[Pw_forum] 2Gb file limit in PWSCF

Francesco Antoniella francesco.antoniella at aquila.infn.it
Tue Jan 20 00:32:16 CET 2004

Il mar, 2004-01-20 alle 00:10, Konstantin Kudin ha scritto:
> --- Francesco Antoniella
> <francesco.antoniella at aquila.infn.it> wrote:
> > so the LAM daemon will start 4 processes on the same
> > node, but beware
> > the memory: if you want to scale the files you must
> > use -pools so you
> > will multiplicate the raw memory occupation.
>  OK. So it will use more memory. What about speed? Are
> these these gonna start in parallel, or will they be
> serialized?
They will undergo an effective serialization, or it will use the 
processor in a time-share or round-fashion.
In fact you will get little worsening in performance unless you have a
multiprocessor or hyperthreading node(like PIV 3.0GHz), of course.
In this case you will find this procedure useful to make two processes
instead only one, and doing so, to use the second processor.

> > P.S.:Wath are you doing with this huge wfc file? A
> > thousand k points on
> > a supercell??
>  It is just a 3x3x3 supercell for Mg with 1 atom taken
> out (53 atoms total). The cutoff is 28. Ry, nbndx=477,
> nbnd=64,natomsfc=477,npwx=20727,nelec=106.0,nkb=212,ngl=6878
>  The k point grid is {4 4 4 1 1 1}, so the total
> number of k points after the symmetry is 52.
>  Perhaps I am missing some obvious parameter that can
> reduce that file size?
I don't think so, only: it is not worth to try before with gamma only 
(and possibily with the Gamma code, halwing the memory) to tackle the 
biggest components of the relaxation?
>  I was gonna let this thing run for a few days on a
> local machine. Now it is probably better to go to a
> bigger system, and run true multiprocessor.
>  Kostya
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