[gmx-users] Replica Exchange: Threads vs MPI

Mark Abraham mark.j.abraham at gmail.com
Mon Apr 6 23:10:31 CEST 2015

On Mon, Apr 6, 2015 at 4:31 PM, Steve Seibold <stevesei at ymail.com> wrote:

> I apologize if this is a really crazy question; I just want to be sure
> that I understand everything.
> I am assuming after reading the Replica Exchange from the on-line gromacs
> site that you cannot run, perform this method with multiple threads on one
> one system. You must have several machines with so many cores each to run
> it...

No, you must compile an MPI-enabled GROMACS (not the default one, which
uses the built-in thread-MPI). Replicas can still use multiple cores via
OpenMP threading.

The mpi code forces you to do this correct??
> I am already running mdrun which uses all my cores on one machine and I
> thought Rep. Exch. would do the same, but I believe that is
> incorrect..right??

I don't know what you think is incorrect. mdrun by default will try to use
all the available resources efficiently.


> Thanks
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