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.