[gmx-users] mdrun vs mdrun_mpi

[Jack Howarth]

    I am puzzled by the exact differences between MPI runs of gromacs
using the mdrun and mdrun_mpi binaries. For example, I can use...

grompp -np 1 ...
mpirun n0 -c 2 mdrun ...

To run a MD simulation on a single node with two processors. Both
cpus appear to be fully utilized. What I don't understand is the
difference between the mdrun and mdrun_mpi binaries. I was originally
under the impression that mdrun_mpi might eliminate the need to use
mpirun to start the MPI md calculations. However I have never been
able to get that to work. So what exactly would...

mpirun n0 -c 2 mdrun_mpi...

do differently from...

mpirun n0 -c 2 mdrun

...since the latter seems to be fully utilizing both processors
already.
    Thanks in advance for any clarifications.
          Jack