[Wien] Speeding up calculations in parallel mose
Peter Blaha
peter.blaha at tuwien.ac.at
Sat Aug 26 14:00:17 CEST 2023
Well, we get only part of the information each time.
You are using a 3x3x3 W supercell with H/He interstitials.
How did you initialize the calculation ? Hopefully in the new batch
type mode with a low precision (0 or 1) !! If not, then:
RKMAX=5.4 seems still very big for the presumably small H/He spheres.
What are the RMTs (set by the program).
If they are small (0.6-1.0 bohr), a much smaller RKMAX (3-4 ?) can be
used. This may make your calculations 100 times faster.
125 k-points: are these the IBZ points (case.klist) - sounds quite too
many-, or what you put as input to x kgen ?
And as was said before: Of course you should use k-parallelization.
Remember: the benchmark test case has 36 atoms/cell and needs 20
seconds/k-point. Your system is bigger (55 atoms), so make it 100
seconds/k-point.
No Inversion symmetry ?, low packing, .. may cost another factor of 2-4
So this makes ~ 5 min/k-point, i.e. with 125 k-points and 8 cores one
scf cycle should take roughly 1 hour.
Remember the general strategy:
First run with "minimum parameters" (init_lapw -prec 0), check timing
and possible parallelization.
Save the calculation, increase k-points and/or RKmax and continue (never
do a full init_lapw again, maybe use init_lapw -prec XX -nodstart)
Am 23.08.2023 um 07:48 schrieb Victor Zenou:
> Dear Laurie and Pavel,
> Thanks for your answer
> 1. In fact I'm using RKMAX 5.4 and 125 kpts
> 0.01 cc and 0.001 ec
>
>
> 2. About my boss, it took me more than one year to get a new computer.
> Please define "fast"!
> Victor
>
>
> בתאריך יום ג׳, 22 באוג׳ 2023 ב-14:35 מאת Laurence Marks
> <laurence.marks at gmail.com <mailto:laurence.marks at gmail.com>>:
>
> Beyond what Pavel said, you are still talking weeks for a
> calculation. A critical issue is whether you are using sensible
> parameters. Maney people have used RKMAX 7 and 1000 kpts assuming
> that those are "right" -- they are not. If your H and He have small
> RMTs then RKMAX should also be smaller. Also, what is needed is a
> k-point density, so the number of k-points is less for a supercell.
>
> I suggest that you copy your case.struct file to a new directory
> then do init_lapw in that directory. 23.2 will pick appropriate
> values for you, and you can then copy them over.
>
> Beyond that, get your boss to buy you a faster computer.
>
> --
> Professor Laurence Marks (Laurie)
> Walter P Murphy Professor Emeritus
> Department of Materials Science and Engineering, Northwestern University
> www.numis.northwestern.edu <http://www.numis.northwestern.edu>
> "Research is to see what everybody else has seen, and to think what
> nobody else has thought" Albert Szent-Györgyi
>
> On Tue, Aug 22, 2023, 04:32 Victor Zenou <zanov at post.bgu.ac.il
> <mailto:zanov at post.bgu.ac.il>> 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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