Thanks for the input. I have looked at that Wikipedia page before, but
never checked it that closely. I just looked mainly to see what
processors supported what extensions. After taking a closer look at
AVX-512, and all the different subdivisions, I see exactly what you're
saying. It's a mess! Compare that to AVX and AVX2, where it's an
all-or-nothing thing. Makes a lot more sense.
Prentice
On 6/19/21 11:49 AM, Gerald Henriksen 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
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