NAME

MPI_Imrecv - Non-blocking receive for a matched message

SYNTAX

C Syntax

#include <mpi.h>
int MPI_Imrecv(void *buf, int count, MPI_Datatype type,
	MPI_Message *message, MPI_Request *request)

Fortran Syntax

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

Fortran 2008 Syntax

USE mpi_f08
MPI_Imrecv(buf, count, datatype, message, request, ierror)
	TYPE(*), DIMENSION(..), ASYNCHRONOUS :: buf
	INTEGER, INTENT(IN) :: count
	TYPE(MPI_Datatype), INTENT(IN) :: datatype
	TYPE(MPI_Message), INTENT(INOUT) :: message
	TYPE(MPI_Request), INTENT(OUT) :: request
	INTEGER, OPTIONAL, INTENT(OUT) :: ierror

C++ Syntax

There is no C++ binding for this function.

INPUT PARAMETERS

count: Number of elements to receive (nonnegative integer).
datatype: Datatype of each send buffer element (handle).
message: Message (handle).

OUTPUT PARAMETERS

buf: Initial address of receive buffer (choice).
request: Request (handle).
IERROR: Fortran only: Error status (integer).

DESCRIPTION

The functions MPI_Mrecv and MPI_Imrecv receive messages that have been previously matched by a matching probe.

The request returned from MPI_Imrecv can be used with any of the MPI_Test and MPI_Wait variants, like any non-blocking receive request.

If MPI_Imrecv is called with MPI_MESSAGE_NULL as the message argument, a call to one of the MPI_Test or MPI_Wait variants will return immediately with the status object set to source = MPI_PROC_NULL, tag = MPI_ANY_TAG, and count = 0, as if a receive from MPI_PROC_NULL was issued.

If reception of a matched message is started with MPI_Imrecv, then it is possible to cancel the returned request with MPI_Cancel. If MPI_Cancel succeeds, the matched message must be found by a subsequent message probe (MPI_Probe, MPI_Iprobe, MPI_Mprobe, or MPI_Improbe), received by a subsequent receive operation or canceled by the sender.

Note, however, that is it possible for the cancellation of operations initiated with MPI_Imrecv to fail. An example of a failing case is when canceling the matched message receive would violate MPI message ordering rules (e.g., if another message matching the same message signature has matched -- and possible received -- before this MPI_Imrecv is canceled).

NOTE

This is an MPI-3 function and has no C++ binding.

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.

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.