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courses:mapreduce-tutorial:step-11 [2012/01/28 22:34]
majlis |
courses:mapreduce-tutorial:step-11 [2012/01/28 23:04]
majlis Added links to previous and next chapter. |
| ===== Exercise ===== | ===== Exercise ===== |
| |
| Improve the {{:courses:mapreduce-tutorial:step-5-solution1.txt|wc-without-combiner.pl}} script by manually combining the results in the Mapper -- create a hash of word occurrences, populate it during the ''map'' calls without outputting results and finally output all (key, value) pairs in the ''cleanup'' method. | Improve the {{:courses:mapreduce-tutorial:step-5-solution1.txt|step-11-wc-without-combiner.pl}} script by manually combining the results in the Mapper -- create a hash of word occurrences, populate it during the ''map'' calls without outputting results and finally output all (key, value) pairs in the ''cleanup'' method. |
| |
| | wget --no-check-certificate 'https://wiki.ufal.ms.mff.cuni.cz/_media/courses:mapreduce-tutorial:step-5-solution1.txt' -O 'step-11-wc-without-combiner.pl' |
| | rm -rf step-11-out-wout; time perl step-11-wc-without-combiner.pl run /home/straka/wiki/cs-text-medium/ step-11-out-wout |
| | less step-11-out-wout/part-* |
| | |
| Measure the improvement. | Measure the improvement. |
| |
| | ==== Solution ==== |
| | You can also download the solution {{:courses:mapreduce-tutorial:step-11-solution.txt|step-11-wc-with-perl-hash.pl}} and check the correct output. |
| | |
| | wget --no-check-certificate 'https://wiki.ufal.ms.mff.cuni.cz/_media/courses:mapreduce-tutorial:step-11-solution.txt' -O 'step-11-wc-with-perl-hash.pl' |
| | rm -rf step-11-out-with-hash; time perl step-11-wc-with-perl-hash.pl run /home/straka/wiki/cs-text-medium/ step-11-out-with-hash |
| | less step-11-out-with-hash/part-* |
| |
| |
| |
| This is even more obvious with larger input data: | This is even more obvious with larger input data: |
| ^ Script ^ Time to complete on ''/home/straka/wiki/cs-text'' ^ | ^ Script ^ Time to complete on ''/home/straka/wiki/cs-text'' ^ Commands ^ |
| | {{:courses:mapreduce-tutorial:step-5-solution1.txt|wc-without-combiner.pl}} | 5mins, 4sec | | | {{:courses:mapreduce-tutorial:step-5-solution1.txt|step-11-wc-without-combiner.pl}} | 5mins, 4sec | <html><pre>wget --no-check-certificate 'https://wiki.ufal.ms.mff.cuni.cz/_media/courses:mapreduce-tutorial:step-5-solution1.txt' -O 'step-11-wc-without-combiner.pl'<br>rm -rf step-11-out-wout; time perl step-11-wc-without-combiner.pl run /home/straka/wiki/cs-text/ step-11-out-wout</pre></html> | |
| | {{:courses:mapreduce-tutorial:step-10.txt|wc-with-combiner.pl}} | 5mins, 33sec | | | {{:courses:mapreduce-tutorial:step-10.txt|step-11-wc-with-combiner.pl}} | 5mins, 33sec | <html><pre>wget --no-check-certificate 'https://wiki.ufal.ms.mff.cuni.cz/_media/courses:mapreduce-tutorial:step-10.txt' -O 'step-11-wc-with-combiner.pl'<br>rm -rf step-11-out-with-combiner; time perl step-11-wc-with-combiner.pl run /home/straka/wiki/cs-text/ step-11-out-with-combiner</pre></html>| |
| | | {{:courses:mapreduce-tutorial:step-11-solution.txt|step-11-wc-with-perl-hash.pl}} | 2mins, 24sec | <html><pre>wget --no-check-certificate 'https://wiki.ufal.ms.mff.cuni.cz/_media/courses:mapreduce-tutorial:step-11-solution.txt' -O 'step-11-wc-with-perl-hash.pl'<br>rm -rf step-11-out-with-perl-hash; time perl step-11-wc-with-perl-hash.pl run /home/straka/wiki/cs-text/ step-11-out-with-perl-hash</pre></html>| |
| |
| |
| Using the combiner is beneficial, although manually combining the word occurrences in mapper manually is still faster. | Using the combiner is beneficial, although manually combining the word occurrences in mapper manually is still faster. |
| |
| | ---- |
| | |
| | <html> |
| | <table style="width:100%"> |
| | <tr> |
| | <td style="text-align:left; width: 33%; "></html>[[step-10|Step 10]]: Combiners.<html></td> |
| | <td style="text-align:center; width: 33%; "></html>[[.|Overview]]<html></td> |
| | <td style="text-align:right; width: 33%; "></html>[[step-12|Step 12]]: Additional output from mappers and reducers.<html></td> |
| | </tr> |
| | </table> |
| | </html> |
