NAME

       MPI_Dist_graph_neighbors  - Returns the neighbors of the calling process in a distributed graph topology.

SYNTAX

C Syntax

       #include <mpi.h>
       int MPI_Dist_graph_neighbors(MPI_Comm comm, int maxindegree, int sources[], int sourceweights[],
                                    int maxoutdegree, int destinations[], int destweights[])

Fortran Syntax

       USE MPI
       ! or the older form: INCLUDE 'mpif.h'
       MPI_DIST_GRAPH_NEIGHBORS(COMM, MAXINDEGREE, SOURCES, SOURCEWEIGHTS,
               MAXOUTDEGREE, DESTINATIONS, DESTWEIGHTS, IERROR)
               INTEGER COMM, MAXINDEGREE, SOURCES(*), SOURCEWEIGHTS(*), MAXOUTDEGREE,
                       DESTINATIONS(*), DESTWEIGHTS(*), IERROR

Fortran 2008 Syntax

       USE mpi_f08
       MPI_Dist_Graph_neighbors(comm, maxindegree, sources, sourceweights,
                 maxoutdegree, destinations, destweights, ierror)
            TYPE(MPI_Comm), INTENT(IN) :: comm
            INTEGER, INTENT(IN) :: maxindegree, maxoutdegree
            INTEGER, INTENT(OUT) :: sources(maxindegree), destinations(maxoutdegree)
            INTEGER :: sourceweights(*), destweights(*)
            INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS

       comm      Communicator with distributed graph topology (handle).

       maxindegree
                 Size of sources and sourceweights arrays (non-negative integer).

       maxoutdegree
                 Size of destinations and destweights arrays (non-negative integer).

OUTPUT PARAMETERS

       sources   Processes for which the calling process is a destination (array of non-negative integers).

       sourceweights
                 Weights of the edges into the calling process (array of non-negative integers).

       destinations
                 Processes for which the calling process is a source (array of non-negative integers).

       destweights
                 Weights of the edges out of the calling process (array of non-negative integers).

       IERROR    Fortran only: Error status (integer).

DESCRIPTION

       MPI_Dist_graph_neighbors returns the source and destination ranks in a distributed graph topology for the
       calling  process.  This  call  will  return up to maxindegree source ranks in the sources array and up to
       maxoutdegree destination ranks in the destinations array. If weights were specified at the  time  of  the
       communicator's  creation  then  the associated weights are returned in the sourceweights and  destweights
       arrays. If the communicator was created with MPI_Dist_graph_create_adjacent then the order of the  values
       in  sources and destinations is identical to the input that was used by the process with the same rank in
       comm_old in the creation call.

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.

SEE ALSO

       MPI_Dist_graph_neighbors_count

4.1.6                                             Sep 30, 2023                       MPI_Dist_graph_neighbors(3)