RE: Re: Machine-precision Expfunction

*To*: mathgroup at smc.vnet.net*Subject*: [mg93674] RE: [mg93645] Re: Machine-precision Expfunction*From*: "Ingolf Dahl" <f9aid at chalmers.se>*Date*: Fri, 21 Nov 2008 05:34:00 -0500 (EST)*Organization*: University of Gothenburg*References*: <200811200955.EAA20583@smc.vnet.net>*Reply-to*: <ingolf.dahl at physics.gu.se>

An answer in the style of Jens: In[64]:= Precision[Exp[-1000.]] Out[64]= 12.9546 ????? Regards Ingolf -----Original Message----- From: Bill Rowe [mailto:readnews at sbcglobal.net] Sent: den 20 november 2008 10:56 To: mathgroup at smc.vnet.net Subject: [mg93674] [mg93645] Re: Machine-precision Expfunction On 11/18/08 at 7:22 AM, rschmied at gmail.com (Roman) wrote: >Bill, I don't agree with your statement: >In[1] := Precision[-1`*^6] Out[1] = MachinePrecision >So there is no such conversion involved. In any case, my question >was not about such conversions, but about avoiding arbitrary-math >routines. Roman. With respect to actually checking the precision in your original example, obviously I didn't do that when i should have. But with respect to avoiding "arbitrary-math routines" which I interpret as meaning avoiding the overhead of Mathematica's arbitrary precision arithmetic, the answer is simple. Just enter all numerical parameters with a decimal point. Then by default, Mathematica uses machine precision arithmetic through-out the computation which will yield the fastest execution time for a given implementation of a given algorithm. And since it takes fewer characters to enter numerical data with a decimal point than it does to specify a specific precision, I really don't understand why anyone would do any thing else to invoke machine precision computations.

**References**:**Re: Machine-precision Expfunction***From:*Bill Rowe <readnews@sbcglobal.net>