17.2.178. MPI_Graph_neighbors_count

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

17.2.178.1. Syntax

17.2.178.1.1. C Syntax

#include <mpi.h>

int MPI_Graph_neighbors_count(MPI_Comm comm, int rank,
    int *nneighbors)

17.2.178.1.2. Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'

MPI_GRAPH_NEIGHBORS_COUNT(COMM, RANK, NNEIGHBORS, IERROR)
    INTEGER COMM, RANK, NNEIGHBORS, IERROR

17.2.178.1.3. Fortran 2008 Syntax

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

17.2.178.2. Input Parameters

  • comm : Communicator with graph topology (handle).

  • rank : Rank of process in group of comm (integer).

17.2.178.3. Output Parameters

  • nneighbors : Number of neighbors of specified process (integer).

  • IERROR : Fortran only: Error status (integer).

17.2.178.4. Description

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.

17.2.178.5. Errors

Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument.

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.