Confusion with parallel run setup.

I am trying to set up a parallel run using CROCO. At the moment I am trying to set up a small simulation, basically to try and get the parallelization right, on my personal pc before running the long simulations on the larger servers.

So, what I do understand from setting up the parallelization, is that one has to define it in the cppdefs.h document, i.e.

define MPI      

and one has to set the NB PROCS to the total number of processors one has in its pc in the run_croco.bash file.

However, what I don’t understand is what happens in the param.h file, where one has to change some of the parallelization settings:

ifdef MPI
  integer NP_XI, NP_ETA, NNODES     
  parameter (NP_XI=1,  NP_ETA=4,  NNODES=NP_XI*NP_ETA)
  parameter (NPP=1)
  parameter (NSUB_X=1, NSUB_E=1)

This is my first time setting up a parallel run, so I am not 100% sure whether I got the process of setting up correctly, but any help will really be appreciated.