/*D
   MPI_Cart_sub - Partitions a communicator into subgroups which form lower-dimensional cartesian subgrids

Synopsis:
.vb
int MPI_Cart_sub(MPI_Comm comm, const int remain_dims[], MPI_Comm *newcomm)
.ve

Input Parameters:
+ comm - communicator with Cartesian structure (handle)
- remain_dims - the i-th entry of remain_dims specifies whether the i-th dimension is kept in the subgrid (true) or is dropped (false)

Output Parameters:
. newcomm - communicator containing the subgrid that includes the calling process (handle)

.N ThreadSafe

.N Fortran

.N Errors
.N MPI_SUCCESS
.N MPI_ERR_ARG
.N MPI_ERR_COMM
.N MPI_ERR_OTHER

D*/

