NAME

MPI_File_iread - Reads a file starting at the location specified by the individual file pointer (nonblocking, noncollective).

SYNTAX

C Syntax

#include <mpi.h>
int MPI_File_iread(MPI_File fh, void  *buf, int  count,
	MPI_Datatype  datatype, MPI_Request  *request)

Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_FILE_IREAD(FH, BUF, COUNT, DATATYPE, REQUEST, IERROR)
	<type>	BUF(*)
	INTEGER	FH, COUNT, DATATYPE, REQUEST, IERROR

Fortran 2008 Syntax

USE mpi_f08
MPI_File_iread(fh, buf, count, datatype, request, ierror)
	TYPE(MPI_File), INTENT(IN) :: fh
	TYPE(*), DIMENSION(..), ASYNCHRONOUS :: buf
	INTEGER, INTENT(IN) :: count
	TYPE(MPI_Datatype), INTENT(IN) :: datatype
	TYPE(MPI_Request), INTENT(OUT) :: request
	INTEGER, OPTIONAL, INTENT(OUT) :: ierror

C++ Syntax

#include <mpi.h>
MPI::Request MPI::File::Iread(void* buf, int count,
	const MPI::Datatype& datatype)

INPUT/OUTPUT PARAMETER

fh

File handle (handle).

INPUT PARAMETERS

count

Number of elements in the buffer (integer).

datatype

Data type of each buffer element (handle).

OUTPUT PARAMETERS

buf

Initial address of buffer (choice).

request

Request object (handle).

IERROR

Fortran only: Error status (integer).

DESCRIPTION

MPI_File_iread is a nonblocking version of MPI_File_read. It attempts to read from the file associated with fh at the current individual file pointer position maintained by the system in which a total number of count data items having datatype type are read into the user's buffer buf. The data is taken out of those parts of the file specified by the current view. MPI_File_iread stores the number of data-type 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.

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.