IOException, InterruptedException {
int row = r.get();
Iterator<Vector.Element> it = v.get().iterateNonZero();
while (it.hasNext()) {
Vector.Element e = it.next();
RandomAccessSparseVector tmp = new RandomAccessSparseVector(Integer.MAX_VALUE, 1);
tmp.setQuick(row, e.get());
r.set(e.index());
ctx.write(r, new VectorWritable(tmp));
}
}
}