[Wannier] [EXTERNAL] Re: pw2wannier very slow on large system

[Daniel Marchand]

Hi Everyone,

Thanks for your responses. A quick question regarding the parallelization settings. Prof. Mostofi, you mention that parallelization is supported across the FFT grid, but I wanted to know if I am enabling its use correctly. So far I am not using any specific flags, as I would with pw.x. Am I correct in assuming that pw2wannier automatically adjust the settings appropriately with the number of cores available? For pw.x there is a -ntg flag to adjust FFW parallelization, yet pw2wannier does not seem to accept this as input. Is there something I’m doing wrong?

Best,

Daniel Marchand
Research Intern – Microsoft Station Q

From: H. Lee <hjunlee at gmail.com>
Sent: Wednesday, November 18, 2020 9:18 AM
To: Daniel Marchand <t-dmarchand at microsoft.com>
Cc: wannier at lists.quantum-espresso.org
Subject: [EXTERNAL] Re: [Wannier] pw2wannier very slow on large system

Dear Daniel:

Regarding this issue, you could try the following recent merge request:

https://gitlab.com/QEF/q-e/-/merge_requests/1176<https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.com%2FQEF%2Fq-e%2F-%2Fmerge_requests%2F1176&data=04%7C01%7Ct-dmarchand%40microsoft.com%7Cdc85f2cb2dbd464e19e008d88bccd014%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C1%7C637413059884299937%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=u%2BBXYM0qtGKHiPuC7A6nV5%2Bry5T030sV96q0IEampgQ%3D&reserved=0>

Sincerely,

Hyungjun Lee
UT Austin

On Mon, Nov 16, 2020 at 1:08 PM Daniel Marchand <t-dmarchand at microsoft.com<mailto:t-dmarchand at microsoft.com>> wrote:
Hi Everyone,

We’re having some trouble running pw2wannier on a very large system as it is running very slow. To give some comparison, we are able to finish the nscf calculation in ~4hours, while pw2wannier has not finished the first MMN: iknum step even after ~8 hours of runtime. It seems like in theory pw2wannier should be parallelizable but we found poor performance beyond a single node.

Is there anything we can do to help speed up the process? Parallelization steps to try out or common pitfalls that we could avoid?

Best,

Daniel
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