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
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_COMM_JOIN(FD, INTERCOMM, IERROR)
INTEGER FD, INTERCOMM, IERROR
Fortran 2008 Syntax
USE mpi_f08
MPI_Comm_join(fd, intercomm, ierror)
INTEGER, INTENT(IN) :: fd
TYPE(MPI_Comm), INTENT(OUT) :: intercomm
INTEGER, OPTIONAL, INTENT(OUT) :: 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 rep-
resenting 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 quies-
cent.
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 addi-
tional processes, through the usual MPI communicator-creation mecha-
nisms.
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++ func-
tions 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
4.1.2 Nov 24, 2021 MPI_Comm_join(3)
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