chtMultiRegionFoam is slower in parallel than serial

froberto · September 11, 2023, 16:41

Hi All,
I am trying to run a multi region case in parallel.
However, it runs slower in parallel than serial.
So, I went back to the tutorial case multiRegionHeater (within heatTransfer/chtMultiRegionFoam) and I ran it both in serial and parallel.
The parallel run is slower than the serial run.
I have also tried other tutorial cases with buoyantPimpleFoam and solidFoam and I was able to run them in parallel, and their performance is better than the serial run's.
Anyone any ideas?
How can I make chtMultiRegionFoam run faster in parallel.

Thanks,
Roberto

P.S. I am using OpenFoam-v2012.

dlahaye · September 11, 2023, 17:27

For small cases (small number of cells) communication (between processors) might (emphasis on might) dominate computations (on each processor).

froberto · September 12, 2023, 14:55

Thanks dlahaye for your response.
You are right.
I have increased the number of volumes in the tutorial example, and now the parallel case runs faster than the serial.
Thanks for the help!

September 11, 2023, 16:41	chtMultiRegionFoam is slower in parallel than serial	#1
froberto New Member Roberto Join Date: Jul 2021 Posts: 4 Rep Power: 5	Hi All, I am trying to run a multi region case in parallel. However, it runs slower in parallel than serial. So, I went back to the tutorial case multiRegionHeater (within heatTransfer/chtMultiRegionFoam) and I ran it both in serial and parallel. The parallel run is slower than the serial run. I have also tried other tutorial cases with buoyantPimpleFoam and solidFoam and I was able to run them in parallel, and their performance is better than the serial run's. Anyone any ideas? How can I make chtMultiRegionFoam run faster in parallel. Thanks, Roberto P.S. I am using OpenFoam-v2012.

September 11, 2023, 17:27		#2
dlahaye Senior Member Domenico Lahaye Join Date: Dec 2013 Posts: 798 Blog Entries: 1 Rep Power: 17	For small cases (small number of cells) communication (between processors) might (emphasis on might) dominate computations (on each processor). froberto likes this.

September 12, 2023, 14:55		#3
froberto New Member Roberto Join Date: Jul 2021 Posts: 4 Rep Power: 5	Thanks dlahaye for your response. You are right. I have increased the number of volumes in the tutorial example, and now the parallel case runs faster than the serial. Thanks for the help! dlahaye likes this.

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