[Pw_forum] Computational Speed for pw.x

[Sitangshu Bhattacharya]

Dear Amar,

I assume that you have 40 cores (hyper-threaded) in your single node.
As per my experience, QE/VASP or any other such computations which uses
openmpi supports 2^n core processors. This is actually total number of core
per physical processor multiplied by 2 (hyperthreaded), check by typing
"htop" in your terminal. You may try locating the wall time results done at
different no. of cores for your computations. The results might be a bit
faster if you use 32 instead of 40 (and so on) and divide them into pools.
Please note that inter-node communications in PWSCF is the main bottleneck
and depends on the 100GBpS or more connectivity switch. Eagerly waiting for
this to be taken care by QE experts!. Image parallelization is supported by
the Ph.x code, however collecting the results is a bit tricky if you are
doing 2nd or 3rd order corrections. Parallelizing diagonalization technique
make my computation a bit slower, probably due to the the less no. of atoms
involved or so.
Check with -np 2 only, first on a simple structure like Si and then
increase this no. to see if this is taking more/less time. You will get an
idea atleast..

Regards

On Thu, Dec 7, 2017 at 2:50 PM, Amar Singh <amarsingh122014 at rediffmail.com>
wrote:

> Dear Dr. Bhattacharya,
> ​Thanks for the link. Though, being very naïve to such computation, I am
> not able to figure out the best possible set of parameters I should start
> with. Would be thankful if you can suggest some typical values for -np,
> -ni, -nk, -nt and -nd for the system with 40 processors and 256 GB RAM.
> ​thanks
> Amar
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
>



-- 
**********************************************
Sitangshu Bhattacharya (সিতাংশু ভট্টাচার্য), Ph.D
Assistant Professor,
Room No. 2221, CC-1,
Nanoscale Electro-Thermal Laboratory,
Department of Electrical and Communication Engineering,
Indian Institute of Information Technology-Allahabad
Uttar Pradesh 211 012
India
Telephone: 91-532-2922000 Extn.: 2131
Web-page: http://profile.iiita.ac.in/sitangshu/
Institute: http://www.iiita.ac.in/
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20171207/7f14eb8e/attachment.html>