Re: CUDA/OpenCL version of Octave for GPGPU?

[Michael Poole]

On Thu, Jun 16, 2011 at 11:14 AM, John Swensen wrote:
>
> On Jun 16, 2011, at 10:23 AM, John W. Eaton wrote:
>
>> On 17-Mar-2011, Tim Rueth wrote:
>>
>> | Have there been any thoughts about a CUDA/OpenCL version of Octave (on 
>> Windows)
>> | that can run on a GPGPU?
>>
>> Is there a complete free software implementation of CUDA libraries
>> that is distributed under terms that are compatible with the GPL?
>>
>> jwe
>
> I have often seen this question come up when discussing CUDA/OpenCL.  My 
> question is whether it is against the spirit or the letter of the law for a 
> GPL program to link against a non-free shared library?  Doesn't essentially 
> every Linux computer that runs X11 and uses the NVidia provided driver do 
> this exact thing?  I'm not trying to be argumentative, I am just trying to 
> understand this aspect of the requirements of the GPL.

The X11 components are not GPL'ed, so there are no license problems
with a proprietary X driver from that perspective.  GPL'ed X clients
use the same interface to talk to both open-source and proprietary X
drivers (whether for 2D, OpenGL, or other things), so the GPL cannot
reach across that interface.

A GPL'ed application that uses a proprietary library can easily be
distributed in source form.  Distributing that application in an
executable form that links -- statically or dynamically -- to the
proprietary library is almost universally believed to violate the GPL.
 Adding an additional permission/grant to the license that allows
binary linking with that library will avoid the problem, but can be
logistically tricky.

OpenCL is a borderline case.  It has a standard interface for both API
and ABI, but it probably does not fall under the GPL's "system
library" exceptions on Linux on account of OpenCL libraries not being
widely distributed with Linux distributions.  (There are reasonable
arguments that go both ways.)  Ironically -- and unfortunately -- it
is probably more legitimate to distribute an OpenCL-linked GPL'ed
executable for Windows or Mac OS X than for any open source operating
system.

Michael Poole