[gmx-developers] Problem with qmmm and mpi combo (4.0.5)

Berk Hess hess at cbr.su.se
Fri Nov 20 16:47:52 CET 2009


My guess is that qmmm has never been tested with domain decomposition
and does not work with it.
Try particle decomposition: mdrun -pd

Note that in most cases running the mm part in parallel does not improve
performance significantly, since qm usually takes more than 90% of the
run time.


Ake Sandgren wrote:
> Hi!
> When building gromacs 4.0.5 for qmmm and mpi something goes wrong
> (unless its in the input data of course :-)
> For the input data I'm using (from a user of ours) i have the following
> problem:
> In qmmm.c update_QMMMrec the gmx_sumi in the parallel excecution part
> have inconsistent values in md->nr, i.e. not the same on process 0 and
> process 1. (Causing a problem in the Allreduce)
> Also fr->QMMMlist_sr.nri is different between processes.
> What might be the cause of this? Input data error or bug in the code?
> I've been trying to backtrace this but it's now friday afternoon and i'm
> giving up :-(

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