[cfe-dev] OpenCL support - using metadata

[Pekka Jääskeläinen]

OK,

I think I got the basic idea...

On 03/04/2011 04:51 PM, David Neto wrote:
> relocatable section.  Accesses are generated as offsets from a base
> pointer.  (You can discard the address space number at this point!)
> When running multiple work groups in parallel, the different work
> groups are given different values for the base pointer.  That is what
> keeps the work groups from stomping on each other's data.

Going into practical details a bit to ensure I understood this
correctly. Say, one implements an OpenCL kernel launcher that scales
to the number of cores at runtime and implements the actual threading,
for example, with pthreads or some other lower level threading API.

Thus, when launching N parallel work group (WG) execution to
utilize N cores, one must

1) allocate space for the local variables for each
parallel WG thread and
2) somehow pass a pointer to this space as a base value to
the launched kernel so the WG threads do not overwrite each other's
data.

Part 2) is a bit unclear to me. Is the base pointer added as an
additional parameter to the kernel function which the "launcher" can
use? Or do you assume the kernel is loaded to the host program as
a runtime lib and assume the linker does the allocation via
its relocation functionality? Thus, to launch N WG threads one needs
to load the dynlib N times?

Thanks,
-- 
Pekka