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https://issues.apache.org/jira/browse/MAHOUT-317?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Drew Farris updated MAHOUT-317:
-------------------------------

    Attachment: MAHOUT-317.patch

This patch addresses the original problem by using the 
Partitioner/OutputValueGroupingComparator to ensure that subgrams and ngrams 
are processed in the proper order in which to avoid having to store values in a 
hash when calculating frequencies.

Submitting this patch to capture the current state of the fix. I suspect 
there's a optimization to be performed to reduce the output of CollocMapper, 
but in its current state this patch works and should address the problem.


> Collocations: Eliminate in-memory frequency calculation
> -------------------------------------------------------
>
>                 Key: MAHOUT-317
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-317
>             Project: Mahout
>          Issue Type: Improvement
>    Affects Versions: 0.3
>            Reporter: Drew Farris
>             Fix For: 0.3
>
>         Attachments: MAHOUT-317.patch
>
>
> see: 
> http://www.lucidimagination.com/search/document/ae484d53e969250e/who_owns_mahout_bucket_on_s3
> The collocation code currently uses maps in the CollocCombiner and 
> CollocReducer to perform frequency calculations which can cause the process 
> to exceed the heap space if a large number of ngrams exist for any given 
> subgram.
> Convert the code to use a composite key / secondary sort to avoid the need 
> for in-memory map for frequency calculations. 

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