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hash.c: improve integer/fixnum hashing

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The low bits of Ruby object IDs are rarely populated in the current
implementation, so ensure the get used.

Early versions of this patch redundantly shifted static symbols in
any_hash, causing regresions with static symbols in hash_aref_sym

* hash.c (any_hash): skip rb_objid_hash for static syms
  (rb_num_hash_start): extract from rb_ident_hash
  (rb_objid_hash): call rb_num_hash_start
  (rb_ident_hash): ditto
  [ruby-core:70181] [Feature #11405]

target 0: a (ruby 2.3.0dev (2015-07-30 trunk 51437) [x86_64-linux]
target 1: b (ruby 2.3.0dev (2015-07-30 patch 51437) [x86_64-linux]

benchmark results from Xeon E3-1230 v3 @ 3.30GHz (turbo disabled):
minimum results in each 10 measurements.
Execution time (sec)
name                a       b
hash_aref_dsym        0.316   0.300
hash_aref_dsym_long   5.106   5.063
hash_aref_fix         0.304   0.297
hash_aref_flo         0.061   0.060
hash_aref_miss        0.433   0.430
hash_aref_str         0.408   0.396
hash_aref_sym         0.312   0.306
hash_aref_sym_long    0.482   0.469
hash_flatten          0.385   0.273
hash_ident_flo        0.036   0.037
hash_ident_num        0.277   0.276
hash_ident_obj        0.291   0.284
hash_ident_str        0.289   0.286
hash_ident_sym        0.285   0.281
hash_keys             0.269   0.271
hash_shift            0.020   0.016
hash_values           0.264   0.264
loop_whileloop2       0.101   0.099
vm2_bighash*          3.066   2.972

Speedup ratio: compare with the result of `a' (greater is better)
name                b
hash_aref_dsym        1.052
hash_aref_dsym_long   1.008
hash_aref_fix         1.024
hash_aref_flo         1.015
hash_aref_miss        1.007
hash_aref_str         1.031
hash_aref_sym         1.018
hash_aref_sym_long    1.027
hash_flatten          1.410
hash_ident_flo        0.994
hash_ident_num        1.001
hash_ident_obj        1.022
hash_ident_str        1.012
hash_ident_sym        1.016
hash_keys             0.992
hash_shift            1.237
hash_values           1.001
loop_whileloop2       1.013
vm2_bighash*          1.032

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51582 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
This commit is contained in:
normal 2015-08-14 19:52:06 +00:00
parent e7bb5d44e6
commit 14470aa6db
2 changed files with 35 additions and 14 deletions
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8
ChangeLog
View file

@ -1,3 +1,11 @@
Sat Aug 15 04:33:39 2015 Eric Wong <e@80x24.org>
* hash.c (any_hash): skip rb_objid_hash for static syms
(rb_num_hash_start): extract from rb_ident_hash
(rb_objid_hash): call rb_num_hash_start
(rb_ident_hash): ditto
[ruby-core:70181] [Feature #11405]
Sat Aug 15 04:16:13 2015 Eric Wong <e@80x24.org>
* iseq.c (rb_iseq_mark): reduce NULL checks

41
hash.c
View file

@ -138,7 +138,8 @@ any_hash(VALUE a, st_index_t (*other_func)(VALUE))
if (SPECIAL_CONST_P(a)) {
if (a == Qundef) return 0;
if (STATIC_SYM_P(a)) {
a >>= (RUBY_SPECIAL_SHIFT + ID_SCOPE_SHIFT);
hnum = a >> (RUBY_SPECIAL_SHIFT + ID_SCOPE_SHIFT);
goto out;
}
else if (FLONUM_P(a)) {
/* prevent pathological behavior: [Bug #10761] */
@ -160,6 +161,7 @@ any_hash(VALUE a, st_index_t (*other_func)(VALUE))
else {
hnum = other_func(a);
}
out:
hnum <<= 1;
return (st_index_t)RSHIFT(hnum, 1);
}
@ -177,10 +179,31 @@ rb_any_hash(VALUE a)
return any_hash(a, obj_any_hash);
}
static st_index_t
rb_num_hash_start(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 most ID scope, +1 worked well initially, too
* n.b.: +1 (instead of 3) 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 (n >> (RUBY_SPECIAL_SHIFT + 3) | (n << 3)) ^ (n >> 3);
}
long
rb_objid_hash(st_index_t index)
{
st_index_t hnum = rb_hash_start(index);
st_index_t hnum = rb_num_hash_start(index);
hnum = rb_hash_start(hnum);
hnum = rb_hash_uint(hnum, (st_index_t)rb_any_hash);
hnum = rb_hash_end(hnum);
return hnum;
@ -215,28 +238,18 @@ static const struct st_hash_type objhash = {
static st_index_t
rb_ident_hash(st_data_t n)
{
#ifdef USE_FLONUM /* RUBY */
/*
* 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.
* - flonum (on 64-bit) is pathologically bad, mix the actual
* float value in, but do not use the float value as-is since
* many integers get interpreted as 2.0 or -2.0 [Bug #10761]
*/
#ifdef USE_FLONUM /* RUBY */
if (FLONUM_P(n)) {
n ^= (st_data_t)rb_float_value(n);
}
#endif
return (st_index_t)((n>>(RUBY_SPECIAL_SHIFT+3)|(n<<3)) ^ (n>>3));
return (st_index_t)rb_num_hash_start((st_index_t)n);
}
static const struct st_hash_type identhash = {