* [PATCH] st.c (st_numhash): mix float value
@ 2015-01-22 0:49 Eric Wong
0 siblings, 0 replies; only message in thread
From: Eric Wong @ 2015-01-22 0:49 UTC (permalink / raw)
To: spew
FLONUM_P appears to generate too many false positives
in real world usage, with too many integers becoming
-2.0 or 2.0
So mix it into the original value and follow the original
shuffling path.
Revised benchmark results from hash benchmarks:
Speedup ratio: compare with the result of `2.1.5' (greater is better)
name trunk built
hash_aref_flo 0.007 1.583
hash_aref_flo_ident 0.004 1.146
hash_aref_miss 1.192 1.179
hash_aref_str 1.214 1.211
hash_aref_sym 1.327 1.321
hash_aref_sym_long 1.319 1.295
hash_flatten 1.386 1.364
hash_ident_num 1.181 1.188
hash_ident_obj 1.219 1.248
hash_ident_str 1.211 1.211
hash_ident_sym 1.207 1.218
hash_keys 0.951 0.951
hash_shift 1.040 1.041
hash_values 0.959 0.960
loop_whileloop2 0.992 0.993
vm2_bighash* 1.338 1.316
---
st.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/st.c b/st.c
index 2ffa986..12f3156 100644
--- a/st.c
+++ b/st.c
@@ -1763,8 +1763,9 @@ st_numhash(st_data_t n)
* shifts and bitmask operations.
*/
#ifdef USE_FLONUM /* RUBY */
- if (FLONUM_P(n))
- return (st_index_t)rb_float_value(n);
+ 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));
--
EW
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2015-01-22 0:49 [PATCH] st.c (st_numhash): mix float value Eric Wong
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