Re: Good eigenvalue/eigenvector test problems for eigs?

[David Bateman]

Quentin Spencer wrote:

> 
> On Fedora, running plain atlas (no sse or sse2) I get:
> Max error: 8.60406e-21
> 
> Come to think of it, I think the eig function that is shipped in both
> the Debian and Fedora atlas packages is taken straight out of lapack
> because it's not provided directly by atlas. So, I think you're using
> the same eig function with or without atlas installed.
> 
> -Quentin
> 

Ok. However, its only partly true that I'm using the same eig function.
The lapack [dz]geev used by the octave eig functions states that it uses
the following external subroutines.

*     ..
*     .. External Subroutines ..
      EXTERNAL           DGEBAK, DGEBAL, DGEHRD, DHSEQR, DLACPY, DLARTG,
     $                   DLASCL, DORGHR, DROT, DSCAL, DTREVC, XERBLA

There are certainly a few of those that are accelerated in atlas. My
sysadmin also installed an unstable version of atlas and so there might
be something there causing the problem as well. I seem to be using
version 3.7.11 of atlas..

Regards
David