From 90f46f884303f7b0d27fd2f895c47c0d88160a9c Mon Sep 17 00:00:00 2001 From: aimuz Date: Wed, 1 May 2024 21:36:59 +0800 Subject: [PATCH] bytes, strings: optimize Cut for single-byte separators MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Optimize the Cut function in both the bytes and strings packages to immediately return slices when the separator is a single byte (or character), avoiding more complex index searching logic. This change can significantly reduce the execution time for these specific cases, as benchmark tests added to each package demonstrate improvements. The optimization checks if the length of the separator is one before proceeding with the existing search strategy. If so, it uses IndexByte for a faster lookup of the separator's position. Additionally, benchmark tests have been added for both packages to demonstrate the performance benefits of this optimization across various scenarios. goos: darwin goarch: arm64 pkg: strings cpu: Apple M2 Max │ old-cut.txt │ new-cut.txt │ │ sec/op │ sec/op vs base │ Cut/Cut-One/2-12 4.026n ± 2% 3.274n ± 2% -18.68% (p=0.000 n=10) Cut/Cut-Two/2-12 8.093n ± 0% 8.357n ± 0% +3.27% (p=0.000 n=10) Cut/Cut-One/4-12 4.048n ± 1% 3.324n ± 2% -17.91% (p=0.000 n=10) Cut/Cut-Two/4-12 8.105n ± 0% 8.377n ± 1% +3.35% (p=0.000 n=10) Cut/Cut-One/8-12 4.089n ± 1% 3.290n ± 1% -19.53% (p=0.000 n=10) Cut/Cut-Two/8-12 8.107n ± 1% 8.359n ± 1% +3.10% (p=0.000 n=10) Cut/Cut-One/16-12 4.127n ± 1% 3.328n ± 1% -19.35% (p=0.000 n=10) Cut/Cut-Two/16-12 8.119n ± 1% 8.374n ± 1% +3.15% (p=0.000 n=10) Cut/Cut-One/32-12 4.545n ± 2% 3.675n ± 1% -19.14% (p=0.000 n=10) Cut/Cut-Two/32-12 8.708n ± 1% 8.963n ± 1% +2.92% (p=0.000 n=10) Cut/Cut-One/64-12 4.825n ± 2% 4.146n ± 1% -14.08% (p=0.000 n=10) Cut/Cut-Two/64-12 9.286n ± 0% 9.315n ± 1% ~ (p=0.105 n=10) geomean 5.983n 5.486n -8.32% │ old-cut.txt │ new-cut.txt │ │ B/op │ B/op vs base │ Cut/Cut-One/2-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-Two/2-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-One/4-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-Two/4-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-One/8-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-Two/8-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-One/16-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-Two/16-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-One/32-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-Two/32-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-One/64-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-Two/64-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ geomean ² +0.00% ² ¹ all samples are equal ² summaries must be >0 to compute geomean │ old-cut.txt │ new-cut.txt │ │ allocs/op │ allocs/op vs base │ Cut/Cut-One/2-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-Two/2-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-One/4-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-Two/4-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-One/8-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-Two/8-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-One/16-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-Two/16-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-One/32-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-Two/32-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-One/64-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ Cut/Cut-Two/64-12 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹ geomean ² +0.00% ² ¹ all samples are equal ² summaries must be >0 to compute geomean For #67101 --- src/bytes/bytes.go | 6 ++++++ src/bytes/bytes_test.go | 28 ++++++++++++++++++++++++++++ src/internal/stringslite/strings.go | 6 ++++++ src/strings/strings_test.go | 28 ++++++++++++++++++++++++++++ 4 files changed, 68 insertions(+) diff --git a/src/bytes/bytes.go b/src/bytes/bytes.go index 1871814c6e0..72ccdfc98eb 100644 --- a/src/bytes/bytes.go +++ b/src/bytes/bytes.go @@ -1330,6 +1330,12 @@ func Index(s, sep []byte) int { // // Cut returns slices of the original slice s, not copies. func Cut(s, sep []byte) (before, after []byte, found bool) { + if len(sep) == 1 { + if i := IndexByte(s, sep[0]); i >= 0 { + return s[:i], s[i+1:], true + } + return s, nil, false + } if i := Index(s, sep); i >= 0 { return s[:i], s[i+len(sep):], true } diff --git a/src/bytes/bytes_test.go b/src/bytes/bytes_test.go index 5e8cf85fd90..7026ad9c583 100644 --- a/src/bytes/bytes_test.go +++ b/src/bytes/bytes_test.go @@ -2263,3 +2263,31 @@ func TestClone(t *testing.T) { } } } + +func BenchmarkCut(b *testing.B) { + b.ReportAllocs() + + for _, skip := range [...]int{2, 4, 8, 16, 32, 64} { + s := Repeat(append(append(Repeat([]byte(" "), skip), 'a', 'a'), Repeat([]byte(" "), skip)...), 1<<16/skip) + b.Run(fmt.Sprintf("Cut-One/%d", skip), func(b *testing.B) { + for range b.N { + _, _, _ = Cut(s, []byte{'a'}) + } + }) + b.Run(fmt.Sprintf("Cut-Two/%d", skip), func(b *testing.B) { + for range b.N { + _, _, _ = Cut(s, []byte{'a', 'a'}) + } + }) + b.Run(fmt.Sprintf("Cut-One-Nil/%d", skip), func(b *testing.B) { + for range b.N { + _, _, _ = Cut(s, []byte{'c'}) + } + }) + b.Run(fmt.Sprintf("Cut-Two-Nil/%d", skip), func(b *testing.B) { + for range b.N { + _, _, _ = Cut(s, []byte{'c', 'c'}) + } + }) + } +} diff --git a/src/internal/stringslite/strings.go b/src/internal/stringslite/strings.go index ce8a913297b..2b30808c528 100644 --- a/src/internal/stringslite/strings.go +++ b/src/internal/stringslite/strings.go @@ -103,6 +103,12 @@ func Index(s, substr string) int { } func Cut(s, sep string) (before, after string, found bool) { + if len(sep) == 1 { + if i := IndexByte(s, sep[0]); i >= 0 { + return s[:i], s[i+1:], true + } + return s, "", false + } if i := Index(s, sep); i >= 0 { return s[:i], s[i+len(sep):], true } diff --git a/src/strings/strings_test.go b/src/strings/strings_test.go index ac493c7dcd4..37db3cb3a27 100644 --- a/src/strings/strings_test.go +++ b/src/strings/strings_test.go @@ -2071,3 +2071,31 @@ func BenchmarkReplaceAll(b *testing.B) { stringSink = ReplaceAll("banana", "a", "<>") } } + +func BenchmarkCut(b *testing.B) { + b.ReportAllocs() + + for _, skip := range [...]int{2, 4, 8, 16, 32, 64} { + s := Repeat(Repeat(" ", skip)+"aa"+Repeat(" ", skip), 1<<16/skip) + b.Run(fmt.Sprintf("Cut-One/%d", skip), func(b *testing.B) { + for range b.N { + _, _, _ = Cut(s, "a") + } + }) + b.Run(fmt.Sprintf("Cut-Two/%d", skip), func(b *testing.B) { + for range b.N { + _, _, _ = Cut(s, "aa") + } + }) + b.Run(fmt.Sprintf("Cut-One-Nil/%d", skip), func(b *testing.B) { + for range b.N { + _, _, _ = Cut(s, "c") + } + }) + b.Run(fmt.Sprintf("Cut-Two-Nil/%d", skip), func(b *testing.B) { + for range b.N { + _, _, _ = Cut(s, "cc") + } + }) + } +}