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MPI_File_read_at_all_begin - Reads a file at explicitly specified
offsets; beginning part of a split collective routine (nonblocking).
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)
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
#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.
- buf
- Initial address of buffer (choice).
- IERROR
- Fortran only: Error status (integer).
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.
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.
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.
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.
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