[gmx-developers] GROMACS OpenCL on Gallium

[Vedran Miletić]

Excellent. This segfaults on my Caicos (probably due to missing
atomics), and runs correctly on my Bonaire. Tonga is completely broken
at the moment [1].

I will try to modify this example to make it fail instruction
selection like GROMACS does.

Regards,
Vedran

[1] https://bugs.freedesktop.org/show_bug.cgi?id=93264

2015-12-14 14:37 GMT+01:00 Szilárd Páll <pall.szilard at gmail.com>:
> Hi,
>
> Last night I grabbed a trivial OpenCL sample code that does vector addition
> (source [1]) and threw in an atomic add on floats: https://pastee.org/8jtbj
> Would this work as a starting point?
>
> If this is too trivial, one option for extending it is to e.g. generate a
> trivial neighbor list (e.g. a random list of index pairs into a coordinate
> array) that the kernel looks over and calculate a distance (or some simple
> pair potential-like function).
>
> Cheers,
> --
> Szilárd
>
> [1] https://www.olcf.ornl.gov/tutorials/opencl-vector-addition/#vecAdd.c
>
>
> On Thu, Dec 10, 2015 at 4:56 PM, Szilárd Páll <pall.szilard at gmail.com>
> wrote:
>>
>> Vedran,
>>
>> Unfortunately, don't think I will have enough time at least in the coming
>> 1-2 weeks. I could help composing the kernel, but that's likely going to be
>> little effort and I am quite inexperienced with OpenCL, especially with the
>> API "glue" code needed to just have a small test kernel running.
>>
>> I could pith in with putting together the kernel, but if the goal is to
>> have a simple test for global memory atomic addition on floats, perhaps the
>> best idea is to strip down an SDK example* like a float vector addition (or
>> reduction) and replace the regular global memory writes with the
>> atomicAdd_g_f() function implemented in
>> src/gromacs/mdlib/nbnxn_ocl/vectype_ops.clh.
>>
>>
>> * Both the AMD SDK and NVIDIA's ancient OpenCL SDK should have ready code,
>> but having checked briefly, a slight stripping down may be needed to remove
>> certain optimizations and avoid utility functions.
>>
>> Cheers,
>> --
>> Szilárd
>>
>> On Wed, Dec 9, 2015 at 10:30 AM, Vedran Miletić <rivanvx at gmail.com> wrote:
>>>
>>> 2015-12-04 18:13 GMT+01:00 Szilárd Páll <pall.szilard at gmail.com>:
>>> > Sounds good, is there anything on our side we can help with?
>>> >
>>> > Cheers,
>>> >
>>> > --
>>> > Szilárd
>>> >
>>>
>>> Szilard,
>>>
>>> actually, there is something that would be very useful, as I am
>>> struggling with testing my changes at the moment. It would be great to
>>> have minimal self-contained OpenCL example programs covering a
>>> spectrum of features we use. As a start, I could use a minimal atomic
>>> compare and swap example that would crash in the same way GROMACS does
>>> now.
>>>
>>> LLVM requires tests for all patches [1]. So I would certainly reuse
>>> these.
>>>
>>> Is this doable? I can try to make them myself, but you mentioned you
>>> are familiar with the code so I'm hoping you could make them quicker.
>>>
>>> Regards,
>>> Vedran
>>>
>>> [1] http://llvm.org/docs/DeveloperPolicy.html
>>>
>>> --
>>> Vedran Miletić
>>> http://vedranmileti.ch/
>>> --
>>> Gromacs Developers mailing list
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>>
>>
>
>
> --
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-- 
Vedran Miletić
http://vedranmileti.ch/