Hi Charlie,

On 4/11/11 23:00 , Charlie Fenton wrote:
> As Rom writes, we are still working on sorting out the OpenCL detection
> and implementation.  One major issue will be when a client has multiple
> GPUs and a mix of CUDA and OpenCL tasks or a mix of CAL and OpenCL tasks
> (or even all three.)  From what we have seen so far, each framework has
> its own way of enumerating GPUs, and there is no "official" way of
> correlating the enumerations.

True. However, I'd think that the device enumeration is at least
deterministic within one platform, such that it should be possible to
enumerate all OpenCL device IDs in the core client and in the science
app with constant order. Given the same device type filter is used both
should agree on a given device's index, right? Have you tested this already?

This might get even more complicated if there are multiple OpenCL
platforms available/installed on one host. In that case we'd need the
platform index (deterministic order again?) as well as device index...

Thinking about the multiple framework issue: shouldn't it be sufficient
to enumerate all devices by all installed frameworks separately? We
could than probably use plan classes to distinguish between the
frameworks (we already do for app selection) and define device selection
and ID propagation schemes for each of them.

> This is of course important to make sure that we don't assigning the
> same GPU to both an OpenCL task and a different CUDA or CAL task. One
> preliminary test indicates that at least on Windows 7, CUDA does return
> the NVIDIA GPUs in the same order as OpenCL, but we have only the one
> sample and we have no test results for CAL or for Macintosh or Linux.

Linux is my current OpenCL development system anyway but I'll also look
into OSX as soon as I got a first Linux port done.

> Rom has filed a spec bug with the Khronos Group over the need for an
> explicit way to map OpenCL devices to their native platform IDs.
> 
> You can find it here:
> <http://www.khronos.org/bugzilla/show_bug.cgi?id=458>

Nice.


Thanks,
Oliver

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