[jira] Commented: (MAHOUT-474) Should compress output of Job pairwiseSimilarity and Job asMatrix

["Han Hui Wen (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAHOUT-474?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12898215#action_12898215 ] 

Han Hui Wen  commented on MAHOUT-474:
-------------------------------------

I have done test for this,
Before using patch,the output of pairwiseSimilarity is 18,7G,
After using patch ,the output of pairwiseSimilarity is about 3.952G( = 247M *16),

{code}
+      SequenceFileOutputFormat.setCompressOutput(pairwiseSimilarity, true);
+      SequenceFileOutputFormat.setOutputCompressorClass(pairwiseSimilarity, GzipCodec.class);
+      SequenceFileOutputFormat.setOutputCompressionType(pairwiseSimilarity, CompressionType.BLOCK);
{code}

Also because RowSimilarityJob run a in separated process ,the properties will lost from the main Job.

The properties must be set by the RecommenderJob

> Should compress output of Job pairwiseSimilarity and Job asMatrix
> -----------------------------------------------------------------
>
>                 Key: MAHOUT-474
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-474
>             Project: Mahout
>          Issue Type: Improvement
>          Components: Collaborative Filtering
>    Affects Versions: 0.4
>            Reporter: Han Hui Wen 
>            Assignee: Sean Owen
>
> !https://issues.apache.org/jira/secure/attachment/12451985/RowSimilarityJob-CooccurrencesMapper-SimilarityReducer.jpg!
>  From above picture ,we can see that the output of pairwiseSimilarity is very large ,we should compress them.
>       SequenceFileOutputFormat.setOutputCompressionType(job, style);
>       SequenceFileOutputFormat.setCompressOutput(job, compress);
>       SequenceFileOutputFormat.setOutputCompressorClass(job, codecClass)

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