From: Bart Braem <bart.braem@...>
Date: 2009-01-24T00:53:24+09:00
Subject: Re: Separate random number generators?

On Jan 23, 4:33 pm, "F. Senault" <f...@lacave.net> wrote:
> Le 23 janvier 2009 à 15:59, Bart Braem a écrit :
>
> > On Jan 23, 3:34 pm, Lars Christensen <lar...@belunktum.dk> wrote:
> >> I do think that my own solution (last on the page) is efficient, but i
> >> can't vouch for the statistical properties (it reseeds the Mersenne
> >> Twister in Ruby every time a number is drawn, although randomly).
>
> > I've tested this setup, with just one RNG. Running my unit tests is
> > about 5 times slower, unfortunately. I am calling the random number
> > very often, more than 10.000 times in 10 seconds in a simulation that
> > uses the standard kernel rand.
> > I can't afford this slowdown, but it seems as though there are no
> > other solutions that do not use a pure-ruby library?
>
> Can you estimate the number of random numbers you'll need ?  Maybe you
> could pre-generate sequences of numbers in a few arrays, then patch the
> rand method to actually read the array instead of generating the
> number ?
>
> The start time and memory consumption will be a lot higher, but maybe it
> makes a good compromise ?
>

That is an idea, but quick calculations show the need of up to 100.000
random numbers. Which is quite a lot to calculate and most importantly
store and retrieve again.