From: Mathieu Bouchard <matju@...>
Date: 2002-01-23T01:12:12+09:00
Subject: Re: swapping arrays


On Wed, 23 Jan 2002, Philippe Monnier wrote:
> I've tried to comput a half array of n*(n-1) of reals
> or arrays of reals
> @prox = Array.new
> for i in 1..@bornesup-1
>    @prox[i]  = Array.new
>    for j in i+1..@bornesup
>      @prox[i][j] = ....
>    end
> end
> I improved big swap with n=510 and each @prox[i][j] containing an
> array with 16 real values.

I guess your matrix takes 55 megs of ram ?

There are lots of tricks to save a little RAM here and there, but the
biggest trick will be to download "narray". when you build your 16-element
arrays, do NArray.double(16). This will take 3 times less
RAM. (note: NArray is also multidimensional, so you could do
NArray.double(510,510,16) once, but it won't make a big difference
compared to the above change.)

and don't forget to number indices starting from 0, or reserve an extra
unused index.

________________________________________________________________
Mathieu Bouchard                   http://hostname.2y.net/~matju