[Pw_forum] PW taskgroups and a large run on a BG/P

[Nichols A. Romero]

David,

You have the:
ortho sub group set to 32*32

Paolo can correct me if I am wrong. This is the Scalapack blacs grid for the
cholesky decomposition. It basically takes the overlap matrix whose
dimensions
are (number of states) by (number of states) and divides into 32-by-32
pieces
according to a 2D block cyclic algorithm. You are using 32*32=1024
processors
to do the cholesky decomposition of a 2560-by-2560.

I would recommend using something like 8*8.

On Wed, Jan 28, 2009 at 4:08 PM, <giannozz at democritos.it> wrote:

> Quoting David Farrell <davidfarrell2008 at u.northwestern.edu>:
>
> > I am trying to run a 1152 atom, 2560 electron pw MD system on a BG/P,
> >  and I believe I am running up against memory issues
>
> set nbnd, diago_david_ndim, mixing_ndim to the smallest possible
> values to save memory. Use the CVS version and try to compile scalapack
> (instructions in the wiki) if you have trouble with subspace
> diagonalization, or else use a smaller set of processors in the "ortho
> group": 1024 seems to me a lot for a system with O(1000) states.
>
> Paolo
>
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-- 
Nichols A. Romero, Ph.D.
Argonne Leadership Computing Facility
Argonne, IL 60490
(630) 252-3441 (O)
(630) 470-0462 (C)
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