[Beowulf] [External] Re: AMD and AVX512

[Prentice Bisbal]

Thanks for the resources. I will definitely read/watch them when I can 
block out some time. I see he uses LAMMPS as one of his benchmarks. I 
was considering adding LAMMPS to my testing regimen, since it's a code I 
have familiarity with, and my own background is in chemistry.

Prentice

On 6/20/21 1:38 AM, John Hearns wrote:
> Regarding benchmarking real world codes on AMD , every year Martyn 
> Guest presents a comprehensive set of benchmark studies to the UK 
> Computing Insights Conference.
> I suggest a Sunday afternoon with the beverage of your choice is a 
> good time to settle down and take time to read these or watch the 
> presentation.
>
> 2019
> https://www.scd.stfc.ac.uk/SiteAssets/Pages/CIUK-2019-Presentations/Martyn_Guest.pdf 
> <https://www.scd.stfc.ac.uk/SiteAssets/Pages/CIUK-2019-Presentations/Martyn_Guest.pdf>
>
>
> 2020 Video session
> https://ukri.zoom.us/rec/share/ajvsxdJ8RM1wzpJtnlcypw4OyrZ9J27nqsfAG7eW49Ehq_Z5igat_7gj21Ge8gWu.78Cd9I1DNIjVViPV?startTime=1607008552000 
> <https://ukri.zoom.us/rec/share/ajvsxdJ8RM1wzpJtnlcypw4OyrZ9J27nqsfAG7eW49Ehq_Z5igat_7gj21Ge8gWu.78Cd9I1DNIjVViPV?startTime=1607008552000>
>
> Skylake / Cascade Lake / AMD Rome
>
> The slides for 2020 do exist - as I remember all the slides from all 
> talks are grouped together, but I cannot find them.
> Watch the video - it is an excellent presentation.
>
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> On Sat, 19 Jun 2021 at 16:49, Gerald Henriksen <ghenriks at gmail.com 
> <mailto:ghenriks at gmail.com>> wrote:
>
>     On Wed, 16 Jun 2021 13:15:40 -0400, you wrote:
>
>     >The answer given, and I'm
>     >not making this up, is that AMD listens to their users and gives the
>     >users what they want, and right now they're not hearing any
>     demand for
>     >AVX512.
>     >
>     >Personally, I call BS on that one. I can't imagine anyone in the HPC
>     >community saying "we'd like processors that offer only 1/2 the
>     floating
>     >point performance of Intel processors".
>
>     I suspect that is marketing speak, which roughly translates to not
>     that no one has asked for it, but rather requests haven't reached a
>     threshold where the requests are viewed as significant enough.
>
>     > Sure, AMD can offer more cores,
>     >but with only AVX2, you'd need twice as many cores as Intel
>     processors,
>     >all other things being equal.
>
>     But of course all other things aren't equal.
>
>     AVX512 is a mess.
>
>     Look at the Wikipedia page(*) and note that AVX512 means different
>     things depending on the processor implementing it.
>
>     So what does the poor software developer target?
>
>     Or that it can for heat reasons cause CPU frequency reductions,
>     meaning real world performance may not match theoritical - thus easier
>     to just go with GPU's.
>
>     The result is that most of the world is quite happily (at least for
>     now) ignoring AVX512 and going with GPU's as necessary - particularly
>     given the convenient libraries that Nvidia offers.
>
>     > I compared a server with dual AMD EPYC >7H12 processors (128)
>     > quad Intel Xeon 8268 >processors (96 cores).
>
>     > From what I've heard, the AMD processors run much hotter than
>     the Intel
>     >processors, too, so I imagine a FLOPS/Watt comparison would be
>     even less
>     >favorable to AMD.
>
>     Spec sheets would indicate AMD runs hotter, but then again you
>     benchmarked twice as many Intel processors.
>
>     So, per spec sheets for you processors above:
>
>     AMD - 280W - 2 processors means system 560W
>     Intel - 205W - 4 processors means system 820W
>
>     (and then you also need to factor in purchase price).
>
>     >An argument can be made that for calculations that lend
>     themselves to
>     >vectorization should be done on GPUs, instead of the main
>     processors but
>     >the last time I checked, GPU jobs are still memory is limited, and
>     >moving data in and out of GPU memory can still take time, so I
>     can see
>     >situations where for large amounts of data using CPUs would be
>     preferred
>     >over GPUs.
>
>     AMD's latest chips support PCI 4 while Intel is still stuck on PCI 3,
>     which may or may not mean a difference.
>
>     But what despite all of the above and the other replies, it is AMD who
>     has been winning the HPC contracts of late, not Intel.
>
>     * - https://en.wikipedia.org/wiki/Advanced_Vector_Extensions
>     <https://en.wikipedia.org/wiki/Advanced_Vector_Extensions>
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