MPI_Imrecv(3) 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

INCLUDE 'mpif.h'
MPI_IMRECV(BUF, COUNT, DATATYPE, MESSAGE, REQUEST, IERROR)
        <type>  BUF(*)
        INTEGER OUNT, DATATYPE, MESSAGE, REQUEST, 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.

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