[QE-users] QE Parallelization for Phonon Dispersion calculations

Tue Nov 24 13:43:11 CET 2020

Dear Kiran,

if I look at the run_example_1 I see that there is only the splitting via the q points.

An irrep, or irreducible representation is the (possibly) degenerated phonon mode

at one q point... Splitting in q points is much easier than on irreps which I would not

recommend it for a beginner...

Cheers

Thomas

--
Dr. rer. nat. Thomas Brumme
Theoretical chemistry
TU Dresden - BAR / II49
Helmholtzstr. 18
01069 Dresden

Tel:  +49 (0)351 463 40844

email: thomas.brumme at tu-dresden.de

________________________________
Von: Kiran Yadav <kiranyadav0816 at gmail.com>
Gesendet: Dienstag, 24. November 2020 13:22
An: Brumme, Thomas
Betreff: Re: [QE-users] QE Parallelization for Phonon Dispersion calculations

Dear Dr Thomas,
Thanks a lot for the reference. I looked at the run example and run example 1, In the run example, they have "Both q-points and irreps are split." If possible please answer on - What are irreps here and how does it affects our phonon calculation parallelization?
From my output file, I got 20 q-points and q in seq '1 20' but couldn't find irr.
KIndly help.
Thanks a lot again

Regards
Kiran Yadav

On Tue, Nov 24, 2020 at 5:10 PM Thomas Brumme <thomas.brumme at tu-dresden.de<mailto:thomas.brumme at tu-dresden.de>> wrote:

Dear Kiran,

please have a look at the GRID_example in the PHonon examples and there the run_example_1 in particular.

Regards

Thomas

--
Dr. rer. nat. Thomas Brumme
Theoretical chemistry
TU Dresden - BAR / II49
Helmholtzstr. 18
01069 Dresden

Tel:  +49 (0)351 463 40844

email: thomas.brumme at tu-dresden.de<mailto:thomas.brumme at tu-dresden.de>

________________________________
Von: users <users-bounces at lists.quantum-espresso.org<mailto:users-bounces at lists.quantum-espresso.org>> im Auftrag von Kiran Yadav <kiranyadav0816 at gmail.com<mailto:kiranyadav0816 at gmail.com>>
Gesendet: Dienstag, 24. November 2020 10:45
An: Quantum ESPRESSO users Forum
Betreff: Re: [QE-users] QE Parallelization for Phonon Dispersion calculations

Dear Lorenzo,
Thanks a lot for the great help.
If possible, please suggest some reference on how to run each q-point simultaneously or do as you have suggested.

Thanks & Regards,
Kiran Yadav

On Tue, Nov 24, 2020 at 3:09 PM Lorenzo Paulatto <paulatz at gmail.com<mailto:paulatz at gmail.com>> wrote:

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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