[gmx-developers] Branches w/working OpenCL support

[Szilárd Páll]

Hi Mirco,

Thanks for running the tests and sharing the logs. Performance looks
reasonable and based on your log file it looks like the large OpenCL
runtime overhead I observed on Linux is not present on Windows.

On Sun, Jun 7, 2015 at 12:23 PM, Mirco Wahab
<mirco.wahab at chemie.tu-freiberg.de> wrote:
> Hi Szilard,
>
> On 31.05.2015 22:15, Szilárd Páll wrote:
>>
>> [...]
>> https://gerrit.gromacs.org/#/c/4314/
>> Use the version in review on gerrit I linked above, that's the most up
>> to date code.
>> [...]
>
>
> I completed some tests using an AMD device (Pitcairn-GPU,
> Radeon R9-270X), and used adh_cubic_vsites, rnase_cubic, and
> villin_vsites from the "gromacs acceleration page".
>
> So far, the simulations appear to run stable and deliver correct
> results if *no pressure coupling* is used. As I noted already with
> the NV opencl test, this affects the AMD opencl implementation too:
> pressure coupling just don't work so far.
>
> Compilation: there needs to be an additional include of
> #include <algorithm> in src/gromacs/gmxana/gmx_wham.cpp
> in order to provide std::min/max for VC. Another problem
> is the use of binary numerals in src\gromacs\listed-forces\bonded.cpp,
> which are C++14. Maybe these could be written in hexadecimal
> numerals in order to avoid problems w/non C++14-compilers?

I can't comment much on these, but I don't think we should be using C++14 code.

> Pressure coupling: Depending on the simulation setup w/pressure
> coupling, gmx will  either crash immediately (when using pme) or
> continuously enlarge the volume (eg. when using rf + berendsen).

Yeah, that should not happen. I did very brief testing, and my guess
is that something is wrong with the shift forces during non-energy
calculating steps.

> I put the log files an a host, these include log files and
> input for a very simple spc water system w/pressure coupling
> (which doesn't work w/opencl but works perfectly using -nb cpu).
> http://spule.compch.tu-freiberg.de/~wahab/gromacs/gmx_opencl_2015-06_szilard.zip
>
> short overview:
>
>  adh_cubic_vsites
>   cpu/pme:      5.738,  gpu/pme:        17.421
>   cpu/rf:       7.913,  gpu/rf:         26.344
>
>  rnase_cubic
>   cpu/pme:      15.001, gpu/pme:        39.363
>   cpu/rf:       24.729, gpu/rf:         59.179
>
>  villin_vsites
>   cpu/pme:      124.86, gpu/pme:        284.213
>   cpu/rf:       151.05, gpu/rf:         310.794
>
>  (water_small_npt/nvt)
>   cpu/pme/npt:  20.00   gpu/pme/npt:    n/a
>   cpu/pme/nvt:  21.65   gpu/pme/nvt:    52.05
>
>
> How is the current status for the planned inclusion of
> opencl into a gromacs release?

I can't comment on that, there are a few issues (including this
pressure bug) that need to be solved before merge can be considered.
Hopefully somebody will have time to look at these.

--
Szilárd

> Regards,
>
>
> M.
>
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