[SciPy-dev] hyper1f1, ticket #659

[Moritz Helias]

Hello,

Johann Cohen-Tanugi wrote:

> hello,
> I confirm this on my linux box with a very recent version of scipy  
> from
> the bzr trunk. It seems somewhat related to
> http://www.scipy.org/scipy/scipy/ticket/419 ....

true. The problem seems to be the error estimation of Kahan's sum  
algorithm which is too optimistic in this case.

>
> Anyway, this should be fixed....
> Johann
>

special/specfun/specfun.f contains an implementation of M(a,b,x) which  
is called chgm.
This works fine for me. It just has to be wrapped (which I did on my  
machine).

Greetings,

Moritz

> Moritz Helias wrote:
>> Hi,
>>
>> I found some strange behavior of the hypergeometric function with  
>> real
>> arguments (hyp1f1). I do not know, who is the specialist on this
>> subject, but
>> could somebody please try to reproduce it (see ticket #659,
>> attached .py file): For large negative x, the function becomes quite
>> jagged.
>>
>> I also described a possible reason and a workaround in the ticket. My
>> work relies on this function, so currently I have to patch each of my
>> scipy installations to continue working.
>> If the bug can be reproduced by others, is there the possibility that
>> I provide a patch?
>>
>> Thanks in advance,
>>
>> greetings,
>>
>> Moritz
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