[Beowulf] HPCG benchmark, again

[Massimiliano Fatica]

HPCG measures memory bandwidth, the FLOPS capability of the chip is
completely irrelevant.
Pretty much all the vendor implementations reach very similar efficiency if
you compare them to the available memory bandwidth.
There is some effect of the network at scale, but you need to have a really
large  system to see it in play.

M

On Fri, Mar 18, 2022 at 5:20 PM Brian Dobbins <bdobbins at gmail.com> wrote:

>
> Hi Jorg,
>
>   We (NCAR - weather/climate applications) tend to find that HPCG more
> closely tracks the performance we see from hardware than Linpack, so it
> definitely is of interest and watched, but our procurements tend to use
> actual code that vendors run as part of the process, so we don't 'just' use
> published HPCG numbers.  Still, I'd say it's still very much a useful
> number, though.
>
>   As one example, while I haven't seen HPCG numbers for the MI250x
> accelerators, Prof. Matuoka of RIKEN tweeted back in November that he
> anticipated that to score around 0.4% of peak on HPCG, vs 2% on the NVIDIA
> A100 (while the A64FX they use hits an impressive 3%):
> https://twitter.com/ProfMatsuoka/status/1458159517590384640
>
>   Why is that relevant?  Well, *on paper*, the MI250X has ~96 TF FP64 w/
> Matrix operations, vs 19.5 TF on the A100.  So, 5x in theory, but Prof
> Matsuoka anticipated a ~5x differential in HPCG, *erasing* that
> differential.  Now, surely *someone* has HPCG numbers on the MI250X, but
> I've not yet seen any.  Would love to know what they are.  But absent that
> information I tend to bet Matsuoka isn't far off the mark.
>
>   Ultimately, it may help knowing more about what kind of applications you
> run - for memory bound CFD-like codes, HPCG tends to be pretty
> representative.
>
>   Maybe it's time to update the saying that 'numbers never lie' to
> something more accurate - 'numbers never lie, but they also rarely tell the
> whole story'.
>
>   Cheers,
>   - Brian
>
>
> On Fri, Mar 18, 2022 at 5:08 PM Jörg Saßmannshausen <
> sassy-work at sassy.formativ.net> wrote:
>
>> Dear all,
>>
>> further the emails back in 2020 around the HPCG benchmark test, as we are
>> in
>> the process of getting a new cluster I was wondering if somebody else in
>> the
>> meantime has used that test to benchmark the particular performance of
>> the
>> cluster.
>> From what I can see, the latest HPCG version is 3.1 from August 2019. I
>> also
>> have noticed that their website has a link to download a version which
>> includes the latest A100 GPUs from nVidia.
>> https://www.hpcg-benchmark.org/software/view.html?id=280
>>
>> What I was wondering is: has anybody else apart from Prentice tried that
>> test
>> and is it somehow useful, or does it just give you another set of numbers?
>>
>> Our new cluster will not be at the same league as the supercomputers, but
>> we
>> would like to have at least some kind of handle so we can compare the
>> various
>> offers from vendors. My hunch is the benchmark will somehow (strongly?)
>> depend
>> on how it is tuned. As my former colleague used to say: I am looking for
>> some
>> war stories (not very apt to say these days!).
>>
>> Either way, I hope you are all well given the strange new world we are
>> living
>> in right now.
>>
>> All the best from a spring like dark London
>>
>> Jörg
>>
>>
>>
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