[GRASS-dev] --with-opencl without a GPU

Maciej Sieczka msieczka at sieczka.org
Wed Jun 26 09:08:04 PDT 2013

I forgot to mention I'm asking this in the context of an Arch G7 
PKGBUILD script I maintain on AUR.

W dniu 26.06.2013 02:24, Hamish pisze:
> Maciek wrote:

>> If I wanted to build G7 --with-opencl on a machine with a
>> non-Intel/nVidia/AMD GPU would everything still build and work fine?

> What other manufacturer(s) of GPUs are still in business?

Those 3 rule at the moment, true. Still, e.g. S3 was around till 2010 or 
so, and there is older hardware still in use around for sure. Trying to 
think future-proof, too - maybe some new players will come.

> The short answer is yes, as long as they provide a libOpenCL.so library
> and C header files to go along with it.

As I can't be sure this would always be the case, I guess I shouldn't 
enable --with-opencl by default.

>> I only have Intel/nVidia machines so can't check this myself reliably I guess.
> note that the intel i7 Ivy Bridge HD4000 driver only supplies OpenCL
> multi-CPU core support for Linux. The same chip has a GPU driver for
> MS Windows and I think Mac OSX. On Linux + Intel graphics you need
> a Xeon chip for driver GPU support currently.
> nVidia have shipped OpenCL support standard with their proprietary
> Linux driver for a while now, although they advertise more about the
> CUDA side of things.
>> Would r.sun utilize more than 1 CPU (I mean once the GSoC OpenCL r.sun
>> stuff is merged into to G7 trunk) on such a machine?
> I hope so, for Linux Ivy Bridge chips that's all you'd be able to get,
> but running multi-core GPCPU is still a time win. I'm not sure if OpenCL
> lets you do GPU+CPU or you have to choose one or the other, or if it
> can do both at the same time if the CPU memory array size gets limited
> by the GPU memory limit.
>> Are the dependencies only the OpenCL headers and the libcl or something
>> more?
> I think that's it, but I'm still learning.

Thanks for sharing this. Unless anyone has more input I'll try to put 
this information together on the GRASS WiKi in the coming days.


Maciej Sieczka

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