[Pw_forum] why my pw.x run with low efficiency?

[Lorenzo Paulatto]

On Ven, Settembre 19, 2008 18:54, vega wrote:
>       PWSCF        :     0d   14h46m CPU time,        2d   18h 4m wall >

This is indeed low!

> Could you tell me what make my CPUs run in a such low efficiency style?

I cannot be sure, but I will try to give a reasonable guess

>  Do you think 10G infiniband is good enough for 39 nodes?

I'm not an hardware junkie, but infiniband has a fame to be quite
performant, it should be ok.

> Could tell me which folders must be on a NFS location so that all the
> nodes can load and write?

Only the pseudopotentials and the input files, all the rest can be written
on local scratch. If you are using the wf_collect option, you may have to
use a network file system for the wavefunctions (I think there is an input
variable to specify the wavefunctions directory). I'm not 100% sure about
that, and it may be improved in future versions...

>  Do you think the pw.x underestimate greatly for the memory?

It is possible indeed, the estimate is hardcoded by hand, unluckily many
of the contributors (me included) haven't updated it to reflect their
changes to the code.

>  any hints on my problem will be deeply appreciated.

Youare already using the maximum number of k-points (one per pool), there
is little you can do. Do not set the outdir to a network filesystem will
help, especially if the filesystem passes on the same network as mpi.
Maybe openmpi is more efficient than the mpich, but I don't really know it
(I'm just assuming than new is better than old).

cheers

-- 
Lorenzo Paulatto
SISSA  &  DEMOCRITOS (Trieste)
phone: +39 040 3787 511
skype: paulatz
www:   http://people.sissa.it/~paulatto/



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