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From "Mayank Lahiri (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-1372) New algorithm for variance() UDAF
Date Wed, 02 Jun 2010 17:05:45 GMT

    [ https://issues.apache.org/jira/browse/HIVE-1372?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12874664#action_12874664
] 

Mayank Lahiri commented on HIVE-1372:
-------------------------------------

Hi John,

Quick question -- where is the 'src' table created for the .q unit tests?
The wiki section for that is empty, so I'll add in some text there as well
once I know.

- Mayank







> 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-1372.2.patch, 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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