[CP2K:3628] NEB: number of replicas, cpus and input files

Jörg Saßmannshausen j.sassma... at ucl.ac.uk
Thu Nov 24 00:48:21 CET 2011


Hi Carlo,

gosh that was quick!

I got 8 cores per box, so that is where the cores come from.
I got 17 points I want to run, hence the 17 files.

Right now I only got 32 cores alltogether.

So my train of thoughts were similar to yours: 8 replicas and each replica is 
using 4 cores adds up to 32 cores. 
However, that crashed with that error message:
ERRORL2 in neb_utils:build_replica_coords processor

So in the end I decided to use 32 replicas and 32 nproc_rep for the 32 cores I 
have. I guess one could do better. ,-)

All the best

Jörg


On Mittwoch 23 November 2011 c.pignedoli wrote:
> Ciao Joerg,
> why 17 files an 8 replicas?
>
> If i remember well:
> if you have 8 replicas an specify 100 nproc_rep
> then if you run with 200 cores
>
> you will have two replicas done at a time (each with 100 cores), then other
> two then other two finally the last two
>
> and you cicle.
>
> if you run with 800 cores all replicas will proceed in parallel
>
> Ciao
>
> Carlo
>
> On 24/nov/2011, at 00:05, Jörg Saßmannshausen <j.sassma... at ucl.ac.uk> 
wrote:
> > Dear all,
> >
> > I am a bit confused.
> > When I am running a frequency calculation or a NEB calculation, I can
> > specify the number of replicas (NUMBER_OF_REPLICA) and the number of
> > processors (NPROC_REP) in the MOTION section. Now, lets say I got 32
> > cores on my hands and I got 17 files which I want to use for the NEB
> > calculation. Now, my understanding was that I could run say 8 replicas
> > and each replica is using 4 cores. That would add up to the 32 cores I
> > have alltogether. However, that does not work out. It appears I got to
> > use 32 replicas and 32 cores for all 32 cores I have available. What is
> > the relationship between replicas and cores (in the input file) with the
> > cores I have available on the machine (an in relation to the number of
> > coordinate files I have). A similar observation was made for a frequency
> > calculation.
> >
> > I seem to have somehow a wrong understanding here :-/
> >
> > All the best from a foggy London
> >
> > Jörg
> >
> >
> > --
> > *************************************************************
> > Jörg Saßmannshausen
> > University College London
> > Department of Chemistry
> > Gordon Street
> > London
> > WC1H 0AJ
> >
> > email: j.sassma... at ucl.ac.uk
> > web: http://sassy.formativ.net
> >
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-- 
*************************************************************
Jörg Saßmannshausen
University College London
Department of Chemistry
Gordon Street
London
WC1H 0AJ 

email: j.sassma... at ucl.ac.uk
web: http://sassy.formativ.net

Please avoid sending me Word or PowerPoint attachments.
See http://www.gnu.org/philosophy/no-word-attachments.html



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