[gmx-developers] random123 library portability issues

[Szilárd Páll]

On Fri, May 30, 2014 at 12:52 PM, Alexey Shvetsov
<alexxy at omrb.pnpi.spb.ru> wrote:
> Hi!
>
> I tryed to build 5.0 branch on ARM board (dual core cortex-a7). It builds (if
> i define arm as allowed arch in features/gccfeatures.h) but some regression
> tests fails.

I was building on Tegra3 + gcc 4.6 and all regressiontests passed
(both for 4.6 and 5.0).

>
> В письме от 30 мая 2014 12:43:29 пользователь Szilárd Páll написал:
>> Hi,
>>
>> A few days ago I did some sanity checks by compiling and
>> regressiontesting the 5.0 branch on ARM. This exercise made me realize
>> that the recently included Random123 library is now the single most
>> limiting factor when it comes to portability. In fact, as it is not
>> optional, v5.0 is ATM practically limited to x86* and Powerpc64 (BGQ)
>> architectures -- based on the docs (see http://goo.gl/YdKofG)
>> Random123 has not been tested (let alone optimized) on anything else.
>> Additionally, note that the code won't even compile on non-supported
>> architectures, so in its current state GROMACS 5.0 won't compile on
>> anything else but x86* and PPC64, e.g. with gcc compilation will be
>> aborted by the "#error" in features/gccfeatures.h:38. Removing these
>> sanity checks does let the code compile on ARM and regressiontests do
>> pass, though.
>>
>> I've exchanged a couple of emails with the developers and they suggest
>> that in practice Threefry should work on ARM (and perhaps other
>> architectures too), but testing/validation is definitely necessary.
>> Performance is not optimized on unsupported architectures, I assume,
>> so some optimization may not hurt too - especially if there are cases
>> where we generate many PRNGs per step (BTW has the potential overhead
>> been assessed?).
>>
>> Cheers,
>> --
>> Szilárd
>
> --
> Best Regards,
> Alexey 'Alexxy' Shvetsov, PhD
> Department of Molecular and Radiation Biophysics
> FSBI Petersburg Nuclear Physics Institute, NRC Kurchatov Institute,
> Leningrad region, Gatchina, Russia
> mailto:alexxyum at gmail.com
> mailto:alexxy at omrb.pnpi.spb.ru
> --
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