I made a mistake in my example.
Given 2 files with the same content:
file 1 | file 2
A 3 | A 3
B 4 | B 4
gives the output
A 6
B 8
On 5 June 2013 21:08, Pedro Sá da Costa <psdc1...@gmail.com> wrote:
> I am trying to create a mapreduce example that add values of same keys.
> E.g.
> the input
> A 1
> A 2
> B 4
>
> get the output
> A 3
> B4
>
> The problem is that I cannot make the program read 2 inputs. How I do that?
>
> Here is my example:
>
> package org.apache.hadoop.examples;
>
> import java.io.IOException;
> import java.util.ArrayList;
> import java.util.Arrays;
> import java.util.Iterator;
> import java.util.List;
> import java.util.StringTokenizer;
>
> import org.apache.hadoop.conf.Configuration;
> import org.apache.hadoop.conf.Configured;
> import org.apache.hadoop.fs.Path;
> import org.apache.hadoop.io.IntWritable;
> import org.apache.hadoop.io.LongWritable;
> import org.apache.hadoop.io.Text;
> import org.apache.hadoop.mapred.FileInputFormat;
> import org.apache.hadoop.mapred.FileOutputFormat;
> import org.apache.hadoop.mapred.JobClient;
> import org.apache.hadoop.mapred.JobConf;
> import org.apache.hadoop.mapred.MapReduceBase;
> import org.apache.hadoop.mapred.Mapper;
> import org.apache.hadoop.mapred.OutputCollector;
> import org.apache.hadoop.mapred.Reducer;
> import org.apache.hadoop.mapred.Reporter;
> import org.apache.hadoop.util.Tool;
> import org.apache.hadoop.util.ToolRunner;
>
> /**
> * This is an example Hadoop Map/Reduce application.
> * It takes in several outputs of the count lines and sum them together
> acordinc the line.
> *
> * To run: bin/hadoop jar build/countlinesaggregator.jar
> * [-m <i>maps</i>] [-r <i>reduces</i>] <i>in-dirs</i>
> <i>out-dir</i>
> * e.g.
> * bin/hadoop jar countlinesaggregator.jar /gutenberg-output1
> /gutenberg-output2 /final-output
> */
> public class CountLinesAggregator extends Configured implements Tool {
> /**
> * Aggregate keys and values.
> * For each line of input, break the line into words and emit them as
> * (<b>lines</b>, <b>val</b>).
> */
> public static class MapClass extends MapReduceBase
> implements Mapper<LongWritable, Text, Text, IntWritable> {
> private Text word = new Text();
>
> public void map(LongWritable key, Text value,
> OutputCollector<Text, IntWritable> output,
> Reporter reporter) throws IOException {
> String line = value.toString();
> StringTokenizer itr = new StringTokenizer(line, "\n");
> while (itr.hasMoreTokens()) {
> String token = itr.nextToken();
> if(token.length() >0 ) {
> System.out.println("Token: " + token);
> String[] splits = token.split("\t");
> if(splits[0] != null && splits[1] != null &&
> splits[0].length() > 0 && splits[1].length() >
> 0) {
> System.out.println(Arrays.deepToString(splits));
> String k = splits[0];
> String v = splits[1];
> word.set(k);
> IntWritable val = new
> IntWritable(Integer.valueOf(v));
> output.collect(word, val);
> }
> }
> }
> }
> }
>
> /**
> * A reducer class that just emits the sum of the input values.
> */
> public static class Reduce extends MapReduceBase
> implements Reducer<Text, IntWritable, Text, IntWritable> {
>
> public void reduce(Text key, Iterator<IntWritable> values,
> OutputCollector<Text, IntWritable> output,
> Reporter reporter) throws IOException {
> int sum = 0;
> while (values.hasNext()) {
> sum += values.next().get();
> }
> output.collect(key, new IntWritable(sum));
> }
> }
>
> static int printUsage() {
> System.out.println("countlinesaggregator [-m <maps>] [-r
> <reduces>] <input1> <input2> <output>");
> ToolRunner.printGenericCommandUsage(System.out);
> return -1;
> }
>
> /**
> * The main driver for word count map/reduce program.
> * Invoke this method to submit the map/reduce job.
> * @throws IOException When there is communication problems with the
> * job tracker.
> */
> public int run(String[] args) throws Exception {
> JobConf conf = new JobConf(getConf(), CountLinesAggregator.class);
> conf.setJobName("countlinesaggregator");
>
> // the keys are words (strings)
> conf.setOutputKeyClass(Text.class);
> // the values are counts (ints)
> conf.setOutputValueClass(IntWritable.class);
>
> conf.setMapperClass(MapClass.class);
> conf.setCombinerClass(Reduce.class);
> conf.setReducerClass(Reduce.class);
> conf.setNumReduceTasks(1);
>
> List<String> other_args = new ArrayList<String>();
> for(int i=0; i < args.length; ++i) {
> try {
> if ("-m".equals(args[i])) {
> conf.setNumMapTasks(Integer.parseInt(args[++i]));
> } else if ("-r".equals(args[i])) {
> conf.setNumReduceTasks(Integer.parseInt(args[++i]));
> } else {
> other_args.add(args[i]);
> }
> } catch (NumberFormatException except) {
> System.out.println("ERROR: Integer expected instead of " +
> args[i]);
> return printUsage();
> } catch (ArrayIndexOutOfBoundsException except) {
> System.out.println("ERROR: Required parameter missing from
> " +
> args[i-1]);
> return printUsage();
> }
> }
> // Make sure there are exactly 2 parameters left.
> if (other_args.size() < 3) {
> System.out.println("ERROR: Wrong number of parameters: " +
> other_args.size());
> return printUsage();
> }
>
> String inputpath = "";
> for(int i=0; i<other_args.size()-1; i++) {
> if(i<other_args.size()-2)
> inputpath += other_args.get(i) + ",";
> else
> inputpath += other_args.get(i);
> }
> String outputpath=other_args.get(other_args.size()-1);
>
> System.out.println("Input path: " + inputpath);
> System.out.println("Output path: " + outputpath);
> FileInputFormat.setInputPaths(conf, inputpath);
> FileOutputFormat.setOutputPath(conf, new Path(outputpath));
>
> JobClient.runJob(conf);
> return 0;
> }
>
>
> public static void main(String[] args) throws Exception {
> int res = ToolRunner.run(new Configuration(), new
> CountLinesAggregator(), args);
> System.exit(res);
> }
> }
>
>
>
>
> --
> Best regards,
>
--
Best regards,
