[Beowulf] Best case performance of HPL on EPYC 7742 processor ...

[Kilian Cavalotti]

Hi Richard,

On Fri, Aug 14, 2020 at 2:30 PM Richard Walsh <rbwcnslt at gmail.com> wrote:
> What have people achieved on this SKU on a single-node using the stock
> HPL 2.3 source... ??

I got similar findings as yours, about 75-80% of peak, albeit using a
different SKU (7702), but consistent over multiple platforms (thus
hopefully averaging manufacturer idiosyncrasies).

I think this page summarizes the most relevant BIOS settings pretty
well: https://hpcadvisorycouncil.atlassian.net/wiki/spaces/HPCWORKS/pages/1280442391/AMD+2nd+Gen+EPYC+CPU+Tuning+Guide+for+InfiniBand+HPC#Configurable-Thermal-Design-Power-(cTDP)

> I have seen a variety of performance claims even as high as 90% of its nominal per node peak of 4.608 TFLOPs.

Interestingly, the theoretical performance of a dual-7742 machine is
4.608 TFLOPs, at *base* clock (2.25 GHz).
In practice, you probably had Turbo on, meaning that the clocks were
probably running closer to the 3.0 GHz range, which means that the
theoretical performance should be in the 6 TF range, hence bringing
the observed efficiency even lower.

An interesting test would be to disable Turbo to fix the core clocks
at 2.25 GHz, and see the HPL numbers you get.

Cheers,
--
Kilian