[allenfieldin]

Hello ,Foamers

I recently bought a workstation which I planned to do some small cases(like 20 processors/job, and two jobs can run at the same time). The workstation is DELL T7810 and it has 20 physical cores, and I was told that it can be expanded to 40 cores if neccessary.

BUT! recently I tried to do the efficiency study with OpenFOAM and foam-extend for my new solver, it seems that a single job does its best when using 15-18 processors, and the single job with 20 processors costs much longer time. AND two jobs (like 18 processors) run at the same time will suffer much much more than expected.

So I searched the thread and find it was told foam does not support Hyper-Threading, which make me quite depressed. See this http://www.cfd-online.com/Forums/ope...threading.html

Has anyone tried to solve this problem? or does it have no solutions at all?

Thanks if anyone can comment on this, if foam really does not support this, it still saves me a lot of time on trying this.

by Allen

[akidess]

Well, the Hyper-Threading technology allows increasing efficiency of the processor in certain cases. In particular, when applications of different nature are used simultaneously.

One important outcome was that memory intensive job mixes perform badly on Hyper-Threading.

The speedup depends mainly on problem size and memory access pattern. Extra care must be taken where the memory access is regular (i.e. matrix operations) which can cause significant penalties in parallel algorithms.

From: http://users.telenet.be/nicvroom/performanceP4.htm, emphasis mine.

You can find more on Google (perhaps also newer information).