Differences

This shows you the differences between two versions of the page.

--- courses:mapreduce-tutorial:step-3 [2012/01/28 11:35]
majlis Added links to previous and next chapter.
+++ courses:mapreduce-tutorial:step-3 [2012/01/30 13:51]
straka
@@ Line 8: / Line 8: @@
 <file perl>
-#!/usr/bin/perl
+package My::Mapper;
-package Mapper;
 use Moose;
 with 'Hadoop::Mapper';
@@ Line 20: / Line 18: @@
 }
-package Main;
+package main;
 use Hadoop::Runner;
 my $runner = Hadoop::Runner->new(
-  mapper => Mapper->new(),
+  mapper => My::Mapper->new(),
   input_format => 'TextInputFormat',
   output_format => 'TextOutputFormat',
   output_compression => 0);
-$runner->run();
+$runner->run();  # Parse arguments in @ARGV and run the Hadoop job.
 </file>
@@ Line 37: / Line 35: @@
   perl script.pl run input_directory output_directory
 All files in input_directory are processes. The output_directory must not exist.
+=== Standard input and output ===
+Standard input and standard output of the Perl script are used to communicate with the Hadoop framework. Therefore you should use standard error output if you want to print some debugging output using ''print STDERR "Message"''.
 ===== Exercise =====
-To check that your Hadoop environment works, try running a MR job on ''/home/straka/wiki/cs-text'', which outputs only articles with names beginning with an ''A'' (ignoring the case). You can download the template {{:courses:mapreduce-tutorial:step-3-exercise.txt|step-3-exercise.pl}}  and execute it.
+To check that your Hadoop environment works, try running a MR job on ''/home/straka/wiki/cs-text-medium'', which outputs only articles with names beginning with an ''A'' (ignoring the case). You can download the template {{:courses:mapreduce-tutorial:step-3-exercise.txt|step-3-exercise.pl}}  and execute it.
   wget --no-check-certificate 'https://wiki.ufal.ms.mff.cuni.cz/_media/courses:mapreduce-tutorial:step-3-exercise.txt' -O 'step-3-exercise.pl'
+  # NOW EDIT THE FILE
+  # $EDITOR step-3-exercise.pl
   rm -rf step-3-out-ex; perl step-3-exercise.pl run /home/straka/wiki/cs-text-medium/ step-3-out-ex
-  less step-3-out-ex/part-m-*
+  less step-3-out-ex/part-*
 ==== Solution ====
 You can also download the solution {{:courses:mapreduce-tutorial:step-3-solution.txt|step-3-solution.pl}} and check the correct output.
   wget --no-check-certificate 'https://wiki.ufal.ms.mff.cuni.cz/_media/courses:mapreduce-tutorial:step-3-solution.txt' -O 'step-3-solution.pl'
+  # NOW VIEW THE FILE
+  # $EDITOR step-3-solution.pl
   rm -rf step-3-out-sol; perl step-3-solution.pl run /home/straka/wiki/cs-text-medium/ step-3-out-sol
-  less step-3-out-sol/part-m-*
+  less step-3-out-sol/part-*
 ----

[ Back to the navigation ] [ Back to the content ]

Institute of Formal and Applied Linguistics Wiki

Differences