/**
* 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.classifier.bayes.mapreduce.common;
import org.apache.hadoop.io.DoubleWritable;
import org.apache.hadoop.io.WritableComparator;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.Partitioner;
import org.apache.mahout.common.StringTuple;
import com.google.common.base.Preconditions;
/**
* ensure that features all make it into the same partition.
*/
public class FeaturePartitioner implements Partitioner<StringTuple,DoubleWritable> {
@Override
public int getPartition(StringTuple key, DoubleWritable value, int numPartitions) {
Preconditions.checkArgument(key.length() >= 2 && key.length() <= 3, "StringTuple length out of bounds");
String feature = key.length() == 2 ? key.stringAt(1) : key.stringAt(2);
int length = feature.length();
int right = 0;
if (length > 0) {
right = (3 + length) % length;
}
int hash = WritableComparator.hashBytes(feature.getBytes(), right);
return (hash & Integer.MAX_VALUE) % numPartitions;
}
@Override
public void configure(JobConf job) {
/* no-op */
}
}