/*
* chombo: Hadoop Map Reduce utility
* Author: Pranab Ghosh
*
* Licensed 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.chombo.mr;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.DoubleWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.FileSplit;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
import org.chombo.util.Tuple;
import org.chombo.util.Utility;
/**
* Aggregates rank of an item from multiple list according to configured aggregation strategy
* @author pranab
*
*/
public class RankAggregator extends Configured implements Tool {
private static final String AGGR_AVG = "average";
private static final String AGGR_WTD_AVG = "weightedAverage";
private static final String AGGR_MED = "median";
private static final String AGGR_MAX = "max";
private static final String AGGR_PROD = "product";
@Override
public int run(String[] args) throws Exception {
Job job = new Job(getConf());
String jobName = "Aggregates rank from multiple rank lists";
job.setJobName(jobName);
job.setJarByClass(RankAggregator.class);
FileInputFormat.addInputPath(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
Utility.setConfiguration(job.getConfiguration(), "chombo");
job.setMapperClass(RankAggregator.AggregateMapper.class);
job.setReducerClass(RankAggregator.AggregationReducer.class);
job.setMapOutputKeyClass(Tuple.class);
job.setMapOutputValueClass(Tuple.class);
job.setOutputKeyClass(NullWritable.class);
job.setOutputValueClass(Text.class);
int numReducer = job.getConfiguration().getInt("raa.num.reducer", -1);
numReducer = -1 == numReducer ? job.getConfiguration().getInt("num.reducer", 1) : numReducer;
job.setNumReduceTasks(numReducer);
int status = job.waitForCompletion(true) ? 0 : 1;
return status;
}
/**
* @author pranab
*
*/
public static class AggregateMapper extends Mapper<LongWritable, Text, Tuple, Tuple> {
private Tuple outKey = new Tuple();
private Tuple outVal = new Tuple();
private String fieldDelimRegex;
private String[] items;
private int[] idOrdinals;
private int rankOrdinal;
private double listWeight;
private Map<String, Double> listWeights;
private String aggregationStrategy;
private static final int SPLIT_PREFIX_LEN = 4;
/* (non-Javadoc)
* @see org.apache.hadoop.mapreduce.Mapper#setup(org.apache.hadoop.mapreduce.Mapper.Context)
*/
protected void setup(Context context) throws IOException, InterruptedException {
Configuration config = context.getConfiguration();
fieldDelimRegex = config.get("field.delim.regex", ",");
idOrdinals = Utility.assertIntArrayConfigParam(config, "raa.id.field.ordinals", Utility.configDelim, "missing id field ordinals");
rankOrdinal = Utility.assertIntConfigParam(config, "raa.rank.attr.ordinal", "missing rank attribute ordinal");
aggregationStrategy = config.get("raa.rank.agg.strategy", AGGR_PROD);
if (aggregationStrategy.equals(AGGR_WTD_AVG)) {
//map 4 alpha numeric split prefix and weight
listWeights = Utility.assertStringDoubleMapConfigParam(config, "raa.list.weightl",
Utility.configDelim, Utility.configSubFieldDelim, "missing split prefix weight");
String splitPrefix = ((FileSplit)context.getInputSplit()).getPath().getName().substring(0, SPLIT_PREFIX_LEN);
listWeight = listWeights.get(splitPrefix);
}
}
/* (non-Javadoc)
* @see org.apache.hadoop.mapreduce.Mapper#map(KEYIN, VALUEIN, org.apache.hadoop.mapreduce.Mapper.Context)
*/
@Override
protected void map(LongWritable key, Text value, Context context)
throws IOException, InterruptedException {
items = value.toString().split(fieldDelimRegex, -1);
Utility.createStringTuple(items, idOrdinals, outKey);
outVal.initialize();
outVal.add(Double.parseDouble(items[rankOrdinal]));
if (aggregationStrategy.equals(AGGR_WTD_AVG)) {
outVal.add(listWeight);
}
context.write(outKey, outVal);
}
}
/**
* @author pranab
*
*/
public static class AggregationReducer extends Reducer<Tuple, Tuple, NullWritable, Text> {
private Text outVal = new Text();
private StringBuilder stBld = new StringBuilder();;
private String fieldDelim;
private int outputPrecision ;
private String aggregationStrategy;
private List<Double> ranks = new ArrayList<Double>();
private List<Double> weights = new ArrayList<Double>();
private double aggrRank;
private double aggr;
private double weightSum;
/* (non-Javadoc)
* @see org.apache.hadoop.mapreduce.Reducer#setup(org.apache.hadoop.mapreduce.Reducer.Context)
*/
protected void setup(Context context) throws IOException, InterruptedException {
Configuration config = context.getConfiguration();
fieldDelim = config.get("field.delim.out", ",");
aggregationStrategy = config.get("raa.rank.agg.strategy", AGGR_PROD);
outputPrecision = config.getInt("raa.output.prec", 3);
}
/* (non-Javadoc)
* @see org.apache.hadoop.mapreduce.Reducer#reduce(KEYIN, java.lang.Iterable, org.apache.hadoop.mapreduce.Reducer.Context)
*/
protected void reduce(Tuple key, Iterable<Tuple> values, Context context)
throws IOException, InterruptedException {
ranks.clear();
weights.clear();
stBld.delete(0, stBld.length());
for (Tuple val : values) {
ranks.add(val.getDouble(0));
if (aggregationStrategy.equals(AGGR_WTD_AVG)) {
weights.add(val.getDouble(1));
}
}
if (ranks.size() == 1) {
aggrRank = ranks.get(0);
} else {
if (aggregationStrategy.equals(AGGR_AVG)) {
//average
aggr = 0;
for (double rank : ranks) {
aggr += rank;
}
aggrRank = aggr / ranks.size();
} if (aggregationStrategy.equals(AGGR_WTD_AVG)) {
//weighted average
aggr = 0;
weightSum = 0;
for (int i = 0; i < ranks.size(); ++i) {
aggr += ranks.get(i) * weights.get(i);
weightSum += weights.get(i);
}
aggrRank = aggr / weightSum;
} else if (aggregationStrategy.equals(AGGR_MED)) {
//median
Collections.sort(ranks);
int mid = ranks.size() / 2;
if (ranks.size() % 2 == 1) {
aggrRank = ranks.get(mid);
} else {
aggrRank = (ranks.get(mid -1) + ranks.get(mid)) / 2 ;
}
} else if (aggregationStrategy.equals(AGGR_MAX)) {
//max
Collections.sort(ranks);
aggrRank = ranks.get(ranks.size() - 1);
} else if (aggregationStrategy.equals(AGGR_PROD)) {
//product
aggr = 1.0;
for (double rank : ranks) {
aggr *= rank;
}
aggrRank = Math.pow(aggr, 1.0 / ranks.size() );
} else {
throw new IllegalArgumentException("invalid rank aggregation strategy");
}
}
stBld.append(key.toString()).append(fieldDelim).append(Utility.formatDouble(aggrRank, outputPrecision));
outVal.set(stBld.toString());
context.write(NullWritable.get(), outVal);
}
}
/**
* @param args
*/
public static void main(String[] args) throws Exception {
int exitCode = ToolRunner.run(new RankAggregator(), args);
System.exit(exitCode);
}
}