Intel's Groveport Platform

By: Brendan (btrotter.delete@this.gmail.com), April 17, 2017 11:48 pm
Room: Moderated Discussions
Hi,

anon (anon.delete@this.anon.com) on April 17, 2017 10:39 pm wrote:
> Brendan (btrotter.delete@this.gmail.com) on April 17, 2017 8:31 pm wrote:
> > anon (anon.delete@this.anon.com) on April 17, 2017 6:32 pm wrote:
> > > Brendan (btrotter.delete@this.gmail.com) on April 17, 2017 5:35 pm wrote:
> > > > Michael S (already5chosen.delete@this.yahoo.com) on April 17, 2017 4:18 pm wrote:
> > > > > Brendan (btrotter.delete@this.gmail.com) on April 17, 2017 3:13 pm wrote:
> > > > > > > IMHO, it's bloody obvious than if KNL has any chance at all to be competitive against "normal" Xeon
> > > > > > > on non-HPC loads then it's *only* when there is a lot of parallel tasks ready all the time. *Much* more
> > > > > > > tasks than mere 32 that are needed for full utilization of a pair of hyperthreaded 8-core Xeons.
> > > > > >
> > > > > > Yes; and it would be extremely foolish to assume that HPC
> > > > > > is the only case where there is a lot of parallel tasks.
> > > > >
> > > > > But HPC, at least some classes of it, is the one of the few tasks, and likely the most important among them
> > > > > by far, where KNL's dual 512-bit SIMD units can be advantageous.
> > > > > Very-high-bandwidth, but not very low latency,
> > > > > HMC-alike memory is also advantageous only for relatively small class of non-HPC workloads.
> > > >
> > > > Um, what?
> > > >
> > > > HPC is mostly "same as mainstream, just more of it",
> > >
> > > It isn't really. Unless you define mainstream so broadly it doesn't mean anything.
> >
> > How else can "mainstream" be defined?
>
> Probably wrong wording on my behalf. Doesn't matter how broad or narrow you define mainstream, HPC
> is never "mostly same as mainstream, just more of it". You can reasonably define it so regular vectorizable
> parallel DFLOPS is a subset of mainstream, but that doesn't make HPC the same as it.

If I use one standard Xeon machine to do some number crunching, then that's (part of) mainstream; and if I use 2 standard Xeon machines that's also (part of) mainstream; but if I add a third standard Xeon machine then it becomes HPC and the work each machine is doing suddenly completely and utterly different? Yes, no, maybe? How many machines do I have to add before I hit the magic "suddenly completely and utterly different" cut-off point? Is the answer 42?

> > > > > No, i didn't say anything like that. KNL is definitely much faster than dual-2620v4 on vectorizable FP, and
> > > > > even somewhat faster (not a lot, 15% or so) at SPECFp2006_rate, probably due to great memory bandwidth.
> > > > > But you were talking about workloads that resemble SPECInt_rate, don't you?
> > > >
> > > > I threw a mixed bag of everything out there (from compilers to amateur CPU generated animated movies).
> > >
> > > None of those you listed would want a Xeon Phi.
> > >
> > > Not an office with 40 thin clients could use Xeon Phi.
> >
> > Depends what the office workers actually do.
>
> Yes, but you implied a general thin client server and presumably associated network and
> storage processing, which Phi is *not* suited to. If they also have significant FP compute
> requirement, then what is it? That is what's relevant, not the thin client part.
>
> >
> > > Not a game developer who wants to support MCDRAM and AVX512 (they will wait at least until
> > > it is in high end consumer stuff, if they are serious developers and want to support it
> > > before that, Intel will provide engineering samples 6 months or so before release).
> >
> > High end consumer stuff?
>
> Yes.
>
> > High bandwidth on-chip RAM
>
> Doesn't need specific support beyond what's mostly already there. Some
> tuning perhaps, which obviously is not the same from Phi to a PC CPU.

Some minor tuning; like completely redesigning memory management to make the most effective use of a new type of limited resource that hasn't existed before.

> > and AVX512 will probably
> > both be in entry level notebooks by the end of the year. It takes years to
> > produce a game engine - "6 months sooner" is about 2 years too late.
>
> It does not take years to port already vectorized codepaths new vector instructions,
> or to use updated libraries or compilers. Also games all come out with patches now.

I'm talking about fundamental design decisions that effect everything, not some low performance Lua script changes. If I have some C++ code with 123 classes (and various numbers of objects per class); which classes should/shouldn't use high bandwidth RAM? Should some classes be split into "frequently accessed" and "less frequently accessed"? If I'm designing a file format for something (levels, meshes, whatever) how much padding for alignment should I use? Is it better to use 32-byte alignment and let scatter-gather deal with it for AVX512, or should I have unnecessary padding for the AVX2 case? When I create a patch; will the compiler's "auto-vetorization" change the file format used by files that I already shipped on read-only DVDs?

> And if they want to use the instructions they can likely already get Xeon engineering samples which would
> be much better to work with. I can't remember the lead time that I got engineering samples from Intel back
> a few years ago when I was working on an open source project they took an interest in. Probably 3-6 months,
> but I was absolute bottom tier. Serious partners and ISVs could get first tapeout samples I'm sure.

How would a person get on the list for next generation Xeon Phi (I've heard they'll support virtualisation, and that Intel has early engineering samples already)?

> > > Not software developers that want to use Xeon Phi as "single server compile farm".
> >
> > Many separate processes (with near zero scalability problems between them) with compilers that can
> > be memory bandwidth sensitive? Throw in some compile-time calculation for some large arrays and a few
> > "floating point heavy" units tests? I wouldn't assume Xeon Phi couldn't be beneficial for some.
>
> I doubt it really, compared with a bunch of cheap low end Xeons. And if you had serious
> FP tests to run, you would presumably want to run them on the same instruction set.

Oh, so we're no longer presuming that you can just let the compiler auto-vectorise and it doesn't matter.

> > > Not a game console called Playstation Pro Extreme.
> >
> > I was mostly joking about that (due to Playstation 3's use
> > of Cell, and people using them for cheap HPC clusters).
> >
> > > Only possible one is amateur rendering videos, but they already have a decent GPU or
> > > two with their rendering software running on it, so they won't pay for a Xeon Phi.
> >
> > Most high-quality rendering for film doesn't use GPU for various reasons (see http://stackoverflow.com/questions/38029698/why-do-we-use-cpus-for-ray-tracing-instead-of-gpus
> >
> > ).
>
> I thought you said amateur video rendering. High end rendering for film is not really what
> I would call mainstream. Actually if you had to put it in a box, it fits HPC better.

In that case, maybe there's a massive number of people who have been doing "one computer only HPC" for years without even realising it.


- Brendan
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TopicPosted ByDate
Intel's Groveport PlatformMS2017/04/11 01:41 PM
  Intel's Groveport PlatformDaveC2017/04/11 05:47 PM
    Intel's Groveport PlatformMichael S2017/04/12 07:14 AM
  Intel's Groveport PlatformBrendan2017/04/12 05:49 AM
    Intel's Groveport PlatformMS2017/04/12 03:23 PM
      Intel's Groveport PlatformBrendan2017/04/12 07:50 PM
        Intel's Groveport PlatformMichael S2017/04/13 10:51 AM
          Intel's Groveport PlatformBrendan2017/04/14 07:40 AM
            Intel's Groveport PlatformMichael S2017/04/14 08:09 AM
              Intel's Groveport PlatformBrendan2017/04/14 12:23 PM
                Intel's Groveport PlatformMichael S2017/04/17 01:43 PM
                  Intel's Groveport PlatformBrendan2017/04/17 03:13 PM
                    Intel's Groveport PlatformMichael S2017/04/17 04:18 PM
                      Intel's Groveport PlatformBrendan2017/04/17 05:35 PM
                        Intel's Groveport Platformanon2017/04/17 06:32 PM
                          Intel's Groveport PlatformBrendan2017/04/17 08:31 PM
                            Intel's Groveport Platformanon2017/04/17 10:39 PM
                              Intel's Groveport PlatformBrendan2017/04/17 11:48 PM
                                Intel's Groveport PlatformMichael S2017/04/18 01:40 AM
                                Intel's Groveport Platformanon2017/04/18 03:32 AM
                                  Intel's Groveport PlatformBrendan2017/04/19 04:43 PM
                                    Intel's Groveport Platformanon2017/04/21 05:10 PM
                                      Intel's Groveport PlatformBrendan2017/04/24 06:21 AM
                                    Intel's Groveport PlatformJukka Larja2017/04/21 11:09 PM
                            Intel's Groveport PlatformMichael S2017/04/18 01:17 AM
                            Intel's Groveport PlatformMichael S2017/04/18 01:29 AM
                        Intel's Groveport PlatformMaynard Handley2017/04/17 09:40 PM
                          Intel's Groveport PlatformBrendan2017/04/17 10:13 PM
                          snowflakesMichael S2017/04/18 01:06 AM
                            snowflakesAaron Spink2017/04/18 07:21 AM
                              strawberries Daniel B2017/04/20 04:31 AM
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