[gmx-developers] Branches w/working OpenCL support

[Mark Abraham]

Hi all,

OpenCL is support is now merged into master branch, so we will see it in
the 5.1 release candidate (probably tomorrow). The latest version Mirco
tested had FastGen still accidentally disabled (sorry), but I was able to
get FastGen working properly with PME tuning, so that the per-run JIT
compilation is now a couple of seconds. That should make the OpenCL port
extremely usable in practice, and we probably don't need to buy any further
trouble with worrying about caching of JIT compilation (for now, anyway).

Mark

On Thu, Jun 25, 2015 at 11:36 PM Mark Abraham <mark.j.abraham at gmail.com>
wrote:

> That's great to hear, Mirco.
>
> A message to stdout before and after compilation does sound like a good
> idea, so users waiting on the terminal know that this is normal.
>
> Mark
>
> On Thu, Jun 25, 2015 at 11:09 PM Mirco Wahab <
> mirco.wahab at chemie.tu-freiberg.de> wrote:
>
>> On 25.06.2015 17:02, Mark Abraham wrote:
>> > I got local access to a machine with two AMD GPUs, and ran into the same
>> > initialization issues I'd seen with Nvidia runtimes, so I have updated
>> > https://gerrit.gromacs.org/4314 so that in 5.1 GROMACS will never use
>> > more than one OpenCL device per node. We can probably fix that in the
>> > longer term, but it seems like issues of host-side concurrency are not
>> > treated in the OpenCL standard (or at least the implementations we've
>> > targeted), and we didn't do a good enough job of anticipating and
>> > managing that.
>>
>> In this moment I completed compilation and run some first tests on
>> my AMD box (AMD Phenom II X6 1090t + R9-270X Pitcairn GCN 1.1).
>>
>> Compilation/Installation:
>>   I fetched refs/changes/14/4314/38 against the current git master,
>>   compilation (VS 2013/MSVC 18.00.31101, AMD App-SDK 3.0.0-beta)
>>   went smooth, not a single error (built against a local fftw 3.3.3),
>>   so that looks really promising ...
>>
>> First run tests (for posting the status here):
>>   - single water box (2916 SPC)
>>   - NVT + RF  ok.
>>   - NVT + PME ok.
>>   - NPT + RF  ok.
>>   - NPT + PME ok.
>>
>> All runs did complete without any problem!
>> Run times are promising too on this
>> very small system (ns/day):
>>
>> cpu only - rf/npt: 32.482, pme/npt: 20.971
>> cpu/gpu  - rf/npt: 63.530, pme/npt: 51.429
>>             rf/nvt: 64.001, pme/nvt: 51.125
>>
>> The gpu kernels do get compiled in this version
>> at the start of every run and are located in the
>> %TEMP% directory - and deleted after loading, So they
>> are not longer cached/stored. The time for gpu kernel
>> compilation is >30 sec on this box (maybe this rewards
>> an extra message). The structure of this file is
>> (looks like) an ELF-binary?
>>
>> As it looks, the OpenCL extension could be a
>> very useable attribute for Gromacs users. I'm
>> impressed.
>>
>>
>> Thanks & Regards
>>
>> M.
>>
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