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bytes: speed up Replace

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This CL is to package bytes what CL 657935 was to package strings.

Add fuzz test and benchmarks for Replace.

The length of parameter old does not change. Move the corresponding length
check outside the loop. Use range-over-int loops where possible.

Some benchmark results (no changes to allocations):

goos: darwin
goarch: amd64
pkg: bytes
cpu: Intel(R) Core(TM) i7-6700HQ CPU @ 2.60GHz
                                 │     old      │                 new                 │
                                 │    sec/op    │   sec/op     vs base                │
Replace/"hello"_"l"_"L"_0-8         27.83n ± 2%   27.22n ± 1%   -2.17% (p=0.000 n=20)
Replace/"hello"_"l"_"L"_-1-8        60.64n ± 0%   57.97n ± 1%   -4.40% (p=0.000 n=20)
Replace/"hello"_"x"_"X"_-1-8        33.99n ± 0%   33.88n ± 0%        ~ (p=0.140 n=20)
Replace/""_"x"_"X"_-1-8             10.40n ± 1%   10.57n ± 0%   +1.64% (p=0.000 n=20)
Replace/"radar"_"r"_"<r>"_-1-8      62.63n ± 0%   61.39n ± 0%   -1.98% (p=0.000 n=20)
Replace/""_""_"<>"_-1-8             29.76n ± 1%   24.18n ± 1%  -18.75% (p=0.000 n=20)
Replace/"banana"_"a"_"<>"_-1-8      77.00n ± 0%   77.10n ± 1%        ~ (p=0.525 n=20)
Replace/"banana"_"a"_"<>"_1-8       44.24n ± 0%   43.57n ± 1%   -1.54% (p=0.000 n=20)
Replace/"banana"_"a"_"<>"_1000-8    78.23n ± 0%   77.16n ± 1%   -1.36% (p=0.000 n=20)
Replace/"banana"_"an"_"<>"_-1-8     72.78n ± 1%   69.97n ± 1%   -3.85% (p=0.000 n=20)
Replace/"banana"_"ana"_"<>"_-1-8    54.41n ± 0%   54.04n ± 1%   -0.67% (p=0.033 n=20)
Replace/"banana"_""_"<>"_-1-8       116.8n ± 1%   103.5n ± 1%  -11.42% (p=0.000 n=20)
Replace/"banana"_""_"<>"_10-8       117.2n ± 1%   103.6n ± 0%  -11.60% (p=0.000 n=20)
Replace/"banana"_""_"<>"_6-8       105.30n ± 0%   92.50n ± 0%  -12.16% (p=0.000 n=20)
Replace/"banana"_""_"<>"_5-8        91.81n ± 0%   79.87n ± 1%  -13.01% (p=0.000 n=20)
Replace/"banana"_""_"<>"_1-8        35.87n ± 1%   30.33n ± 1%  -15.43% (p=0.000 n=20)
Replace/"banana"_"a"_"a"_-1-8       70.84n ± 0%   68.83n ± 0%   -2.84% (p=0.000 n=20)
Replace/"banana"_"a"_"a"_1-8        44.27n ± 1%   43.47n ± 1%   -1.80% (p=0.000 n=20)
Replace/"☺☻☹"_""_"<>"_-1-8         104.25n ± 1%   93.33n ± 0%  -10.48% (p=0.000 n=20)
geomean                             56.31n        52.88n        -6.09%

Change-Id: I5daf44ccfd887da445d8c681415c32de7c2b85d1
GitHub-Last-Rev: d1caf1f0845a402a026764068a1db4dcf73e9017
GitHub-Pull-Request: golang/go#72967
Reviewed-on: https://go-review.googlesource.com/c/go/+/659515
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Jorropo <jorropo.pgm@gmail.com>
Reviewed-by: Jorropo <jorropo.pgm@gmail.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
This commit is contained in:
Julien Cretel 2025-03-20 20:42:05 +00:00 committed by Gopher Robot
parent 2bf57a3534
commit 44fef2aa4d
2 changed files with 92 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
src/bytes/bytes.go
View File

@ -1192,19 +1192,22 @@ func Replace(s, old, new []byte, n int) []byte {
t := make([]byte, len(s)+n*(len(new)-len(old)))
w := 0
start := 0
for i := 0; i < n; i++ {
j := start
if len(old) == 0 {
if i > 0 {
_, wid := utf8.DecodeRune(s[start:])
j += wid
}
} else {
j += Index(s[start:], old)
if len(old) > 0 {
for range n {
j := start + Index(s[start:], old)
w += copy(t[w:], s[start:j])
w += copy(t[w:], new)
start = j + len(old)
}
w += copy(t[w:], s[start:j])
} else { // len(old) == 0
w += copy(t[w:], new)
start = j + len(old)
for range n - 1 {
_, wid := utf8.DecodeRune(s[start:])
j := start + wid
w += copy(t[w:], s[start:j])
w += copy(t[w:], new)
start = j
}
}
w += copy(t[w:], s[start:])
return t[0:w]

81
src/bytes/bytes_test.go
View File

@ -7,6 +7,7 @@ package bytes_test
import (
. "bytes"
"fmt"
"internal/asan"
"internal/testenv"
"iter"
"math"
@ -1786,9 +1787,20 @@ var ReplaceTests = []ReplaceTest{
func TestReplace(t *testing.T) {
for _, tt := range ReplaceTests {
in := append([]byte(tt.in), "<spare>"...)
var (
in = []byte(tt.in)
old = []byte(tt.old)
new = []byte(tt.new)
)
if !asan.Enabled {
allocs := testing.AllocsPerRun(10, func() { Replace(in, old, new, tt.n) })
if allocs > 1 {
t.Errorf("Replace(%q, %q, %q, %d) allocates %.2f objects", tt.in, tt.old, tt.new, tt.n, allocs)
}
}
in = append(in, "<spare>"...)
in = in[:len(tt.in)]
out := Replace(in, []byte(tt.old), []byte(tt.new), tt.n)
out := Replace(in, old, new, tt.n)
if s := string(out); s != tt.out {
t.Errorf("Replace(%q, %q, %q, %d) = %q, want %q", tt.in, tt.old, tt.new, tt.n, s, tt.out)
}
@ -1796,7 +1808,7 @@ func TestReplace(t *testing.T) {
t.Errorf("Replace(%q, %q, %q, %d) didn't copy", tt.in, tt.old, tt.new, tt.n)
}
if tt.n == -1 {
out := ReplaceAll(in, []byte(tt.old), []byte(tt.new))
out := ReplaceAll(in, old, new)
if s := string(out); s != tt.out {
t.Errorf("ReplaceAll(%q, %q, %q) = %q, want %q", tt.in, tt.old, tt.new, s, tt.out)
}
@ -1804,6 +1816,69 @@ func TestReplace(t *testing.T) {
}
}
func FuzzReplace(f *testing.F) {
for _, tt := range ReplaceTests {
f.Add([]byte(tt.in), []byte(tt.old), []byte(tt.new), tt.n)
}
f.Fuzz(func(t *testing.T, in, old, new []byte, n int) {
differentImpl := func(in, old, new []byte, n int) []byte {
var out Buffer
if n < 0 {
n = math.MaxInt
}
for i := 0; i < len(in); {
if n == 0 {
out.Write(in[i:])
break
}
if HasPrefix(in[i:], old) {
out.Write(new)
i += len(old)
n--
if len(old) != 0 {
continue
}
if i == len(in) {
break
}
}
if len(old) == 0 {
_, length := utf8.DecodeRune(in[i:])
out.Write(in[i : i+length])
i += length
} else {
out.WriteByte(in[i])
i++
}
}
if len(old) == 0 && n != 0 {
out.Write(new)
}
return out.Bytes()
}
if simple, replace := differentImpl(in, old, new, n), Replace(in, old, new, n); !slices.Equal(simple, replace) {
t.Errorf("The two implementations do not match %q != %q for Replace(%q, %q, %q, %d)", simple, replace, in, old, new, n)
}
})
}
func BenchmarkReplace(b *testing.B) {
for _, tt := range ReplaceTests {
desc := fmt.Sprintf("%q %q %q %d", tt.in, tt.old, tt.new, tt.n)
var (
in = []byte(tt.in)
old = []byte(tt.old)
new = []byte(tt.new)
)
b.Run(desc, func(b *testing.B) {
b.ReportAllocs()
for b.Loop() {
Replace(in, old, new, tt.n)
}
})
}
}
type TitleTest struct {
in, out string
}