mirrors/cpython
1
0
Fork 0
mirror of https://github.com/python/cpython.git synced 2025-12-05 00:52:25 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 10

Issue #28731: Optimize _PyDict_NewPresized() to create correct size dict

Browse source 
Improve speed of dict literal with constant keys up to 30%.
This commit is contained in:
INADA Naoki 2016-11-22 00:57:02 +09:00
parent c0be040b48
commit 92c50eee52
2 changed files with 22 additions and 5 deletions
Download patch file Download diff file Expand all files Collapse all files

3
Misc/NEWS
View file

@ -10,6 +10,9 @@ What's New in Python 3.7.0 alpha 1
Core and Builtins Core and Builtins
----------------- -----------------
- Issue #28731: Optimize _PyDict_NewPresized() to create correct size dict.
Improve speed of dict literal with constant keys up to 30%.
- Issue #28532: Show sys.version when -V option is supplied twice. - Issue #28532: Show sys.version when -V option is supplied twice.
- Issue #28746: Fix the set_inheritable() file descriptor method on platforms - Issue #28746: Fix the set_inheritable() file descriptor method on platforms

24
Objects/dictobject.c
View file

@ -389,7 +389,7 @@ dk_set_index(PyDictKeysObject *keys, Py_ssize_t i, Py_ssize_t ix)
* This can be used to reserve enough size to insert n entries without * This can be used to reserve enough size to insert n entries without
* resizing. * resizing.
*/ */
#define ESTIMATE_SIZE(n) (((n)*3) >> 1) #define ESTIMATE_SIZE(n) (((n)*3+1) >> 1)
/* Alternative fraction that is otherwise close enough to 2n/3 to make /* Alternative fraction that is otherwise close enough to 2n/3 to make
* little difference. 8 * 2/3 == 8 * 5/8 == 5. 16 * 2/3 == 16 * 5/8 == 10. * little difference. 8 * 2/3 == 8 * 5/8 == 5. 16 * 2/3 == 16 * 5/8 == 10.
@ -1361,12 +1361,26 @@ make_keys_shared(PyObject *op)
PyObject * PyObject *
_PyDict_NewPresized(Py_ssize_t minused) _PyDict_NewPresized(Py_ssize_t minused)
{ {
const Py_ssize_t max_presize = 128 * 1024;
Py_ssize_t newsize; Py_ssize_t newsize;
PyDictKeysObject *new_keys; PyDictKeysObject *new_keys;
for (newsize = PyDict_MINSIZE;
newsize <= minused && newsize > 0; /* There are no strict guarantee that returned dict can contain minused
newsize <<= 1) * items without resize. So we create medium size dict instead of very
; * large dict or MemoryError.
*/
if (minused > USABLE_FRACTION(max_presize)) {
newsize = max_presize;
}
else {
Py_ssize_t minsize = ESTIMATE_SIZE(minused);
newsize = PyDict_MINSIZE;
while (newsize < minsize) {
newsize <<= 1;
}
}
assert(IS_POWER_OF_2(newsize));
new_keys = new_keys_object(newsize); new_keys = new_keys_object(newsize);
if (new_keys == NULL) if (new_keys == NULL)
return NULL; return NULL;