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bpo-33205: dict: Change GROWTH_RATE to used*3 (GH-6350)

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INADA Naoki 2018-04-17 15:53:34 +09:00 • committed by GitHub
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2 changed files with 8 additions and 6 deletions
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Objects/dictobject.c
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@ -396,17 +396,16 @@ dk_set_index(PyDictKeysObject *keys, Py_ssize_t i, Py_ssize_t ix)
*/
/* GROWTH_RATE. Growth rate upon hitting maximum load.
* Currently set to used*2 + capacity/2.
* Currently set to used*3.
* 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.
* number of insertions. See also bpo-17563 and bpo-33205.
*
* GROWTH_RATE was set to used*4 up to version 3.2.
* GROWTH_RATE was set to used*2 in version 3.3.0
* GROWTH_RATE was set to used*2 + capacity/2 in 3.4.0-3.6.0.
*/
#define GROWTH_RATE(d) (((d)->ma_used*2)+((d)->ma_keys->dk_size>>1))
#define GROWTH_RATE(d) ((d)->ma_used*3)
#define ENSURE_ALLOWS_DELETIONS(d) \
if ((d)->ma_keys->dk_lookup == lookdict_unicode_nodummy) { \