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-   -   OpenFOAM + Hyperthreading (http://www.cfd-online.com/Forums/openfoam/101434-openfoam-hyperthreading.html)

Mister_K May 3, 2012 21:40

OpenFOAM + Hyperthreading
 
I asked my engineering supervisor whether Intel's hyperthreading technology benefits OpenFOAM computing, which to my surprise it does not.

He explained because there are only 4 physical cores doing work, and tasks will just bounce between either the physical or virtual core pair.

Is this correct?

linnemann May 4, 2012 00:55

yes that is correct

Mister_K May 4, 2012 02:15

Thanks for the reply ;)

Giuliano69 May 26, 2012 14:33

You came to and old debate, that face AMD opteron multi-core, against Intel multi thread....You can find many 3d on this subj on this forum...


Inter HT CPU have 2 thread per core.
The MAIN point is that each core can have just ONE single thread working at any time.
Where is the deal ?
IF a memory I/O is required, when the thread is working for fetching the data, the other thread can proceed on the same core.

In general terms, this lead to a performance improvement.(approx 20%-30%)

BUT, coming to HPC on CFD, another consideration becomes important: Memory access/bandwidth consideration.
if the memory accessed by the thread are on "different" memory area, so that the chace doesn't help, HT on more thread could give performance downgrade, instande of speed up.
It is the case of CFD with a huge cell number.

Even more, dividing the memory bandwidth between more cores/Threads degrade the memory access performance for each single core/thread.
(it's the origin of the debate AMD/Intel: it is better a multi CPU (AMD) or a multi core (Intel) based workstation ?)

You can find interesting result and comparison on a "famous" article:
http://www.anandtech.com/show/4486/s...mark-session/4

hope it helps...

Bye


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