NAME

       MPI_Neighbor_allgather  -   In  this function, each process i gathers data items from each
       process j if an edge (j,i) exists in the topology graph, and each process i sends the same
       data  items to all processes j where an edge (i,j) exists. The send buffer is sent to each
       neighboring process and the l-th block in the receive buffer is  received  from  the  l-th
       neighbor.

SYNOPSIS

       int MPI_Neighbor_allgather(const void *sendbuf, int sendcount, MPI_Datatype sendtype, void *recvbuf, int recvcount, MPI_Datatype recvtype, MPI_Comm comm)

INPUT PARAMETERS

       sendbuf
              - starting address of the send buffer (choice)
       sendcount
              - number of elements sent to each neighbor (non-negative integer)
       sendtype
              - data type of send buffer elements (handle)
       recvcount
              - number of elements received from each neighbor (non-negative integer)
       recvtype
              - data type of receive buffer elements (handle)
       comm   - communicator (handle)

OUTPUT PARAMETERS

       recvbuf
              - starting address of the receive buffer (choice)

THREAD AND INTERRUPT SAFETY

       This  routine is thread-safe.  This means that this routine may be safely used by multiple
       threads without the need for any user-provided thread locks.  However, the routine is  not
       interrupt  safe.   Typically, this is due to the use of memory allocation routines such as
       malloc or other non-MPICH runtime routines that are themselves not interrupt-safe.

NOTES FOR FORTRAN

       All MPI routines in Fortran (except for MPI_WTIME  and  MPI_WTICK  )  have  an  additional
       argument  ierr  at  the  end  of  the  argument list.  ierr is an integer and has the same
       meaning as the  return  value  of  the  routine  in  C.   In  Fortran,  MPI  routines  are
       subroutines, and are invoked with the call statement.

       All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in Fortran.

ERRORS

       All  MPI  routines  (except MPI_Wtime and MPI_Wtick ) return an error value; C routines as
       the value of the function and Fortran routines in the last argument.  Before the value  is
       returned,  the current MPI error handler is called.  By default, this error handler aborts
       the MPI  job.   The  error  handler  may  be  changed  with  MPI_Comm_set_errhandler  (for
       communicators),  MPI_File_set_errhandler  (for files), and MPI_Win_set_errhandler (for RMA
       windows).  The MPI-1 routine MPI_Errhandler_set may be used but  its  use  is  deprecated.
       The  predefined  error  handler  MPI_ERRORS_RETURN may be used to cause error values to be
       returned.  Note that MPI does not guarentee that an  MPI  program  can  continue  past  an
       error; however, MPI implementations will attempt to continue whenever possible.

                                            11/12/2016                  MPI_Neighbor_allgather(3)