[gmx-users] MPI issue

Carsten Kutzner ckutzne at gwdg.de
Thu Jan 17 08:46:08 CET 2008

Hi Paul,

is this version 3.3.1? If I am not missing something, the only two
instances where MPI_Allreduce could be used are in pme.c and in
network.c, but the respective parts of the code have to be explicitly
switched on by a preprocessor directive. Anyway, the communicator on
which they operate is MPI_COMM_WORLD and this should never be NULL.

Or does the error happen at the very end of the simulations? Then maybe
it's a problem with MPI_Finalize (you might want to have a look at
gmx_finalize in network.c then).

If you are using the CVS version things are different, because Allreduce
is used more often. Is there additional information in the error report
that tells in which routine the problem occurs?


Paul Whitford wrote:
> I am running gromacs on a machine with altivec support.  My
> understanding is I have to use MVAPICH on this machine.
> I occasionally have runs crash and I receive the following error
> n559(0): Loaded with Money
> n536(14): 14 - MPI_ALLREDUCE : Null communicator
> n536(14): [14] [] Aborting Program!
> n559(0): 0 - MPI_ALLREDUCE : Null communicator
> n559(0): [0] [] Aborting Program!
> Cleaning up all processes ...Cleaning up all processes ...done.
> Does this indicate a problem with the machine, mvapich, or gromacs? 
> Again, this doesn't always happen, just sometimes (which makes me
> suspect it is a machine issue).  Any advice on where the problem might
> be would be helpful.  thanks in advance.
> -Paul
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Dr. Carsten Kutzner
Max Planck Institute for Biophysical Chemistry
Theoretical and Computational Biophysics Department
Am Fassberg 11
37077 Goettingen, Germany
Tel. +49-551-2012313, Fax: +49-551-2012302

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