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