17.2.254. MPI_Mprobe

MPI_Mprobe - Blocking matched probe for a message.

17.2.254.1. SYNTAX

17.2.254.1.1. C Syntax

#include <mpi.h>

int MPI_Mprobe(int source, int tag, MPI_Comm comm,
     MPI_Message *message, MPI_Status *status)

17.2.254.1.2. Fortran Syntax

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

17.2.254.1.3. Fortran 2008 Syntax

USE mpi_f08
MPI_Mprobe(source, tag, comm, message, status, ierror)
     INTEGER, INTENT(IN) :: source, tag
     TYPE(MPI_Comm), INTENT(IN) :: comm
     TYPE(MPI_Message), INTENT(OUT) :: message
     TYPE(MPI_Status) :: status
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

17.2.254.2. INPUT PARAMETERS

  • source: Source rank or MPI_ANY_SOURCE (integer).

  • tag: Tag value or MPI_ANY_TAG (integer).

  • comm: Communicator (handle).

17.2.254.3. OUTPUT PARAMETERS

  • message: Message (handle).

  • status: Status object (status).

  • IERROR: Fortran only: Error status (integer).

17.2.254.4. 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 message = MPI_MESSAGE_NO_PROC, and the status object returns source = MPI_PROC_NULL, tag = MPI_ANY_TAG, and count = 0.

When MPI_Mprobe returns (from a non-MPI_PROC_NULL source), the matched message can then be received by passing the message handle to the MPI_Mrecv or MPI_Imrecv functions.

17.2.254.5. ERRORS

Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument.

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.