Re: [ublas] [patch] matrix norms are inefficient for sparse matrices

From: Gunter Winkler (guwi17_at_[hidden])
Date: 2005-07-10 02:38:49

Zitat von Georg Baum <georg.baum_at_[hidden]>:

> Hello,
>
> while playing a bit with the profiler I noticed that matrix_norm_inf
> computes the norm by iterating over each element (i, j). The same is true
> for matrix_norm_1 and matrix_norm_frobenius. This is of course
> inefficient for sparse matrices.
> I wonder why that is the case? I can't believe that such an inefficient
> implementation is used without reason. Now I am wondering if I have to
> expect more surprises like that? Or did I miss something?

Maybe you are the first one who uses these norms for non-dense matrices.

> I attach the patch I aam currently using for interested people to play
> with. It to optimize the matrix norms and seems to work for
> matrix_norm_inf (I did not yet test the other norms).

Looking at the patch I see that you provided a better implementation for row
major matrices. Did you also try column major matrices?

mfg
Gunter