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Re: [Bug-gsl] bugs when using gsl_sf_hyperg_U

From: Patrick Alken
Subject: Re: [Bug-gsl] bugs when using gsl_sf_hyperg_U
Date: Tue, 11 Mar 2014 14:00:19 -0600
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0

Hi, I've entered your bug report into the bug tracker so it won't be lost. Unfortunately it may be some time before it is fixed, since I'm not an expert on these functions and I'm not sure if the other GSL developers have experience/interest in working on the special functions.

In the meantime, if you want to continue to investigate the problem and possibly look into fixing the issues, we would be glad to get your feedback.


On 03/10/2014 08:38 PM, Feng Gao wrote:

Sorry for so many emails... I also tried the GSL SHELL software and it
seemse that sf.hypergU(1, -500, 0.1) can be calculated correctly. However,
I found that any negative non-integers of b for U(a, b, x) cannot be
calculated. These negative non-integers should be suitable arguments and
the manual states that b is of type double.

Thanks very much for your attention and I will be very grateful if you can
resolve these problems.

Best Regards,


2014-03-10 21:01 GMT-04:00 Feng Gao <address@hidden>:

Sorry for the typo but for example 1) listed in the previous email:

gsl_sf_hyperg_U(1, -500, 0.1) gives the correct value: ~1.99e-3.

The problem happens when calculating gsl_sf_hyperg_U(1, -500, 40): gsl:
gsl: hyperg.c:165: ERROR: overflow. The value should be ~0.00184 so I
suppose this is a bug.

Again, thanks very much if you can help me solve this problem since I very
much need it in my research.

Best Regards,


2014-03-10 19:53 GMT-04:00 Feng Gao <address@hidden>:

I have been using the gsl_sf_hyperg_U function for a while and I found
several bugs when calculating normal values. For example,

1) gsl_sf_hyperg_U(1, -500, 0.1) gives incorrect value: 9.3246e+03, which
actually should be around 0.19.

2) Many domain error bugs. For example, gsl_sf_hyperg_U(1, -6.67, 1)
should have value ~0.128 but will invoke domain error for gsl.

Hope that you can further investigate this and come up with solutions.

Best Regards,


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