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| author | normal <normal@b2dd03c8-39d4-4d8f-98ff-823fe69b080e> | 2014-03-22 23:34:21 +0000 |
|---|---|---|
| committer | normal <normal@b2dd03c8-39d4-4d8f-98ff-823fe69b080e> | 2014-03-22 23:34:21 +0000 |
| commit | ef59670a44f30df7f07dd7a1438a2c27652bcb3c (patch) | |
| tree | 71d0daccc60c19f4d3a43ac3a444b6893cca2757 /NEWS | |
| parent | 14c9cf885c2b486fcb5eade23ec4fcdc36ee87f0 (diff) | |
| download | ruby-ef59670a44f30df7f07dd7a1438a2c27652bcb3c.tar.gz | |
st.c: use power-of-two sizes to avoid slow modulo ops
* st.c (hash_pos): use bitwise AND to avoid slow modulo op
(new_size): power-of-two sizes for hash_pos change
(st_numhash): adjust for common keys due to lack of prime modulo
[Feature #9425]
* hash.c (rb_any_hash): right shift for symbols
* benchmark/bm_hash_aref_miss.rb: added to show improvement
* benchmark/bm_hash_aref_sym_long.rb: ditto
* benchmark/bm_hash_aref_str.rb: ditto
* benchmark/bm_hash_aref_sym.rb: ditto
* benchmark/bm_hash_ident_num.rb: added to prevent regression
* benchmark/bm_hash_ident_obj.rb: ditto
* benchmark/bm_hash_ident_str.rb: ditto
* benchmark/bm_hash_ident_sym.rb: ditto
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45384 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Diffstat (limited to 'NEWS')
| -rw-r--r-- | NEWS | 6 |
1 files changed, 6 insertions, 0 deletions
@@ -84,3 +84,9 @@ with all sufficient information, see the ChangeLog file. * struct RBignum is hidden. [Feature #6083] Use rb_integer_pack and rb_integer_unpack instead. + +* st hash table uses power-of-two sizes for speed [Feature #9425]. + Lookups are 10-25% faster if using appropriate hash functions. + However, weaknesses in hash distribution can no longer be masked + by prime number-sized tables, so extensions may need to tweak + hash functions to ensure good distribution. |