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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, 01 Sep 2010 23:36:54 GMT

    [ https://issues.apache.org/jira/browse/MATH-375?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12905314#action_12905314
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William Rossi commented on MATH-375:
------------------------------------

Thanks Jeff.  I will take a look at your tests.   As for my test, the last number on the line
shows the error in ULPs, so its just outside the threshold.  I may have set the tolerance
a bit too tight.

> 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
>             Fix For: 2.2
>
>         Attachments: atanpatch.txt.gz, FastMath.tar.gz, test_fastmath_wr.zip
>
>
> 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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