CPU for both post-process and solving

bramv101 · January 17, 2021, 09:32

Hi All,

I would need some help advising a setup that has both good single core performance (post processing) and multi (solving CFD)
Threadripper is apparently a nogo? But i am doubting on the dual epyc builds recommended here due to the "lower" single core performance.
Is there perhaps a good Intel solution I am overlooking?
And is there a difference from using Openfoam vs Fluent vs StarCCM?

- max cell count around 30E6, external aero, but also transient thermal - sporadic FEA
- budget 6k euro (located in Germany)

Overall I would say I am looking for a more broad build than a pure CFD solver build?

danbence · January 17, 2021, 12:24

Yes, generally the high core count + high bandwidth CPUs do not have the highest single thread performance. As post processing does not use many cores, the post-processing speed will suffer.

Might be worth looking at the new Threadripper PRO, which has double the number of memory channels as a normal threadripper AND has a respectable boost speed.

I think they are only available at the moment through Lenovo. Search for “Thinkstation P620 tower”

bramv101 · January 18, 2021, 03:12

Threadripper Pro is indeed something to consider, However if the Lenovo website is somewhat correct those prices are very steep compared to an DIY Epyc build.
Since they would release to consumers in March this year, I might wait for that..

flotus1 · January 18, 2021, 14:49

If you wait for that anyway, you might as well go for 3rd gen Epyc.
The generational improvements will make up for most of the frequency disadvantage compared to threadripper pro. If the prices turn out reasonable (and that's a big if at the moment), it will be a no-brainer. It's all just guess-work so far, but AMD would have to price their TR pro CPUs very aggressively to not make them obsolete the second Epyc Milan becomes available.

JBeilke · January 18, 2021, 16:04

StarCCM+ can do parallel preprocessing. The only seriell part is the surface remesher. Postprocessing runs in decomposed mode so it is also parallel.

My prefered option would be a 2 processor epyc AND a Ryzen7 5800X. So you switch on the epyc only for number crunching. This option has some charm when you pay for electricity yourself.

January 17, 2021, 09:32	CPU for both post-process and solving	#1
bramv101 Member TonyD Join Date: Apr 2009 Posts: 85 Rep Power: 17	Hi All, I would need some help advising a setup that has both good single core performance (post processing) and multi (solving CFD) Threadripper is apparently a nogo? But i am doubting on the dual epyc builds recommended here due to the "lower" single core performance. Is there perhaps a good Intel solution I am overlooking? And is there a difference from using Openfoam vs Fluent vs StarCCM? - max cell count around 30E6, external aero, but also transient thermal - sporadic FEA - budget 6k euro (located in Germany) Overall I would say I am looking for a more broad build than a pure CFD solver build?

January 18, 2021, 03:12		#3
bramv101 Member TonyD Join Date: Apr 2009 Posts: 85 Rep Power: 17	Threadripper Pro is indeed something to consider, However if the Lenovo website is somewhat correct those prices are very steep compared to an DIY Epyc build. Since they would release to consumers in March this year, I might wait for that.. Last edited by bramv101; January 18, 2021 at 10:11.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Error when solving p_rgh	bob94	OpenFOAM	0	March 17, 2020 08:12
Foam::error::printStack after large bounding epsilon events	StoneCFD727	OpenFOAM Running, Solving & CFD	1	January 1, 2018 17:04
HeatSource BC to the whole region in chtMultiRegionHeater	xsa	OpenFOAM Running, Solving & CFD	3	November 7, 2016 05:07
Why RNGkepsilon model gives floating error	shipman	OpenFOAM Running, Solving & CFD	3	September 7, 2013 08:00
IcoFoam parallel woes	msrinath80	OpenFOAM Running, Solving & CFD	9	July 22, 2007 02:58

January 17, 2021, 12:24		#2
danbence Member dab bence Join Date: Mar 2013 Posts: 47 Rep Power: 13	Yes, generally the high core count + high bandwidth CPUs do not have the highest single thread performance. As post processing does not use many cores, the post-processing speed will suffer. Might be worth looking at the new Threadripper PRO, which has double the number of memory channels as a normal threadripper AND has a respectable boost speed. I think they are only available at the moment through Lenovo. Search for “Thinkstation P620 tower”

January 18, 2021, 14:49		#4
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,399 Rep Power: 46	If you wait for that anyway, you might as well go for 3rd gen Epyc. The generational improvements will make up for most of the frequency disadvantage compared to threadripper pro. If the prices turn out reasonable (and that's a big if at the moment), it will be a no-brainer. It's all just guess-work so far, but AMD would have to price their TR pro CPUs very aggressively to not make them obsolete the second Epyc Milan becomes available.

January 18, 2021, 16:04		#5
JBeilke Senior Member Joern Beilke Join Date: Mar 2009 Location: Dresden Posts: 498 Rep Power: 20	StarCCM+ can do parallel preprocessing. The only seriell part is the surface remesher. Postprocessing runs in decomposed mode so it is also parallel. My prefered option would be a 2 processor epyc AND a Ryzen7 5800X. So you switch on the epyc only for number crunching. This option has some charm when you pay for electricity yourself.