Which hardware for openEMS?

How to use openEMS. Discussion on examples, tutorials etc

Moderator: thorsten

thorsten
Posts: 1393
Joined: Mon 27 Jun 2011, 12:26

Re: Which hardware for openEMS?

Post by thorsten » Thu 29 Nov 2018, 12:19

I see. Well, If I can make use of all my cores available that would be good.
In my experience openEMS does not scale to well with many cores. Usually only 2 or 4 threads is good. Much more than that and it looses speed. Again the CPU-Cache and main memory is the bottle neck. If too many cores fight for the data it does not help...

Hale_812
Posts: 171
Joined: Fri 13 May 2016, 02:54

Re: Which hardware for openEMS?

Post by Hale_812 » Fri 30 Nov 2018, 02:56

PaulUK wrote:
Thu 29 Nov 2018, 12:12
I see. Well, If I can make use of all my cores available that would be good.
it often happens with non-optimized codes that running them on N-1 cores, or with "below average" priority gives better results, because the "unused" time constitutes an important overhead for OS operations, supporting the code execution. I'ts like you make underlying OS interfaces more responsive and boost I/O. It is not a rule, but a common situation in Windows. Bthw, that is the reason why multicore is so good for windows machines. And as a cherry on the top you get some 2-5% turbo-boost benefit, when some cores are parked.

PaulUK
Posts: 76
Joined: Wed 28 Oct 2015, 14:23

Re: Which hardware for openEMS?

Post by PaulUK » Fri 30 Nov 2018, 13:01

I see. Thank you.

As Thorston said, I found that 3 cores on my works 4 core laptop gave the fastest runtime. However in my dual processor computer I got the fastest runtime with between 4 and 6 cores. It's useful to know but I wont spend more time on this, and rather spend more time in learning the software and try to determine what I can and can't do with it and to put it to good use.

Hale_812
Posts: 171
Joined: Fri 13 May 2016, 02:54

Re: Which hardware for openEMS?

Post by Hale_812 » Tue 04 Dec 2018, 06:20

Avoid using dual processing for simulations that greatly exceed CPU cache, and do not use mirrored memory per CPU unit.
Although, Intel introduced certain advances in inter-CPU RAM access mechanisms, these things are oriented primarily on server marked, not on high-performance computations. So the throughput can be high, but the latency can be worse. As a result, sometimes you can get a boost, sometimes it can drag behind i7 4-core (the situation I had with HFSS 13), depending on the result of CPU scheduler efforts.

Well, you a right, it is just an information for the future, when your simulation will exceed 1 week of running... I had plenty of such cases.

PaulUK
Posts: 76
Joined: Wed 28 Oct 2015, 14:23

Re: Which hardware for openEMS?

Post by PaulUK » Sun 16 Dec 2018, 01:19

I've just installed more memory in my computer and it's now quad channel and it seems to have made quite a difference. Using the same, large simulation with two large data dump planes, I did a number of tests increasing the number of cpu cores.

I find a setting of 7 cores gives the greatest MC/s for this particular simulation where as a Dell Precision M6800 was best with 3 or 4 cores. Anyway, I better get back to doing something useful with it.

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