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Fix terminology in comment and add more design rationale. (#3335)

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* Fix terminology in comment and add more design rationale.

* Fix extra space
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Raymond Hettinger 2017-09-04 18:54:16 -07:00 committed by GitHub
parent 550370957c
commit 64263dfd18
1 changed files with 10 additions and 3 deletions
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13
Objects/setobject.c
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@ -12,16 +12,23 @@
To improve cache locality, each probe inspects a series of consecutive
nearby entries before moving on to probes elsewhere in memory. This leaves
us with a hybrid of linear probing and open addressing. The linear probing
us with a hybrid of linear probing and randomized probing. The linear probing
reduces the cost of hash collisions because consecutive memory accesses
tend to be much cheaper than scattered probes. After LINEAR_PROBES steps,
we then use open addressing with the upper bits from the hash value. This
helps break-up long chains of collisions.
we then use more of the upper bits from the hash value and apply a simple
linear congruential random number genearator. This helps break-up long
chains of collisions.
All arithmetic on hash should ignore overflow.
Unlike the dictionary implementation, the lookkey function can return
NULL if the rich comparison returns an error.
Use cases for sets differ considerably from dictionaries where looked-up
keys are more likely to be present. In contrast, sets are primarily
about membership testing where the presence of an element is not known in
advance. Accordingly, the set implementation needs to optimize for both
the found and not-found case.
*/
#include "Python.h"