running WRF-HYDRO in parallel using MPI

[jbensabat]

Hello I am using the parallel option to run the code. I have to set the number of processors
I read that I can set in
namelist.hrldas
nproc_x = npx
nproc_y = npy
and the number of processors to be used in MPI is npx*npy

I have also read that i could set this value in
hydro.namelist
hydro_nproc_x = npx
hydro_nproc_y = npy

so my question is what is the correct way to do that ?
best
jac