First time here? Check out the Help page!

Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page
Ask Your Question
2

EnergyPlus simulation runtime - CPU performance

asked 1 year ago

Tokarzewski's avatar

updated 1 year ago

Hi,

I have difficulty finding the root cause and resolving the following issue. Any help would be appreciated. I am running the same EnergyPlus model on 2 separate machines (laptop and desktop) with different CPUs and the simulation runtime is 3x longer on a laptop.

Desktop CPU: AMD Ryzen 9 3900X Runtime: 10 min

Laptop CPU: i5-1235U Runtime: 27 min

My understanding of the issue is the following: Because the difference is so large and the synthetic single-thread benchmarks say the opposite about the performance… I don’t think the issue is related to CPU peak performance. https://www.topcpu.net/en/cpu-c/Intel...

I think it has more to do with software, meaning how the EP engine or CPU drivers are asking or controlling the CPUs frequency. Although the CPU peak performance may be similar.. laptops bottom performance is lower, laptops CPUs can be at 0.8 GHz rather than using the available 4.0 Ghz. EnergyPlus in laptops can’t ask for higher frequency to boost performance, so the CPUs have lower utilisation, and desktops don’t have any battery mode settings that optimise the battery use over performance.

I am not 100% sure if this is the correct diagnosis nor how can I force the CPU to boost the frequency.

Again, any help would be appreciated.

Preview: (hide)

Comments

I need to test the CPU core temperatures. Maybe it is throttling, so the CPU driver lowers the frequency and voltage to decrease the temps...

Tokarzewski's avatar Tokarzewski  ( 1 year ago )
3

Are you requesting a lot of output variables / detailed timestep? I/O file operations can be a culprit (like writting to the ESO / SQL files), eg if one has a faster SSD and the other a regular HDD. Check RAM usage too. Make sure you set your laptop to "performance" mode (not power optimization) too. What operating system do you use on both?

Julien Marrec's avatar Julien Marrec  ( 1 year ago )
2

"desktops don’t have any battery mode settings that optimise the battery use over performance". That's not true, in the sense that it does have settings for CPU power consumption (though obviously not related to battery). For eg: On my Ubuntu Linux with a Ryzen 1800X, I can use cpupower frequency-set --governor performance to switch the profile used (and it is NOT the default)

Julien Marrec's avatar Julien Marrec  ( 1 year ago )

1 Answer

Sort by » oldest newest most voted
1

answered Oct 17

Tokarzewski's avatar

updated Oct 17

Overriding the "process priority" from "normal" to "high" on the laptop improved the runtime from 27min to 11min.

Preview: (hide)
link

Comments

No, EnergyPlus does not use OpenMP or take advantage of multiple threads, see https://github.com/NREL/EnergyPlus/is... for example.

shorowit's avatar shorowit  ( Oct 17 )
1

An EnergyPlus developer confirmed with me that that never made it into the official EnergyPlus (with maybe one small exception around ground HX calcs). They said, "The 10x project had high hopes for implementing it, but the system overhead and the interconnectedness of EnergyPlus thwarted that".

shorowit's avatar shorowit  ( Oct 17 )

And if you look at the last slide of the presentation, you can see that some models got slower w/ OpenMP.

shorowit's avatar shorowit  ( Oct 17 )

@shorowit thank you for the clarification. I removed my false hypothesis.

Tokarzewski's avatar Tokarzewski  ( Oct 17 )

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

Training Workshops

Careers

Question Tools

2 followers

Stats

Asked: 1 year ago

Seen: 170 times

Last updated: Oct 17 '24