Ubuntu Manpage: MPI_File_set_view - Changes process's view of data in file (collective).

NAME

       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 (see FORTRAN 77 NOTES)

       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

C++ Syntax

       #include <mpi.h>
       void MPI::File::Set_view(MPI::Offset disp,
            const MPI::Datatype& etype,
            const MPI::Datatype& filetype, const char* datarep,
            const MPI::Info& info)

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  (or  "native"),  pass  NULL.  The user can also pass
       information via the info argument. See the HINTS section for a list of hints that can be  set.  For  more
       information, see the MPI-2 standard.

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. (See NOTE, below.)

- noncoll_write_bufsize: Maximum size of the buffer used by MPI I/O to satisfy write requests in the
noncollective data-access routines. (See NOTE, below.)

- coll_read_bufsize: Maximum size of the buffer used by MPI I/O to satisfy read requests in the
collective data-access routines. (See NOTE, below.)

- coll_write_bufsize: Maximum size of the buffer used by MPI I/O to satisfy write requests in the
collective data-access routines. (See NOTE, below.)

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.

- 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.

FORTRAN 77 NOTES

       The MPI standard prescribes portable Fortran syntax for the DISP argument only for Fortran  90.   FORTRAN
       77 users may use the non-portable syntax

            INTEGER*MPI_OFFSET_KIND DISP

       where  MPI_OFFSET_KIND  is  a  constant defined in mpif.h and gives the length of the declared integer in
       bytes.

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++ functions 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. For MPI I/O function errors,
       the default  error  handler  is  set  to  MPI_ERRORS_RETURN.  The  error  handler  may  be  changed  with
       MPI_File_set_errhandler; the predefined error handler MPI_ERRORS_ARE_FATAL may be used to make I/O errors
       fatal. Note that MPI does not guarantee that an MPI program can continue past an error.

2.1.1                                             May 10, 2017                              MPI_File_set_view(3)