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max cpu performance on interFoam

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Old   April 28, 2020, 23:42
Default max cpu performance on interFoam
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Josh McCraney
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Hi FOAMers!

I am running 16 cores in parallel over 128 gb of ram in 8 memory channels. Runrunning openfoam in parallel I execute 'sensors' to view my workload and there are 18 processes running at 3% CPU, which implies 54% cpu used. Is there a way to give interFoam more power here? Seems like there should be, but perhaps I'm wrong.
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Old   April 30, 2020, 05:31
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Thomas Sprich
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Hi Josh,


Does your computer have threads? Sensors may be calculating usage as a percentage of the threads which might be 32. If usage was calculated as a percentage of physical cores you would see 18 processes using 6%. 6 * 18 = 104%. With a little rounding errors, this could be right.



This does not mean you should try and use all the threads. Generally, OpenFOAM only gains benefit from the physical cores and not threads. You can google this, as there is some debate. Some people have seen improvement from running on threads as well.


I hope this helps.



Regards,

Thomas
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Old   April 30, 2020, 13:38
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Quote:
Originally Posted by Swift View Post
Hi Josh,


Does your computer have threads? Sensors may be calculating usage as a percentage of the threads which might be 32. If usage was calculated as a percentage of physical cores you would see 18 processes using 6%. 6 * 18 = 104%. With a little rounding errors, this could be right.



This does not mean you should try and use all the threads. Generally, OpenFOAM only gains benefit from the physical cores and not threads. You can google this, as there is some debate. Some people have seen improvement from running on threads as well.


I hope this helps.



Regards,

Thomas
Hi Thomas

My cpu does have 32 threads. And yes, I read about thread vs cores, and I agree. Thanks for your response!
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