help-octave
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: elements of a sparse matrix


From: Søren Hauberg
Subject: Re: elements of a sparse matrix
Date: Mon, 27 Dec 2010 17:42:50 +0100

man, 27 12 2010 kl. 18:32 +0200, skrev Jaana Tommiska:
> I wrote these lines
> B=sprand(20000,10000,0.01);
> A=B'*B;
> A(10000,10000) 
> or
> A(10000*10000)
> 
> I am interested if the matrix A is too big to fit in the memory?

So, the 'B' matrix will contain roughly

  20000 * 10000 *0.01 = 2 million

non-zero elements. That will roughly require 16 MB when using double
precision, so that shouldn't be a problem.

The 'A' matrix will *not* be sparse, so it will contain

  10000 * 10000 = 100 million

elements. Each requires 8 bytes, so that's 800 megabytes of data. If you
can have that in memory or depends on your machine, but it is a big
matrix if you ask me.

Søren



reply via email to

[Prev in Thread] Current Thread [Next in Thread]