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https://issues.apache.org/jira/browse/MAHOUT-767?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sebastian Schelter resolved MAHOUT-767.
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Resolution: Fixed
> Improve RowSimilarityJob performance
> ------------------------------------
>
> Key: MAHOUT-767
> URL: https://issues.apache.org/jira/browse/MAHOUT-767
> Project: Mahout
> Issue Type: Improvement
> Components: Collaborative Filtering
> Affects Versions: 0.5
> Reporter: Grant Ingersoll
> Assignee: Sebastian Schelter
> Fix For: 0.6
>
> Attachments: MAHOUT-767-2.patch, MAHOUT-767.patch
>
>
> (See
> http://www.lucidimagination.com/search/document/40c4f124795c6b5/rowsimilarity_s#42ab816c27c6a9e7
> for background)
> Currently, the RowSimilarityJob defers the calculation of the similarity
> metric until the reduce phase, while emitting many Cooccurrence objects. For
> similarity metrics that are algebraic
> (http://pig.apache.org/docs/r0.8.1/udf.html#Aggregate+Functions) we should be
> able to do much of the computation during the Mapper part of this phase and
> also take advantage of a Combiner.
> We should use a marker interface to know whether a similarity metric is
> algebraic and then make use of an appropriate Mapper implementation,
> otherwise we can fall back on our existing implementation.
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