[Wien] wien and hyperthreading

[Michael Gurnett]

Was just getting desperate to squeeze more speed out of the system. As no 
one seems to have a got linux mpi version working (or at least no one has 
answered previous posts). The system I'm working on now takes only 28 
minutes in lapw1, but 40 minutes in lapw0 (this is why mpi would be nice) 
and 1h20 in lapw2

So obviously any extra speed would have been nice

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
>
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