On 05:43 PM - Apr 27 2016, Samuel Pitoiset wrote: > > > On 04/27/2016 05:24 PM, Ilia Mirkin wrote: > >On Wed, Apr 27, 2016 at 11:19 AM, Hans de Goede <hdego...@redhat.com> wrote: > >>Hi, > >> > >>On 27-04-16 16:49, Ilia Mirkin wrote: > >>> > >>>Please add this semantic to src/gallium/docs and explain what it > >>>means. > >> > >> > >>Ah, I was under the impression these were not documented, but I > >>now see they are, will fix. > >> > >>>(I'm not even sure what this is, and the easily-found opencl > >>> > >>>docs helpfully indicate that get_work_dim returns the work_dim...) > >>>This wasn't done for some of the other compute-specific semantics. > >> > >> > >>When launching a grid through clEnqueueNDRangeKernel the user > >>can tell how many dimensions of the pipe_grid_info->grid / > >>pipe_grid_info->block equivalent the user is actually passing in > >>this is done through a parameter to that function called work_dim: > >> > >>https://www.khronos.org/registry/cl/sdk/1.0/docs/man/xhtml/clEnqueueNDRangeKernel.html > >> > >>Clover pads the y and z values (if unused) to 1, so it always > >>ends up giving a 3 dimensional grid and block sizes to the driver. > >> > >>But an opencl kernel can use the opencl builtin get_work_dim > >>function, which returns how much dimensions where actually > >>passed into clEnqueueNDRangeKernel. > >> > >>Note that passing in e.g. work_dim = 3 with a grid size of { 4, 1, 1 } > >>is perfectly legal and then get_work_dim should actually return 3. > >> > >>So we need to store the clEnqueueNDRangeKernel workdim parameter > >>somewhere, and allow getting it from a kernel. Using a system-value > >>seems the best solution for this to me. > >> > >>I hope this helps to explain things, if not keep asking :) > >> > >>Also if you've a better solution, I'm all ears. > > > >Sounds like there's no real way to distinguish it from the kernel, the > >parameters given to the hw are all the same, so it's just a thing that > >needs to be passed along. I think that what you have is a fine > >solution, although I question the usefulness of this being an OpenCL > >builtin. But we're not about to change that now. > > > >An alternative would be for clover to stick it into a uniform and have > >the kernel read it out from there. If there are going to be a ton of > >these, that might be preferable. If it's just the one (or maybe two), > >not worth it. > > I think your solution is fine too. Storing the number of dimensions passed > to clEnqueueNDRangeKernel() as well as the local/global sizes makes sense.
Later versions of OpenCL are adding a few more of those (see [OpenCL 1.0][1] compared to [OpenCL 2.0][2]). So putting it in a uniform would be better, but we can just switch to a uniform the day we reach OpenCL 2.0. Pierre [1]: https://www.khronos.org/registry/cl/sdk/1.0/docs/man/xhtml/workItemFunctions.html [2]: https://www.khronos.org/registry/cl/sdk/2.0/docs/man/xhtml/workItemFunctions.html > > > > > -ilia > > > > -- > -Samuel > _______________________________________________ > mesa-dev mailing list > mesa-dev@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/mesa-dev
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