[Pkg-opencl-devel] pocl ITP, and opencl-icd selection

[Simon Richter]

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Hi,

On 07.02.2014 10:09, Vincent Danjean wrote:

> Your two proposal are also very interesting. The difference with
> xorg is that xorg choose the "good" driver at runtime if all are
> installed. This is not the case with OpenCL. For example, if
> beignet is installed on a machine where it does not work, it can be
> selected as the default implementation by libOpenCL.so.1 (but if
> its initializer does not report any plateform on non-supported 
> environment, I did not checked).

Beignet should show a platform, but no devices, in the same way it
should show two devices if there are two compatible cards.

It is up to the application to select which devices to use. I'm not
sure the ICD loader should present a "default", and the OpenCL API
does not really suggest that the first platform is in any way meant to
be used that way.

> I think the first step is to package pocl. Then, we can try to
> improve dependencies so that OpenCL applications work on all
> machine by default (sometime, OpenCL applications require 
> specifically a GPU device. Should we fallback on CPU device if none
> are available ?).

No. Applications usually have their reasons for selecting one or the
other.

> Perhaps, the ICD loader of ocl-icl can be improved to add specific
> runtime detection in order to choose the best default
> implementation when several are available (perhaps with the help of
> ICDs themselves).

The only real conflict I see is AMD's CPU based ICD vs pocl, because
these would be competing for the same resource, and there is no
standardized way of finding this out.

I'm occasionally hacking on an ICD that distributes work across a
network, which would then show multiple CPU and GPU devices with
different characteristics.

   Simon
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