.\" -*- nroff -*-
.\" Copyright 2013 Los Alamos National Security, LLC. All rights reserved.
.\" Copyright (c) 2010-2015 Cisco Systems, Inc.  All rights reserved.
.\" Copyright 2006-2008 Sun Microsystems, Inc.
.\" Copyright (c) 1996 Thinking Machines Corporation
.\" $COPYRIGHT$
.TH MPI_Irsend 3 "Sep 30, 2023" "4.1.6" "Open MPI"
.SH NAME
\fBMPI_Irsend\fP \- Starts a ready-mode nonblocking send.

.SH SYNTAX
.ft R
.SH C Syntax
.nf
#include <mpi.h>
int MPI_Irsend(const void *\fIbuf\fP, int\fI count\fP, MPI_Datatype\fI datatype\fP, int\fI dest\fP,
	int\fI tag\fP, MPI_Comm\fI comm\fP, MPI_Request\fI *request\fP)

.fi
.SH Fortran Syntax
.nf
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_IRSEND(\fIBUF, COUNT, DATATYPE, DEST, TAG, COMM, REQUEST, IERROR\fP)
	<type>	\fIBUF\fP(*)
	INTEGER	\fICOUNT, DATATYPE, DEST, TAG, COMM, REQUEST, IERROR\fP

.fi
.SH Fortran 2008 Syntax
.nf
USE mpi_f08
MPI_Irsend(\fIbuf\fP, \fIcount\fP, \fIdatatype\fP, \fIdest\fP, \fItag\fP, \fIcomm\fP, \fIrequest\fP, \fIierror\fP)
	TYPE(*), DIMENSION(..), INTENT(IN), ASYNCHRONOUS :: \fIbuf\fP
	INTEGER, INTENT(IN) :: \fIcount\fP, \fIdest\fP, \fItag\fP
	TYPE(MPI_Datatype), INTENT(IN) :: \fIdatatype\fP
	TYPE(MPI_Comm), INTENT(IN) :: \fIcomm\fP
	TYPE(MPI_Request), INTENT(OUT) :: \fIrequest\fP
	INTEGER, OPTIONAL, INTENT(OUT) :: \fIierror\fP

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

.fi
.SH INPUT PARAMETERS
.ft R
.TP 1i
buf
Initial address of send buffer (choice).
.TP 1i
count
Number of elements in send buffer (integer).
.TP 1i
datatype
Datatype of each send buffer element (handle).
.TP 1i
dest
Rank of destination (integer).
.TP 1i
tag
Message tag (integer).
.TP 1i
comm
Communicator (handle).

.SH OUTPUT PARAMETERS
.ft R
.TP 1i
request
Communication request (handle).
.ft R
.TP 1i
IERROR
Fortran only: Error status (integer).

.SH DESCRIPTION
.ft R
MPI_Irsend starts a ready-mode nonblocking send. Nonblocking calls allocate a communication request object and associate it with the request handle (the argument request). The request can be used later to query the status of the communication or to wait for its completion.
.sp
A nonblocking send call indicates that the system may start copying data out of the send buffer. The sender should not modify any part of the send buffer after a nonblocking send operation is called, until the send completes.

.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. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error.

.SH SEE ALSO
MPI_Rsend