Hi Kevin, Thanks. You are right exp(-100) returns 3.7e-44. Actually, during mathematical programming. We are encountering such scenarios while calculating probability density function. As structure of probability density function is as follows. Pdf = (expression_1) * (exponential (expression_2).
Now during our calculation we are encountering the situation where expression_2 is getting evaluated to such values like -800.0. In this case exponential (-800.0) is zero. So how do we deal with such situations what will be pdf in this case. Thanks Ashish -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Kevin Channon Sent: Wednesday, February 11, 2009 6:49 PM To: Ashish Negi Cc: [email protected] Subject: Re: [Help-gsl] Exponential calculation 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 _______________________________________________ Help-gsl mailing list [email protected] http://lists.gnu.org/mailman/listinfo/help-gsl
