MPI_Graph_neighbors_count(3) Open MPI MPI_Graph_neighbors_count(3)

MPI_Graph_neighbors_count - Returns the number of neighbors of a node associated with a graph topology.

#include <mpi.h>
int MPI_Graph_neighbors_count(MPI_Comm comm, int rank,
	int *nneighbors)

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_GRAPH_NEIGHBORS_COUNT(COMM, RANK, NNEIGHBORS, IERROR)
	INTEGER	COMM, RANK, NNEIGHBORS, IERROR

USE mpi_f08
MPI_Graph_neighbors_count(comm, rank, nneighbors, ierror)
	TYPE(MPI_Comm), INTENT(IN) :: comm
	INTEGER, INTENT(IN) :: rank
	INTEGER, INTENT(OUT) :: nneighbors
	INTEGER, OPTIONAL, INTENT(OUT) :: ierror

#include <mpi.h>
int Graphcomm::Get_neighbors_count(int rank) const

Communicator with graph topology (handle).
Rank of process in group of comm (integer).

Number of neighbors of specified process (integer).
Fortran only: Error status (integer).

MPI_Graph_neighbors_count and MPI_Graph_neighbors provide adjacency information for a general, graph topology. MPI_Graph_neighbors_count returns the number of neighbors for the process signified by rank.

Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ functions do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism will be used to throw an MPI::Exception object.

Before the error value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error.

MPI_Graph_neighbors

May 26, 2022 4.1.4