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From Luc Maisonobe <>
Subject Re: [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 17:14:56 GMT
Le 09/06/2010 18:59, William Rossi (JIRA) a écrit :
>     [
> 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.

If it is used in the test cases, it should be included in the source
release (which are what Apache promotes) and hence should be published
with an Apache compatible license like Apache Software License V2 (of
course) but also BSD for example.

> 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.

You are right, the foundation does not ask for the copyright, it only
requires a license allowing it to redistribute the code under the terms
of the Apache Software License V2. The copyright still belongs to you.
One minor glitch is that in the commons projects, we prefer not to have
@author javadoc tags in the source but rather the names placed in the
contributor section of the pom file (and hence publickly acknowledged in
an automatically built page on the component site) and possibly in the
NOTICE.txt file.


>> Elementary functions in JDK are slower than necessary and not as accurate as they
could be.
>> -------------------------------------------------------------------------------------------
>>                 Key: MATH-375
>>                 URL:
>>             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
>> 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
>> 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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