NAME¶
MPI_File_read_at_all_begin - Reads a file at explicitly specified
offsets; beginning part of a split collective routine (nonblocking).
SYNTAX¶
C Syntax
#include <mpi.h>
int MPI_File_read_at_all_begin(MPI_File fh, MPI_Offset
offset, void *buf, int count, MPI_Datatype
datatype)
Fortran Syntax (see FORTRAN 77 NOTES)¶
INCLUDE 'mpif.h'
MPI_FILE_READ_AT_ALL_BEGIN( FH, OFFSET, BUF,
COUNT, DATATYPE, IERROR)
<type> BUF(*)
INTEGER FH, COUNT, DATATYPE, IERROR
INTEGER(KIND=MPI_OFFSET_KIND) OFFSET
C++ Syntax¶
#include <mpi.h>
void MPI::File::Read_at_all_begin(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.
OUTPUT PARAMETERS¶
- buf
- Initial address of buffer (choice).
- IERROR
- Fortran only: Error status (integer).
DESCRIPTION¶
MPI_File_read_at_all_begin is the beginning part of a split collective routine
that 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.
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.
NOTES¶
All the nonblocking collective routines for data access are "split"
into two routines, each with _begin or _end as a suffix. These split
collective routines are subject to the semantic rules described in Section
9.4.5 of the MPI-2 standard.
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.