Re: [Starpu-devel] Only 2 OpenCL Devices available

[Sylvain HENRY <sylvain.henry@inria.fr>]

Hello,

OpenCL CPU implementations do not show CPU cores as separate devices.

Sub devices have been introduced in latter revisions of the spec (1.2 if 
I remember correctly) but StarPU does not use them : 
http://www.khronos.org/registry/cl/sdk/1.2/docs/man/xhtml/clCreateSubDevices.html

Enabling OpenCL on CPU in StarPU has no influence on the activation of 
the CPU driver. In fact there is no interaction between the two drivers 
and the same CPU cores can be used simultaneously through both drivers 
(CPU and OpenCL) without StarPU preventing it. Moreover, kernels 
executed with OpenCL on CPU may use the cores reserved by StarPU to 
execute the GPU workers.

Sylvain


Le 10/11/2013 19:51, Samuel Thibault a écrit :
> Hello,
>
> Please *always* keep the list in Cc.  That not only increases the
> chances of getting an answer quickly, but that also increases the
> chances of getting a useful answer at all.
>
> "Julian Holzmüller", le Sun 10 Nov 2013 19:39:04 +0100, a écrit :
> > StarPU has found :
> >
> >     2 CPU cores
> >         CPU 0
> >         CPU 1
> >     0 CUDA devices
> >     2 OpenCL devices
> >         OpenCL 0 (Intel(R) Core(TM) i7 CPU       Q 720  @ 1.60GHz)
> >         OpenCL 1 (Quadro FX 880M)
> >
> > I can only use 1 core as an OpenCL device.
> Maybe in the CPU case we didn't think of automatically disabling the CPU
> driver.  Nathalie, Sylvain, do you know about it?  I indeed don't see
> that in the source code.
>
> In the meanwhile, you can use STARPU_NCPU=0 to disable the CPU driver.
> I believe the OpenCL driver actually does use all 4 cores, and it just
> doesn't show up in StarPU just because that's hidden by the OpenCL
> layer.
>
> Samuel
>
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