Re: [Bug-gsl] [bug #45926] error in generalized hypergeometric function

[Raymond Rogers]

Yes, this is one of the problems I looked at.  I didn't go so far as to 
follow it up; and have no recommendations.  Except there is a problem 
with the loop terminating.  As I recall similar errors are in a couple 
of other places as well.
Ray


On 11/19/2015 05:16 PM, Patrick Alken wrote:
> Follow-up Comment #1, bug #45926 (project gsl):
>
> from shufflesky =at= hotmail =dot= com
>
> I've investigated bug #45929 "error in generalized hypergeometric function".
> The problem is in the
> file specfunc/hyperg_2F1.c in the first function the file,
> hyperg_2F1_series(). There is a loop starting
> at line 59 which is intended to converge to the solution, and within this loop
> is a check to insure the
> loop is not executed more than 30000 times. This code is actually working and
> computing the correct
> value, but the error terms del_pos and del_neg eventually get no smaller and
> so the loop executes the
> full 30000 iterations and then reports GSL_EMAXITER error, even though it does
> have the correct
> value calculated.
>
> I would fix this by saving the previous error terms and insuring they are
> becoming smaller with each
> iteration. If they are not getting smaller, machine precision has been reached
> and the value can be
> returned to the user. I can supply code or could check in myself through git
> if I can get access. I have
> 30+ years of experience with C code and want to begin helping maintain GSL.
>
> -Bill Maier                                     
>
>      _______________________________________________________
>
> Reply to this item at:
>
>    <http://savannah.gnu.org/bugs/?45926>
>
> _______________________________________________
>    Message sent via/by Savannah
>    http://savannah.gnu.org/

--
 Two views on life:
life is an art not to be learned by observation.
George Santayana:Interpretations of Poetry and Religion
It's kinda nice to participate in your life
Raymond Rogers