/**
* 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.meanshift;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.MapReduceBase;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reducer;
import org.apache.hadoop.mapred.Reporter;
import org.apache.mahout.matrix.DenseVector;
import org.apache.mahout.matrix.Vector;
import java.io.IOException;
import java.util.Iterator;
public class MeanShiftCanopyCombiner extends MapReduceBase implements
Reducer<Text, WritableComparable<?>, Text, WritableComparable<?>> {
@Override
public void reduce(Text key, Iterator<WritableComparable<?>> values,
OutputCollector<Text, WritableComparable<?>> output, Reporter reporter)
throws IOException {
MeanShiftCanopy canopy = new MeanShiftCanopy(key.toString());
while (values.hasNext()) {
Writable value = values.next();
String valueStr = value.toString();
if (valueStr.startsWith("new"))
canopy.init(MeanShiftCanopy.decodeCanopy(valueStr.substring(4)));
else if (valueStr.startsWith("merge"))
canopy.merge(MeanShiftCanopy.decodeCanopy(valueStr.substring(6)));
else {
Vector formatString = DenseVector.decodeFormat(new Text(valueStr));
int number = Integer.parseInt(valueStr.substring(valueStr.indexOf(']') + 2));
canopy.addPoints(formatString, number);
}
}
// Combiner may see situations where a canopy touched others in the mapper
// before it was merged. This causes points to be added to it in the
// combiner, but since the canopy was merged it has no center. Ignore
// these cases.
if (canopy.getCenter() != null) {
canopy.shiftToMean();
output.collect(new Text("canopy"), new Text(MeanShiftCanopy
.formatCanopy(canopy)));
}
}
@Override
public void configure(JobConf job) {
super.configure(job);
MeanShiftCanopy.configure(job);
}
}