[Bf-cycles] Apple OpenCL and Cycles

Brecht Van Lommel brechtvanlommel at pandora.be
Mon Dec 17 15:35:15 CET 2012


I believe the main problem with AMD is a hardware limitation that we
are running into, so using the Apple compiler would not help solving
that particular problem. But I can't be sure, the compiler is not
outputting particularly useful information when it fails. Also note
that the OpenCL kernel currently has many features disabled, they can
be enabled in kernel_types.h.

I don't think anyone is looking into OpenCL on Apple at the moment. I
didn't test the latest compiler, but my experience has been that
OpenCL on the CPU is not a problem, it's when compiling for the GPU
that the problems start. Regarding performance it's probably not going
to be great if you get it working, each graphics card tends to have
some specific things that need to be optimized, so it wouldn't be
possible to make a judgement on that immediately.


On Mon, Dec 17, 2012 at 1:57 PM, Marcio Andrade <migueletto at yahoo.com> wrote:
> Hello,
> I read that OpenCL development on Cycles is on hold, mainly because of compiler/driver problems in the AMD SDK. I have been doing some experiments with OpenCL on a Mac, and so far I did not encounter thouse kind of problems. After making some small changes to the kernel (basically enabling some defines that were commented out in kernel_types.h and fixing one compile error), I gave it a try.
> Compilation is fast and does not give memory errors. On my system the kernel is compiled in under 5 seconds. My Mac has a Intel HD 3000 GPU, which does not support OpenCL, so in order to make these tests I enabled OpenCL on the CPU (a small change to device_opencl.cpp). When I run the kernel in Blender, rendering time is close to the normal render using CPU, which is expected, since OpenCL Kernel on CPU should be close to the C++ Kernel on CPU.
> Apple is the original author of OpenCL, and OpenCL support on Macs seems to be pretty decent (no need to install anything, it is already bundled). So, is there anyone else trying Cycles/OpenCL on Apple hardware ? I would like to know how OpenCL performs on a Mac with a true GPU, to see if its worth pursuing this direction.
> Regards,
> migueletto
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