[Pw_forum] parallel scaling in PWSCF

[Fernando A Reboredo]

Nichols
The largest things I have run with pwscf are cobalt clusters with stuff on 
the surface
55 Co atoms 12 CO molecules and 12au of vacuum around, 45 Ry ecut.
~560 electron including spin and PBE. Those calculation run in 48 nodes 90 
processors. I did not study the scaling carefully. The scaling was 
reasonably good provided the number of proccessors was a submultiple of the 
FFT grid dimension.
 Fernando Reboredo

----- Original Message ----- 
From: "Axel Kohlmeyer" <akohlmey at cmm.upenn.edu>
To: <pw_forum at pwscf.org>
Sent: Wednesday, April 26, 2006 1:38 PM
Subject: Re: [Pw_forum] parallel scaling in PWSCF


On 4/26/06, Nichols A. Romero <naromero at gmail.com> wrote:
> Hi,

hi.

> Has anyone performed any very-large scale DFT calculations on PWSCF
> using over 64 processors and over 1000 atoms? Does anyone know what
> its current limits (system sizes and processors) are on parallel
> computing environments with fast interconnects?

i've recently run a comparatively large job (272 atoms, 560 electrons,
4x4x4 k-points) across 768 processors on a Cray XT3. i had to hack
some constants to make it work. however the scaling is not (yet)
so good and depending on what kind of atoms you want to put into
your system, i.e. if it is metallic, you may be better of with gamma
only and car-parrinello dynamics. i ran the same system as above
with a car-parrinello code (one that is not in quantum espresso) and
would scale out at 512 nodes for gamma point only on an IBM BG/L.
even though i had to use a much smaller time step, i did get much
more trajectory that way.

judging from the CVS commit messages, efforts to optimize the
quantum espresso codes for that kind of machine with large numbers
of nodes are underway. note, that for systems as large as that,
you might run into the scaling limitations of DFT with plane waves,
so for a system that big using one of those 'linear scaling' DFT codes
could be a more promising alternative.

best regards,
     axel.


>
> Thanks,
> --
> Nichols A. Romero, Ph.D.
> 1613 Denise Dr. Apt. D
> Forest Hill, MD 21050
> 443-567-8328 (C)
> 410-306-0709 (O)
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>


--
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Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
  Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
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