MPI_FILE_SET_VIEW(3)				     Open MPI				      MPI_FILE_SET_VIEW(3)

MPI_File_set_view — Changes process’s view of data in file (collective).

SYNTAX
   C Syntax
	  #include <mpi.h>

	  int MPI_File_set_view(MPI_File fh, MPI_Offset disp,
	       MPI_Datatype etype, MPI_Datatype filetype,
	       const char *datarep, MPI_Info info)

   Fortran Syntax
	  USE MPI
	  ! or the older form: INCLUDE 'mpif.h'
	  MPI_FILE_SET_VIEW(FH, DISP, ETYPE,
	       FILETYPE, DATAREP, INFO, IERROR)
	       INTEGER FH, ETYPE, FILETYPE, INFO, IERROR
	       CHARACTER*(*)   DATAREP
	       INTEGER(KIND=MPI_OFFSET_KIND)   DISP

   Fortran 2008 Syntax
	  USE mpi_f08
	  MPI_File_set_view(fh, disp, etype, filetype, datarep, info, ierror)
	       TYPE(MPI_File), INTENT(IN) :: fh
	       INTEGER(KIND=MPI_OFFSET_KIND), INTENT(IN) :: disp
	       TYPE(MPI_Datatype), INTENT(IN) :: etype, filetype
	       CHARACTER(LEN=*), INTENT(IN) :: datarep
	       TYPE(MPI_Info), INTENT(IN) :: info
	       INTEGER, OPTIONAL, INTENT(OUT) :: ierror

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

INPUT PARAMETERS
       • disp: Displacement (integer).

       • etype: Elementary data type (handle).

       • filetype: File type (handle). See Restrictions, below.

       • datarep: Data representation (string).

       • info: Info object (handle).

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

DESCRIPTION
       The  MPI_File_set_view  routine	changes	 the process’s view of the data in the file — the beginning of the
       data accessible in the file through that view is set to disp; the type of data is set  to  etype;  and  the
       distribution of data to processes is set to filetype. In addition, MPI_File_set_view resets the independent
       file  pointers  and  the	 shared	 file  pointer to zero. MPI_File_set_view is collective across the fh; all
       processes in the group must pass identical values for datarep  and  provide  an	etype  with  an	 identical
       extent.	The  values  for disp, filetype, and info may vary. It is erroneous to use the shared file pointer
       data-access routines unless identical values for disp and filetype are also given. The data types passed in
       etype and filetype must be committed.

       The disp displacement argument specifies the position (absolute offset in bytes from the beginning  of  the
       file) where the view begins.

       The  MPI_File_set_view  interface  allows  the user to pass a data-representation string to MPI I/O via the
       datarep argument. To obtain the default value pass the value “native”. The user can also	 pass  information
       via the info argument. See the HINTS section for a list of hints that can be set.

HINTS
       The following hints can be used as values for the info argument.

       SETTABLE HINTS

       • MPI_INFO_NULL

       • shared_file_timeout:  Amount  of  time	 (in seconds) to wait for access to the shared file pointer before
	 exiting with MPI_ERR_TIMEDOUT.

       • rwlock_timeout: Amount of time (in seconds) to wait for obtaining a read or write lock	 on  a	contiguous
	 chunk of a UNIX file before exiting with MPI_ERR_TIMEDOUT.

       • noncoll_read_bufsize:	Maximum	 size  of  the	buffer	used  by  MPI  I/O to satisfy read requests in the
	 noncollective data-access routines.

	 Note:
	    A buffer size smaller than the distance (in bytes) in a UNIX file between the first byte and the  last
	    byte  of  the  access  request  causes  MPI I/O to iterate and perform multiple UNIX read() or write()
	    calls. If the request includes multiple noncontiguous chunks of data, and the buffer size  is  greater
	    than the size of those chunks, then the UNIX read() or write() (made at the MPI I/O level) will access
	    data  not requested by this process in order to reduce the total number of write() calls made. If this
	    is not desirable behavior, you should reduce this buffer size to equal  the	 size  of  the	contiguous
	    chunks within the aggregate request.

       • noncoll_write_bufsize:	 Maximum  size	of  the	 buffer	 used  by MPI I/O to satisfy write requests in the
	 noncollective data-access routines.

	 See the above note in noncoll_read_bufsize.

       • coll_read_bufsize: Maximum size of the buffer used by MPI I/O to satisfy read requests in the	collective
	 data-access routines.

	 See the above note in noncoll_read_bufsize.

       • coll_write_bufsize:  Maximum  size  of	 the  buffer  used  by	MPI  I/O  to satisfy write requests in the
	 collective data-access routines.

	 See the above note in noncoll_read_bufsize.

       • mpiio_concurrency: (boolean) controls whether nonblocking I/O routines can bind an  extra  thread  to	an
	 LWP.

       • mpiio_coll_contiguous:	 (boolean)  controls  whether  subsequent  collective  data  accesses will request
	 collectively contiguous regions of the file.

       NON-SETTABLE HINTS

       • filename: Access this hint to get the name of the file.

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_SET_VIEW(3)
