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bpo-41431: Optimize dict_merge for copy (GH-21674)

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Inada Naoki 2020-08-04 11:08:06 +09:00 committed by GitHub
parent 602a971a2a
commit db6d9a50ce
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 75 additions and 34 deletions
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11
Lib/test/test_ordered_dict.py
View File

@ -740,20 +740,21 @@ class CPythonOrderedDictTests(OrderedDictTests, unittest.TestCase):
size = support.calcobjsize
check = self.check_sizeof
basicsize = size('nQ2P' + '3PnPn2P') + calcsize('2nP2n')
basicsize = size('nQ2P' + '3PnPn2P')
keysize = calcsize('2nP2n')
entrysize = calcsize('n2P')
p = calcsize('P')
nodesize = calcsize('Pn2P')
od = OrderedDict()
check(od, basicsize + 8 + 5*entrysize) # 8byte indices + 8*2//3 * entry table
check(od, basicsize) # 8byte indices + 8*2//3 * entry table
od.x = 1
check(od, basicsize + 8 + 5*entrysize)
check(od, basicsize)
od.update([(i, i) for i in range(3)])
check(od, basicsize + 8*p + 8 + 5*entrysize + 3*nodesize)
check(od, basicsize + keysize + 8*p + 8 + 5*entrysize + 3*nodesize)
od.update([(i, i) for i in range(3, 10)])
check(od, basicsize + 16*p + 16 + 10*entrysize + 10*nodesize)
check(od, basicsize + keysize + 16*p + 16 + 10*entrysize + 10*nodesize)
check(od.keys(), size('P'))
check(od.items(), size('P'))

2
Misc/NEWS.d/next/Core and Builtins/2020-08-02-15-53-12.bpo-41431.TblUBT.rst Normal file
View File

@ -0,0 +1,2 @@
Optimize ``dict_merge()`` for copying dict (e.g. ``dict(d)`` and
``{}.update(d)``).

96
Objects/dictobject.c
View File

@ -674,10 +674,11 @@ new_dict_with_shared_keys(PyDictKeysObject *keys)
}
static PyObject *
clone_combined_dict(PyDictObject *orig)
static PyDictKeysObject *
clone_combined_dict_keys(PyDictObject *orig)
{
assert(PyDict_CheckExact(orig));
assert(PyDict_Check(orig));
assert(Py_TYPE(orig)->tp_iter == (getiterfunc)dict_iter);
assert(orig->ma_values == NULL);
assert(orig->ma_keys->dk_refcnt == 1);
@ -704,19 +705,6 @@ clone_combined_dict(PyDictObject *orig)
}
}
PyDictObject *new = (PyDictObject *)new_dict(keys, NULL);
if (new == NULL) {
/* In case of an error, `new_dict()` takes care of
cleaning up `keys`. */
return NULL;
}
new->ma_used = orig->ma_used;
ASSERT_CONSISTENT(new);
if (_PyObject_GC_IS_TRACKED(orig)) {
/* Maintain tracking. */
_PyObject_GC_TRACK(new);
}
/* Since we copied the keys table we now have an extra reference
in the system. Manually call increment _Py_RefTotal to signal that
we have it now; calling dictkeys_incref would be an error as
@ -724,8 +712,7 @@ clone_combined_dict(PyDictObject *orig)
#ifdef Py_REF_DEBUG
_Py_RefTotal++;
#endif
return (PyObject *)new;
return keys;
}
PyObject *
@ -2527,12 +2514,45 @@ dict_merge(PyObject *a, PyObject *b, int override)
if (other == mp || other->ma_used == 0)
/* a.update(a) or a.update({}); nothing to do */
return 0;
if (mp->ma_used == 0)
if (mp->ma_used == 0) {
/* Since the target dict is empty, PyDict_GetItem()
* always returns NULL. Setting override to 1
* skips the unnecessary test.
*/
override = 1;
PyDictKeysObject *okeys = other->ma_keys;
// If other is clean, combined, and just allocated, just clone it.
if (other->ma_values == NULL &&
other->ma_used == okeys->dk_nentries &&
(okeys->dk_size == PyDict_MINSIZE ||
USABLE_FRACTION(okeys->dk_size/2) < other->ma_used)) {
PyDictKeysObject *keys = clone_combined_dict_keys(other);
if (keys == NULL) {
return -1;
}
dictkeys_decref(mp->ma_keys);
mp->ma_keys = keys;
if (mp->ma_values != NULL) {
if (mp->ma_values != empty_values) {
free_values(mp->ma_values);
}
mp->ma_values = NULL;
}
mp->ma_used = other->ma_used;
mp->ma_version_tag = DICT_NEXT_VERSION();
ASSERT_CONSISTENT(mp);
if (_PyObject_GC_IS_TRACKED(other) && !_PyObject_GC_IS_TRACKED(mp)) {
/* Maintain tracking. */
_PyObject_GC_TRACK(mp);
}
return 0;
}
}
/* Do one big resize at the start, rather than
* incrementally resizing as we insert new items. Expect
* that there will be no (or few) overlapping keys.
@ -2718,12 +2738,13 @@ PyDict_Copy(PyObject *o)
return (PyObject *)split_copy;
}
if (PyDict_CheckExact(mp) && mp->ma_values == NULL &&
if (Py_TYPE(mp)->tp_iter == (getiterfunc)dict_iter &&
mp->ma_values == NULL &&
(mp->ma_used >= (mp->ma_keys->dk_nentries * 2) / 3))
{
/* Use fast-copy if:
(1) 'mp' is an instance of a subclassed dict; and
(1) type(mp) doesn't override tp_iter; and
(2) 'mp' is not a split-dict; and
@ -2735,13 +2756,31 @@ PyDict_Copy(PyObject *o)
operations and copied after that. In cases like this, we defer to
PyDict_Merge, which produces a compacted copy.
*/
return clone_combined_dict(mp);
PyDictKeysObject *keys = clone_combined_dict_keys(mp);
if (keys == NULL) {
return NULL;
}
PyDictObject *new = (PyDictObject *)new_dict(keys, NULL);
if (new == NULL) {
/* In case of an error, `new_dict()` takes care of
cleaning up `keys`. */
return NULL;
}
new->ma_used = mp->ma_used;
ASSERT_CONSISTENT(new);
if (_PyObject_GC_IS_TRACKED(mp)) {
/* Maintain tracking. */
_PyObject_GC_TRACK(new);
}
return (PyObject *)new;
}
copy = PyDict_New();
if (copy == NULL)
return NULL;
if (PyDict_Merge(copy, o, 1) == 0)
if (dict_merge(copy, o, 1) == 0)
return copy;
Py_DECREF(copy);
return NULL;
@ -3359,16 +3398,15 @@ dict_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
d = (PyDictObject *)self;
/* The object has been implicitly tracked by tp_alloc */
if (type == &PyDict_Type)
if (type == &PyDict_Type) {
_PyObject_GC_UNTRACK(d);
}
d->ma_used = 0;
d->ma_version_tag = DICT_NEXT_VERSION();
d->ma_keys = new_keys_object(PyDict_MINSIZE);
if (d->ma_keys == NULL) {
Py_DECREF(self);
return NULL;
}
dictkeys_incref(Py_EMPTY_KEYS);
d->ma_keys = Py_EMPTY_KEYS;
d->ma_values = empty_values;
ASSERT_CONSISTENT(d);
return self;
}