/**
* 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.fpm.pfpgrowth;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.mahout.common.Parameters;
import org.apache.mahout.fpm.pfpgrowth.convertors.string.TopKStringPatterns;
import java.io.IOException;
import java.util.Iterator;
/**
*
* {@link AggregatorReducer} groups all Frequent Patterns containing an item and
* outputs the top K patterns containing that particular item
*
*/
public class AggregatorReducer extends
Reducer<Text, TopKStringPatterns, Text, TopKStringPatterns> {
private int maxHeapSize = 50;
@Override
protected void reduce(Text key, Iterable<TopKStringPatterns> values,
Context context) throws IOException, InterruptedException {
TopKStringPatterns patterns = new TopKStringPatterns();
for (TopKStringPatterns value : values) {
context.setStatus("Aggregator Reducer: Selecting TopK patterns for: " + key);
patterns = patterns.merge(value, maxHeapSize);
}
context.write(key, patterns);
}
@Override
protected void setup(Context context) throws IOException,
InterruptedException {
super.setup(context);
Parameters params = Parameters.fromString(context.getConfiguration().get(
"pfp.parameters", ""));
maxHeapSize = Integer.valueOf(params.get("maxHeapSize", "50"));
}
}