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author | nobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e> | 2016-12-21 06:22:16 +0000 |
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committer | nobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e> | 2016-12-21 06:22:16 +0000 |
commit | c0ff5f4dd7913c458d62d7b7eea352ef1ef2994e (patch) | |
tree | de299827cb037fcd393cbb658b53924708b5fc4b /win32 | |
parent | 7a4fe57adb1cfd7c92fdcdc6991f82836c0b67fb (diff) |
st.c: fix st_hash* functions [Bug #13019]
Previous implementation had an issues:
- macros murmur1 assumes murmur_step takes rotation value
as a second argument
- but murmur_step second argument is "next block"
- this makes st_hash_uint and st_hash_end to not mix high bits of
hash value into lower bits
- this leads to pure hash behavior on doubles and mixing hashes using
st_hash_uint.
It didn't matter when bins amount were prime numbers, but it hurts
when bins are powers of two.
Mistake were created cause of attempt to co-exist Murmur1 and Murmur2
in a same code.
Change it to single hash-function implementation.
- block function is in a spirit of Murmur functions,
but handles inter-block dependency a bit better (imho).
- final block is read in bit more optimal way on CPU with unaligned word access,
- final block is mixed in simple way,
- finalizer is taken from MurmurHash3 (it makes most of magic :) )
(64bit finalizer is taken from
http://zimbry.blogspot.ru/2011/09/better-bit-mixing-improving-on.html)
Also remove ST_USE_FNV1: it lacks implementation of many functions,
and looks to be abandoned
Author: Sokolov Yura aka funny_falcon <funny.falcon@gmail.com>
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57134 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Diffstat (limited to 'win32')
0 files changed, 0 insertions, 0 deletions