[petsc-dev] OpenCL platform and device query routines

[Matthew Knepley]

On Fri, Apr 12, 2013 at 4:51 PM, Karl Rupp <rupp at mcs.anl.gov> wrote:

> Dear PETScians,
>
> in order to make proper use of OpenCL functionality, we need some
> diagnostics for the user such that the correct device is used. Such
> functionality is partly also desired for CUDA, but less urgent (only
> addresses NVIDIA GPUs anyway).
>
> OpenCL defines platforms (think of it as SDKs from the various vendors)
> and devices with one type out of {CPU, GPU, ACCELERATOR}. Each platform may
> support multiple devices, but not necessarily all OpenCL-enabled devices on
> the machine. For example, the AMD SDK (platform) does not provide support
> for NVIDIA GPUs, but it supports Intel CPUs (x86 ftw!). Since multiple SDKs
> can be installed in parallel, information on the proper enumeration is
> quite important to use the correct device.
>
> Example: A machine equipped with an Intel CPU and an NVIDIA GPU with
> OpenCL SDKs from Intel, AMD, and NVIDIA installed. Within OpenCL one will
> 'see' the following:
>
> - Platform 0:
>   - Vendor: Intel
>   - Device 0: Intel i7 whatever (CPU)
>
> - Platform 1:
>   - Vendor: AMD
>   - Device 0: Intel i7 whatever (CPU)
>
> - Platform 2:
>   - Vendor NVIDIA
>   - Device 0: NVIDIA GTX whatever (GPU)
>
> (Maybe in different order. Matters can get worse with Xeon Phi, AMD APUs,
> etc.)
>
> To provide the necessary diagnostics, I suggest in line with -vec_view the
> flag
>   -opencl_view
> to print the OpenCL infrastructure available on the system.
> Is there any better naming scheme/proposal? -cuda_view and maybe some time
> later -threadcomm_view (-numa_view?) would follow from this choice. Note
> that this should be independent of external linear algebra libraries such
> as CUSP, ViennaCL, etc. to avoid unnecessary code duplication. However, the
> actual platform/device *setter* flags (e.g. pick device 0 from platform 1)
> need to be package-specific.
>

Do we want to have a concept, of which opencl, cuda, and threadcomm are
instantiations? -device_opencl_view?

   Matt


> Best regards,
> Karli
>



-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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