[Wien] Speeding up calculations in parallel mose

[Gavin Abo]

Sometimes it can be better to have a cheap computer if you can remote 
connect to a high performance computing (hpc) [1] cluster.

There can be quite a bit of difference in the computing resources that a 
thousand dollar desktop computer provides compared at a million dollar 
hpc [2].

If your in academia, there are usually more options available for 
getting access to a hpc such as use your own university's or 
department's one if available, use a research center if there is one 
nearby, collaborate with a professor at another university that has one, 
get a research grant to pay to use a commercial one (e.g., Amazon Cloud 
[3]), and so on.  If in industry, it might be harder to get access to 
one unless you work at a large corporation that has one.

Desktop computers used to ship with 100 Mbps cards.   However, in new 
computers nowadays, you will likely find them to have 1 Gbps cards.  A 
Gigabit switch used to be expensive, but they have probably come down in 
price now.

If you can find some buddies (aka fellow researchers) at your local site 
and can connect them up to a Gigabit switch, while not as good as a hpc 
with InfiniBand [4], you may be able to Beowulf cluster [5] them to be 
better than a single desktop computer.

You might recall reading, since it has been in the archive and has been 
re-posted a few times, the post at [6] about how a Gigabit network of 
computers with i7 processors worked relatively well.

[1] https://en.wikipedia.org/wiki/High-performance_computing
[2] 
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg22676.html
[3] https://aws.amazon.com/education/
[4] https://en.wikipedia.org/wiki/InfiniBand
[5] https://en.wikipedia.org/wiki/Beowulf_cluster
[6] 
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg09334.html

Kind Regards,

Gavin
WIEN2k user

On 8/22/2023 11:48 PM, Victor Zenou wrote:
> 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>:‬
>
>     Beyond what Pavel said, you are still talking weeks for a
>     calculation. A critical issue is whether you are using sensible
>     parameters. Many 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> 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
>
>         _______________________________________________
>         Wien mailing list
>         Wien at zeus.theochem.tuwien.ac.at
>         http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>         SEARCH the MAILING-LIST at:
>         http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://zeus.theochem.tuwien.ac.at/pipermail/wien/attachments/20230823/2b6696b2/attachment.htm>