NAME¶
MPI_File_read_ordered_begin - Reads a file at a location specified by a
shared file pointer; beginning part of a split collective routine
(nonblocking).
SYNTAX¶
C Syntax
#include <mpi.h>
int MPI_File_read_ordered_begin(MPI_File fh, void *buf,
int count, MPI_Datatype datatype)
Fortran Syntax¶
INCLUDE 'mpif.h'
MPI_FILE_READ_ORDERED_BEGIN( FH, BUF, COUNT, DATATYPE, IERROR)
<type> BUF(*)
INTEGER FH, COUNT, DATATYPE, IERROR
C++ Syntax¶
#include <mpi.h>
void MPI::File::Read_ordered_begin(void* buf, int count,
const MPI::Datatype& datatype)
- fh
- File handle (handle).
- count
- Number of elements in buffer (integer).
- datatype
- Data type of each buffer element (handle).
OUTPUT PARAMETERS¶
- buf
- Initial address of buffer (choice).
- IERROR
- Fortran only: Error status (integer).
DESCRIPTION¶
MPI_File_read_ordered_begin is the beginning part of a split collective,
nonblocking routine that must be called by all processes in the communicator
group associated with the file handle
fh. Each process may pass
different argument values for the
datatype and
count arguments.
Each process attempts to read, from the file associated with
fh, a
total number of
count data items having
datatype type into the
user's buffer
buf. For each process, the location in the file at which
data is read is the position at which the shared file pointer would be after
all processes whose ranks within the group are less than that of this process
had read their data.
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.