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.
-ilia
--
-Samuel
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