MPI_FILE_WRITE_ORDERED_BEGIN(3)			     Open MPI			   MPI_FILE_WRITE_ORDERED_BEGIN(3)

MPI_File_write_ordered_begin — Writes a file at a location specified by a shared file pointer; beginning part of a
split collective routine (nonblocking).

SYNTAX
   C Syntax
	  #include <mpi.h>

	  int MPI_File_write_ordered_begin(MPI_File fh, const void *buf,
	      int count, MPI_Datatype datatype)

   Fortran Syntax
	  USE MPI
	  ! or the older form: INCLUDE 'mpif.h'

	  MPI_FILE_WRITE_ORDERED_BEGIN(FH, BUF, COUNT, DATATYPE, IERROR)
	      <type>  BUF(*)
	      INTEGER FH, COUNT, DATATYPE, IERROR

   Fortran 2008 Syntax
	  USE mpi_f08

	  MPI_File_write_ordered_begin(fh, buf, count, datatype, ierror)
	      TYPE(MPI_File), INTENT(IN) :: fh
	      TYPE(*), DIMENSION(..), INTENT(IN), ASYNCHRONOUS :: buf
	      INTEGER, INTENT(IN) :: count
	      TYPE(MPI_Datatype), INTENT(IN) :: datatype
	      INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT/OUTPUT PARAMETER
       • fh : File handle (handle).

INPUT PARAMETERS
       • buf : Initial address of buffer (choice).

       • count : Number of elements in buffer (integer).

       • datatype : Data type of each buffer element (handle).

OUTPUT PARAMETER
       • ierror : Fortran only: Error status (integer).

DESCRIPTION
       MPI_File_write_ordered_begin  is the beginning part of a split collective, nonblocking routine that must be
       called by all processes in the communicator group associated with the file handle fh. Each process may pass
       different argument values for the datatype and count arguments. After  all  processes  of  the  group  have
       issued  their  respective  calls, each process attempts to write, into the file associated with fh, a total
       number of count data items having datatype type contained in the user’s buffer buf. For each  process,  the
       location	 in  the  file	at which data is written is the position at which the shared file pointer would be
       after all processes whose ranks within the group are less than that of this process had written their data.

NOTES
       All the nonblocking collective routines for data access are “split” into two routines, each with _begin	or
       _end  as	 a  suffix. These split collective routines are subject to the semantic rules described in Section
       9.4.5 of the MPI-2 standard.

ERRORS
       Almost all MPI routines return an error value; C routines as the return result of the function and  Fortran
       routines in the last argument.

       Before  the error value is returned, the current MPI error handler associated with the communication object
       (e.g., communicator, window, file) is called.  If no communication object is associated with the MPI  call,
       then  the call is considered attached to MPI_COMM_SELF and will call the associated MPI error handler. When
       MPI_COMM_SELF is not initialized (i.e.,	before	MPI_Init  <#mpi-init>/MPI_Init_thread  <#mpi-init-thread>,
       after  MPI_Finalize  <#mpi-finalize>,  or  when	using the Sessions Model exclusively) the error raises the
       initial error handler. The initial error handler can  be	 changed  by  calling  MPI_Comm_set_errhandler	<#
       mpi-comm-set-errhandler>	 on  MPI_COMM_SELF  when  using the World model, or the mpi_initial_errhandler CLI
       argument	 to  mpiexec  or  info	key   to   MPI_Comm_spawn   <#mpi-comm-spawn>/MPI_Comm_spawn_multiple	<#
       mpi-comm-spawn-multiple>.   If  no other appropriate error handler has been set, then the MPI_ERRORS_RETURN
       error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error  handler  is  called  for  all
       other MPI functions.

       Open MPI includes three predefined error handlers that can be used:

       • MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI processes.

       • MPI_ERRORS_ABORT  An  error handler that can be invoked on a communicator, window, file, or session. When
	 called on a communicator, it acts as if MPI_Abort <#mpi-abort> was called on that communicator. If called
	 on a window or file, acts as if MPI_Abort <#mpi-abort> was called on a communicator containing the  group
	 of processes in the corresponding window or file. If called on a session, aborts only the local process.

       • MPI_ERRORS_RETURN Returns an error code to the application.

       MPI applications can also implement their own error handlers by calling:

       • MPI_Comm_create_errhandler	 <#mpi-comm-create-errhandler>	   then	    MPI_Comm_set_errhandler	<#
	 mpi-comm-set-errhandler>

       • MPI_File_create_errhandler	<#mpi-file-create-errhandler>	  then	   MPI_File_set_errhandler	<#
	 mpi-file-set-errhandler>

       • MPI_Session_create_errhandler	 <#mpi-session-create-errhandler>   then   MPI_Session_set_errhandler	<#
	 mpi-session-set-errhandler> or at MPI_Session_init <#mpi-session-init>

       • MPI_Win_create_errhandler	<#mpi-win-create-errhandler>	  then	    MPI_Win_set_errhandler	<#
	 mpi-win-set-errhandler>

       Note that MPI does not guarantee that an MPI program can continue past an error.

       See the MPI man page <#open-mpi> for a full list of MPI error codes <#open-mpi-errors>.

       See the Error Handling section of the MPI-3.1 standard for more information.

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026			   MPI_FILE_WRITE_ORDERED_BEGIN(3)
