MPI_CART_SUB(comm, remain_dims, newcomm)

[ IN comm] communicator with cartesian structure (handle)

[ IN 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`) (logical vector)

[ OUT newcomm] communicator containing the subgrid that includes the calling process (handle)

` int MPI_Cart_sub(MPI_Comm comm, int *remain_dims, MPI_Comm *newcomm) `

` MPI_CART_SUB(COMM, REMAIN_DIMS, NEWCOMM, IERROR) INTEGER COMM, NEWCOMM, IERROR LOGICAL REMAIN_DIMS(*) `

If a cartesian topology has been created with MPI_CART_CREATE, the
function

MPI_CART_SUB can be used to partition the
communicator group into subgroups that form lower-dimensional cartesian
subgrids, and to build for each subgroup a communicator with the associated
subgrid cartesian topology. (This function is closely related to
MPI_COMM_SPLIT.)

** Example**

Assume that MPI_CART_CREATE(..., comm) has defined a
grid. Let ` remain_dims = (true, false, true)`.
Then a call to,

will create three communicators each with eight processes in a cartesian topology. IfMPI_CART_SUB(comm, remain_dims, comm_new),

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