[gmx-users] Difficulties with MPI in gromacs 4.6.3

[Kate Stafford]

Hi all,

I'm trying to install and test gromacs 4.6.3 on our new cluster, and am
having difficulty with MPI. Gromacs has been compiled against openMPI
1.6.5. The symptom is, running a very simple MPI process for any of the
DHFR test systems:

orterun -np 2 mdrun_mpi -s topol.tpr

produces this openMPI warning:

--------------------------------------------------------------------------
An MPI process has executed an operation involving a call to the
"fork()" system call to create a child process.  Open MPI is currently
operating in a condition that could result in memory corruption or
other system errors; your MPI job may hang, crash, or produce silent
data corruption.  The use of fork() (or system() or other calls that
create child processes) is strongly discouraged.

The process that invoked fork was:

  Local host:          hb0c1n1.hpc (PID 58374)
  MPI_COMM_WORLD rank: 1

If you are *absolutely sure* that your application will successfully
and correctly survive a call to fork(), you may disable this warning
by setting the mpi_warn_on_fork MCA parameter to 0.
--------------------------------------------------------------------------

...which is immediately followed by program termination by the cluster
queue due to exceeding the allotted memory for the job. This behavior
persists no matter how much memory I use, up to 16GB per thread, which is
surely excessive for any of the DHFR benchmarks. Turning the warning off,
of course, simply suppresses the output, but doesn't affect the memory
usage.

The openMPI install works fine with other MPI-enabled programs, including
gromacs 4.5.5, so the problem is specific to 4.6.3. The thread-MPI version
of 4.6.3 is also fine.

The 4.6.3 MPI executable was compiled with:

cmake .. -DGMX_GPU=ON -DCUDA_TOOLKIT_ROOT_DIR=/nfs/apps/cuda/5.5.22
-DGMX_MPI=ON -DBUILD_SHARED_LIBS=OFF -DGMX_PREFER_STATIC_LIBS=ON

But the presence of the GPU or static libs related flags seems not to
affect the behavior. The gcc version (4.4 or 4.8) doesn't matter either.

Any insight as to what I'm doing wrong here?

Thanks!

-Kate