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## Re: [Help-gsl] ln gamma |x| too large error

**From**: |
Brian Gough |

**Subject**: |
Re: [Help-gsl] ln gamma |x| too large error |

**Date**: |
Tue, 20 Mar 2007 12:35:47 +0000 |

**User-agent**: |
Wanderlust/2.14.0 (Africa) Emacs/21.3 Mule/5.0 (SAKAKI) |

At Fri, 16 Mar 2007 10:38:48 +0000 (GMT),
Clare Quarman wrote:
>* When using the special function lngamma_sgn_e, sometimes I receive an*
>* error, the only info is that it's from line 1249 in gamma.c. Looking at*
>* this bit of gamma.c, a nearby comment states that |x| is too large for the *
>* fractional part to be extracted.*
>* *
>* I'm wondering if this restriction the same both for +ve and -ve values of*
>* x, and what constitutes too large a magnitude for x?*
>* *
>* Does anyone understand what's going on here?*
The gamma function has a singularity at every negative integer, and
for x < -1e15 there isn't enough precision to distinguish between
integer and non-integer values in double-precision -- that is when
this error should occur.
--
Brian Gough
Network Theory Ltd,
Publishing Free Software Manuals --- http://www.network-theory.co.uk/