[Wien] Speeding up calculations in parallel mose

[Pavel Ondračka]

Dear Viktor,

at 54 atoms, you should have enough k-points to run k-parallel which is
probably going to be the fastest option. So lapw1 + lapw2 k-parallel
and the rest OpenMP parallelized.

An example .machines file for your 8 cores could look like this:

1:localhost
1:localhost
1:localhost
1:localhost
1:localhost
1:localhost
1:localhost
1:localhost
omp_global:8
omp_lapw1:1
omp_lapw2:1

Additionally double check that you are indeed using the correct
libraries, go to you WIENROOT folder and do "ldd lapw1" you will see a
list of libraries it is inked against, make sure there is a
"libopenblas.so" and "libmvec.so" between them.
Also do the same for lapw0 and double check that it is compiled with
OpenMP (links to libgomp and links an OpenMP parallel openblas, I'm not
familiar with Ubuntu but it should be the library that comes with the
libopenblas-openmp package)).

That should hopefully do the trick. In general you can also test the
serial Wien2k benchmark. At single thread it should run around 20s on
your CPU and it should scale quite reasonably maybe up to 4-6 threads
with OMP_NUM_THREADS so that is also something you can check.

Best regards
Pavel

On Tue, 2023-08-22 at 12:30 +0300, Victor Zenou wrote:
> Dear Wien2k users!I’m investigating  a 54 tungsten atoms  supercell ,
> with 1 helium atom and 1 hydrogen atom (primitive cell) at different
> interstitial sites.  It takes ~ 46 hr per  calculation cycle, and
> half of it (~23 hr) in parallel mode.  The Wien2k version 23.2 was
> installed on Ubuntu 22.04.2 LTS. using gfortran and I set
> OMP_NUM_THREADS to  1, and used 2 parallel_jobs in the current work.
> The computer is build from  i7-10700 processor @ 2.90GHz (8 cores; 16
> Threads), 32 GB memory and 500 GB SSD. 
> In the past using the same computer , it took me ~ 14 hr per cycle
> for the same calculations, meaning 2-4 times faster than today. The
> wien2k version was 21.1, bur I can’t remember if the calculations
> were done in parallel, probably yes (I think  the number of parallel
> jobs was chosen automatically), and I think I set   OMP_NUM_THREADS
> to  4, but again I’m not sure.
> How can I speed up my calculations using the same computer?
> Best regards, Victor
> 
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