MPI_File_set_view(3) Open MPI MPI_File_set_view(3)NAMEMPI_File_set_view - Changes process's view of data in file (collec‐
tive).
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)
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, file‐
type, 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 commit‐
ted.
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-repre‐
sentation string to MPI I/O via the datarep argument. To obtain the
default value (or "native"), pass NULL. The user can also pass informa‐
tion 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 rou‐
tines can bind an extra thread to an LWP.
- mpiio_coll_contiguous: (boolean) controls whether subsequent collec‐
tive 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 argu‐
ment 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++ 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. 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.
1.7.4 Feb 04, 2014 MPI_File_set_view(3)
