Sorry for too much speculation, it seems like the problem comes from the
generator, not the OpenCL SDK.
Seems like I'm way too suspicious, sorry :D
The good news is that the converter being done, I can have a better
workflow now. ^^
Best regards,
Philippe
2013/8/20 Karl Rupp <r...@iue.tuwien.ac.at>
> 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
> > >
> > >
> > >
> > >
> >
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> >
> > --
> > -Evan Bollig
> > bol...@gmail.com <mailto:bol...@gmail.com>
> > bol...@scs.fsu.edu <mailto:bol...@scs.fsu.edu>
> >
> >
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