From: Siep Korteling <s.korteling@...>
Date: 2009-03-17T06:06:05+09:00
Subject: Re: upping numerical precision

rpardee@gmail.com wrote:
> Hey All,
(...)
>   chi = -2.0 * Math.log(p)
> 
> I'm finding that p is often going to 0.0 b/c the numbers returned by
> calc_prob are sometimes outlandishly small 
(...)
> That works, but makes me wonder if there's a smarter thing to do w/
> those rational and mathn libs to really get the effect I hoped for
> just from including them in my script.
> 
> Is there?
> 
> Many thanks!
> 
> -Roy

Are you sure you required 'mathn' before defining your calc_prob method?

big = 10**100

small = 1/big
p small.zero? # true

require 'mathn'
small = 1/big
p small.zero? # false
p small.class # Rational

p -2.0*Math.log(small)

hth,

Siep

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