[jira] Resolved: (MATH-151) MathUtils.round incorrect result

["Phil Steitz (JIRA)" <ji...@apache.org>]

     [ http://issues.apache.org/jira/browse/MATH-151?page=all ]
     
Phil Steitz resolved MATH-151:
------------------------------

    Resolution: Fixed

Patch applied.  Thanks!

I understand that the patch is not really satisfying, but it makes the code better and resolves the reported problem.   A more elegant solution may be possible, but the patch improves the code and resolves the reported problem, so it should be applied.  If we find a better way to handle correct rounding of "bad" IEEE754 numbers, we can reopen or create a separate issue.

Thanks for the patch!

> MathUtils.round incorrect result
> --------------------------------
>
>          Key: MATH-151
>          URL: http://issues.apache.org/jira/browse/MATH-151
>      Project: Commons Math
>         Type: Bug

>     Versions: 1.1 Final
>  Environment: Win2K, Sun JDK1.5.0_05 b05
>     Reporter: Buza Zoltán
>  Attachments: math-151.patch
>
> MathUtils.round(39.245, 2) results 39.24, however it should be 39.25, with default rounding mode BigDecimal.ROUND_HALF_UP.
> I found that internally MathUtils.round multiplies the given number by 10^scale.
>  39.245 * 100.0 results 3924.49999...5 , and after this the calculation is not correct any more.

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