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--- courses:mapreduce-tutorial:step-4 [2012/01/28 11:58]
majlis Added links to previous and next chapter.
+++ courses:mapreduce-tutorial:step-4 [2012/01/31 09:40] (current)
straka Change Perl commandline syntax.
@@ Line 3: / Line 3: @@
 Sometimes it is useful to count events differently than outputting them as (key, value) pairs. For that reason Hadoop offers simple counter framework.
-Hadoop maintains a collection of pre-defined and user-defined counters. Every counter is identified by its group name and counter name. To increment a counter, the following code can be used:
+Hadoop maintains a collection of pre-defined and user-defined counters. Every counter is identified by its group name and counter name. The group name and counter name is an arbitrary string -- for example group "Documents" and name "Number of words". To increment a counter, the following code can be used:
 <code perl>
@@ Line 17: / Line 17: @@
 ===== Exercise =====
-Run a Hadoop job on ''/home/straka/wiki/cs-text-medium'', which uses counters to count the number of articles according to their first letter (ignoring the case and possible diacritics). You can download the template {{:courses:mapreduce-tutorial:step-4-exercise.txt|step-4-exercise.pl}}  and execute it.
+Run a Hadoop job on ''/home/straka/wiki/cs-text-medium'', which uses counters to count the number of articles according to their first letter (ignoring the case). You can download the template {{:courses:mapreduce-tutorial:step-4-exercise.txt|step-4-exercise.pl}}  and execute it.
   wget --no-check-certificate 'https://wiki.ufal.ms.mff.cuni.cz/_media/courses:mapreduce-tutorial:step-4-exercise.txt' -O 'step-4-exercise.pl'
-  rm -rf step-4-out-ex; perl step-4-exercise.pl run /home/straka/wiki/cs-text-medium/ step-4-out-ex
+  # NOW EDIT THE FILE
+  # $EDITOR step-4-exercise.pl
+  rm -rf step-4-out-ex; perl step-4-exercise.pl /home/straka/wiki/cs-text-medium/ step-4-out-ex
+  less step-4-out-ex/part-*
 ==== Solution ====
 You can also download the solution {{:courses:mapreduce-tutorial:step-4-solution.txt|step-4-solution.pl}} and check the correct output.
   wget --no-check-certificate 'https://wiki.ufal.ms.mff.cuni.cz/_media/courses:mapreduce-tutorial:step-4-solution.txt' -O 'step-4-solution.pl'
-  rm -rf step-4-out-sol; perl step-4-solution.pl run /home/straka/wiki/cs-text-medium/ step-4-out-sol
+  # NOW VIEW THE FILE
+  # $EDITOR step-3-solution.pl
+  rm -rf step-4-out-sol; perl step-4-solution.pl /home/straka/wiki/cs-text-medium/ step-4-out-sol
+  less step-4-out-sol/part-*
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