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Re: [Help-gsl] bug in gsl_sf_lncosh?

From: Brian Gough
Subject: Re: [Help-gsl] bug in gsl_sf_lncosh?
Date: Fri, 15 Jul 2011 23:16:45 +0100
User-agent: Wanderlust/2.15.6 (Almost Unreal) Emacs/23.3 Mule/6.0 (HANACHIRUSATO)

At Wed, 13 Jul 2011 11:54:42 +0200,
Maximilian Treiber wrote:
> the function f(x)=ln(cosh(x)) is obviously symmetric, ie f(x)=f(-x),
> right?
> The current implementation in gsl seems to be incorrect for negative
> values:
> The second elseif is met for large negative numbers, while the
> correct asymptotic limit would be "f(x->-inf) = |x|-ln(2)".
> Replacing x by fabs(x) everywhere should fix the problem ...

Hi. Thanks for the bug report, you are right. I've just committed a
patch for the problem.

Brian Gough

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