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From Sébastien Brisard <sebastien.bris...@m4x.org>
Subject Re: [math] Changes in the Gamma class
Date Fri, 17 Aug 2012 03:42:20 GMT
Hi

2012/8/16 Gilles Sadowski <gilles@harfang.homelinux.org>:
> On Wed, Aug 15, 2012 at 04:58:39PM +0200, Sébastien Brisard wrote:
>> Dear All,
>> I'm currently working on accuracy improvements of the incomplete beta
>> function, based on the NSWC library [1]. It's quite a long work, but it
>> looks promising, since the implementation of the Gamma function they
>> propose (I had to work first on Gamma before starting the actual work on
>> Beta) seems to be much more accurate than the current implementation in CM3
>> (3-4 ulps, TBC).
>>
>> When I'm done, I think I will replace the current impl of Gamma with the
>> NSWC. The problem is that a few months ago, while working on MATH-753, I
>> exposed a few constants as well as the method lanczos, which will probably
>> no longer be necessary (NSWC does not use Lanczos, but minimax rational
>> approximations). My worry is that we are approaching the release of 3.1,
>> and I think it would be a shame if we froze the exposition of these
>> constants and methods. The trouble is that my current work on Gamma and
>> Beta is quite slow, I'm not sure I can finish it before the expected
>> release.
>>
>> So, should I revert the changes made for MATH-753, and reopen this issue?
>> This would allow the removal of method lanczos and constant LANCZOS_G,
>
> For traceability, that could be a good idea to indicate in MATH-753 that you
> changed your mind, and decided to make those "private". ;-)
>
For the time being, I can't make these fields private, because they
are needed by other classes (GammaDistribution), which are not even in
the same package. So basically, once I've reimplemented Gamma, I need
to find another fix to MATH-753...

>> which would lay out the path to the new implementation. Alternatively, I
>> can deprecate these fields.
>
> Not necessary to go through this step since those fields appeared after the
> last release (IIRC).
>
Yes. My concern is that you want to release soon, and I'm not sure I
can clean this up before release. Fortunately, progress has been
smooth on the Gamma side those last days. So, instead of working on
MATH-738 (which all this is about), I will concentrate on replacing
the old impl of Gamma with the new one, and re-fixing MATH-753.
Hopefully this will all happen soon!

Sébastien
>
> Regards,
> Gilles
>
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