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Date: Tue, 29 May 2012 01:43:12 +0200
From: magnum <>
Subject: Re: GPU options

On 05/29/2012 01:26 AM, Lukas Odzioba wrote:
> 2012/5/29 magnum <>:
>> On 05/29/2012 12:58 AM, Lukas Odzioba wrote:
>>> 2012/5/29 magnum <>:
>>>> On 05/29/2012 12:40 AM, Lukas Odzioba wrote:
>>>>> --platform=N (or =LIST)   set OpenCL platform, default 0
>>>>> --device=N                set OpenCL device, default 0
>>>>> I thought that LIST means sth like 1,2 isn't it misleading for user?
>>>>> Just asking.
>>>> I just mimiced existing options, like --subformat=LIST. But hey, you
>>>> have a point: If/when we are going to support multiple devices it could
>>>> be given as eg. --device=0,1.
>>> This looks natural, I like it.
>> Yes... but I now realize it wont suffice. In most cases you'd run a
>> couple of same-model GPU's and they would probably be platform 0,
>> devices 0 and 1. But on Bull, the Nvidia is platform 0, device 0 and the
>> 7970 is platform 1, device 0. That would mean --platform=0,1 and
>> --device=0 and it starts to get vague... and on some system we might
>> want to run (platform,device) 0,1 and 1,0. I'm not sure how to
>> accommodate that. Ideally we should come up with a better syntax for all
>> of this before the Jumbo release.
> So let's do not divide platform and device as a separate parameters
> and use just  device like that: --device=0:1,0:2, where first number
> is platform id and second is device id. What do you think about that?

That should work. So we drop the --platform option entirely. But we
might want to support the following:

1. no --device option given. Default to using the first GPU found. If
none found, use device 0:0

2. --device=N without a second number. Either we do not support that for
OpenCL, or we parse it as platform N, device 0, or we parse it as
platform N, first GPU found... but maybe this is always 0 anyway?

> If we will drop platform option as I stated previously, we could use
> --device=LIST for both cuda and opencl. For opencl it could print also
> platform information.

Yes. Do you have (or know of) some trivial CUDA device listing code?


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