NAME

MPI_Improbe - Non-blocking matched probe for a message.

SYNTAX

C Syntax

#include <mpi.h>
int MPI_Improbe(int source, int tag, MPI_Comm comm,
	int *flag, MPI_Message *message, MPI_Status *status)

Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_IMPROBE(SOURCE, TAG, COMM, FLAG, MESSAGE, STATUS, IERROR)
	LOGICAL	FLAG
	INTEGER	SOURCE, TAG, COMM, MESSAGE
	INTEGER	STATUS(MPI_STATUS_SIZE), IERROR

C++ Syntax

There is no C++ binding for this function.

INPUT PARAMETERS

source: Source rank or MPI_ANY_SOURCE (integer).
tag: Tag value or MPI_ANY_TAG (integer).
comm: Communicator (handle).

OUTPUT PARAMETERS

flag: Flag (logical).
message: Message (handle).
status: Status object (status).
IERROR: Fortran only: Error status (integer).

DESCRIPTION

Like MPI_Probe and MPI_Iprobe, the MPI_Mprobe and MPI_Improbe operations allow incoming messages to be queried without actually receiving them, except that MPI_Mprobe and MPI_Improbe provide a mechanism to receive the specific message that was matched regardless of other intervening probe or receive operations. This gives the application an opportunity to decide how to receive the message, based on the information returned by the probe. In particular, the application may allocate memory for the receive buffer according to the length of the probed message.

A matching probe with MPI_PROC_NULL as source returns flag = true, message = MPI_MESSAGE_NO_PROC, and the status object returns source = MPI_PROC_NULL, tag = MPI_ANY_TAG, and count = 0.

MPI_Iprobe returns a true value in flag if a message has been matched and can be received by passing the message handle to the MPI_Mrecv or MPI_Imrecv functions, provided the source was not MPI_PROC_NULL.

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.