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MPI_Mprobe.3.rst

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MPI_Mprobe

:ref:`MPI_Mprobe` |mdash| Blocking matched probe for a message.

SYNTAX

C Syntax

#include <mpi.h>

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

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

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

INPUT PARAMETERS

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

OUTPUT PARAMETERS

  • message: Message (handle).
  • status: Status object (status).
  • ierror: Fortran only: Error status (integer).

DESCRIPTION

Like :ref:`MPI_Probe` and :ref:`MPI_Iprobe`, the :ref:`MPI_Mprobe` and :ref:`MPI_Improbe` operations allow incoming messages to be queried without actually receiving them, except that :ref:`MPI_Mprobe` and :ref:`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 :ref:`MPI_Mprobe` returns (from a non-MPI_PROC_NULL source), the matched message can then be received by passing the message handle to the :ref:`MPI_Mrecv` or :ref:`MPI_Imrecv` functions.

ERRORS

.. seealso::
   * :ref:`MPI_Improbe`
   * :ref:`MPI_Probe`
   * :ref:`MPI_Iprobe`
   * :ref:`MPI_Mrecv`
   * :ref:`MPI_Imrecv`
   * :ref:`MPI_Cancel`