GPU use for my fluent analysis

Abbas Dorri · November 8, 2022, 00:46

Hi everybody,

I have a laptop with specification of core i9 12 generation, 32 GB RAM, 8 GB graphics RTX 3070 Ti.
To achieve the best performance from my laptop capabilities, how much should I set the number of CPUs and GPUs at the beginning of the fluent launch?
I want the optimum numbers.
I searched a lot, but I could not understand what I should do.
please help me. I really need help.

Thank you so much.

flotus1 · November 8, 2022, 05:55

For the number of threads, use the amount of physical P-cores your CPU has. That's either 6 or 8 depending on the exact model. And then cross your fingers that the Windows scheduler assigns the threads to the right cores.

For GPU usage...my recommendation would be to leave that off for now, unless you are sure that your CFD models benefit from it. With the GPU you have, the values set in the GUI are ignored anyway. You would need to force GPU usage via text commands.

Abbas Dorri · November 8, 2022, 11:49

Quote:

Originally Posted by flotus1

For the number of threads, use the amount of physical P-cores your CPU has. That's either 6 or 8 depending on the exact model. And then cross your fingers that the Windows scheduler assigns the threads to the right cores.

For GPU usage...my recommendation would be to leave that off for now, unless you are sure that your CFD models benefit from it. With the GPU you have, the values set in the GUI are ignored anyway. You would need to force GPU usage via text commands.

My number of logical processors is 20. I think the number of physical cores is 14, so what do you suggest the number of Gpu?

flotus1 · November 8, 2022, 13:32

Your CPU has P-cores and E-cores. Forget about the E-cores. If you use them, the simulation will run slower. Use P-cores exclusively, of which your CPU has either 6 or 8. There are different models of 12th gen "I9" mobile CPUs.
However many P-cores your CPU has, use that for the number of solver processes in the Fluent launcher.

"0" for the number of GPUs.

Abbas Dorri · November 10, 2022, 13:04

Thank you so much for your guidance. Isn't it unfair to set GPU zero?

flotus1 · November 10, 2022, 13:27

I wouldn't exactly call it unfair.
You don't have to take my word for it, you can easily try it yourself:
Just run one of your simulations without GPU acceleration and measure how long it takes. Then "enable" GPU acceleration by setting the number of GPGPUs to 1, and run the same sim again.
Outside of normal run-to-run variance, you won't see a difference in performance.

Abbas Dorri · November 10, 2022, 13:43

Very nice. I definitely do the job to track the differences. Thank you for your help.

November 8, 2022, 00:46	GPU use for my fluent analysis	#1
Abbas Dorri New Member Abbas Dorri Join Date: Nov 2022 Posts: 7 Rep Power: 3	Hi everybody, I have a laptop with specification of core i9 12 generation, 32 GB RAM, 8 GB graphics RTX 3070 Ti. To achieve the best performance from my laptop capabilities, how much should I set the number of CPUs and GPUs at the beginning of the fluent launch? I want the optimum numbers. I searched a lot, but I could not understand what I should do. please help me. I really need help. Thank you so much.

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November 8, 2022, 05:55		#2
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,400 Rep Power: 47	For the number of threads, use the amount of physical P-cores your CPU has. That's either 6 or 8 depending on the exact model. And then cross your fingers that the Windows scheduler assigns the threads to the right cores. For GPU usage...my recommendation would be to leave that off for now, unless you are sure that your CFD models benefit from it. With the GPU you have, the values set in the GUI are ignored anyway. You would need to force GPU usage via text commands.

November 8, 2022, 13:32		#4
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,400 Rep Power: 47	Your CPU has P-cores and E-cores. Forget about the E-cores. If you use them, the simulation will run slower. Use P-cores exclusively, of which your CPU has either 6 or 8. There are different models of 12th gen "I9" mobile CPUs. However many P-cores your CPU has, use that for the number of solver processes in the Fluent launcher. "0" for the number of GPUs.

November 10, 2022, 13:04		#5
Abbas Dorri New Member Abbas Dorri Join Date: Nov 2022 Posts: 7 Rep Power: 3	Thank you so much for your guidance. Isn't it unfair to set GPU zero?

November 10, 2022, 13:27		#6
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,400 Rep Power: 47	I wouldn't exactly call it unfair. You don't have to take my word for it, you can easily try it yourself: Just run one of your simulations without GPU acceleration and measure how long it takes. Then "enable" GPU acceleration by setting the number of GPGPUs to 1, and run the same sim again. Outside of normal run-to-run variance, you won't see a difference in performance.

November 10, 2022, 13:43		#7
Abbas Dorri New Member Abbas Dorri Join Date: Nov 2022 Posts: 7 Rep Power: 3	Very nice. I definitely do the job to track the differences. Thank you for your help.