[QE-users] Running efficiently on multiple nodes

[Paolo Giannozzi]

Are there fast communications between the two nodes? if not, the parallel
distributed 3D FFT will be very slow (note the time taken by fft_scatt_yz).
You might find convenient to exploit k-point parallelization, that requires
much less communication: for instance, "mpirun -n 32 pw.x -nk 2" (2 pools
of 16 processors, each pool performing parallel FFT), but you have to
figure out a way to convince the first pool of 16 processors on node 1, the
second on node 2 (or vice versa, as long as FFT parallelization happens
inside a node, k-point parallelization across nodes )

Paolo

On Thu, Nov 5, 2020 at 7:29 PM Baer, Bradly via users <
users at lists.quantum-espresso.org> wrote:

> Paolo,
>
> Thank you for your suggestion.  I will add recompiling to move to 6.6 to
> my to do list.  For now, I corrected the pseudopotential files as you
> indicated and the calculation ran successfully.  It has become slightly
> faster, but still much slower than running on a single node (3:30s vs
> 0:30s).  Is there more that I should be doing to improve performance or is
> my test problem too small to see the benefits of parallelization?
>
> Thanks,
> Brad
>
> --------------------------------------------------------
> Bradly Baer
> Graduate Research Assistant, Walker Lab
> Interdisciplinary Materials Science
> Vanderbilt University
>
>
> ------------------------------
> *From:* users <users-bounces at lists.quantum-espresso.org> on behalf of
> Paolo Giannozzi <p.giannozzi at gmail.com>
> *Sent:* Thursday, November 5, 2020 10:01 AM
> *To:* Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org>
> *Subject:* Re: [QE-users] Running efficiently on multiple nodes
>
> On Thu, Nov 5, 2020 at 3:05 PM Baer, Bradly <bradly.b.baer at vanderbilt.edu>
> wrote:
>
>
> *Pseudo file Ga.pbe-dn-kjpaw_psl.1.0.0.UPF has been fixed on the fly.*
> *To avoid this message in the future, permanently fix *
> * your pseudo files following these instructions: *
> *https://gitlab.com/QEF/q-e/blob/master/upftools/how_to_fix_upf.md
> <https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.com%2FQEF%2Fq-e%2Fblob%2Fmaster%2Fupftools%2Fhow_to_fix_upf.md&data=04%7C01%7Cbradly.b.baer%40vanderbilt.edu%7C73a5a5e938ac4ee11cb808d881a440f4%7Cba5a7f39e3be4ab3b45067fa80faecad%7C0%7C0%7C637401889751409012%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=511bORLQwH1OKUCoHg%2BbMb5I%2FiOEuHIFEbDlNl28678%3D&reserved=0>*
>
>
> This is a possible source of trouble if the output directory is not
> visible to all processors. Please try one of the following:
> - do what it is suggested (or simply: edit Ga.pbe-dn-kjpaw_psl.1.0.0.UPF,
> replace all occurrences of "&" with "&")
> - get version 6.6, that reads the pseudopotential file on one processor
> and broadcast its contents to all other processes
> - get the development version, that in addition is not sensitive to the
> presence of nonstandard "&" in the files,
>
> Paolo
>
>
>
> -Brad
>
> --------------------------------------------------------
> Bradly Baer
> Graduate Research Assistant, Walker Lab
> Interdisciplinary Materials Science
> Vanderbilt University
>
>
> ------------------------------
> *From:* users <users-bounces at lists.quantum-espresso.org> on behalf of
> Paolo Giannozzi <p.giannozzi at gmail.com>
> *Sent:* Thursday, November 5, 2020 2:33 AM
> *To:* Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org>
> *Subject:* Re: [QE-users] Running efficiently on multiple nodes
>
> On Wed, Nov 4, 2020 at 11:28 PM Baer, Bradly <bradly.b.baer at vanderbilt.edu>
> wrote:
>
>
> Now that I have two nodes, the script for a single node results in a crash
> shortly after reading in the pseudopotentials.
>
>
> which version of QE are you using, and which crash do you obtain, with
> which executable?
>
> Paolo
> --
> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
> _________________
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>
> --
> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
> users mailing list users at lists.quantum-espresso.org
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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