[Beowulf] AMD and AVX512

Stu Midgley sdm900 at gmail.com
Thu Jun 17 02:53:04 UTC 2021

I've told AMD brass that we need AVX512 many many times.

I've also told them that we need more memory bandwidth and that adding
dimms is not the answer.  We don't need more capacity - just more bandwidth.

We have a stack load of KNL systems and have invested heavily in AVX512
(writing with intrinsics) and shifting those codes away from it would be
considerable work.

Bring on Sapphire Rapids :)

On Thu, Jun 17, 2021 at 1:16 AM Prentice Bisbal via Beowulf <
beowulf at beowulf.org> wrote:

> Did anyone else attend this webinar panel discussion with AMD hosted by
> HPCWire yesterday? It was titled "AMD HPC Solutions: Enabling Your
> Success in HPC"
> https://www.hpcwire.com/amd-hpc-solutions-enabling-your-success-in-hpc/
> I attended it, and noticed there was no mention of AMD supporting
> AVX512, so during the question and answer portion of the program, I
> asked when AMD processors will support AVX512. 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". 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.
> Last fall I evaluated potential new cluster nodes for a large cluster
> purchase using the HPL benchmark. I compared a server with dual AMD EPYC
> 7H12 processors (128) cores to a server with quad Intel Xeon 8268
> processors (96 cores). I measured 5,389 GFLOPS for the Xeon 8268, and
> only 3,446.00 GFLOPS for the AMD 7H12. That's LINPACK score that only
> 64% of the Xeon 8268 system, despite having 33% more 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.
> 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.
> Your thoughts?
> --
> Prentice
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Dr Stuart Midgley
sdm900 at gmail.com
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