From: "t3ch.dude" <t3ch.dude@...>
Date: 2009-03-18T03:12:29+09:00
Subject: Re: upping numerical precision

On Mar 16, 10:56 pm, Roy Pardee <rpar...@gmail.com> wrote:
>
> Thanks for the response!  I think the issue may be that I'm not doing
> any division--just multiplication.  Check it out:
>
>   irb(main):001:0> require 'mathn'
>   => true
>   irb(main):002:0> x = 0.5
>   => 0.5
>   irb(main):003:0> 1000.times do
>   irb(main):004:1* x *= x
>   irb(main):005:1> end
>   => 1000
>   irb(main):006:0> x
>   => 0.0
>   irb(main):007:0> x.class
>   => Float
>   irb(main):008:0>
>
> But the more I think about it, the more I think I'm fussing over
> nothing (ha ha!).  I think if my p var goes to zero, I should just set
> it = Float::MIN & break out of that loop.  My calc_prob method will
> only ever return values <= 1, so there's no sense in letting it
> continue to spin down the value of p (if you can tell what I'm trying
> to say).
>
> Thanks!
>
> -Roy

Roy,

It all depends on how much range of data you want. If you need more
granularity at the tiny end, you can always re-normalize... just
initialize p to be 1e6 or something, rather than 1. Then after the log
you can just subtract the constant exponent to get back to your
original range.

-t3ch.dude