[gmx-developers] GROMACS OpenCL on Gallium

[Vedran Miletić]

Hello Szilard and others,

I have just been talking to Tom Stellard from AMD regarding the same
topic (synchronicity, anyone?). Getting stuff to work on open source
stack without any proprietary components and have it neatly packaged
in downstream distributions has been my primary motive here as well.

The problem at this point is not on GROMACS side, but on the side of
open source driver for Radeon GPUs. There are two Radeon drivers in
Mesa which support OpenCL:
1) r600g, which roughly supports HD 5000/6000 and low-end HD 7000/8000
(pre-GCN architecture),
2) radeonsi, which supports high-end HD 7000 and newer cards (GCN architecture).

The main issue with GROMACS, perhaps among other issues, is missing
image support. r600g image support was implemented in a GSoC project
[1]. Patches have not been upstreamed yet, but they are available on
GitHub [2]. I have a Caicos card, and I plan to give those patches a
shot if it is not too much work. Given that I get it working, I might
go the extra mile and try to make them ready for inclusion in upstream
Mesa, but no promises here.

On the side of radeonsi, I will be working on the OpenCL image support
in the coming weeks/months. My goal is to get GROMACS working first,
and then see if we can do anything with regards to performance on the
Radeon driver side or GROMACS side. I have already allocated the time
for it, and I have a Bonaire card to work with and will get a Tonga
card soon.

Regards,
Vedran Miletic

[1] https://www.google-melange.com/gsoc/project/details/google/gsoc2015/zogi/5738600293466112
[2] https://github.com/zogi/mesa/commits/gsoc

2015-11-26 19:04 GMT+01:00 Szilárd Páll <pall.szilard at gmail.com>:
> One more thing!
>
> Let me take the opportunity to invite everyone interested to contribute
> (with either code, testing, docs) and help improving features and
> performance of our truly portable GPU/accelerator OpenCL code-path!
>
> Our OpenCL implementation is stable and solid, but is lacking thorough
> tuning for AMD GPUs and support for integrated CPU+GPU architectures would
> be great too. There are a number of known to be useful extensions &
> optimizations (and probably even more that we have not thought of) that
> could be pursued, but due to the lack of time/resources we have not done it
> yet.
>
> I'd be happy to share ideas and collaborate with the goal of improving the
> OpenCL support for the next release!
>
> So if you're interested, get in touch!
>
> Cheers,
>
> --
> Szilárd
>
> On Thu, Nov 26, 2015 at 6:52 PM, Szilárd Páll <pall.szilard at gmail.com>
> wrote:
>>
>> Hi!
>>
>> My reply got quite delayed, sorry about that.
>>
>> Just wanted to let you know that I am personally interested in getting
>> Gallium support to work. I can't drive the work, ATM have very limited time
>> to put into this, but I would love to help with fixing small things and with
>> code review!
>>
>> It would be nice to be able to use GROMACS on GPUs without any proprietary
>> stuff. I'm sure distros will be happy to be able to provide a GROMACS
>> package with no proprietary dependencies for GPUs. Of course, the
>> performance matters too, but first thing is to get it to work.
>>
>> If somebody is interested in taking up the task of driving the work,
>> please file a (some) redimine issue (list the concrete tasks if they're
>> known)!
>>
>> Cheers,
>> --
>> Szilárd
>>
>>

-- 
Vedran Miletić
http://vedranmileti.ch/