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MPI_Start(3)                       Open MPI                       MPI_Start(3)

NAME
       MPI_Start  -  Initiates a communication using a persistent request han-
       dle.

SYNTAX
C Syntax
       #include <mpi.h>
       int MPI_Start(MPI_Request *request)

Fortran Syntax
       USE MPI
       ! or the older form: INCLUDE 'mpif.h'
       MPI_START(REQUEST, IERROR)
            INTEGER   REQUEST, IERROR

Fortran 2008 Syntax
       USE mpi_f08
       MPI_Start(request, ierror)
            TYPE(MPI_Request), INTENT(INOUT) :: request
            INTEGER, OPTIONAL, INTENT(OUT) :: ierror

C++ Syntax
       #include <mpi.h>
       void Prequest::Start()

INPUT PARAMETER
       request   Communication request (handle).

OUTPUT PARAMETER
       IERROR    Fortran only: Error status (integer).

DESCRIPTION
       A communication (send or receive) that uses  a  persistent  request  is
       initiated by the function MPI_Start.

       The  argument,  request,  is a handle returned by one of the persistent
       communication-request    initialization    functions    (MPI_Send_init,
       MPI_Bsend_init,   MPI_Ssend_init,  MPI_Rsend_init,  MPI_Recv_init). The
       associated request should be inactive and becomes active once the  call
       is made.

       If  the  request is for a send with ready mode, then a matching receive
       should be posted before the call is made. From the  time  the  call  is
       made  until  after  the  operation  completes, the communication buffer
       should not be accessed.

       The call is local, with semantics similar to the nonblocking communica-
       tion  operations  (see  Section 3.7 in the MPI-1 Standard, "Nonblocking
       Communication.") That is, a call to MPI_Start with a request created by
       MPI_Send_init  starts  a  communication in the same manner as a call to
       MPI_Isend; a call to MPI_Start with a request created by MPI_Bsend_init
       starts  a communication in the same manner as a call to MPI_Ibsend; and
       so on.

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 ALSO
       MPI_Bsend_init
       MPI_Rsend_init
       MPI_Send_init
       MPI_Sssend_init
       MPI_Recv_init
       MPI_Startall

4.1.2                            Nov 24, 2021                     MPI_Start(3)

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