/*
* Cloud9: A Hadoop toolkit for working with big data
*
* 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 edu.umd.cloud9.example.bigram;
import java.io.IOException;
import java.util.Arrays;
import java.util.Iterator;
import java.util.StringTokenizer;
import org.apache.commons.cli.CommandLine;
import org.apache.commons.cli.CommandLineParser;
import org.apache.commons.cli.GnuParser;
import org.apache.commons.cli.HelpFormatter;
import org.apache.commons.cli.OptionBuilder;
import org.apache.commons.cli.Options;
import org.apache.commons.cli.ParseException;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.FloatWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Partitioner;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.SequenceFileOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
import org.apache.log4j.Logger;
import tl.lin.data.pair.PairOfStrings;
public class BigramRelativeFrequency extends Configured implements Tool {
private static final Logger LOG = Logger.getLogger(BigramRelativeFrequency.class);
protected static class MyMapper extends Mapper<LongWritable, Text, PairOfStrings, FloatWritable> {
private static final FloatWritable ONE = new FloatWritable(1);
private static final PairOfStrings BIGRAM = new PairOfStrings();
@Override
public void map(LongWritable key, Text value, Context context)
throws IOException, InterruptedException {
String line = value.toString();
String prev = null;
StringTokenizer itr = new StringTokenizer(line);
while (itr.hasMoreTokens()) {
String cur = itr.nextToken();
// Emit only if we have an actual bigram.
if (prev != null) {
// Simple way to truncate tokens that are too long.
if (cur.length() > 100) {
cur = cur.substring(0, 100);
}
if (prev.length() > 100) {
prev = prev.substring(0, 100);
}
BIGRAM.set(prev, cur);
context.write(BIGRAM, ONE);
BIGRAM.set(prev, "*");
context.write(BIGRAM, ONE);
}
prev = cur;
}
}
}
protected static class MyCombiner extends
Reducer<PairOfStrings, FloatWritable, PairOfStrings, FloatWritable> {
private static final FloatWritable SUM = new FloatWritable();
@Override
public void reduce(PairOfStrings key, Iterable<FloatWritable> values, Context context)
throws IOException, InterruptedException {
int sum = 0;
Iterator<FloatWritable> iter = values.iterator();
while (iter.hasNext()) {
sum += iter.next().get();
}
SUM.set(sum);
context.write(key, SUM);
}
}
protected static class MyReducer extends
Reducer<PairOfStrings, FloatWritable, PairOfStrings, FloatWritable> {
private static final FloatWritable VALUE = new FloatWritable();
private float marginal = 0.0f;
@Override
public void reduce(PairOfStrings key, Iterable<FloatWritable> values, Context context)
throws IOException, InterruptedException {
float sum = 0.0f;
Iterator<FloatWritable> iter = values.iterator();
while (iter.hasNext()) {
sum += iter.next().get();
}
if (key.getRightElement().equals("*")) {
VALUE.set(sum);
context.write(key, VALUE);
marginal = sum;
} else {
VALUE.set(sum / marginal);
context.write(key, VALUE);
}
}
}
protected static class MyPartitioner extends Partitioner<PairOfStrings, FloatWritable> {
@Override
public int getPartition(PairOfStrings key, FloatWritable value, int numReduceTasks) {
return (key.getLeftElement().hashCode() & Integer.MAX_VALUE) % numReduceTasks;
}
}
private BigramRelativeFrequency() {}
private static final String INPUT = "input";
private static final String OUTPUT = "output";
private static final String NUM_REDUCERS = "numReducers";
/**
* Runs this tool.
*/
@SuppressWarnings({ "static-access" })
public int run(String[] args) throws Exception {
Options options = new Options();
options.addOption(OptionBuilder.withArgName("path").hasArg()
.withDescription("input path").create(INPUT));
options.addOption(OptionBuilder.withArgName("path").hasArg()
.withDescription("output path").create(OUTPUT));
options.addOption(OptionBuilder.withArgName("num").hasArg()
.withDescription("number of reducers").create(NUM_REDUCERS));
CommandLine cmdline;
CommandLineParser parser = new GnuParser();
try {
cmdline = parser.parse(options, args);
} catch (ParseException exp) {
System.err.println("Error parsing command line: " + exp.getMessage());
return -1;
}
if (!cmdline.hasOption(INPUT) || !cmdline.hasOption(OUTPUT)) {
System.out.println("args: " + Arrays.toString(args));
HelpFormatter formatter = new HelpFormatter();
formatter.setWidth(120);
formatter.printHelp(this.getClass().getName(), options);
ToolRunner.printGenericCommandUsage(System.out);
return -1;
}
String inputPath = cmdline.getOptionValue(INPUT);
String outputPath = cmdline.getOptionValue(OUTPUT);
int reduceTasks = cmdline.hasOption(NUM_REDUCERS) ?
Integer.parseInt(cmdline.getOptionValue(NUM_REDUCERS)) : 1;
LOG.info("Tool name: " + BigramRelativeFrequency.class.getSimpleName());
LOG.info(" - input path: " + inputPath);
LOG.info(" - output path: " + outputPath);
LOG.info(" - num reducers: " + reduceTasks);
Job job = Job.getInstance(getConf());
job.setJobName(BigramRelativeFrequency.class.getSimpleName());
job.setJarByClass(BigramRelativeFrequency.class);
job.setNumReduceTasks(reduceTasks);
FileInputFormat.setInputPaths(job, new Path(inputPath));
FileOutputFormat.setOutputPath(job, new Path(outputPath));
job.setMapOutputKeyClass(PairOfStrings.class);
job.setMapOutputValueClass(FloatWritable.class);
job.setOutputKeyClass(PairOfStrings.class);
job.setOutputValueClass(FloatWritable.class);
job.setOutputFormatClass(SequenceFileOutputFormat.class);
job.setMapperClass(MyMapper.class);
job.setCombinerClass(MyCombiner.class);
job.setReducerClass(MyReducer.class);
job.setPartitionerClass(MyPartitioner.class);
// Delete the output directory if it exists already.
Path outputDir = new Path(outputPath);
FileSystem.get(getConf()).delete(outputDir, true);
long startTime = System.currentTimeMillis();
job.waitForCompletion(true);
System.out.println("Job Finished in " + (System.currentTimeMillis() - startTime) / 1000.0 + " seconds");
return 0;
}
/**
* Dispatches command-line arguments to the tool via the {@code ToolRunner}.
*/
public static void main(String[] args) throws Exception {
ToolRunner.run(new BigramRelativeFrequency(), args);
}
}