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Re: the competition's expm vs ours


From: Marco Caliari
Subject: Re: the competition's expm vs ours
Date: Wed, 03 Dec 2008 08:38:28 +0100 (CET)

On Wed, Dec 3, 2008 at 1:10 AM, Jordi GutiƩrrez Hermoso
<address@hidden> wrote:
2008/12/1 Marco Caliari <address@hidden>:
On my laptop, I got the following results for a 500x500 matrix:

Octave 3.0.3 (with ATLAS): 4.3 seconds
Octave 3.0.3, removing the extra steps: 4.0 seconds
Matlab 7.6.0: 1.2 seconds
Octave 3.0.3, rewriting in a better way the Pade' approximation (and with
the extra steps): 3.7 seconds

So, I don't think the extra steps produce the difference and they are
suggested also in "The scaling and squaring method for the matrix
exponential revisited" by N.J. Higham.

Hrm... Are you using sources that incorporate Jaroslav's indexing
improvements? I guess we could profile Octave to see where the actual
slowdown is instead of guessing...

- Jordi G. H.


Another slowdown in the m-file is caused by the fact that the expressions

Dear Jaroslav,

I computed the cputime of the builtin functions, not the m-file implementations.

Best regards,

Maco

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