| 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(*)
MPI::Cartcomm MPI::Cartcomm::Sub(const bool remain_dims[]) const
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.
If all entries in remain_dims are false or comm is already associated
with a zero-dimensional Cartesian topology then newcomm is associated
with a zero-dimensional Cartesian topology.
(This function is closely related to
MPI_COMM_SPLIT.)
Example
Assume that MPI_CART_CREATE(..., comm) has defined a
(2 × 3 × 4) grid. Let remain_dims = (true, false, true).
Then a call to,
MPI_CART_SUB(comm, remain_dims, comm_new),will create three communicators each with eight processes in a 2 × 4 Cartesian topology. If remain_dims = (false, false, true) then the call to MPI_CART_SUB(comm, remain_dims, comm_new) will create six non-overlapping communicators, each with four processes, in a one-dimensional Cartesian topology.