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Issue 18771: Make it possible to set the number linear probes at compile-time.

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Raymond Hettinger 2013-09-15 14:57:15 -07:00
parent e6d35dba3c
commit 8408dc581e
2 changed files with 28 additions and 7 deletions
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Doc/whatsnew/3.4.rst
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@ -444,8 +444,15 @@ Major performance enhancements have been added:
* The UTF-32 decoder is now 3x to 4x faster.
* The cost of hash collisions for sets is now reduced. Each hash table
probe now checks a second key/hash pair for each cache line retrieved.
This exploits cache locality to make collision resolution less expensive.
probe now checks a series of consecutive, adjacent key/hash pairs before
continuing to make random probes through the hash table. This exploits
cache locality to make collision resolution less expensive.
The collision resolution scheme can be described as a hybrid of linear
probing and open addressing. The number of additional linear probes
defaults to nine. This can be changed at compile-time by defining
LINEAR_PROBES to be any value. Set LINEAR_PROBES=0 to turn-off
linear probing entirely.
(Contributed by Raymond Hettinger in :issue"`18771`.)