[gmx-users] how to increase GMX_OPENMP_MAX_THREADS

[Kutzner, Carsten]

Hi,

> On 25. Feb 2019, at 21:15, Schulz, Roland <roland.schulz at intel.com> wrote:
> 
> That's not my experience. In my experience , for single node runs, it is usually faster to use 72 OPENMP threads rather than using 72 (t)MPI threads.
wouldn’t a combination of OpenMP threads * (t)MPI threads be faster, e.g. 8x9?

Carsten

> 
> Roland
> 
>> -----Original Message-----
>> From: gromacs.org_gmx-users-bounces at maillist.sys.kth.se
>> [mailto:gromacs.org_gmx-users-bounces at maillist.sys.kth.se] On Behalf Of
>> Szilárd Páll
>> Sent: Monday, February 25, 2019 7:31 AM
>> To: Discussion list for GROMACS users <gmx-users at gromacs.org>
>> Subject: Re: [gmx-users] how to increase GMX_OPENMP_MAX_THREADS
>> 
>> What are you trying to do? Using 72 threads per rank in most cases (except
>> some extreme and unusual) will not be efficient at all. If you are sure that
>> you still want to do that, you can override this at compile time using cmake -
>> DGMX_OPENMP_MAX_THREADS=
>> 
>> 
>> 
>> --
>> Szilárd
>> 
>> 
>> On Thu, Feb 21, 2019 at 5:58 AM Lalehan Ozalp <lalehan.ozalp at gmail.com>
>> wrote:
>> 
>>> Hello all,
>>> I'd been running simulation with GROMACS 2018 using 72 open mpi
>>> threads without problem until (I assume) it was updated to 2019
>>> version. When I execute mdrun with option -nt 72 (which is the number
>>> of cores of my
>>> terminal) it says:
>>> 
>>> "you are using 72 openmp threads, which is larger than
>>> GMX_OPENMP_MAX_THREADS (64). Decrease the number of OpenMP
>> threads or
>>> rebuild GROMACS with a larger value for GMX_OPENMP_MAX_THREADS."
>>> 
>>> In the documentation of GROMACS 2019 release, it's written:  "mdrun
>>> can run with more than GMX_OPENMP_MAX_THREADS threads."
>>> 
>>> Could you please help me how to get around this issue?
>>> 
>>> Thank you in advance.
>>> Lalehan
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