[Bf-cycles] Non-Progressive integrator on GPU

Thomas Dinges blender at dingto.org
Sun May 19 15:10:36 CEST 2013

Hi Brecht,
thank you for the memmove alternative, works fine. :)

I agree with you that this is nothing for Trunk, we can re-evaluate this 
when switch to a new Toolkit.
Toolkit 5.0 already works better with our big kernel, but brings a 
slowdown. Fingers crossed for 5.x, hope nvidia will release that soon.

In the meantime, everyone interested in GPU Non-Progressive rendering 
can use this:

Patch: http://blender.dingto.org/patches/non_progressive_gpu.diff
Build (Windows x64): 

This still comes with disabled Hair support on the GPU, so basically 
Blender 2.67 feature set, just with Non-Progressive on the GPU.

Best regards,

Am 19.05.2013 06:23, schrieb Brecht Van Lommel:
> Hi,
> On Sun, May 19, 2013 at 1:50 AM, Thomas Dinges <blender at dingto.org> wrote:
>> Hi Brecht,
>> I looked into enabling the Non-Progressive integrator on GPU and want to
>> share my findings.
>> As far as I can tell there is 1 problem (maybe 2).
>> 1) CUDA does not know memset(), called from within
>> shader_merge_closures() in kernel_shaders.h.
>> I could not find a direct alternative, but it seems there are
>> workarounds for it.
>> https://devtalk.nvidia.com/default/topic/394123/moving-memory-cudamemmove-/
> We don't need memmove, can just be replaced with:
> for(int k = 0; k < size; k++)
>      scj[k] = scj[k+1];
>> (2) With Non Progressive integrator enabled, the CUDA compiler takes a
>> lot of memory. I had to disable __HAIR__ in order to keep my RAM alive,
>> but even then it took 4.5 GB (just the compiler process, peak) to
>> compile the sm_21 kernel.
> To reduce memory you could try replacing __device with
> __device_noinline for some big functions called from the
> non-progressive integrator code. It might reduce performance for the
> progressive integrator but might also not, needs testing.
> Still not sure we want to have a kernel that pushes against memory
> limits again, we should keep it manageable so that things don't break
> on every feature added.
> Brecht.
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Thomas Dinges
Blender Developer, Artist and Musician


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