Re: [Bug-gsl] Problem with function gsl_sf_exp in gsl-1.12

[Brian Gough]

At Tue, 3 Feb 2009 13:54:55 +0100,
Pierrick Bruneau wrote:
> 
> Hello,
> 
> I had little trouble with the function (double) gsl_sf_exp(double) :  
> when a pretty low value is passed as parameter (empirically : lower  
> than -750.0), this function causes a crash in the calling program.
> 
> This is rather surprising as exp is theorically defined for arbitrary  
> low values.
> I overcame the problem with a little patch block,

Thanks for your email.  The function returns an underflow error
(GSL_EUNDERFLOW) since the result is too small to represent but is not
zero. This is intentional so you can either disable the error handler
or check the argument first in a wrapper function as you've done.  The
function gsl_sf_exp_e10_e also has an extended range if you need it.

-- 
Brian Gough
(GSL Maintainer)

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