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Re: [Help-gsl] Bug in implementing Kummer's U?
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From: |
Brian Gough |
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Subject: |
Re: [Help-gsl] Bug in implementing Kummer's U? |
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Date: |
Tue, 7 Feb 2006 11:45:48 +0000 |
George Japaridze writes:
> U(a, 0.5 ,z) = sqrt(pi) ( 1F1(a, 0.5, z)/gamma(a+0.5) - 2*sqrt(z)*1F1
> (a+0.5, 1.5, z)/gamma(a) ) (1)
The RHS is a difference of two nearly equal large numbers for large z
so you are going to get a huge cancellation error just from the
subtraction.
--
Brian Gough
Network Theory Ltd,
Publishing the GSL Manual --- http://www.network-theory.co.uk/gsl/manual/