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

[Berk Hess]

Hi,

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.

Berk

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 :-(
>
>