NPAR

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nkwem · #1 Post by **nkwem** » Thu Mar 19, 2015 3:12 pm

Dear all,

I know that NPAR = sqrt(number of cores) but I'm not sure if number of cores are per node or is it the total cores that I have requested. Please help

Regards,
Nkwe

alex · #2 Post by **alex** » Thu Mar 19, 2015 5:19 pm

I'd like to see the number as number of tasks.

Cheers,

alex

nkwem · #3 Post by **nkwem** » Mon Mar 23, 2015 10:16 am

Hi Alex,

Thank you for the reply.

Is it number of tasks per node or total number of tasks?

Regards,
Nkwe

andydihao · #4 Post by **andydihao** » Tue Mar 24, 2015 1:47 pm

I put it as sqrt(cores per node) and it worked fine for PBE.

Best regards,
Andy

marsoner · #5 Post by **marsoner** » Wed Mar 25, 2015 8:57 am

This might help:

https://www.nsc.liu.se/~pla/blog/2011/06/30/vaspnpar/

Best regards,
Lukas

alex · #6 Post by **alex** » Thu Mar 26, 2015 10:36 am

Hello Nkwe,

sorry for the late answer. My browser seems to have swallowed it. :-O

NPAR relates to the total number of tasks. E.g. 8 CPUs with 8 cores each, one task on every core = 64 tasks. Then you start with an NPAR of 8.
Please consider it as a starting point. As Lukas pointed out, there might be an optimum setting for your own machine, which might be different from that starting point.

I normally do some steps in wavefunction optimisation for different NPAR settings and pick the fastest. Starting point is sqrt(tasks).

Cheers,

alex

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