150 GFLOP/s measured?

Article: PhysX87: Software Deficiency
By: anon (anon.delete@this.anon.com), July 19, 2010 6:39 am
Room: Moderated Discussions
Ian Ollmann (iano@apple.com) on 7/19/10 wrote:
---------------------------
>David Kanter (dkanter@realworldtech.com) on 7/9/10 wrote:
>---------------------------
>>Aaron Spink (aaronspink@notearthlink.net) on 7/8/10 wrote:
>>---------------------------
>>>anon (anon@anon.anon) on 7/8/10 wrote:
>>>---------------------------
>>>>so how do you get the level of efficiency? sse4 (?) and lots of hand-tuned code?
>>>>
>>>good compilers, good libraries, easy to optimize target >architecture. ICC, MKL/IPP/TBB, x86.
>>
>>It's also about having a microarchitecture that specifically invests a lot of area/power
>>into techniques that improve utilization. Out-of-order execution comes to mind
>>here, and techniques like branch prediction, etc. that let a CPU execute latency
>>bound code (e.g. things that are not totally parallel) with good performance.
>
>I personally find the OoO engine to be a bit of a hinderance to performance. Its
>great for the massively overwhelming amount of code out there written with a C/C++
>compiler with not too much thought to performance. (read: 99.99%+ of code) There,
>you might get 10% of peak instead of 3% of peak. However, when you are trying to
>get the last drop out of the architecture and are willing to go to assembly, something
>with a simpler execution engine, typically an in order machine with non-destructive
>ISA, is far easier to take to close to peak performance. In my experience, the
>OoO engine starts to trip over itself somewhere in the 50-80% peak performance range,
>and you start having to do a lot of "nonsense" optimizations (that might work only
>in your benchmark app on that particular core with that cache config and that code
>alignment on the page, etc) to get over that. These things usually break in the
>next gen, so often aren't worth it, unless you have a lot of time and money on your hands.

I don't see how an OOOE engine can possibly "trip over itself" simply due to being OOOE. Most heuristics or things that can go wrong such as caches, prefetching, and branch prediction are equally applicable and desirable on any performance oriented in-order architecture too.

Are you worried that it may have the ability to follow further down speculative branch chains, increasing the likeliness it will do incorrect speculative calculations and memory loads?

Profiling can be a lot harder because you can see cycles accumulate where the engine runs out of work to do rather than where it caused the longest latency event, and at mispredicts. Haven't profiled on in-order architectures for a long time, but IIRC non blocking caches and branch prediction gives similar problems.
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TopicPosted ByDate
A bit off baseJohn Mann2010/07/07 07:04 AM
  A bit off baseDavid Kanter2010/07/07 11:28 AM
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      SSE vs x87Michael S2010/07/07 01:07 PM
        SSE vs x87hobold2010/07/08 05:12 AM
      SSE vs x87David Kanter2010/07/07 02:55 PM
        SSE vs x87Andi Kleen2010/07/08 02:43 AM
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            80 bit FPDavid Kanter2010/07/08 11:14 AM
              80 bit FPKevin G2010/07/08 02:12 PM
                80 bit FPIan Ollmann2010/07/19 12:49 AM
                  80 bit FPDavid Kanter2010/07/19 11:33 AM
                    80 bit FPAnil Maliyekkel2010/07/19 04:49 PM
                      80 bit FPrwessel2010/07/19 05:41 PM
                    80 bit FPMatt Waldhauer2010/07/21 11:11 AM
            80 bit FPEmil Briggs2010/07/22 09:06 AM
    A bit off baseJohn Mann2010/07/08 11:06 AM
      A bit off baseDavid Kanter2010/07/08 11:27 AM
        A bit off baseIan Ameline2010/07/09 10:10 AM
          A bit off baseMichael S2010/07/10 02:13 PM
            A bit off baseIan Ameline2010/07/11 07:51 AM
  A bit off baseDavid Kanter2010/07/07 09:46 PM
    A bit off baseAnon2010/07/08 12:47 AM
      A bit off baseanon2010/07/08 02:15 AM
        A bit off baseGabriele Svelto2010/07/08 04:11 AM
          Physics engine historyPeter Clare2010/07/08 04:49 AM
            Physics engine historyNull Pointer Exception2010/07/08 06:07 AM
              Physics engine historyRalf2010/07/08 03:09 PM
                Physics engine historyDavid Kanter2010/07/08 04:16 PM
                  Physics engine historysJ2010/07/08 11:36 PM
                    Physics engine historyGabriele Svelto2010/07/09 12:59 AM
                      Physics engine historysJ2010/07/13 06:35 AM
                    Physics engine historyDavid Kanter2010/07/09 09:25 AM
                      Physics engine historysJ2010/07/13 06:49 AM
                      Physics engine historyfvdbergh2010/07/13 07:27 AM
    A bit off baseJohn Mann2010/07/08 11:11 AM
      A bit off baseDavid Kanter2010/07/08 11:31 AM
        150 GFLOP/s measured?anon2010/07/08 07:10 PM
          150 GFLOP/s measured?David Kanter2010/07/08 07:53 PM
            150 GFLOP/s measured?Aaron Spink2010/07/08 09:05 PM
              150 GFLOP/s measured?anon2010/07/08 09:31 PM
                150 GFLOP/s measured?Aaron Spink2010/07/08 10:43 PM
                  150 GFLOP/s measured?David Kanter2010/07/08 11:27 PM
                    150 GFLOP/s measured?Ian Ollmann2010/07/19 01:14 AM
                      150 GFLOP/s measured?anon2010/07/19 06:39 AM
                        150 GFLOP/s measured?hobold2010/07/19 07:26 AM
                          Philosophy for achieving peakDavid Kanter2010/07/19 11:49 AM
                      150 GFLOP/s measured?Linus Torvalds2010/07/19 07:36 AM
                        150 GFLOP/s measured?Richard Cownie2010/07/19 08:42 AM
                          150 GFLOP/s measured?Aaron Spink2010/07/19 08:56 AM
                            150 GFLOP/s measured?hobold2010/07/19 09:30 AM
                              150 GFLOP/s measured?Groo2010/07/19 02:31 PM
                                150 GFLOP/s measured?hobold2010/07/19 04:17 PM
                                  150 GFLOP/s measured?Groo2010/07/19 06:18 PM
                              150 GFLOP/s measured?Anon2010/07/19 06:18 PM
                            150 GFLOP/s measured?Mark Roulo2010/07/19 11:47 AM
                              150 GFLOP/s measured?slacker2010/07/19 12:55 PM
                                150 GFLOP/s measured?Mark Roulo2010/07/19 01:00 PM
                              150 GFLOP/s measured?anonymous422010/07/25 12:31 PM
                            150 GFLOP/s measured?Richard Cownie2010/07/19 12:41 PM
                              150 GFLOP/s measured?Linus Torvalds2010/07/19 02:57 PM
                                150 GFLOP/s measured?Richard Cownie2010/07/19 04:10 PM
                                150 GFLOP/s measured?Richard Cownie2010/07/19 04:10 PM
                                  150 GFLOP/s measured?hobold2010/07/19 04:25 PM
                                  150 GFLOP/s measured?Linus Torvalds2010/07/19 04:31 PM
                                    150 GFLOP/s measured?Richard Cownie2010/07/20 06:04 AM
                                150 GFLOP/s measured?jrl2010/07/20 01:18 AM
                            150 GFLOP/s measured?anonymous422010/07/25 12:00 PM
                              150 GFLOP/s measured?David Kanter2010/07/25 12:52 PM
                          150 GFLOP/s measured?Anon2010/07/19 06:15 PM
                            150 GFLOP/s measured?Linus Torvalds2010/07/19 07:27 PM
                              150 GFLOP/s measured?Anon2010/07/19 09:54 PM
                                150 GFLOP/s measured?anon2010/07/19 11:45 PM
                        150 GFLOP/s measured?hobold2010/07/19 09:14 AM
                          150 GFLOP/s measured?Linus Torvalds2010/07/19 11:56 AM
                            150 GFLOP/s measured?a reader2010/07/21 08:16 PM
                              150 GFLOP/s measured?Linus Torvalds2010/07/21 09:05 PM
                                150 GFLOP/s measured?anon2010/07/22 02:09 AM
                                  150 GFLOP/s measured?a reader2010/07/22 07:53 PM
                                    150 GFLOP/s measured?gallier22010/07/23 05:58 AM
                                      150 GFLOP/s measured?a reader2010/07/25 08:35 AM
                                        150 GFLOP/s measured?David Kanter2010/07/25 11:49 AM
                                          150 GFLOP/s measured?a reader2010/07/26 07:03 PM
                                            150 GFLOP/s measured?Michael S2010/07/28 01:38 AM
                                              150 GFLOP/s measured?Gabriele Svelto2010/07/28 01:44 AM
                                    150 GFLOP/s measured?anon2010/07/23 04:55 PM
                                      150 GFLOP/s measured?slacker2010/07/24 12:48 AM
                                        150 GFLOP/s measured?anon2010/07/24 02:36 AM
                                    150 GFLOP/s measured?Vincent Diepeveen2010/07/27 05:37 PM
                                      150 GFLOP/s measured??2010/07/27 11:42 PM
                                        150 GFLOP/s measured?slacker2010/07/28 05:55 AM
                                      Intel's clock rate projectionsAM2010/07/28 02:03 AM
                                        nostalgia ain't what it used to besomeone2010/07/28 05:38 AM
                                          Intel's clock rate projectionsAM2010/07/28 10:12 PM
                        Separate the OoO-ness from speculative-ness?2010/07/20 07:19 AM
                          Separate the OoO-ness from speculative-nessMark Christiansen2010/07/20 02:26 PM
                          Separate the OoO-ness from speculative-nessslacker2010/07/20 06:04 PM
                            Separate the OoO-ness from speculative-nessMatt Sayler2010/07/20 06:10 PM
                              Separate the OoO-ness from speculative-nessslacker2010/07/20 09:37 PM
                                Separate the OoO-ness from speculative-ness?2010/07/20 11:51 PM
                                  Separate the OoO-ness from speculative-nessanon2010/07/21 02:16 AM
                                    Separate the OoO-ness from speculative-ness?2010/07/21 07:05 AM
                                      Software conventionsPaul A. Clayton2010/07/21 08:52 AM
                                        Software conventions?2010/07/22 05:43 AM
                                      SpeculationDavid Kanter2010/07/21 10:32 AM
                                        Pipelining affects the ISA?2010/07/22 10:58 PM
                                          Pipelining affects the ISA?2010/07/22 11:14 PM
                                          Pipelining affects the ISArwessel2010/07/23 12:03 AM
                                            Pipelining affects the ISA?2010/07/23 05:50 AM
                                            Pipelining affects the ISA?2010/07/23 06:10 AM
                                              Pipelining affects the ISAThiago Kurovski2010/07/23 02:59 PM
                                                Pipelining affects the ISAanon2010/07/24 07:35 AM
                                                  Pipelining affects the ISAThiago Kurovski2010/07/24 11:12 AM
                                          Pipelining affects the ISAGabriele Svelto2010/07/26 02:50 AM
                                            Pipelining affects the ISAIlleglWpns2010/07/26 05:14 AM
                                              Pipelining affects the ISAMichael S2010/07/26 03:33 PM
                                      Separate the OoO-ness from speculative-nessanon2010/07/21 05:53 PM
                                        Separate the OoO-ness from speculative-ness?2010/07/22 04:15 AM
                                          Separate the OoO-ness from speculative-nessanon2010/07/22 04:27 AM
                                      Separate the OoO-ness from speculative-nessslacker2010/07/21 07:45 PM
                                        Separate the OoO-ness from speculative-nessanon2010/07/22 01:57 AM
                                        Separate the OoO-ness from speculative-ness?2010/07/22 05:26 AM
                                          Separate the OoO-ness from speculative-nessDan Downs2010/07/22 08:14 AM
                                          Confusing and not very useful definitionDavid Kanter2010/07/22 12:41 PM
                                            Confusing and not very useful definition?2010/07/22 10:58 PM
                                              Confusing and not very useful definitionUngo2010/07/24 12:06 PM
                                                Confusing and not very useful definition?2010/07/25 10:23 PM
                            Separate the OoO-ness from speculative-nesssomeone2010/07/20 08:02 PM
                              Separate the OoO-ness from speculative-nessThiago Kurovski2010/07/21 04:13 PM
            You are just quoting SINGLE precision flops? OMG what planet do you live? Vincent Diepeveen2010/07/19 10:26 AM
              The prior poster was talking about SP (NT)David Kanter2010/07/19 11:34 AM
                All FFT's need double precisionVincent Diepeveen2010/07/19 02:02 PM
                  All FFT's need double precisionDavid Kanter2010/07/19 02:09 PM
                    All FFT's need double precisionVincent Diepeveen2010/07/19 04:06 PM
                  All FFT's need double precision - notMichael S2010/07/20 01:16 AM
                    All FFT's need double precision - notUngo2010/07/21 12:04 AM
                      All FFT's need double precision - notMichael S2010/07/21 02:35 PM
                      All FFT's need double precision - notEduardoS2010/07/21 02:52 PM
                        All FFT's need double precision - notAnon2010/07/21 05:23 PM
                          All FFT's need double precision - notRicardo B2010/07/26 07:46 AM
                        I'm on a boat!anon2010/07/22 11:42 AM
                        All FFT's need double precision - notVincent Diepeveen2010/07/24 11:39 PM
                          All FFT's need double precision - notslacker2010/07/25 03:27 AM
                            All FFT's need double precision - notRicardo B2010/07/26 07:40 AM
                          All FFT's need double precision - notEduardoS2010/07/25 08:37 AM
                            All FFT's need double precision - notMichael S2010/07/25 10:43 AM
                    All FFT's need double precision - notVincent Diepeveen2010/07/24 11:19 PM
      A bit off baseEduardoS2010/07/08 04:08 PM
        A bit off baseGroo2010/07/08 06:11 PM
          A bit off basejohn mann2010/07/08 06:58 PM
            All right...let's cool it...David Kanter2010/07/08 07:54 PM
    A bit off baseVincent Diepeveen2010/07/19 03:36 PM
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