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MPI_Improbe.3.rst

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MPI_Improbe

:ref:`MPI_Improbe` |mdash| 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

Fortran 2008 Syntax

USE mpi_f08
MPI_Improbe(source, tag, comm, flag, message, status, ierror)
     INTEGER, INTENT(IN) :: source, tag
     TYPE(MPI_Comm), INTENT(IN) :: comm
     INTEGER, INTENT(OUT) :: flag
     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

  • flag: Flag (logical).
  • 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 flag = true,

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

:ref:`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 :ref:`MPI_Mrecv` or :ref:`MPI_Imrecv` functions, provided the source was not MPI_PROC_NULL.

ERRORS

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