/**
* 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.clustering.minhash;
import com.google.common.collect.Lists;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.mahout.common.commandline.MinhashOptionCreator;
import org.apache.mahout.math.Vector;
import org.apache.mahout.math.VectorWritable;
import java.io.IOException;
import java.util.Collection;
public class MinHashReducer extends Reducer<Text,Writable,Text,Writable> {
private int minClusterSize;
private boolean debugOutput;
enum Clusters {
ACCEPTED,
DISCARDED
}
@Override
protected void setup(Context context) throws IOException, InterruptedException {
super.setup(context);
Configuration conf = context.getConfiguration();
this.minClusterSize = conf.getInt(MinhashOptionCreator.MIN_CLUSTER_SIZE, 5);
this.debugOutput = conf.getBoolean(MinhashOptionCreator.DEBUG_OUTPUT, false);
}
/**
* output the items clustered
*/
@Override
protected void reduce(Text cluster, Iterable<Writable> points, Context context)
throws IOException, InterruptedException {
Collection<Writable> pointList = Lists.newArrayList();
for (Writable point : points) {
if (debugOutput) {
Vector pointVector = ((VectorWritable) point).get().clone();
Writable writablePointVector = new VectorWritable(pointVector);
pointList.add(writablePointVector);
} else {
Writable pointText = new Text(point.toString());
pointList.add(pointText);
}
}
if (pointList.size() >= minClusterSize) {
context.getCounter(Clusters.ACCEPTED).increment(1);
for (Writable point : pointList) {
context.write(cluster, point);
}
} else {
context.getCounter(Clusters.DISCARDED).increment(1);
}
}
}