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Re: Making some minor contributions to GSL
On Tue, Jan 13, 2004 at 03:56:00PM -0700, Gerard Jungman wrote:
> On Tue, 2004-01-13 at 11:17, linas@austin.ibm.com wrote:
> >
> > Polygamma functions, Abramowitz & Stegun chapter 6.4 -- these
> > are derivatives of the gamma (factorial) function. The algo
> > I have is fairly straightforward ... and is accurate to about
> > 1e-14 or so for "small" orders and arguments. (The "multiplication
> > theorm" breaks down above order 30 or 40 or so, i.e. for arguments
> > greater than a 100 or 200 or so. I'm not sure why.)
>
> I have never made a study of robustness of the GSL
> implementation, in gsl_sf_psi_n(). There are only
p.s. I forgot to mention that the problems alluded to above
only affect my implementation, and they're not as bad as I thought,
the errors are only 1.0e-14, I thought they were worse. The gsl
implementation passes my tests with better than 1e-15 accuracy.
So other than the negative argument issue, there is no problem.
--linas