1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
|
.. _mpi_test:
MPI_Test
========
.. include_body
:ref:`MPI_Test` |mdash| Tests for the completion of a specific send or receive.
SYNTAX
------
C Syntax
^^^^^^^^
.. code-block:: c
#include <mpi.h>
int MPI_Test(MPI_Request *request, int *flag, MPI_Status *status)
Fortran Syntax
^^^^^^^^^^^^^^
.. code-block:: fortran
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
^^^^^^^^^^^^^^^^^^^
.. code-block:: fortran
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 the "Return Status" subsection of
the "Point-to-Point Communication" chapter in the `MPI Standard
<https://www.mpi-forum.org/docs/>`_. The status object for a send
operation carries information that can be accessed by a call to
:ref:`MPI_Test_cancelled` (see the "Probe and Cancel" section of the
`MPI Standard <https://www.mpi-forum.org/docs/>`_).
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
------
.. include:: ./ERRORS.rst
Note that per the "Return Status" section in the "Point-to-Point
Communication" chapter in the `MPI Standard
<https://www.mpi-forum.org/docs/>`_, 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 always 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`
|
