[Wien] Configuring SCRATCH variable for parallel computation

[Oleg Rubel]

It is getting complicated when you do both MPI + k-point
parallelization. In large calculations there is usually less k-points. Will
it be possible to test MPI with the local scratch without k-point
parallelization (i.e., k-point run sequentially)? This will help to mediate
problems mentioned by Michael.

Oleg


On Thu, Feb 13, 2014 at 11:15 AM, Michael Sluydts
<Michael.Sluydts at ugent.be>wrote:

>  Hello César,
>
> To perform parallel calculations you do need a shared directory between
> all nodes. As you have described '/home' appears to be a form of shared
> storage.
>
> What its intention is, is of course not well-known to us. If it is shared
> there is no direct reason it cannot function for wien, however the problems
> that might occur are:
> -the connection to the shared storage is too slow - if it is not meant to
> transfer files from and to during a calculation
> -there is not enough space - if it is just meant for temporary storage and
> user settings
> -the /home is meant as a login system and not for actual user usage
>
> Maybe contact the person who set up this cluster and ask them what they
> recommend.
>
>
> Regards,
>
> Michael Sluydts
>
> César de la Fuente schreef op 13/02/2014 17:09:
>
> Hi,
>
> I 'm doing some tests in the Memento cluster of the University of Zaragoza
> on TiC system with a k- 100k pts , 4 nodes with 64 CPUs per node. It is a
> system that does not share RAM and hard disks between nodes during
> calculations. Initially the parallel computation with Wien2k stopped in the
> first cycle because a file system problem. The variable $ SCRATCH point to
> the local hard disks of each node used in the parallel computation.
> Fortunately I was able to finish the calculation re-directing the variable $
> SCRATCH to /home directory that it is shared by all nodes. The calculation
> finish fine and it is correct, but I think that something is wrong. Wien2k
> not seems  to be originally designed for a parallel calculation using /home
> as SCARTCH.
>
> Is it correct to use the /home directory as SCRATCH in Wien2k ? , Can this
> cause problems in the OS of Memento's cluster or in  future wien2k
> calculations?. In fact, I'm having other problems with wien2k in other
> systems but I'm not sure if it is because SCRATCH points to /home directory
> or not.
>
> Thank you for your attention and appreciate any comment.
>
> Sincerely,
>
> Dr. César de la Fuente.
> Depto. de Física de la Materia Condensada.
> Edificio Torres-Quevedo
> EINA-Universidad de Zaragoza.
> C/María de Luna 3, 50018-Zaragoza (SPAIN).
>
>
>
>
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