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From "William Rossi (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MATH-375) Elementary functions in JDK are slower than necessary and not as accurate as they could be.
Date Wed, 09 Jun 2010 16:59:14 GMT

    [ https://issues.apache.org/jira/browse/MATH-375?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12877132#action_12877132
] 

William Rossi commented on MATH-375:
------------------------------------


I'm not as well versed in these copyright issues I as I should be, but my 
understanding is that as the copyright holder of the dfp library, I could 
dual license it.  In any event, dfp is not required by the software, its 
only used in the supporting test cases.

Which also why I whould be hesitant to assign copyright to ASF, if I were 
to do that and ASF decides not to persue the project then I'm left with 
nothing.  By maintaining the copyright, I can issue licenses to other 
parties as I see fit.

The ASF software grant agreement doesn't ask me to assign copyright to 
ASF, but to mearly agree to specific license terms.




> Elementary functions in JDK are slower than necessary and not as accurate as they could
be.
> -------------------------------------------------------------------------------------------
>
>                 Key: MATH-375
>                 URL: https://issues.apache.org/jira/browse/MATH-375
>             Project: Commons Math
>          Issue Type: New Feature
>         Environment: JDK 1.4 - 1.6
>            Reporter: William Rossi
>         Attachments: FastMath.tar.gz
>
>
> I would like to contribute improved versions on exp(), log(), pow(), etc.  to the project.
 Please refer to this discussion thread http://markmail.org/message/zyeoguw6gwtofm62.
> I have developed over the past year a set of elementary functions similar to those in
java.lang.Math, but with the following characteristics:
> * Higher performance.
> * Better accuracy.  Results are accurate to slightly more that +/- 0.5 ULP.
> * Pure Java.  The standard Math class is impleneted via JNI, and thus takes a performance
hit.
> Note that some functions such as exp are nearly twice as fast in my implementation.  
I've seen it 3 times faster on different processors.   The preformance varies by the relative
speed of calculation vs memory lookups.
> The functions are implemented as tables of values in extra precision (approx 70 bits),
and then interpolated with a minimax polynomial.

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