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https://issues.apache.org/jira/browse/HIVE-1372?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12873111#action_12873111
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John Sichi commented on HIVE-1372:
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For the expression m*(n+m), could overflow be a concern? These are 64-bit
integers, so if m and n (or just m) is bigger than a 32-bit integer, the
product could overflow before the conversion to double.
> New algorithm for variance() UDAF
> ---------------------------------
>
> Key: HIVE-1372
> URL: https://issues.apache.org/jira/browse/HIVE-1372
> Project: Hadoop Hive
> Issue Type: Improvement
> Components: Query Processor
> Affects Versions: 0.6.0
> Reporter: Mayank Lahiri
> Assignee: Mayank Lahiri
> Priority: Minor
> Fix For: 0.6.0
>
> Attachments: HIVE-1372.patch
>
>
> A new algorithm for the UDAF that computes variance. This is pretty much a
> drop-in replacement for the current UDAF, and has two benefits: provably
> numerically stable (reference included in comments), and reduces arithmetic
> operations by about half.
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