[Pw_forum] how to control the writing of wavefunction

[xu yuehua]

thank you for your detailed analysis.  your guess is right .my outdir is set
to a place,not local to the nodes.i know the reason of my slow job,although
i did not know it through.
as for how to use a local directory as outdir ,it seems another new thing
for me.
would it be possible to tell me about that ?
thank you in advance



your sincerely
 xuyuehua

2007/12/13, Lorenzo Paulatto <paulatto at sissa.it>:
>
>
> On Thu, December 13, 2007 13:42, xu yuehua wrote:
> > yes,maybe once i set  disk_io="none" ,when something goes wrong ,like
> > power
> > is off suddenly,you have to start from  scratch .from this point ,it is
> > wasting time in deed.
> > but is there  an better idea ?
> > i am wondering
>
> I think it is highly unlikely that you have more RAM than disk space, so
> disk space should be no issue. Furthermore it should not be so slow, as
> long as you are leaving wfc_collect=.false. which is the default.
>
> From these assumptions I can guess that you are using a network share as
> temporary directory for your calculation; in other words your outdir is
> set to some place, probably in you home directory, which is not local to
> nodes but stays on a server and is shared via NFS (network file system).
>
> If this is your case, every time wavefunctions are written the data has to
> pass trough the network, it is somehow equivalent to collect_wfc=.true.
> but done externally by the operating system. Furthermore if you are using
> the same network for NFS and mpi when the traffic from NFS suddenly bursts
> it is likely to conflict with mpi and slow it down a lot.
>
> To avoid this problem you must use a local directory as outdir (like
> /tmp), but you to have to remember that if you want to restart a job you
> have to use exactly the same node you used before in order for them to
> find their wavefunctions. Otherwise you may have to recollect the data by
> hand, which is probably not trivial (I have never tried).
>
> I hope what I wrote was not already known to you, goodbye.
> --
> Lorenzo Paulatto
> +39 040 3787 511
> http://people.sissa.it/~paulatto/
>
>
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-- 
Xu Yuehua
physics Department of Nanjing university
China
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