trusty (3) MPI_Comm_join.3.gz

NAME

       MPI_Comm_join -  Connect two MPI processed joined by a socket

SYNOPSIS

       #include <mpi.h>
       int
       MPI_Comm_join(int fd, MPI_Comm *newcomm)

INPUT PARAMETER

       fd     - socket file descriptor

OUTPUT PARAMETER

       newcomm
              - intercommunicator with client as remote group

DESCRIPTION

       This  function only works between two LAM/MPI processes that are connected by a socket.  They either must
       have the same endian orientation, or not have used  the  homogeneous  flag  to  mpirun  (1)  (-O).   Both
       processes  must  be in a single LAM universe -- they must share LAM daemons that are already connected to
       each other.  That is, they were either initially lamboot(1)ed together, or a lamgrow(1) command was given
       to grow an initial LAM universe such that the resulting set includes the two hosts in question.

       The  socket  may  not  be  used  by  the  calling  application  until  MPI_Comm_join has completed.  When
       MPI_Comm_join completes, fd may be used by the calling application.  Per MPI-2, the socket is  only  used
       for  initial handshaking -- it will not be used as the communications channel between the newly connected
       processes.

SAMPLE

       The following code shows an abbreviated example using MPI_Comm_join since no example is provided  in  the
       MPI-2  standard.   Note  that  only one rank in each MPI application should call this function since each
       socket can only have two endpoints (i.e., an endpoint in each process).  Upon successful completion,  the
       intercommunicator that is returned will have two members -- the local process and the remote process.

       MPI_Comm
       do_join(char* server_name, int port) {
       int sfd, fd = -1;
       unsigned char addr[4];
       MPI_Comm intercomm;
       if (server_name != NULL) {
       if (getinetaddr(server_name, &addr) == 0)
       fd = open_socket_to_server(addr, port);
       } else {
       if ((sfd = open_listening_socket(&port)) >= 0) {
       fd = accept_client_socket(sfd, -1);
       close(sfd);
       }
       }
       if (fd < 0)
       MPI_Abort(MPI_COMM_WORLD, 0);
       MPI_Comm_join(fd, &intercomm);
       return intercomm;
       }

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.

USAGE WITH IMPI EXTENSIONS

       The  IMPI  standard  only  supports  MPI-1  functions.  Hence, this function is currently not designed to
       operate within an IMPI job.

ERRORS

       If an error occurs in an MPI function, the current MPI error handler is called to handle it.  By default,
       this  error  handler  aborts the MPI job.  The error handler may be changed with MPI_Errhandler_set ; the
       predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be  returned  (in  C  and
       Fortran;  this  error  handler is less useful in with the C++ MPI bindings.  The predefined error handler
       MPI::ERRORS_THROW_EXCEPTIONS should be used in C++ if the error value needs to be recovered).  Note  that
       MPI does not guarantee that an MPI program can continue past an error.

       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.  The C++ bindings for MPI do not return error values;
       instead,  error  values  are  communicated  by  throwing  exceptions  of  type MPI::Exception (but not by
       default).  Exceptions are only thrown if the error value is not MPI::SUCCESS .

       Note that if the MPI::ERRORS_RETURN handler is set in C++, while MPI functions will return upon an error,
       there will be no way to recover what the actual error value was.
       MPI_SUCCESS
              - No error; MPI routine completed successfully.
       MPI_ERR_ARG
              -  Invalid  argument.   Some  argument is invalid and is not identified by a specific error class.
              This is typically a NULL pointer or other such error.
       MPI_ERR_INTERN
              - An internal error has been detected.  This is fatal.  Please  send  a  bug  report  to  the  LAM
              mailing list (see http://www.lam-mpi.org/contact.php ).
       MPI_ERR_OTHER
              - Other error; use MPI_Error_string to get more information about this error code.

SEE ALSO

       lamboot(1), lamgrow(1), mpirun(1), MPI_Finalize(3)

MORE INFORMATION

       For  more  information,  please  see the official MPI Forum web site, which contains the text of both the
       MPI-1 and MPI-2 standards.  These documents contain detailed information about each MPI function (most of
       which is not duplicated in these man pages).

       http://www.mpi-forum.org/

LOCATION

       join.c