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MPI_Imrecv.3.rst

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MPI_Imrecv

:ref:`MPI_Imrecv` - 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

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_IMRECV(BUF, COUNT, DATATYPE, MESSAGE, REQUEST, IERROR)
     <type>  BUF(*)
     INTEGER COUNT, DATATYPE, MESSAGE, REQUEST, IERROR

Fortran 2008 Syntax

USE mpi_f08
MPI_Imrecv(buf, count, datatype, message, request, ierror)
     TYPE(*), DIMENSION(..), ASYNCHRONOUS :: buf
     INTEGER, INTENT(IN) :: count
     TYPE(MPI_Datatype), INTENT(IN) :: datatype
     TYPE(MPI_Message), INTENT(INOUT) :: message
     TYPE(MPI_Request), INTENT(OUT) :: request
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

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 :ref:`MPI_Mrecv` and :ref:`MPI_Imrecv` receive messages that have been previously matched by a matching probe.

The request returned from :ref:`MPI_Imrecv` can be used with any of the :ref:`MPI_Test` and :ref:`MPI_Wait` variants, like any non-blocking receive request.

If :ref:`MPI_Imrecv` is called with MPI_MESSAGE_NULL as the message argument, a call to one of the :ref:`MPI_Test` or :ref:`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 :ref:`MPI_Imrecv`, then it is possible to cancel the returned request with :ref:`MPI_Cancel`. If :ref:`MPI_Cancel` succeeds, the matched message must be found by a subsequent message probe (:ref:`MPI_Probe`, :ref:`MPI_Iprobe`, :ref:`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 :ref:`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 :ref:`MPI_Imrecv` is canceled).

ERRORS

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