[SciPy-user] Random sparse matrices

[Nathan Bell]

On Fri, Apr 25, 2008 at 9:17 AM, Mico Filós <elmico.filos at gmail.com> wrote:
> Dear all,
>
>  here is my first attempt. I basically use Nathan's suggested
>  functions, and _rand_sparse incorporates the algorithm proposed by
>  David to avoid ending up with fewer nonzero elements than expected. It
>  is the first time I propose an update
>  for scipy code, so be lenient with me :)

Thanks for your contribution Mico.  Unfortunately, the line
   rand_seq = permutation(m*n)[:nnz]
is a *dense* MxN operation, so we cannot use this approach.

MATLAB's sprand() and sprandn() have the same artifact as the code I
presented, so I don't know whether it's worth trying to avoid the
duplicate entries.

If you can figure out an economial way to produce exactly nnz elements
in the result, then we would probably use it.  I wasn't able to come
up with anything better than the MATLAB approach.

-- 
Nathan Bell wnbell at gmail.com
http://graphics.cs.uiuc.edu/~wnbell/