Defining a Cartesian Topology

The routine MPI_Cart_create creates a Cartesian decomposition of the processes, with the number of dimensions given by the ndim argument.

dims(1)    = 4 
   dims(2)    = 3 
   periods(1) = .false. 
   periods(2) = .false. 
   reorder    = .true. 
   ndim       = 2 
   call MPI_CART_CREATE( MPI_COMM_WORLD, ndim, dims,  
  $                      periods, reorder, comm2d, ierr )