[Beowulf] HPCG benchmark, again

[Richard Walsh]

J,

Trying to add a bit to the preceding useful answers … 

In my experience running these codes on very large systems for acceptances, to get optimal (HPCG or HPL) performance on GPUs (MI200 or A100) you need to obtain the optimized versions from the vendors which include scripts with ENV variable tunings specific the their versions and optimal affinity settings to manage the non-simple relationship between the NICs, the GPUs, and CPUs … you have iterate through the settings to find optimal settings for you system. 

If you set out to do this on your own, the chances of getting values similar to those posted on the TOP500 website are vanishingly small … 

As already noted, buyers of large HPC systems almost always require large scale runs of both HPCG (to demonstrate peak bandwidth) and HPL (to demonstrated peak processor) performance. 

Cheers!

rbw

Sent from my iPhone

> On Mar 18, 2022, at 7:35 PM, Massimiliano Fatica <mfatica at gmail.com> wrote:
> 
> 
> 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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