[Wien] Speeding up calculations in parallel mose
Victor Zenou
zanov at post.bgu.ac.il
Mon Aug 28 08:18:39 CEST 2023
Hi
I didn't use the new batch type mode, as I'm sorry to say I've never heard
about it till now.
I used 0.85, 1.0 and 1.8 RMT's for H, He and W, respectively.
Yes, no inversion symmetry as I choose primitive cell, each time filled
with 1 H atom and/or a He atom, at different location/s.
I found that 125 k-points (63 IBZ) are good enough for the convergence
criterions I wanted: 0.001 ec and 0.01 cc.
I used:
W-H: Rmt*Kmax=3
W-He: Rmt*Kmax=3*1/0.85=3.5
W: Rmt*Kmax=3*1.8/0.85=6.35
However Rmt*Kmax for W should be ~8, In that case:
W: Rmt*Kmax=8
W-H: Rmt*Kmax=8*0.85/1.8=3.77
W-He: Rmt*Kmax=8*1/1.8=4.44
I will check the strategy you suggested, and re-check my parameters.
Thanks,
Victor
בתאריך שבת, 26 באוג׳ 2023 ב-15:00 מאת Peter Blaha <
peter.blaha at tuwien.ac.at>:
> 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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> --
> --------------------------------------------------------------------------
> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Phone: +43-1-58801-165300
> Email: peter.blaha at tuwien.ac.at WIEN2k: http://www.wien2k.at
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