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MPI_Testany.3.rst

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MPI_Testany

:ref:`MPI_Testany` - Tests for completion of any one previously initiated communication in a list.

SYNTAX

C Syntax

#include <mpi.h>

int MPI_Testany(int count, MPI_Request array_of_requests[],
     int *index, int *flag, MPI_Status *status)

Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_TESTANY(COUNT, ARRAY_OF_REQUESTS, INDEX, FLAG, STATUS, IERROR)
     LOGICAL FLAG
     INTEGER COUNT, ARRAY_OF_REQUESTS(*), INDEX
     INTEGER STATUS(MPI_STATUS_SIZE), IERROR

Fortran 2008 Syntax

USE mpi_f08
MPI_Testany(count, array_of_requests, index, flag, status, ierror)
     INTEGER, INTENT(IN) :: count
     TYPE(MPI_Request), INTENT(INOUT) :: array_of_requests(count)
     INTEGER, INTENT(OUT) :: index
     LOGICAL, INTENT(OUT) :: flag
     TYPE(MPI_Status) :: status
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS

  • count: List length (integer).
  • array_of_requests: Array of requests (array of handles).

OUTPUT PARAMETERS

  • index: Index of operation that completed, or MPI_UNDEFINED if none completed (integer).
  • flag: True if one of the operations is complete (logical).
  • status: Status object (status).
  • ierror: Fortran only: Error status (integer).

DESCRIPTION

:ref:`MPI_Testany` tests for completion of either one or none of the operations associated with active handles. In the former case, it returns flag = true, returns in index the index of this request in the array, and returns in status the status of that operation; if the request was allocated by a nonblocking communication call then the request is deallocated and the handle is set to MPI_REQUEST_NULL. (The array is indexed from 0 in C, and from 1 in Fortran.) In the latter case (no operation completed), it returns flag = false, returns a value of MPI_UNDEFINED in index, and status is undefined.

The array may contain null or inactive handles. If the array contains no active handles then the call returns immediately with flag = true, index = MPI_UNDEFINED, and an empty status.

If the array of requests contains active handles then the execution of MPI_Testany(count, array_of_requests, index, status) has the same effect as the execution of MPI_Test(&array_of_requests[i], flag, status), for i=0,1,...,count-1, in some arbitrary order, until one call returns flag = true, or all fail. In the former case, index is set to the last value of i, and in the latter case, it is set to MPI_UNDEFINED. :ref:`MPI_Testany` with an array containing one active entry is equivalent to :ref:`MPI_Test`.

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.

ERRORS

Note that per MPI-1 section 3.2.5, MPI errors on requests passed to :ref:`MPI_TESTANY` 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_TESTANY` 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_Test`
   * :ref:`MPI_Testall`
   * :ref:`MPI_Testsome`
   * :ref:`MPI_Wait`
   * :ref:`MPI_Waitall`
   * :ref:`MPI_Waitany`
   * :ref:`MPI_Waitsome`
   * :ref:`MPI_Win_set_errhandler`