plucky (3) MPI_File_set_view.openmpi.3.gz

Provided by: openmpi-doc_5.0.7-1_all bug

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_thread,  after
       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 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_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 was called on  that  communicator.  If  called  on  a
         window  or file, acts as if 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 then MPI_Comm_set_errhandler

       • MPI_File_create_errhandler then MPI_File_set_errhandler

       • MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init

       • MPI_Win_create_errhandler then MPI_Win_set_errhandler

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

       See the MPI man page for a full list of MPI error codes.

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


       2003-2025, The Open MPI Community

                                                  Feb 17, 2025                              MPI_FILE_SET_VIEW(3)