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bytes: make IndexRune faster

re-implement IndexRune by IndexByte and Index which are well optimized
to get performance gain.

name                  old time/op   new time/op     delta
IndexRune/10-4         53.2ns ± 1%     29.1ns ± 1%    -45.32%  (p=0.008 n=5+5)
IndexRune/32-4          191ns ± 1%       27ns ± 1%    -85.75%  (p=0.008 n=5+5)
IndexRune/4K-4         23.5µs ± 1%      1.0µs ± 1%    -95.77%  (p=0.008 n=5+5)
IndexRune/4M-4         23.8ms ± 0%      1.0ms ± 2%    -95.90%  (p=0.008 n=5+5)
IndexRune/64M-4         384ms ± 1%       15ms ± 1%    -95.98%  (p=0.008 n=5+5)
IndexRuneASCII/10-4    61.5ns ± 0%     10.3ns ± 4%    -83.17%  (p=0.008 n=5+5)
IndexRuneASCII/32-4     203ns ± 0%       11ns ± 5%    -94.68%  (p=0.008 n=5+5)
IndexRuneASCII/4K-4    23.4µs ± 0%      0.3µs ± 2%    -98.60%  (p=0.008 n=5+5)
IndexRuneASCII/4M-4    24.0ms ± 1%      0.3ms ± 1%    -98.60%  (p=0.008 n=5+5)
IndexRuneASCII/64M-4    386ms ± 2%        6ms ± 1%    -98.57%  (p=0.008 n=5+5)

name                  old speed     new speed       delta
IndexRune/10-4        188MB/s ± 1%    344MB/s ± 1%    +82.91%  (p=0.008 n=5+5)
IndexRune/32-4        167MB/s ± 0%   1175MB/s ± 1%   +603.52%  (p=0.008 n=5+5)
IndexRune/4K-4        174MB/s ± 1%   4117MB/s ± 1%  +2262.71%  (p=0.008 n=5+5)
IndexRune/4M-4        176MB/s ± 0%   4299MB/s ± 2%  +2340.46%  (p=0.008 n=5+5)
IndexRune/64M-4       175MB/s ± 1%   4354MB/s ± 1%  +2388.57%  (p=0.008 n=5+5)
IndexRuneASCII/10-4   163MB/s ± 0%    968MB/s ± 4%   +494.66%  (p=0.008 n=5+5)
IndexRuneASCII/32-4   157MB/s ± 0%   2974MB/s ± 4%  +1788.59%  (p=0.008 n=5+5)
IndexRuneASCII/4K-4   175MB/s ± 0%  12481MB/s ± 2%  +7027.71%  (p=0.008 n=5+5)
IndexRuneASCII/4M-4   175MB/s ± 1%  12510MB/s ± 1%  +7061.15%  (p=0.008 n=5+5)
IndexRuneASCII/64M-4  174MB/s ± 2%  12143MB/s ± 1%  +6881.70%  (p=0.008 n=5+5)

Change-Id: I0632eadb83937c2a9daa7f0ce79df1dee64f992e
Reviewed-on: https://go-review.googlesource.com/28537
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
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hirochachacha authored and bradfitz committed Sep 5, 2016
1 parent 8259cf3 commit e10286aeda6b1412f8f64734412bff74836637f9
Showing with 59 additions and 7 deletions.
  1. +5 −7 src/bytes/bytes.go
  2. +2 −0 src/bytes/bytes_amd64.go
  3. +52 −0 src/bytes/bytes_test.go
View
@@ -131,14 +131,12 @@ func LastIndexByte(s []byte, c byte) int {
// It returns the byte index of the first occurrence in s of the given rune.
// It returns -1 if rune is not present in s.
func IndexRune(s []byte, r rune) int {
- for i := 0; i < len(s); {
- r1, size := utf8.DecodeRune(s[i:])
- if r == r1 {
- return i
- }
- i += size
+ if r < utf8.RuneSelf {
+ return IndexByte(s, byte(r))
}
- return -1
+ var b [utf8.UTFMax]byte
+ n := utf8.EncodeRune(b[:], r)
+ return Index(s, b[:n])
}
// IndexAny interprets s as a sequence of UTF-8-encoded Unicode code points.
View
@@ -4,6 +4,8 @@
package bytes
+//go:noescape
+
// indexShortStr returns the index of the first instance of c in s, or -1 if c is not present in s.
// indexShortStr requires 2 <= len(c) <= shortStringLen
func indexShortStr(s, c []byte) int // ../runtime/asm_$GOARCH.s
View
@@ -354,6 +354,20 @@ func TestIndexRune(t *testing.T) {
t.Errorf(`IndexRune(%q, '%c') = %v`, tt.a, r, pos)
}
}
+
+ haystack := []byte("test世界")
+
+ allocs := testing.AllocsPerRun(1000, func() {
+ if i := IndexRune(haystack, 's'); i != 2 {
+ t.Fatalf("'s' at %d; want 2", i)
+ }
+ if i := IndexRune(haystack, ''); i != 4 {
+ t.Fatalf("'世' at %d; want 4", i)
+ }
+ })
+ if allocs != 0 {
+ t.Errorf(`expected no allocations, got %f`, allocs)
+ }
}
var bmbuf []byte
@@ -404,6 +418,44 @@ func bmIndexByte(index func([]byte, byte) int) func(b *testing.B, n int) {
}
}
+func BenchmarkIndexRune(b *testing.B) {
+ benchBytes(b, indexSizes, bmIndexRune(IndexRune))
+}
+
+func BenchmarkIndexRuneASCII(b *testing.B) {
+ benchBytes(b, indexSizes, bmIndexRuneASCII(IndexRune))
+}
+
+func bmIndexRuneASCII(index func([]byte, rune) int) func(b *testing.B, n int) {
+ return func(b *testing.B, n int) {
+ buf := bmbuf[0:n]
+ buf[n-1] = 'x'
+ for i := 0; i < b.N; i++ {
+ j := index(buf, 'x')
+ if j != n-1 {
+ b.Fatal("bad index", j)
+ }
+ }
+ buf[n-1] = '\x00'
+ }
+}
+
+func bmIndexRune(index func([]byte, rune) int) func(b *testing.B, n int) {
+ return func(b *testing.B, n int) {
+ buf := bmbuf[0:n]
+ utf8.EncodeRune(buf[n-3:], '')
+ for i := 0; i < b.N; i++ {
+ j := index(buf, '')
+ if j != n-3 {
+ b.Fatal("bad index", j)
+ }
+ }
+ buf[n-3] = '\x00'
+ buf[n-2] = '\x00'
+ buf[n-1] = '\x00'
+ }
+}
+
func BenchmarkEqual(b *testing.B) {
b.Run("0", func(b *testing.B) {
var buf [4]byte

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