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Issue #17563: Fix dict resize performance regression.

This commit is contained in:
Raymond Hettinger 2013-05-17 03:01:13 -07:00
parent b37706f306
commit 36f74aa7f7
1 changed files with 11 additions and 7 deletions
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18
Objects/dictobject.c
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@ -305,14 +305,18 @@ PyDict_Fini(void)
* #define USABLE_FRACTION(n) (((n) >> 1) + ((n) >> 2) - ((n) >> 3))
*/
/* GROWTH_RATE. Growth rate upon hitting maximum load. Currently set to *2.
* Raising this to *4 doubles memory consumption depending on the size of
/* GROWTH_RATE. Growth rate upon hitting maximum load.
* Currently set to used*2 + capacity/2.
* This means that dicts double in size when growing without deletions,
* but have more head room when the number of deletions is on a par with the
* number of insertions.
* Raising this to used*4 doubles memory consumption depending on the size of
* the dictionary, but results in half the number of resizes, less effort to
* resize and better sparseness for some (but not all dict sizes).
* Setting to *4 eliminates every other resize step.
* GROWTH_RATE was set to *4 up to version 3.2.
* resize.
* GROWTH_RATE was set to used*4 up to version 3.2.
* GROWTH_RATE was set to used*2 in version 3.3.0
*/
#define GROWTH_RATE(x) ((x) * 2)
#define GROWTH_RATE(d) (((d)->ma_used*2)+((d)->ma_keys->dk_size>>1))
#define ENSURE_ALLOWS_DELETIONS(d) \
if ((d)->ma_keys->dk_lookup == lookdict_unicode_nodummy) { \
@ -790,7 +794,7 @@ find_empty_slot(PyDictObject *mp, PyObject *key, Py_hash_t hash,
static int
insertion_resize(PyDictObject *mp)
{
return dictresize(mp, GROWTH_RATE(mp->ma_used));
return dictresize(mp, GROWTH_RATE(mp));
}
/*