[QE-users] QE Parallelization for Phonon Dispersion calculations

[Lorenzo Paulatto]

Images are only used inside each q-point, if I remember correctly, so it 
would not matter in our question.

But, you can decrease walltime much more by running each q-point 
simultaneously and independently using startq, startq options and a job 
for each. It is sufficient to use a different prefix or outdir. The data 
from pw can be copied or repeated, it does not usually matter in terms 
of CPU time.

cheers

On 2020-11-24 10:27, Kiran Yadav wrote:
> Dear Lorenzo,
> Is there any parallelization method so that I can make images such 
> that 20 dyn files will get distributed unequally on the equal number 
> of processors or dyn files will get distributed equally on unequal 
> number of processors ?
>
> Because in my case as per my observation dyn1-10 are not taking too 
> much time, most of the time has been spent on dyn11-dyn20 generation. 
> So, If I could run dyn 1-10  on one image and distribute remaining 
> dyn11-20 on 3 images CPU walltime can be decreased. Is it possible to 
> do something like that?
>
> I tried parallelization on 256 processors (#PBS -l select=16:ncpus=16) 
> for 10hrs using the following parallelization command
> time -p mpirun -np $PBS_NTASKS ph.x -ni 4 -nk 4 -nt 4 -nd 16 -input 
> ph.in <http://ph.in/> > ph.out
> in this case 20dyn files got distributed in 4 images i.e 5 dyn on one 
> image.  256/4=
>
> Thanks & Regards,
> Kiran Yadav
> Research Scholar
> Electronic Materials Laboratory (TX-200G)
> Dept. of Materials Science & Engineering
> Indian Institute of Technology, Delhi
> /
>
> /
>
>
> On Tue, Nov 24, 2020 at 1:19 PM Lorenzo Paulatto <paulatz at gmail.com 
> <mailto:paulatz at gmail.com>> wrote:
>
>
>     > I have been trying to calculate Phonon dispersion with 6*6*6 nq
>     grid.
>     > It generates dyn0+20 other dynamical matrices, but the time
>     taken by
>     > each dynamical matrix file is different for completion. I ran these
>     > phonon dispersion calculations using parallelization, but couldn't
>     > optimize correctly.
>
>     This is normal, because different q-points have different symmetries,
>     the code has to use different numbers of k-points.
>
>
>     regards
>
>
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