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https://issues.apache.org/jira/browse/MAHOUT-1261?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Carl Clark updated MAHOUT-1261:
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Attachment: (was: MAHOUT-1261.patch)
> TasteHadoopUtils.idToIndex can return an int that has size Integer.MAX_VALUE
> ----------------------------------------------------------------------------
>
> Key: MAHOUT-1261
> URL: https://issues.apache.org/jira/browse/MAHOUT-1261
> Project: Mahout
> Issue Type: Bug
> Components: Collaborative Filtering
> Affects Versions: 0.8
> Reporter: Dan Filimon
> Priority: Minor
>
> I'm running ItemSimilarityJob on a very large (~600M by 4B) matrix that's
> very sparse (total set of associations is 630MB).
> The job fails because of an IndexException in ToUserVectorsReducer.
> TasteHadoopUtils.idToIndex(long id) hashes a long with:
> 0x7fffffff & Longs.hashCode(id) (line
> o.a.m.cf.taste.hadoop.TasteHadoopUtils:57).
> For some id (I don't know what value), the result returned is
> Integer.MAX_VALUE.
> This cannot be set in the userVector because the cardinality of that is also
> Integer.MAX_VALUE and it throws an exception.
> So, the issue is that values from 0 to INT_MAX are returned by idToIndex but
> the vector only has 0 to INT_MAX - 1 possible entries.
> It's a nasty little off-by-one bug.
> I'm thinking of just % size when setting.
> [~ssc] & everyone else, thoughts? :)
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