NAME¶
MPI_File_read_at - Reads a file at an explicitly specified offset
(blocking, noncollective).
SYNTAX¶
C Syntax
#include <mpi.h>
int MPI_File_read_at(MPI_File fh, MPI_Offset offset,
void *buf, int count, MPI_Datatype datatype,
MPI_Status *status)
Fortran Syntax (see FORTRAN 77 NOTES)¶
INCLUDE 'mpif.h'
MPI_FILE_READ_AT( FH, OFFSET, BUF, COUNT,
DATATYPE, STATUS, IERROR)
<type> BUF(*)
INTEGER FH, COUNT, DATATYPE, STATUS(MPI_STATUS_SIZE), IERROR
INTEGER(KIND=MPI_OFFSET_KIND) OFFSET
C++ Syntax¶
#include <mpi.h>
void MPI::File::Read_at(MPI::Offset offset, void* buf,
int count, const MPI::Datatype& datatype,
MPI::Status& status)
void MPI::File::Read_at(MPI::Offset offset, void* buf,
int count, const MPI::Datatype& datatype)
- fh
- File handle (handle).
- offset
- File offset (integer).
- count
- Number of elements in buffer (integer).
- datatype
- Data type of each buffer element (handle).
OUTPUT PARAMETERS¶
- buf
- Initial address of buffer (choice).
- status
- Status object (status).
- IERROR
- Fortran only: Error status (integer).
DESCRIPTION¶
MPI_File_read_at attempts to read from the file associated with
fh (at
the
offset position) a total number of
count data items having
datatype type into the user's buffer
buf. The
offset is
in
etype units relative to the current view. That is, holes are not
counted when locating an offset. The data is taken out of those parts of the
file specified by the current view. MPI_File_read_at stores the number of
datatype elements actually read in
status. All other fields of
status are undefined. It is erroneous to call this function if
MPI_MODE_SEQUENTIAL mode was specified when the file was opened.
FORTRAN 77 NOTES¶
The MPI standard prescribes portable Fortran syntax for the
OFFSET
argument only for Fortran 90. FORTRAN 77 users may use the non-portable syntax
INTEGER*MPI_OFFSET_KIND OFFSET
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.