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Date: Tue, 12 Jun 2012 14:07:43 +0000 (UTC)
From: "Mikkel Meyer Andersen (JIRA)" <jira@apache.org>
To: issues@commons.apache.org
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Subject: [jira] [Commented] (MATH-790) Mann-Whitney U Test Suffers From
 Integer Overflow With Large Data Sets
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    [ https://issues.apache.org/jira/browse/MATH-790?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13293644#comment-13293644 ] 

Mikkel Meyer Andersen commented on MATH-790:
--------------------------------------------

I agree - I just wanted to have it in writing :-). Thanks for this.
                
> Mann-Whitney U Test Suffers From Integer Overflow With Large Data Sets
> ----------------------------------------------------------------------
>
>                 Key: MATH-790
>                 URL: https://issues.apache.org/jira/browse/MATH-790
>             Project: Commons Math
>          Issue Type: Bug
>    Affects Versions: 3.0, Nightly Builds
>         Environment: Ubuntu Linux x64, Sun Java 6
>            Reporter: James Pickering
>            Assignee: Mikkel Meyer Andersen
>            Priority: Minor
>              Labels: newbie, patch
>             Fix For: 3.1
>
>         Attachments: MannWhitnetUOVerflowPatch.diff
>
>   Original Estimate: 1h
>  Remaining Estimate: 1h
>
> When performing a Mann-Whitney U Test on large data sets (the attached test uses two 1500 element sets), intermediate integer values used in calculateAsymptoticPValue can overflow, leading to invalid results, such as p-values of NaN, or incorrect calculations.
> Attached is a patch, including a test, and a fix, which modifies the affected code to use doubles

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