[QE-users] Optimizing QE Install

[Ari P Seitsonen]

Dear Robert,

   Adding to the comments and hints by Lorenzo and Paolo, I would just like 
to add that i) I usually use OpenBLAS (https://www.OpenBLAS.net/) instead 
of the NetLib versions of BLAS+LAPACK (compiled from source, it easily 
adapts to the underlying hardware, with few options and it seems to me to 
be close to the performance of Intel MKL et co; despite its name it also 
contains LAPACK, not only BLAS) and ii) why OpenMPI 1.x.y, as the latest 
versions are at 4.x.y?

   I would also ensure that the environmental variable 'OMP_NUM_THREADS' is 
indeed set correctly, even if at '1', to avoid a burst of OpenMP threads. 
The correct number of course depends on the number of cores available, 
hyper-threading or not (or how is it called on the AMD EPYC), the number 
of MPI tasks and the amount of memory available, should the latter become 
a bottleneck.

     Greetings from Paris,

        apsi

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   Ari Paavo Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/


On Sat, 23 Jan 2021, Robert Stanton wrote:

> Dear all,
>      I am able to successfully install parallel QE and get everything to run smoothly, however after testing against an install on an
> externally maintained cluster I'm finding my speed to be slower by a factor of 5-10x when keeping the system, core number, QE version,
> etc. the same. 
> 
>     I'm not sure the degree to which this could be a hardware discrepancy (Xeon Silvers vs new EPYCs), v.s. how much could be a
> sub-optimal compilation of QE. The slower QE install is being done with blas/lapack 3.8.0 and openmpi 1.10.7. I'm just curious if
> there is anything very clearly not ideal about this environment, or if it is likely something I'll just need to troubleshoot with
> smaller settings? Thanks so much in advance for any insights you can provide!
> 
> Regards, 
> Robert Stanton
> Graduate Student
> Clarkson University
> 
>