I made a small mistake when creating these "conservative" profiles. GEMV
runs with only one work group. I'll fix this, don't worry :)
2014-07-06 13:31 GMT+02:00 Karl Rupp <r...@iue.tuwien.ac.at>:
> Hey,
>
> > I'm getting on the plane in a couple of hours, so this might be the last
> > you here from me till the middle of the night Europe time.
>
> Have a good flight and enjoy Texas! :-)
>
>
>
> >> > I suggest we start unifying in a couple of days indeed. I still
> have a
> >>> couple of things to merge, essentially having GEMM dynamically
> generated
> >>> for some cases and publishing the repo for auto-tuning using
> pyviennacl.
> >>> These have to be done soon so that Toby can present some good
> benchmarks
> >>> at the talk.
> >
> > I'm currently struggling to get decent performance out of viennacl-dev
> > master, even when not doing GEMM. Consider single-precision dense GEMV
> > using a square matrix and vector with 4096 rows/cols. On the GTX 470 on
> > krupp2, one execution takes ~0.100s; on the C2050, ~0.106s. Execution
> > overhead is about 0.0003s. But NumPy with MKL takes only ~0.004s; I know
> > that krupp2 has an 8(?)-core i7, so (something like) 512 rows/cols per
> > core, but I still didn't expect the gap to be like that. It's strange,
> > because my GeForce 610M takes ~0.090s, and my Intel Ivy Bridge M GT2 GPU
> > takes ~0.001s (at last competitive with MKL, though I'm waiting to test
> > correctness as I write this). And NumPy with OpenBLAS on my i5 takes
> > ~0.009s. Any hints?
>
> So 16M entries with 4 bytes each need to be transferred for the matrix,
> which amounts to 64 MB of data. At an execution time of 0.1 sec, this is
> equivalent to 640 MB/sec of memory bandwidth, which is about a factor of
> 100 off the peak. Way too low. I'll check this today, it can only be a
> tiny detail in the generator integration.
>
>
> >> These are all valid points. What about cropping this 'offset' and use
> >> something like the following:
> >>
> >> namespace viennacl { namespace linalg {
> >>
> >> void some_api_function() { ... }
> >>
> >> namespace detail
> >> {
> >> void some_implementation_detail() { ... }
> >> }
> >>
> >> }}
> >>
> >> This would preserve the benefit of a visual separation of public API and
> >> private implementations, yet remove the 'global' indent offset from the
> >> source file.
> >
> > I like this; and indeed is what I tend to do when indentation gets out
> > of hand.
>
> Thanks for the feedback :-)
>
> Best regards,
> Karli
>
>
>
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Quickly connect people, data, and systems into organized workflows
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http://p.sf.net/sfu/Bonitasoft
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