What happens if you use a high number of CPUs?

[Andrea-ARPAPUGLIA]

I run WRF model on 3 domains according to the following scheme:

dx =18000, 6000, 2000
e_we =223, 205 , 181
e_sn =223, 205 , 181

There is a rule for choosing the number of CPUs to use:

<<
For your smallest-sized domain:
((e_we)/25) * ((e_sn)/25) = most amount of processors you should use

For your largest-sized domain:
((e_we)/100) * ((e_sn)/100) = least amount of processors you should use. >>

Following this rule in my case I should use at least 5 CPUs and no more than 52 CPUs.

I tried to run with 80 CPUs with a positive result and excellent execution times (5 instead of 10 hours).

Could, using more processors than recommended, cause errors in the results?

Thanks for your reply

 

[kwerner]

Hi,
As long as your follow the rules at the top of this FAQ description and ensure that each grid space is no smaller than 10x10, you SHOULD be okay. That said, you probably want more than 10x10 for a better result (e.g., 20x20).

 

[Andrea-ARPAPUGLIA]

Thanks very much for the clarification.
I still take advantage of your valuable experience.
What is meant by "a better result"?
When changing the number of CPUs, can different values of the weather variables be found?