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bpo-33521: Add 1.32x faster C implementation of asyncio.isfuture(). #6876

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bpo-33521 Optimize asyncio.isfuture by providing C implementation.
May 15, 2018
d689d5f
bpo-33521: Add 1.32x faster C implementation of asyncio.isfuture().
May 15, 2018
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1 change: 1 addition & 0 deletions Lib/asyncio/futures.py
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Original file line number Diff line number Diff line change
Expand Up @@ -381,4 +381,5 @@ def wrap_future(future, *, loop=None):
pass
else:
# _CFuture is needed for tests.
isfuture = _asyncio.isfuture
Future = _CFuture = _asyncio.Future
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2018-05-15-16-00-08.bpo-33521.GjWHfn.rst
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@@ -0,0 +1 @@
Add 1.32x faster C implementation of asyncio.isfuture().
46 changes: 46 additions & 0 deletions Modules/_asynciomodule.c
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Expand Up @@ -193,6 +193,51 @@ is_coroutine(PyObject *coro)
return has_it;
}

/*[clinic input]
_asyncio.isfuture

obj: object
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Make the argument positional-only.

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In pratice, it means adding "/" on a new line, aligned with "obj", and run "make clinic" again.

/

Return True if obj is a Future instance.

This returns True when obj is a Future instance or is advertising
itself as duck-type compatible by setting _asyncio_future_blocking.
See comment in Future for more details.

[clinic start generated code]*/

static PyObject *
_asyncio_isfuture(PyObject *module, PyObject *obj)
/*[clinic end generated code: output=3c79d083f507d4fa input=a71fdef4d9b354b4]*/
{
_Py_IDENTIFIER(__class__);
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Why not use Future_CheckExact() / Future_Check() as very fast happy path here?

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Good idea.

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@asvetlov @1st1 isfuture check if _asyncio_future_blocking exists and is not None because mock object has _asyncio_future_blocking as None and we want to return isfuture() as False in this case.
See test case

cpython/Lib/test/test_asyncio/test_futures.py

Lines 123 to 124 in 8425de4

# As `isinstance(Mock(), Future)` returns `False`
self.assertFalse(asyncio.isfuture(mock.Mock()))

Do we really want to use Future_CheckExact to return fast?

PyObject* class = _PyObject_GetAttrId(obj, &PyId___class__);
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It is better to use Py_TYPE() for convenience and speed . There is a subtle difference between the type and the __class__ attribute, but it is usually ignored when write C accelerations.

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I suggested to @jimmylai to get the class attribute to make sure that the C implementation behaves as the Python implementation: see PEP 399. If someone wants to use type(), I would prefer to see the same change in the Python implementation as well.

@1st1, @asvetlov: Do you know the rationale for checking class here?

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I suggested to use Py_TYPE as well.

I think it was I who used __class__ there, and there's no rationale behind that :)

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@1st1 1st1 May 22, 2018 •
edited
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So the Python version can be updated to use type() too.

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@1st1 @serhiy-storchaka
use type() won't work.
Original isfuture: return (hasattr(obj.__class__, '_asyncio_future_blocking') and obj._asyncio_future_blocking is not None)

Use type: return (hasattr(type(obj), '_asyncio_future_blocking') and obj._asyncio_future_blocking is not None)

Unit tests fail when use type()
Did I use type() wrong?

======================================================================
FAIL: test_isfuture (test.test_asyncio.test_futures.CFutureTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/jimmylai/workspace/cpython/Lib/test/test_asyncio/test_futures.py", line 131, in test_isfuture
    self.assertTrue(asyncio.isfuture(mock.Mock(type(f))))
AssertionError: False is not true

======================================================================
FAIL: test_isfuture (test.test_asyncio.test_futures.CSubFutureTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/jimmylai/workspace/cpython/Lib/test/test_asyncio/test_futures.py", line 131, in test_isfuture
    self.assertTrue(asyncio.isfuture(mock.Mock(type(f))))
AssertionError: False is not true

======================================================================
FAIL: test_isfuture (test.test_asyncio.test_futures.PyFutureTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/jimmylai/workspace/cpython/Lib/test/test_asyncio/test_futures.py", line 131, in test_isfuture
    self.assertTrue(asyncio.isfuture(mock.Mock(type(f))))
AssertionError: False is not true

if (class == NULL) {
return NULL;
}
_Py_IDENTIFIER(_asyncio_future_blocking);
int class_has_attr = _PyObject_HasAttrId(
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Is it needed?

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class may not have attr _asyncio_future_blocking
It's needed.

class, &PyId__asyncio_future_blocking);
Py_DECREF(class);
if (class_has_attr < 0) {
return NULL;
}
if (!class_has_attr) {
Py_RETURN_FALSE;
}
PyObject* obj_attr = _PyObject_GetAttrId(obj, &PyId__asyncio_future_blocking);
if (obj_attr == NULL) {
return NULL;
}
if (obj_attr != Py_None) {
Py_DECREF(obj_attr);
Py_RETURN_TRUE;
}
Py_DECREF(obj_attr);
Py_RETURN_FALSE;
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obj_attr is leaked here.

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added Py_DECREF(obj_attr);

}


static PyObject *
get_future_loop(PyObject *fut)
Expand Down Expand Up @@ -3276,6 +3321,7 @@ PyDoc_STRVAR(module_doc, "Accelerator module for asyncio");

static PyMethodDef asyncio_methods[] = {
_ASYNCIO_GET_EVENT_LOOP_METHODDEF
_ASYNCIO_ISFUTURE_METHODDEF
_ASYNCIO_GET_RUNNING_LOOP_METHODDEF
_ASYNCIO__GET_RUNNING_LOOP_METHODDEF
_ASYNCIO__SET_RUNNING_LOOP_METHODDEF
Expand Down
15 changes: 14 additions & 1 deletion Modules/clinic/_asynciomodule.c.h
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,19 @@
preserve
[clinic start generated code]*/

PyDoc_STRVAR(_asyncio_isfuture__doc__,
"isfuture($module, obj, /)\n"
"--\n"
"\n"
"Return True if obj is a Future instance.\n"
"\n"
"This returns True when obj is a Future instance or is advertising\n"
"itself as duck-type compatible by setting _asyncio_future_blocking.\n"
"See comment in Future for more details.");

#define _ASYNCIO_ISFUTURE_METHODDEF \
{"isfuture", (PyCFunction)_asyncio_isfuture, METH_O, _asyncio_isfuture__doc__},

PyDoc_STRVAR(_asyncio_Future___init____doc__,
"Future(*, loop=None)\n"
"--\n"
Expand Down Expand Up @@ -711,4 +724,4 @@ _asyncio__leave_task(PyObject *module, PyObject *const *args, Py_ssize_t nargs,
exit:
return return_value;
}
/*[clinic end generated code: output=b6148b0134e7a819 input=a9049054013a1b77]*/
/*[clinic end generated code: output=9ddba804d97cdf0d input=a9049054013a1b77]*/