Re: [Discuss-gnuradio] Tesla C2000 series and CUDA and Gnu Radio

[Thomas Hobiger]

Hi Marcus,

Actually we are doing all our processing on the GPU. We use GNURADIO to 
bring in the data and then run everything on the GPU and only copy back 
the results.
As you wrote in your mail CPU-GPU resp. GPU-CPU copies can be 
bottlenecks and should be avoided or reduced whenever possible. With the 
current blocks it only makes sense to utilize the GPU if ALL blocks are 
also available for the GPU. E.g. if you do a cross-correlation (as we 
do) it does not make sense to do the FFTs on the GPU, but do the complex 
multiplication on the CPU as there is a data-transfer GPU-CPU-GPU before 
you can run the IFFTs.
For us the GPU is the device which enables our application to run in 
real-time, which we could hardly achieve with the CPU. But getting the 
GPU into GNURADIO is another story, I guess...

Regards,
  Thomas

On 12/01/2010 03:40 PM, Marcus D. Leech wrote:
> Is anyone out there taking another look at CUDA + Gnu Radio?
>
> Some of the couple-of-years-old charts I've looked at suggest that
> speedups for some of the
>    most important transforms we use vary between modest and disappointing.
>
> Cross-over points for things like FFTs are usually up in the atmospheric
> levels of FFT sizes before
>    a CUDA-based transform would win even slightly against a
> multi-threaded CPU-based FFTW, for
>    example.  But that was a couple of years ago.  Anything new along
> those lines?
>
> It seems like the kinds of things that do well on a GPU are ones that
> take a small amount of input
>    data, compute ferociously, and produce modest amounts of output data.
> Or schemes that might
>    consume deluges of input data, but produce output data only
> occasionally--a flow that did
>    a bunch of FFTs and produced averaged mag-squared outputs only "once
> in a while" might fare
>    well on a GPU.
>
> On a related note, has anyone looked at enabling the multi-threaded FFTW
> stuff?  The cross-over
>    points there (between FFTW in a single-thread and FFTW in
> multiple-threads) seem to be lower-down
>    on the FFT-size curve.
>
>    


--
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Dr. Thomas Hobiger
Space-Time Measurement Project
Space-Time Standards Group
New Generation Network Research Center
National Institute of Information and Communications Technology
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