Bug#783770: Fwd: [Patch] Shall we update CUDA to 7.0.28 ? (#783770)

[Samuel Thibault]

Hello,

My few cents about it:

lumin, on Fri 13 Nov 2015 13:55:52 +0000, wrote:
> Debian's CUDA/experimental is QUITE OUT OF DATE so that
> it fails to work with GCC-5.

It's cuda 6.5.  Cuda 7.0 is not *that* new.  AIUI, it was officially
released by Nvidia in March 2015.

Yes, the push to gcc-5 posed a lot of problems, CUDA is one of
them.  That's actually exactly why I make the starpu-contrib package
build-depend on older versions of gcc instead of the default version of
gcc.

> but I don't understand why Debian experimental holds such an
> .......... 6.5 version, compared with the one Archlinux ships.
[...]
> Following is my dch, and you can see there are still some items remained to be
> done:

You named it :)

Thanks for your contribution that will hopefully help getting cuda 7.0
or 7.5 packages out faster.

> FYI: As far as I know, in my experiments,
> a Tesla K20C GPU works 5+ times faster than an Intel Xeon W3690.

That's not a reason for rushing to CUDA 7.0 or later.  A K20C will work
fine with CUDA 6.5.  Also, helping free software to support NVIDIA GPUs
would help avoiding the issue :)

> I'm afraid that I have to bump CUDA to 7.5, to solve the FTBFS of Caffe.
> which really fixes CUDA's attitude towards GCC-5.

I guess there is no way to backport the CUDA 7.5 fixes to support GCC-5?
(damn the non-free software...)

> What makes me happy is, the compilation for gcc-4.9 on *.cu files
> of Caffe runs well. CUDA-7.0.28 supports up to g{cc,++}-4.9, but
> still not working with g{cc,++}-5.

Urgl, so CUDA 7.0 is not even enough?

I guess we may want to skip 7.0 and directly upload 7.5.

> The caffe builds failed because liking ELFs to v5libs with g{cc,++}-4.9,
> so it matches my expectation.

Ok, so your case is indeed completely screwed for now, due to the
unfortunate combination of libstdc++ transition, late release of gcc-5,
and thus late support of gcc-5 in CUDA (a couple of months ago only).
That's basically a "flag day^Wmonth" issue.

So yes, the answer is: "please be patient, we are working on it. Help is
welcome".

Samuel