NAME

       MPI_Neighbor_alltoall  -   In  this function, each process i receives data items from each
       process j if an edge (j,i) exists in the topology graph or Cartesian topology.  Similarly,
       each  process  i sends data items to all processes j where an edge (i,j) exists. This call
       is more general than MPI_NEIGHBOR_ALLGATHER in that different data items can  be  sent  to
       each  neighbor.  The k-th block in send buffer is sent to the k-th neighboring process and
       the l-th block in the receive buffer is received from the l-th neighbor.

SYNOPSIS

       int MPI_Neighbor_alltoall(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.

LOCATION

       src/mpi/topo/nhb_alltoall.c

                                            4/24/2013                    MPI_Neighbor_alltoall(3)