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Re: [Help-gsl] Exponential calculation


From: Kevin Channon
Subject: Re: [Help-gsl] Exponential calculation
Date: Wed, 11 Feb 2009 13:19:00 +0000

Hi Ashish,

> Is there any known mathematical method to calculate : exponential( -
> val), when val is too small number like -100

You don't need gsl for this, just use the standard c library math.h (or
cmath in c++)

printf("%g\n", exp(-100));

returns the correct answer of 3.7e-44

There might be some penalty in terms of speed and accuracy, I don't
know, but it does return a value that should be at least in the ballpark

>
> If there is any such instance during probability density function
> calculation when exp( - x2/ 2) is calculated, How to handle such events?

You might need to clarify this a bit more, I'm not sure that I understand
what you're asking

Cheers,
        Kevin
-- 
Kevin Channon

School of Chemistry
University of Bristol
UK




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