[gmx-users] Intel vs gcc compilers

[Pedro Lacerda]

On Tue, Jun 25, 2013 at 8:53 AM, Mark Abraham <mark.j.abraham at gmail.com>wrote:

> You're using a real-MPI process per core, and you have six cores per
> processor. The recommended procedure is to map cores to OpenMP
> threads, and choose the number of MPI processes per processor (and
> thus the number of OpenMP threads per MPI process) to maximize
> performance. See
>
> http://www.gromacs.org/Documentation/Acceleration_and_parallelization#Multi-level_parallelization.3a_MPI.2fthread-MPI_.2b_OpenMP


The page says:

> at the moment, the multi-level parallelization will surpass the
> (thread-)MPI-only parallelization only in case of highly parallel runs
> and/or with a slow network.


What "highly parallel runs" mean? I'm sure it works for Djurre as he has 72
nodes, but how many six-core nodes are considered highly parallel?