[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
## Re: [Bug-gsl] hyperg_U(a,b,x) Questions about x<0 and values

**From**: |
Raymond Rogers |

**Subject**: |
Re: [Bug-gsl] hyperg_U(a,b,x) Questions about x<0 and values |

**Date**: |
Thu, 08 Jul 2010 11:49:15 -0500 |

**User-agent**: |
Thunderbird 2.0.0.24 (X11/20100411) |

Brian Gough <address@hidden>
Subject: Re: [Bug-gsl] hyperg_U(a,b,x) Questions about x<0 and values
of a
To: address@hidden
Cc: address@hidden
Message-ID: <address@hidden>
Content-Type: text/plain; charset=US-ASCII
At Wed, 07 Jul 2010 10:14:34 -0500,
Raymond Rogers wrote:
>* > *
>* > 1) I was unable to find the valid domain of the argument a when x<0. *
>* > Experimenting yields what seem to be erratic results. Apparently*
>* > correct answers occur when {x<0&a<0& a integer}. References would be*
>* > sufficient. Unfortunately {x<0,a<0} is exactly the wrong range for my*
>* > problem; but the recursion relations can be used to stretch to a>0. If*
>* > I can find a range of correct operation for the domain of "a" of width >1.*
>* *
| Brian Gough
| Thanks for the email. There are some comments about the domain for
| the hyperg_U_negx function in specfunc/hyperg_U.c -- do they help?
They explain some things, but I believe the section
if (b_int && b >= 2 && !(a_int && a <= (b - 2))){}
else {}
is implemented incorrectly; and probably the preceding section as well. Some
restructuring of the code would make things clearer; but things like that
should probably done in a different forum: email, blog, etc...
I think the switches might be wrong. In any case it seems that b=1 has a hole.
Is there a source for this code?
Note: the new NIST Mathematical handbook might have better algorithms. I am
certainly no expert on implementing mathematical functions (except for finding
ways to make them fail).
Ray

[Prev in Thread] |
**Current Thread** |
[Next in Thread] |

**Re: [Bug-gsl] hyperg_U(a,b,x) Questions about x<0 and values**,
*Raymond Rogers* **<=**