Re: [Starpu-devel] Performance with SOCL on multiple devices

[Samuel Pitoiset <samuel.pitoiset@inria.fr>]

Hi,

SOCL is known as an experimental feature and it doesn't seem to be 
maintained and/or used. Anyway, it should not reduce your performance as 
much.

Did you try to run your Galerkin solver with only one GPU?

It would be good to know if your issue is related to using SOCL with 
multiple devices or if it's a major bottleneck even with a single 
compute device.

Thanks.

On 01/06/2016 11:22 AM, Malcolm Roberts wrote:
> Hello.
>
> Thanks to your help, I managed to compile and install StarPU on the
> machines that I plan on using.  I get some strange segfaults on some
> machines with certain tests in my project (which is schnaps,
> http://schnaps.gforge.inria.fr/ ).  Importantly, however, it works fine
> on atlas4 in our local cluster, which has 4 k80 GPUs.  However, the code
> is twice as slow when using SOCL than it is when using OpenCL.
>
> The code is a discontinuous Galerkin solver using a second or fourth
> order Runge Kutta time-stepper.  The field is divided into macrocells
> (we can choose the number of macrocells as we want), and each macrocell
> has its own OpenCL buffer.  My understanding is that SOCL should
> distribute the buffers and associated tasks between OpenCL devices and
> take care of memory allocation and transfers. However, it seems to just
> run on one GPU, and takes twice as long as OpenCL while doing so.  I am
> using the default settings, however, so perhaps there's something to be
> done here.  Is there some way to improve this performance?
>
> Best,
>
> ~Malcolm