Re: Slow sqp execution in Ubuntu compared to Win7?

[Carlo de Falco]

On 2 Apr 2010, at 17:38, Tottish wrote:

> Hello!
> I'm pretty new to Octave but I've managed to write an algorithm for a
> nonlinear optimization problem that I have using the sqp-function.  
> It's
> working great but after I went over to a Linux machine the execution  
> speed
> was considerably lower which seems odd to me. I'm sure I've missed  
> something
> so please correct me.
>
> I've set a tic-toc timer to measure the execution speed and on my AMD
> Sempron 3600+ running Win7 64bit I get execution speeds of about 0.08
> seconds while I get around 0.25 seconds on a dualcore atom motherboard
> running Ubuntu 9.10 32-bit.
> Granted, the dualcore processor most likely doesn't use it's full  
> potential
> in the 32-bit environment and yes it is a bit slower but still,  
> doesn't this
> seem a little off?
>
> My guess was that Linux was a more suitable environment for fast  
> responses
> and would produce a similar or shorter execution time but I am just  
> starting
> out with Linux so I don't actually know much about that.
>
> Could someone shine a little light on this?
> Thanks for a great application!
> /Tottish


Most likely this is due to linking to a slow version of BLAS/LAPACK.
How did you install Octave on ubuntu? If you used the Octave binary  
package fro the Karmik Koala universe repository you get a choice
of different packages providing BLAS/LAPACK to use as a dependency for  
Octave.
If the ones you have installed are the basic reference implementations  
then you can improve performance by switching to a more optimized  
version. I doubt there is a version specifically tuned for your  
architecture but probably already switching to a generic version of  
ATLAS will give an improvement.
c.