How to choose hardware for electric arcs simulation in CS 5

[rodion]

Hello everyone,

I am about to get a new computer for simulation of electric arcs in Code_Saturne 5 on Windows 7 and on a virtual machine with Lubuntu. The meshes size in my models is about 200 000 to 1 000 000 cells. Usually I do about 10 000 to 30 000 time steps with output frequency about 50 to 200 time steps.
Could you please explain, what should I pay attention to, when I choose the hardware, and which parts are important?

1. Processor: should I get a multi core Intel Xeon (for example Intel Xeon E5-2683V3 with 14 2.0GHz) or an Intel i7 with high-performance cores (for example i7-8700K with 6 cores 3.70GHz)?

2. How should I choose the memory and the motherboard?

3. Is SSD more preferable than HDD for simulation in Code_Saturne?

Thank you in advance.
Best regards,
Rodion

[Yvan Fournier]

Hello,

I'm not too sure what impact going through the virtual machine will have on your computation, but I would expect a Xeon to have better performance due to better cache and memory bandwith (but the best is to compare those values between ranks; we have observed very different scalability results between different Xeon models)... In any case, the code is more memory-bound than compute bound, so memory bandwidth and latency (and cache) is at least as important as the theoretical compute performance.

The more frequent the output, the more useful an SSD may be useful, but even at output every 50 time steps, IO performance is not usually critical, so an SSD will not probably gain you much (on current cases with version 5.0, you can use the timer_stats.csv file to compare time spent in output to the rest).

Regards,

Yvan

[rodion]

Thank you for your answer, Yvan!

As far as I understand, the processor clock rate doesn't have a big impact to the computation speed, right? If I choose among different Intel Xeons should I take more cores or a higher processor clock rate?

Could you please advise something for the RAM and the motherboard? Is it better to have, for example, 4x4GB RAM or 2x8GB?

Regarding the HDD, I have noticed, that when I start several simulation cases in Code_Saturne on the same PC even with a low output frequency, all the cases become very slow, several times slower compared to a single case started alone. Can the HDD be the bottleneck?

Best regards,
Rodion

[Yvan Fournier]

Hello,

I am not sure how the HDD can be the botleneck with medium frequency output, but the virtual machine might have an effect, and in any case, you should trus benchmarking and experience more than theory (though theory can/should help analyse and understand the results).

It is up to you to decide whether you run several computations simultaneously or not, which might have an influence deciding whether the extra price of a SSD is worthwhile relative to a better processor or memory.

In any case, we have limited feedback, especially on virtual machines (we use VM's mainly for testing and debugging, where performance is not the main metric, and most of our large production runs are done on clusters (no VM's, and all nodes have the same model of processor so most feedback is limited to a few processor models, though most external users seem to have similar performance on other machines).

Regards,

Yvan

[rodion]

Thank you for your answer, Yvan!

As far as I understand, the processor clock rate doesn't have a big impact to the computation speed, right? If I choose among different Intel Xeons should I take more cores or a higher processor clock rate?

Could you please advise something for the RAM and the motherboard? Is it better to have, for example, 4x4GB RAM or 2x8GB?

Best regards,
Rodion

[Yvan Fournier]

Hello,

I would assume more sockets is better, but this is just a general guess. Other factors can also influence performance, so without benchmarking, I can't really say more with any degree of certainty...

Regards,

Yvan

[Claws]

Thank you for your answer, Yvan!

As far as I understand, the processor clock rate doesn't have a big impact to the computation speed, right? If I choose among different Intel Xeons should I take more cores or a higher processor clock rate?

Could you please advise something for the RAM and the motherboard? Is it better to have, for example, 4x4GB RAM or 2x8GB?

Best regards,
Rodion

Running RAM in dual channel vs. single channel (or quad channel) can give you a performance boost in RAM access. Have a search for single channel vs dual channel, and judge for yourself.

Filling up the RAM sockets now will prevent you from upgrading later, without having to discard the old modules. That is worth a thought.

/C

[rodion]

Thank you very much for your answers!

Best regards,
Rodion