Skip to content

Latest commit

 

History

History
122 lines (85 loc) · 3.24 KB

MPI_Test.3.rst

File metadata and controls

122 lines (85 loc) · 3.24 KB
Raw

MPI_Test

:ref:`MPI_Test` - Tests for the completion of a specific send or receive.

SYNTAX

C Syntax

#include <mpi.h>

int MPI_Test(MPI_Request *request, int *flag, MPI_Status *status)

Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_TEST(REQUEST, FLAG, STATUS, IERROR)
     LOGICAL FLAG
     INTEGER REQUEST, STATUS(MPI_STATUS_SIZE), IERROR

Fortran 2008 Syntax

USE mpi_f08
MPI_Test(request, flag, status, ierror)
     TYPE(MPI_Request), INTENT(INOUT) :: request
     LOGICAL, INTENT(OUT) :: flag
     TYPE(MPI_Status) :: status
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETER

  • request: Communication request (handle).

OUTPUT PARAMETERS

  • flag: True if operation completed (logical).
  • status: Status object (status).
  • ierror: Fortran only: Error status (integer).

DESCRIPTION

A call to :ref:`MPI_Test` returns flag = true if the operation identified by request is complete. In such a case, the status object is set to contain information on the completed operation; if the communication object was created by a nonblocking send or receive, then it is deallocated and the request handle is set to MPI_REQUEST_NULL. The call returns flag = false, otherwise. In this case, the value of the status object is undefined. :ref:`MPI_Test` is a local operation.

The return status object for a receive operation carries information that can be accessed as described in Section 3.2.5 of the MPI-1 Standard, "Return Status." The status object for a send operation carries information that can be accessed by a call to :ref:`MPI_Test_cancelled` (see Section 3.8 of the MPI-1 Standard, "Probe and Cancel").

If your application does not need to examine the status field, you can save resources by using the predefined constant MPI_STATUS_IGNORE as a special value for the status argument.

One is allowed to call :ref:`MPI_Test` with a null or inactive request argument. In such a case the operation returns with flag = true and empty status.

The functions :ref:`MPI_Wait` and :ref:`MPI_Test` can be used to complete both sends and receives.

NOTES

The use of the nonblocking :ref:`MPI_Test` call allows the user to schedule alternative activities within a single thread of execution. An event-driven thread scheduler can be emulated with periodic calls to :ref:`MPI_Test`.

ERRORS

Note that per MPI-1 section 3.2.5, MPI errors on requests passed to :ref:`MPI_TEST` do not set the status.MPI_ERROR field in the returned status. The error code is passed to the back-end error handler and may be passed back to the caller through the return value of :ref:`MPI_TEST` if the back-end error handler returns it. The pre-defined MPI error handler MPI_ERRORS_RETURN exhibits this behavior, for example.

.. seealso::
   * :ref:`MPI_Comm_set_errhandler`
   * :ref:`MPI_File_set_errhandler`
   * :ref:`MPI_Testall`
   * :ref:`MPI_Testany`
   * :ref:`MPI_Testsome`
   * :ref:`MPI_Wait`
   * :ref:`MPI_Waitall`
   * :ref:`MPI_Waitany`
   * :ref:`MPI_Waitsome`
   * :ref:`MPI_Win_set_errhandler`