From: funny.falcon@... Date: 2016-07-13T11:04:01+00:00 Subject: [ruby-core:76364] [Ruby trunk Feature#12142] Hash tables with open addressing Issue #12142 has been updated by Yura Sokolov. Good day, everyone. I've updated my version of st.c and hashing patch. Main difference in st implementation from Vladimir Makarov's patch is usage of closed addressing instead of open addressing. Code size approximately: - my version of st.c is near 1000 lines - Makarov's one is near 1250 lines (both without huge comments and tables of sizes, Makarov's without Quadratic probing also). Also there are: - fixes for Murmur (it had issues with st_hash_uint and st_hash_end) (i've also replaced Murmur1/2 to Murmur3). - make Murmur seeded, and use it for 'identity' hashes. - suggestion to use SipHash13 instead SipHash24 ( Rust already accepted it) - suggestion to use 32bit SipHash's cousine for 32bit architecture Overall performance is on par with Vladimir's patch. (note: Vladimir's patch removes seeding for fixnum/double/symbol hashing, so it could be faster for keys of such types) (I've tested against Eric's Wong mailbox applied on trunk, so no CityHash) Uploaded mailbox patch: https://bugs.ruby-lang.org/attachments/download/6061/hash_improvements_and_st_implementation_changes.mbox Also could be seen on github: https://github.com/funny-falcon/ruby/compare/trunk...funny-falcon:st_table_with_array2 https://github.com/funny-falcon/ruby/compare/trunk...funny-falcon:st_table_with_array2.patch Performance of Redmine (software that runs bugs.ruby-lang.org): ```` ab -n 1000 -c 10 http://localhost:3000/projects/general/issues trunk Requests per second: 27.51 [#/sec] (mean) Requests per second: 27.54 [#/sec] (mean) Requests per second: 27.69 [#/sec] (mean) makarov Requests per second: 28.29 [#/sec] (mean) Requests per second: 28.12 [#/sec] (mean) Requests per second: 28.30 [#/sec] (mean) falcon Requests per second: 28.31 [#/sec] (mean) Requests per second: 28.16 [#/sec] (mean) Requests per second: 28.26 [#/sec] (mean) ab -n 1000 -c 10 http://localhost:3000/issues/1 trunk Requests per second: 26.37 [#/sec] (mean) Requests per second: 26.51 [#/sec] (mean) Requests per second: 26.48 [#/sec] (mean) makarov Requests per second: 27.39 [#/sec] (mean) Requests per second: 27.41 [#/sec] (mean) Requests per second: 27.75 [#/sec] (mean) falcon Requests per second: 27.54 [#/sec] (mean) Requests per second: 27.23 [#/sec] (mean) Requests per second: 27.47 [#/sec] (mean) ```` Tests using benchmark/driver.rb (tested miniruby): ```` Speedup ratio: compare with the result of `trunk' (greater is better) 64bit + jemalloc name makarov falcon bighash 1.320 1.447 hash_aref_dsym 0.976 1.009 hash_aref_dsym_long 1.474 1.459 hash_aref_fix 1.042 1.023 hash_aref_flo 1.671 1.595 hash_aref_miss 1.014 1.154 hash_aref_str 1.023 1.123 hash_aref_sym 0.997 1.016 hash_aref_sym_long 1.014 1.005 hash_flatten 1.179 1.097 hash_ident_flo 0.975 1.008 hash_ident_num 0.960 0.991 hash_ident_obj 0.939 0.967 hash_ident_str 0.949 0.958 hash_ident_sym 0.965 0.969 hash_keys 1.956 1.998 hash_long 1.004 1.203 hash_shift 1.280 1.324 hash_shift_u16 1.270 1.315 hash_shift_u24 1.263 1.304 hash_shift_u32 1.256 1.298 hash_small2 1.065 1.063 hash_small4 1.061 1.055 hash_small8 1.818 1.608 hash_to_proc 1.006 0.976 hash_values 1.749 1.775 loop_whileloop2 1.003 0.997 vm2_bighash* 3.465 3.101 64bit no jemalloc name makarov falcon bighash 1.741 1.840 hash_aref_dsym 0.934 0.970 hash_aref_dsym_long 1.546 1.519 hash_aref_fix 1.045 1.041 hash_aref_flo 1.734 1.654 hash_aref_miss 0.980 1.022 hash_aref_str 1.016 1.068 hash_aref_sym 1.000 1.015 hash_aref_sym_long 1.017 1.004 hash_flatten 1.172 1.179 hash_ident_flo 0.955 0.987 hash_ident_num 0.960 0.955 hash_ident_obj 0.952 0.963 hash_ident_str 0.947 0.956 hash_ident_sym 0.990 1.005 hash_keys 2.820 2.870 hash_long 0.995 1.206 hash_shift 1.437 1.461 hash_shift_u16 1.397 1.426 hash_shift_u24 1.389 1.426 hash_shift_u32 1.385 1.412 hash_small2 1.059 1.015 hash_small4 1.068 1.020 hash_small8 2.275 1.886 hash_to_proc 1.037 1.014 hash_values 2.811 2.850 loop_whileloop2 1.002 1.007 vm2_bighash* 3.429 3.372 32bit no jemalloc name makarov falcon bighash 1.103 1.267 hash_aref_dsym 0.991 1.014 hash_aref_dsym_long 1.356 1.444 hash_aref_fix 0.992 1.017 hash_aref_flo 1.175 2.051 hash_aref_miss 1.017 1.468 hash_aref_str 1.010 1.530 hash_aref_sym 1.021 1.051 hash_aref_sym_long 1.032 1.052 hash_flatten 1.073 1.122 hash_ident_flo 1.124 1.114 hash_ident_num 0.900 0.914 hash_ident_obj 0.921 0.947 hash_ident_str 0.908 0.945 hash_ident_sym 0.910 0.949 hash_keys 2.083 2.095 hash_long 0.997 2.146 hash_shift 1.437 1.442 hash_shift_u16 1.316 1.383 hash_shift_u24 1.319 1.348 hash_shift_u32 1.446 1.752 hash_small2 1.041 0.955 hash_small4 1.044 0.961 hash_small8 1.570 1.378 hash_to_proc 1.007 0.989 hash_values 2.215 2.252 loop_whileloop2 1.002 1.000 vm2_bighash* 3.268 2.969 ```` ---------------------------------------- Feature #12142: Hash tables with open addressing https://bugs.ruby-lang.org/issues/12142#change-59612 * Author: Vladimir Makarov * Status: Open * Priority: Normal * Assignee: ---------------------------------------- ~~~ Hello, the following patch contains a new implementation of hash tables (major files st.c and include/ruby/st.h). Modern processors have several levels of cache. Usually,the CPU reads one or a few lines of the cache from memory (or another level of cache). So CPU is much faster at reading data stored close to each other. The current implementation of Ruby hash tables does not fit well to modern processor cache organization, which requires better data locality for faster program speed. The new hash table implementation achieves a better data locality mainly by o switching to open addressing hash tables for access by keys. Removing hash collision lists lets us avoid *pointer chasing*, a common problem that produces bad data locality. I see a tendency to move from chaining hash tables to open addressing hash tables due to their better fit to modern CPU memory organizations. CPython recently made such switch (https://hg.python.org/cpython/file/ff1938d12240/Objects/dictobject.c). PHP did this a bit earlier https://nikic.github.io/2014/12/22/PHPs-new-hashtable-implementation.html. GCC has widely-used such hash tables (https://gcc.gnu.org/svn/gcc/trunk/libiberty/hashtab.c) internally for more than 15 years. o removing doubly linked lists and putting the elements into an array for accessing to elements by their inclusion order. That also removes pointer chaising on the doubly linked lists used for traversing elements by their inclusion order. A more detailed description of the proposed implementation can be found in the top comment of the file st.c. The new implementation was benchmarked on 21 MRI hash table benchmarks for two most widely used targets x86-64 (Intel 4.2GHz i7-4790K) and ARM (Exynos 5410 - 1.6GHz Cortex-A15): make benchmark-each ITEM=bm_hash OPTS='-r 3 -v' COMPARE_RUBY='' Here the results for x86-64: hash_aref_dsym 1.094 hash_aref_dsym_long 1.383 hash_aref_fix 1.048 hash_aref_flo 1.860 hash_aref_miss 1.107 hash_aref_str 1.107 hash_aref_sym 1.191 hash_aref_sym_long 1.113 hash_flatten 1.258 hash_ident_flo 1.627 hash_ident_num 1.045 hash_ident_obj 1.143 hash_ident_str 1.127 hash_ident_sym 1.152 hash_keys 2.714 hash_shift 2.209 hash_shift_u16 1.442 hash_shift_u24 1.413 hash_shift_u32 1.396 hash_to_proc 2.831 hash_values 2.701 The average performance improvement is more 50%. ARM results are analogous -- no any benchmark performance degradation and about the same average improvement. The patch can be seen as https://github.com/vnmakarov/ruby/compare/trunk...hash_tables_with_open_addressing.patch or in a less convenient way as pull request changes https://github.com/ruby/ruby/pull/1264/files This is my first patch for MRI and may be my proposal and implementation have pitfalls. But I am keen to learn and work on inclusion of this code into MRI. ~~~ ---Files-------------------------------- 0001-st.c-change-st_table-implementation.patch (59.4 KB) st-march31.patch (114 KB) base.patch (93.8 KB) hash.patch (4.48 KB) strong_hash.patch (8.08 KB) city.patch (19.4 KB) new-hash-table-benchmarks.patch (1.34 KB) hash_improvements_and_st_implementation_changes.mbox (101 KB) -- https://bugs.ruby-lang.org/ Unsubscribe: