.\" -*- nroff -*-
.\" Copyright 2013 Los Alamos National Security, LLC. All rights reserved.
.\" Copyright 2010 Cisco Systems, Inc.  All rights reserved.
.\" Copyright 2006-2008 Sun Microsystems, Inc.
.\" Copyright (c) 1996 Thinking Machines Corporation
.TH MPI_File_iwrite 3 "#OMPI_DATE#" "#PACKAGE_VERSION#" "#PACKAGE_NAME#"
.SH NAME
\fBMPI_File_iwrite\fP \- Writes a file starting at the location specified by the individual file pointer (nonblocking, noncollective).

.SH SYNTAX
.ft R
.nf
C Syntax
    #include <mpi.h>
    int MPI_File_iwrite(MPI_File \fIfh\fP, const void \fI*buf\fP, int \fIcount\fP,
    	      MPI_Datatype \fIdatatype\fP, MPI_Request \fI*request\fP)

.fi
.SH Fortran Syntax
.nf
    INCLUDE 'mpif.h'
    MPI_FILE_IWRITE(\fIFH\fP, \fIBUF\fP, \fICOUNT\fP, \fIDATATYPE\fP, \fIREQUEST\fP,\fI IERROR\fP)
		<TYPE>		BUF(*)
        	INTEGER		FH, COUNT, DATATYPE, REQUEST, IERROR

.fi
.SH C++ Syntax
.nf
#include <mpi.h>
MPI::Request MPI::File::Iwrite(const void* \fIbuf\fP, int \fIcount\fP,
	const MPI::Datatype& \fIdatatype\fP)

.fi
.SH INPUT/OUTPUT PARAMETER
.ft R
.TP 1i
fh    
File handle (handle).

.SH INPUT PARAMETERS
.ft R
.TP 1i
buf
Initial address of buffer (choice).
.ft R
.TP 1i
count
Number of elements in buffer (integer).
.ft R
.TP 1i
datatype
Data type of each buffer element (handle).

.SH OUTPUT PARAMETER
.ft R
.TP 1i
request
Request object (handle). 
.TP 1i
IERROR
Fortran only: Error status (integer). 

.SH DESCRIPTION
.ft R
MPI_File_iwrite is a nonblocking version of the MPI_File_write interface. It attempts to write into the file associated with 
.I fh
(at the current individual file pointer position maintained by the system) a total number of 
.I count 
data items having
.I datatype 
type from the user's buffer 
.I buf.
The data is written into those parts of the
file specified by the current view. MPI_File_iwrite stores the
number of 
.I datatype 
elements actually written in 
.I status. 
All other fields of 
.I status 
are undefined.
.sp
It is erroneous to call this function if MPI_MODE_SEQUENTIAL mode was specified when the file was open. 

.SH 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.
.sp
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.