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https://issues.apache.org/jira/browse/MAHOUT-317?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12839688#action_12839688
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Ankur commented on MAHOUT-317:
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You can also make some gains by using a simple Combiner to reduce the amount on
ngrams and subgrams from the mappers. The OutputValueGroupingComparator is not
applied in the map-phase so Combiner gets all the values for a particular
ngrams/subgram. Package o.a.m.cf.taste.hadoop.cooccurence has a Bigram class
that implements binary comparison.
> 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, 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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