MPI_Comm_join(3)                   Open MPI                   MPI_Comm_join(3)



NAME
       MPI_Comm_join - Establishes communication between MPI jobs


SYNTAX
C Syntax
       #include <mpi.h>
       int MPI_Comm_join(int fd, MPI_Comm *intercomm)


Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_COMM_JOIN(FD, INTERCOMM, IERROR)
            INTEGER   FD, INTERCOMM, IERROR


C++ Syntax
       #include <mpi.h>
       MPI::Intercomm MPI::Comm::Join(const int fd)


INPUT PARAMETER
       fd        socket file descriptor (socket).


OUTPUT PARAMETERS
       intercomm Intercommunicator between processes (handle).

       IERROR    Fortran only: Error status (integer).


DESCRIPTION
       MPI_Comm_join creates an intercommunicator from the union of two MPI
       processes that are connected by a socket. fd is a file descriptor
       representing a socket of type SOCK_STREAM (a two-way reliable byte-
       stream connection). Nonblocking I/O and asynchronous notification via
       SIGIO must not be enabled for the socket. The socket must be in a
       connected state, and must be quiescent when MPI_Comm_join is called.

       MPI_Comm_join must be called by the process at each end of the socket.
       It does not return until both processes have called MPI_Comm_join.


NOTES
       There are no MPI library calls for opening and manipulating a socket.
       The socket fd can be opened using standard socket API calls.  MPI uses
       the socket to bootstrap creation of the intercommunicator, and for
       nothing else. Upon return, the file descriptor will be open and
       quiescent.

       In a multithreaded process, the application must ensure that other
       threads do not access the socket while one is in the midst of calling
       MPI_Comm_join.

       The returned communicator will contain the two processes connected by
       the socket, and may be used to establish MPI communication with
       additional processes, through the usual MPI communicator-creation
       mechanisms.


ERRORS
       Almost all MPI routines return an error value; C routines as the value
       of the function and Fortran routines in the last argument. C++
       functions do not return errors. If the default error handler is set to
       MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism
       will be used to throw an MPI:Exception object.

       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 the MPI man page for a full list of MPI error codes.


SEE ALSO
       socket(3SOCKET)
       MPI_Comm_create
       MPI_Comm_group




1.4.1                            Jan 14, 2010                 MPI_Comm_join(3)
