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From Gilles Sadowski <gil...@harfang.homelinux.org>
Subject Re: [math] Changes in the Gamma class
Date Fri, 17 Aug 2012 10:01:35 GMT
Hi.

> 
> 2012/8/16 Gilles Sadowski <gilles@harfang.homelinux.org>:
> > On Wed, Aug 15, 2012 at 04:58:39PM +0200, S├ębastien 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...

Copy the fields where they are needed.
As they are "private" here and there, they can be removed whenever they are
not needed anymore.

> 
> >> 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!

With the above workaround, no need to hurry or focus on this particular
issue. Duplicates could be removed in 3.2.

Best,
Gilles

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