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Reduce load factor (from 66% to 60%) to improve effectiveness of line…

…ar probing.

Decreased density gives better collision statistics (average of 2.5 probes in a
full table versus 3.0 previously) and fewer occurences of starting a second
possibly overlapping sequence of 10 linear probes.  Makes resizes a little more
frequent but each with less work (fewer insertions and fewer collisions).
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rhettinger committed Feb 4, 2017
1 parent b451f91 commit 5cd87a8d61246b0a6233bfb8503d4718b693cef0
Showing with 3 additions and 3 deletions.
  1. +3 −3 Objects/setobject.c
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@@ -234,7 +234,7 @@ set_add_entry(PySetObject *so, PyObject *key, Py_hash_t hash)
so->used++;
entry->key = key;
entry->hash = hash;
if ((size_t)so->fill*3 < mask*2)
if ((size_t)so->fill*5 < mask*3)
return 0;
return set_table_resize(so, so->used);
@@ -642,7 +642,7 @@ set_merge(PySetObject *so, PyObject *otherset)
* incrementally resizing as we insert new keys. Expect
* that there will be no (or few) overlapping keys.
*/
if ((so->fill + other->used)*3 >= so->mask*2) {
if ((so->fill + other->used)*5 >= so->mask*3) {
if (set_table_resize(so, so->used + other->used) != 0)
return -1;
}
@@ -986,7 +986,7 @@ set_update_internal(PySetObject *so, PyObject *other)
*/
if (dictsize < 0)
return -1;
if ((so->fill + dictsize)*3 >= so->mask*2) {
if ((so->fill + dictsize)*5 >= so->mask*3) {
if (set_table_resize(so, so->used + dictsize) != 0)
return -1;
}

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