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st.c: use power-of-two sizes to avoid slow modulo ops

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* 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
This commit is contained in:
normal 2014-03-22 23:34:21 +00:00
parent 14c9cf885c
commit ef59670a44
12 changed files with 77 additions and 57 deletions
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74
st.c
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@ -33,8 +33,7 @@ typedef struct st_packed_entry {
#define STATIC_ASSERT(name, expr) typedef int static_assert_##name##_check[(expr) ? 1 : -1];
#define ST_DEFAULT_MAX_DENSITY 5
#define ST_DEFAULT_INIT_TABLE_SIZE 11
#define ST_DEFAULT_SECOND_TABLE_SIZE 19
#define ST_DEFAULT_INIT_TABLE_SIZE 16
#define ST_DEFAULT_PACKED_TABLE_SIZE 18
#define PACKED_UNIT (int)(sizeof(st_packed_entry) / sizeof(st_table_entry*))
#define MAX_PACKED_HASH (int)(ST_DEFAULT_PACKED_TABLE_SIZE * sizeof(st_table_entry*) / sizeof(st_packed_entry))
@ -85,7 +84,7 @@ static void rehash(st_table *);
#define EQUAL(table,x,y) ((x)==(y) || (*(table)->type->compare)((x),(y)) == 0)
#define do_hash(key,table) (st_index_t)(*(table)->type->hash)((key))
#define hash_pos(h,n) ((h) % (n))
#define hash_pos(h,n) ((h) & (n - 1))
#define do_hash_bin(key,table) hash_pos(do_hash((key), (table)), (table)->num_bins)
/* preparation for possible allocation improvements */
@ -140,69 +139,18 @@ remove_safe_packed_entry(st_table *table, st_index_t i, st_data_t never)
PHASH_SET(table, i, 0);
}
/*
* MINSIZE is the minimum size of a dictionary.
*/
#define MINSIZE 8
/*
Table of prime numbers 2^n+a, 2<=n<=30.
*/
static const unsigned int primes[] = {
ST_DEFAULT_INIT_TABLE_SIZE,
ST_DEFAULT_SECOND_TABLE_SIZE,
32 + 5,
64 + 3,
128 + 3,
256 + 27,
512 + 9,
1024 + 9,
2048 + 5,
4096 + 3,
8192 + 27,
16384 + 43,
32768 + 3,
65536 + 45,
131072 + 29,
262144 + 3,
524288 + 21,
1048576 + 7,
2097152 + 17,
4194304 + 15,
8388608 + 9,
16777216 + 43,
33554432 + 35,
67108864 + 15,
134217728 + 29,
268435456 + 3,
536870912 + 11,
1073741824 + 85,
0
};
static st_index_t
new_size(st_index_t size)
{
int i;
st_index_t i;
#if 0
for (i=3; i<31; i++) {
if ((1<<i) > size) return 1<<i;
if ((st_index_t)(1<<i) > size) return 1<<i;
}
return -1;
#else
st_index_t newsize;
for (i = 0, newsize = MINSIZE; i < numberof(primes); i++, newsize <<= 1) {
if (newsize > size) return primes[i];
}
/* Ran out of primes */
#ifndef NOT_RUBY
rb_raise(rb_eRuntimeError, "st_table too big");
#endif
return -1; /* should raise exception */
#endif
}
#ifdef HASH_LOG
@ -1685,5 +1633,17 @@ st_numcmp(st_data_t x, st_data_t y)
st_index_t
st_numhash(st_data_t n)
{
return (st_index_t)n;
/*
* This hash function is lightly-tuned for Ruby. Further tuning
* should be possible. Notes:
*
* - (n >> 3) alone is great for heap objects and OK for fixnum,
* however symbols perform poorly.
* - (n >> (RUBY_SPECIAL_SHIFT+3)) was added to make symbols hash well,
* n.b.: +3 to remove ID scope, +1 worked well initially, too
* - (n << 3) was finally added to avoid losing bits for fixnums
* - avoid expensive modulo instructions, it is currently only
* shifts and bitmask operations.
*/
return (st_index_t)((n>>(RUBY_SPECIAL_SHIFT+3)|(n<<3)) ^ (n>>3));
}