[gmx-users] problems with parallel mdrun

[Gurpreet Singh]

Dear gmx users,

I am using a current CVS version of Gromacs and using the newly introduced
options for simulations with walls. I am facing the following two
problems.

I get the following errors while using paralled version of mdrun compiled
with openmpi.
mpirun -np 4 mdrun_d_mpi -np 4 -v -deffnm EQUI1
*****
Program mdrun_d_mpi, VERSION 3.3.99_development_20070720
Source code file: gmx_parallel_3dfft.c, line: 90

Fatal error:
nx (50) and ny (50) must be divisible by the number of nodes (4).
*******
I am using a cubic box of 5nm and grid spacing is 0.1. The simulations
runs fine if i use 5 nodes
I am using a machines with 2 dual xeon processors so -np 4 is more
appropriate for my sytems.
 Is there any way to use -np 4  without changing the gridspacing 
or box size?

second question is regarding wall_denstiy option.

As i understood from the manual the wall density is a number density in
units of number/nm2 in case of 10-4 potential
and is number/nm3 in case of 9-3 potential.
please correct me if i am wrong.

Thank you in advance
With Regards,
Gurpreet