Hi Philippe, rather than having too much speculation here, what about adding a quick OpenCL-to-CUDA translator (just string substitution, you don't need more) to the generator? Put the best kernels for Fermi and Kepler into a compilation unit and then hopefully Denis or Evan will give it a try? You can verify the proper execution on our GTX 470 machine.
Best regards, Karli On 08/20/2013 10:30 AM, Philippe Tillet wrote: > Yes, it is :) > The generator can find a kernel at 630GFLOP/s for the GTX470, and it > cannot find a kernel at more than 550GFLOP/s for the GTX680, which means > that the best Fermi Kernel performs very poorly on the Kepler > architecture, while NVidia claim themself the architecture is similar, > and that kernels should show improved performance without any code > modification... > Now, it may come from Apple's implementation, but I'm doubtful here. > Since NVidia has releasing any OpenCL-related stuff since 2010 (OpenCL > 1.1), even dropping OpenCL tools in CUDA5, it would not surprising that > they just ensure correctness since then, leading to poor performance on > post 2010 GPUs (ie Kepler)... > > Philippe > > > 2013/8/20 Evan Bollig <bol...@gmail.com <mailto:bol...@gmail.com>> > > You suspect NVidia is throttling CL kernels? > > -E > > On Tue, Aug 20, 2013 at 10:10 AM, Philippe Tillet > <phil.til...@gmail.com <mailto:phil.til...@gmail.com>> wrote: > > Hi again, > > > > Actually, I think that it would be worth it to convert the best > GEMM kernel > > from OpenCL to CUDA, and to observe whether the performance is > still bad or > > not. It may be even worth it to also do this with the best Kepler > kernel > > (pretty different from the best Fermi kernel!). > > > > Best regards, > > Philippe > > > > > > 2013/8/20 Philippe Tillet <phil.til...@gmail.com > <mailto:phil.til...@gmail.com>> > >> > >> Hi everybody, > >> > >> Thanks to Evan and Denis, I can confirm that our GEMM kernels > exhibit bad > >> performance on Kepler (~25% of the peak for both the GTX680mx > and the Tesla > >> K20) > >> What is weird here is that Magma's Fermi kernel seems to work > well enough > >> on Kepler, while our Fermi GEMM kernel clearly doesn't work well on > >> Kepler... which doesn't make sense to me. > >> > >> Has anybody ever heard of a good OpenCL kernel for the Kepler > architecture > >> ? > >> I'm aware of what big companies may want to do to promote their own > >> solution, and I want to consider every option, especially since > the Kepler > >> was released at the time OpenCL 1.2 - which is still not > supported by NVidia > >> - came out. > >> I have some links to support my paranoia: > >> http://parallelis.com/kepler-underperform-on-gpgpu-gtx680/ > >> > >> > > http://www.tonymacx86.com/343-os-x-10-8-3-nvidia-6xx-opencl-benchmarks.html > >> > >> Best regards, > >> Philippe > > > > > > > > > > ------------------------------------------------------------------------------ > > Introducing Performance Central, a new site from SourceForge and > > AppDynamics. Performance Central is your source for news, insights, > > analysis and resources for efficient Application Performance > Management. > > Visit us today! > > > > http://pubads.g.doubleclick.net/gampad/clk?id=48897511&iu=/4140/ostg.clktrk > > _______________________________________________ > > ViennaCL-devel mailing list > > ViennaCL-devel@lists.sourceforge.net > <mailto:ViennaCL-devel@lists.sourceforge.net> > > https://lists.sourceforge.net/lists/listinfo/viennacl-devel > > > > > > -- > -Evan Bollig > bol...@gmail.com <mailto:bol...@gmail.com> > bol...@scs.fsu.edu <mailto:bol...@scs.fsu.edu> > > > > > ------------------------------------------------------------------------------ > Introducing Performance Central, a new site from SourceForge and > AppDynamics. Performance Central is your source for news, insights, > analysis and resources for efficient Application Performance Management. > Visit us today! > http://pubads.g.doubleclick.net/gampad/clk?id=48897511&iu=/4140/ostg.clktrk > > > > _______________________________________________ > ViennaCL-devel mailing list > ViennaCL-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/viennacl-devel > ------------------------------------------------------------------------------ Introducing Performance Central, a new site from SourceForge and AppDynamics. Performance Central is your source for news, insights, analysis and resources for efficient Application Performance Management. Visit us today! http://pubads.g.doubleclick.net/gampad/clk?id=48897511&iu=/4140/ostg.clktrk _______________________________________________ ViennaCL-devel mailing list ViennaCL-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/viennacl-devel
