[Wien] wien and hyperthreading

[Michael Gurnett]

Yes I figured that it might be something like that. I know that mkl doesn't 
see much speed increase (if any). I guess Wien spends most of its time in 
the maths libraries

Mick

----- Original Message ----- 
From: "Jeff Spirko" <spirko at lehigh.edu>
To: <wien at zeus.theochem.tuwien.ac.at>
Sent: Monday, March 14, 2005 4:42 PM
Subject: Re: [Wien] wien and hyperthreading


> With hyperthreading, you don't actually get to do twice as many
> calculations per second on a single processor.  It allows the
> processor to quickly switch from one process or thread to another
> when the first process is waiting for something (like memory, disk,
> etc.)  If both processes are using the floating point unit (FPU)
> intensively, as Wien2k does through the BLAS library, the net result
> is that the two threads just take turns calculating.
>
> What HT might do is allow Wien2k and "regular" stuff like Netscape
> and X Windows to run side-by-side a little more efficiently, because
> they use different resources.  See how much playing a movie slows down
> Wien2k with and without HT on.  There you should see some improvement.
>
> Regards,
> -Jeff Spirko
>
> On Mon, Mar 14, 2005 at 03:31:08PM +0100, Michael Gurnett wrote:
>>    I  was running some tests to compare speeds with hyperthreading on and
>>    off  using  the latest kernels for redhat 7.3. However, I was not able
>>    to  see any difference in speed between the two cases. I was wondering
>>    if anyone else has seen this and possibly explain why this is.
>>    Michael
>
> -- 
> Jeff Spirko   spirko at lehigh.edu   spirko at yahoo.com   WD3V   |=>
>
> The study of non-linear physics is like the study of non-elephant biology.
>
> All theoretical chemistry is really physics;
> and all theoretical chemists know it. -- Richard P. Feynman
>
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>
>