Gromacs Parallelization Related....

Acceleration and parallelization

http://www.gromacs.org/Documentation/Acceleration_and_parallelization

Getting good performance from mdrun

http://manual.gromacs.org/documentation/5.1/user-guide/mdrun-performance.html

Performance checklist

http://www.gromacs.org/Documentation/Performance_checklist

mpirun -np 64 --hostfile hostfile.txt gmx_mpi mdrun -v -deffnm step6.5_equilibration -pin on -npme 4