Best case for GPUs

Article: Computational Efficiency for CPUs and GPUs in 2012
By: Chuck (dont.delete@this.thanks.com), July 25, 2012 8:13 pm
Room: Moderated Discussions
David Kanter (dkanter.delete@this.realworldtech.com) on July 25, 2012 11:28 am wrote:
> someone (someone.delete@this.somewhere.com) on July 25, 2012 9:58 am
> wrote:
> > David Kanter (dkanter.delete@this.realworldtech.com) on July 25,
> 2012 1:37 am
> > wrote:
> > > New computational efficiency data shows
> GPUs with a clear edge over
> > CPUs, but
> > > the gap is narrowing as
> CPUs adopt wide vectors (e.g. AVX).
> > Surprisingly, a
> > >
> throughput CPU is the most energy efficient processor,
> > offering hope for
> future
> > > architectures. Our data also shows some
> > advantages of
> AMD's Bulldozer, and the
> > > overhead associated with highly
> >
> scalable server CPUs.
> > >
> > > Comments and feedback
> > >
> welcome!
> > >
> >
> > > David
> >
> > Calling FLOPS/W and
> FLOPs/mm2 efficiency is highly misleading
> > because it has no
> > concept
> of effective FLOPs while doing something useful. The
> > FP functional
> units
> > of a general purpose MPU is a tiny fraction of device area
> >
> and power budget. Why?
>
> That's right, no cache, no branch prediction, no
> bypassing, no store forwarding, etc.
>
> There's a reason why I focus on compute
> efficiency, as opposed to performance efficiency. Compute != performance.
>
>
> > Everything else there SUPPORTS feeding those units
> > over a huge
> spectrum of usage
> > in terms of data access and control complexity
> >
> without demanding quite unreasonable
> > effort and methods for programming.
> GPUs
> > have less silicon overhead per FP unit
> > because they are very
> less generally
> > useful. For HPC algorithms with complex data
> > access
> and control paths GPUs are
> > hugely inefficient and can only approach a
> tiny
> > fraction of their theoretical
> > peak FLOPs. Why hasn't anyone
> run published a SPECfp
> > score running entirely on
> > a GPU yet?
> :-D
>
> I totally agree. The easiest way to see that is to compare the cache for
> say, IVB (2MB/core) vs. Fermi (guessing ~64KB/core).
>
> > In a modern
> process I could tile a 200 mm2 die with nothing
> > but FMACs and clock
> >
> and power distribution and blow away everything on your
> > graph but it
> would not be
> > capable of anything useful. But hey, what
> > "efficiency"
> woot!
>
> I agree (see Tilera!). However, if you want to talk about realizable
> FP performance, now you need to pick a workload.
>
> What workload should we
> use?
>
> What meaningful workload has been run (and reported) on all of those
> systems?
>
> The closest is Linpack, but that hasn't been run on the T4 for
> obvious reasons.
>
> No, what this chart measures is the *BEST CASE* for a GPU
> (i.e. something akin to Linpack). Any real workload will change the positions
> substantially and more complex ones will show that GPUs are less
> efficient.
>
> David


I think what Paul is getting at is that you're presenting a limited and artificial characterization of efficiency of modern chips intended for high FP loads.

For example you repeatedly castigate Wilco for bringing up Dhrystone and CoreMark in defense of ARM processors, as being unrepresentative. Yet here you're essentially presenting efficiency data for computational kernels, not real world parallel FP applications.

An uncharitable person would call you a hypocrite. You are a hypocrite.

If you don't like SPECfp_rate then at least man up, get some Nvidia, Intel, and AMD/ATI chips and benchmark them with either SPLASH-2 (old), SPEChpc2002, or (preferably) PARSEC.

Be a man.
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TopicPosted ByDate
New Article: Compute Efficiency 2012David Kanter2012/07/25 01:37 AM
  New Article: Compute Efficiency 2012SHK2012/07/25 02:31 AM
    New Article: Compute Efficiency 2012David Kanter2012/07/25 02:42 AM
  New Article: Compute Efficiency 2012none2012/07/25 03:18 AM
    New Article: Compute Efficiency 2012David Kanter2012/07/25 11:25 AM
  GCN (NT)EBFE2012/07/25 03:25 AM
    GCN - TFLOP DPjp2012/08/09 01:58 PM
      GCN - TFLOP DPDavid Kanter2012/08/09 03:32 PM
        GCN - TFLOP DPKevin G2012/08/11 05:22 PM
      GCN - TFLOP DPEric2012/08/09 05:12 PM
        GCN - TFLOP DPjp2012/08/10 01:23 AM
          GCN - TFLOP DPEBFE2012/08/12 08:27 PM
            GCN - TFLOP DPjp2012/08/13 02:02 AM
              GCN - TFLOP DPEBFE2012/08/13 07:45 PM
                GCN - TFLOP DPjp2012/08/14 01:21 AM
  New Article: Compute Efficiency 2012Adrian2012/07/25 04:39 AM
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    New Article: Compute Efficiency 2012David Kanter2012/07/25 11:11 AM
  New Article: Compute Efficiency 2012sf2012/07/25 06:46 AM
    New Article: Compute Efficiency 2012aaron spink2012/07/25 09:08 AM
      New Article: Compute Efficiency 2012someone2012/07/25 10:06 AM
    New Article: Compute Efficiency 2012David Kanter2012/07/25 11:14 AM
      New Article: Compute Efficiency 2012EBFE2012/07/26 02:27 AM
        BG/QDavid Kanter2012/07/26 09:31 AM
          VR-ZONE KNC B0 leak, poor number?EBFE2012/08/03 01:57 AM
            VR-ZONE KNC B0 leak, poor number?Eric2012/08/03 07:59 AM
              VR-ZONE KNC B0 leak, poor number?EBFE2012/08/04 06:37 AM
                VR-ZONE KNC B0 leak, poor number?aaron spink2012/08/04 06:51 PM
                Leaks != productsDavid Kanter2012/08/05 03:19 AM
                  Leaks != productsEBFE2012/08/06 02:49 AM
                VR-ZONE KNC B0 leak, poor number?Eric2012/08/05 10:37 AM
                  VR-ZONE KNC B0 leak, poor number?EBFE2012/08/06 03:09 AM
                    VR-ZONE KNC B0 leak, poor number?aaron spink2012/08/06 04:33 AM
                      VR-ZONE KNC B0 leak, poor number?jp2012/08/07 03:08 AM
                        VR-ZONE KNC B0 leak, poor number?Eric2012/08/07 04:58 AM
                          VR-ZONE KNC B0 leak, poor number?jp2012/08/07 05:17 AM
                            VR-ZONE KNC B0 leak, poor number?Eric2012/08/07 05:22 AM
                              VR-ZONE KNC B0 leak, poor number?anonymou52012/08/07 09:43 AM
                            VR-ZONE KNC B0 leak, poor number?jp2012/08/07 05:23 AM
                              VR-ZONE KNC B0 leak, poor number?aaron spink2012/08/07 07:24 AM
                        VR-ZONE KNC B0 leak, poor number?aaron spink2012/08/07 07:20 AM
                          VR-ZONE KNC B0 leak, poor number?jp2012/08/07 11:22 AM
                            VR-ZONE KNC B0 leak, poor number?EduardoS2012/08/07 03:15 PM
                        KNC has FMADavid Kanter2012/08/07 09:17 AM
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        New Article: Compute Efficiency 2012Eric2012/07/27 12:51 PM
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            New Article: Compute Efficiency 2012Eric2012/07/27 03:29 PM
        New Article: Compute Efficiency 2012anon2012/07/29 02:25 AM
          New Article: Compute Efficiency 2012hobold2012/07/29 11:53 AM
  Efficiency? No, lack of highly useful featuressomeone2012/07/25 09:58 AM
    Best case for GPUsDavid Kanter2012/07/25 11:28 AM
      Best case for GPUsfranzliszt2012/07/25 01:39 PM
      Best case for GPUsChuck2012/07/25 08:13 PM
        Best case for GPUsDavid Kanter2012/07/25 09:45 PM
        Best case for GPUsEric2012/07/27 05:51 AM
  Silverthorn data pointMichael S2012/07/25 02:45 PM
    Silverthorn data pointDavid Kanter2012/07/25 04:06 PM
  New Article: Compute Efficiency 2012Unununium2012/07/25 05:55 PM
    New Article: Compute Efficiency 2012EduardoS2012/07/25 08:12 PM
      Ops... I'm wrong...EduardoS2012/07/25 08:14 PM
  New Article: Compute Efficiency 2012TacoBell2012/07/25 08:36 PM
    New Article: Compute Efficiency 2012David Kanter2012/07/25 09:49 PM
    New Article: Compute Efficiency 2012Michael S2012/07/26 02:33 AM
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    Line and factorPeter Boyle2012/07/27 07:57 AM
      not entirelyMoritz2012/07/27 12:22 PM
      Line and factorEduardoS2012/07/27 05:24 PM
        Line and factorMoritz2012/07/28 12:52 PM
  tables Michael S2012/07/26 02:39 AM
  Interlagos L2+L3Rana2012/07/26 03:13 AM
    Interlagos L2+L3Rana2012/07/26 03:13 AM
    Interlagos L2+L3David Kanter2012/07/26 09:21 AM
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        SP vs DP & performance metricsEric2012/07/27 07:57 AM
          SP vs DP & performance metricsjp2012/07/27 09:18 AM
            SP vs DP & performance metricsaaron spink2012/07/27 09:36 AM
              SP vs DP & performance metricsjp2012/07/27 09:47 AM
                "Global" --> systemPaul A. Clayton2012/07/27 10:31 AM
                  "Global" --> systemjp2012/07/27 03:55 PM
                    "Global" --> systemaaron spink2012/07/27 07:33 PM
                      "Global" --> systemjp2012/07/28 02:00 AM
                        "Global" --> systemaaron spink2012/07/28 06:54 AM
                          "Global" --> systemjp2012/07/29 02:12 AM
                            "Global" --> systemaaron spink2012/07/29 05:03 AM
                              "Global" --> systemnone2012/07/29 09:05 AM
                                "Global" --> systemEduardoS2012/07/29 10:26 AM
                                "Global" --> systemjp2012/07/30 02:24 AM
                                  "Global" --> systemaaron spink2012/07/30 03:05 AM
                                "Global" --> systemaaron spink2012/07/30 03:03 AM
                                  daxpy is STREAM TRIADPaul A. Clayton2012/07/30 06:10 AM
                SP vs DP & performance metricsaaron spink2012/07/27 07:25 PM
                  SP vs DP & performance metricsEmil Briggs2012/07/28 06:40 AM
                    SP vs DP & performance metricsaaron spink2012/07/28 07:05 AM
                      SP vs DP & performance metricsjp2012/07/28 11:04 AM
                        SP vs DP & performance metricsBrett2012/07/28 03:32 PM
                      SP vs DP & performance metricsEmil Briggs2012/07/28 06:11 PM
                        SP vs DP & performance metricsanon2012/07/29 02:53 AM
                        SP vs DP & performance metricsaaron spink2012/07/29 05:39 AM
                          Coherency for discretesRohit2012/07/29 09:24 AM
                          SP vs DP & performance metricsanon2012/07/29 11:09 AM
                          SP vs DP & performance metricsEric2012/07/29 01:08 PM
        SP vs DP & performance metricsaaron spink2012/07/27 09:25 AM
  Regular updates?Joe2012/07/27 09:35 AM
  New Article: Compute Efficiency 20123092012/07/27 10:34 PM
  New Article: Compute Efficiency 2012Ingeneer2012/07/30 09:01 AM
    New Article: Compute Efficiency 2012David Kanter2012/07/30 01:11 PM
      New Article: Compute Efficiency 2012Ingeneer2012/07/30 08:04 PM
        New Article: Compute Efficiency 2012David Kanter2012/07/30 09:32 PM
          Memory power and bandwidth?Iain McClatchie2012/08/03 04:35 PM
            Memory power and bandwidth?David Kanter2012/08/04 11:22 AM
              Memory power and bandwidth?Michael S2012/08/04 02:36 PM
              Memory power and bandwidth?Iain McClatchie2012/08/06 02:09 PM
              Memory power and bandwidth?Eric2012/08/07 06:28 PM
                WorkloadsDavid Kanter2012/08/08 10:49 AM
                  WorkloadsEric2012/08/09 05:21 PM
                Latency and bandwidth bottlenecks Paul A. Clayton2012/08/08 04:02 PM
                  Latency and bandwidth bottlenecks Eric2012/08/09 05:32 PM
                    Latency and bandwidth bottlenecks none2012/08/10 06:06 AM
                  Latency and bandwidth bottlenecks -> BDPajensen2012/08/11 03:21 PM
            Memory power and bandwidth?Ingeneer2012/08/06 11:26 AM
  NV aims for 1.8+ TFLOPS DP ?jp2012/08/11 01:21 PM
    NV aims for 1.8+ TFLOPS DP ?David Kanter2012/08/11 09:25 PM
      NV aims for 1.8+ TFLOPS DP ?jp2012/08/12 02:45 AM
      NV aims for 1.8+ TFLOPS DP ?EBFE2012/08/12 10:02 PM
        NV aims for 1.8+ TFLOPS DP ?jp2012/08/13 01:54 AM
          NV aims for 1.8+ TFLOPS DP ?Gabriele Svelto2012/08/13 09:16 AM
            NV aims for 1.8+ TFLOPS DP ?Vincent Diepeveen2012/08/14 03:04 AM
          NV aims for 1.8+ TFLOPS DP ?David Kanter2012/08/13 09:50 AM
            NV aims for 1.8+ TFLOPS DP ?jp2012/08/13 11:17 AM
        NV aims for 1.8+ TFLOPS DP ?EduardoS2012/08/13 06:45 AM
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