RGBCube/serenity
1
Fork 0
mirror of https://github.com/RGBCube/serenity synced 2025-05-14 09:24:57 +00:00
Code Issues Activity Actions

AK: Redesign HashTable to use closed hashing

Browse source 
Instead of each hash bucket being a SinglyLinkedList, switch to using
closed hashing (open addressing). Buckets are chained together via
double hashing (hashing the hash until we find an unused bucket.)

This greatly reduces malloc traffic, since each added element no longer
allocates a new linked list node.

Appears performance neutral on test-js. Can definitely be tuned and
could use proper management of load factor, etc.
This commit is contained in:
Andreas Kling 2020-10-15 23:34:07 +02:00
parent 4387590e65
commit 4e50079f36
2 changed files with 248 additions and 267 deletions
Download patch file Download diff file Expand all files Collapse all files

10
AK/HashFunctions.h
View file

@ -39,6 +39,16 @@ inline unsigned int_hash(u32 key)
return key;
}
inline unsigned double_hash(u32 key)
{
key = ~key + (key >> 23);
key ^= (key << 12);
key ^= (key >> 7);
key ^= (key << 2);
key ^= (key >> 20);
return key;
}
inline unsigned pair_int_hash(u32 key1, u32 key2)
{
return int_hash((int_hash(key1) * 209) ^ (int_hash(key2 * 413)));