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Merged
XQ-Gang merged 3 commits into from
Dec 29, 2025
+107 −2
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feat(gslice): initial set capacity for union #31

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b2ddeb5
feat(gslice): initial set capacity for union
XQ-Gang Dec 22, 2025
702228e
test: add benchmark
XQ-Gang Dec 25, 2025
b24a7b7
Update gslice/gslice_bench_test.go
SilverRainZ Dec 27, 2025
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5 changes: 3 additions & 2 deletions gslice/gslice.go
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Original file line number Diff line number Diff line change
Expand Up @@ -875,8 +875,9 @@ func Union[S ~[]T, T comparable](ss ...S) S {
if len(ss) == 1 {
return Uniq(ss[0])
}
members := set.New[T]()
ret := S{} // TODO: Guess a cap.
size := Sum(Map(ss, func(s S) int { return len(s) }))
members := set.NewWithCap[T](size)
ret := make(S, 0, size/2)
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@SilverRainZ SilverRainZ Dec 23, 2025

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Can you please add a benchmark for this?

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@XQ-Gang XQ-Gang Dec 25, 2025

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go test ./gslice -bench=BenchmarkUnion -benchmem

goos: darwin
goarch: arm64
pkg: github.com/bytedance/gg/gslice
cpu: Apple M4 Pro
BenchmarkUnion/new-union-diff-2-10-14            3053234               373.5 ns/op           944 B/op          8 allocs/op
BenchmarkUnion/old-union-diff-2-10-14            2819313               412.5 ns/op          1744 B/op         10 allocs/op
BenchmarkUnion/new-union-diff-5-100-14            178990              6407 ns/op           24736 B/op          8 allocs/op
BenchmarkUnion/old-union-diff-5-100-14             73288             16443 ns/op           44624 B/op         22 allocs/op
BenchmarkUnion/new-union-same-2-10-14            5271890               218.1 ns/op           784 B/op          7 allocs/op
BenchmarkUnion/old-union-same-2-10-14            5344665               226.7 ns/op          1248 B/op          5 allocs/op
BenchmarkUnion/new-union-same-5-100-14            368089              3117 ns/op           20640 B/op          7 allocs/op
BenchmarkUnion/old-union-same-5-100-14            603517              2002 ns/op            1248 B/op          5 allocs/op
BenchmarkUnion/new-union-half-2-100-14            668262              1811 ns/op            5888 B/op          7 allocs/op
BenchmarkUnion/old-union-half-2-100-14            415273              2723 ns/op            5616 B/op         14 allocs/op

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@SilverRainZ SilverRainZ Dec 26, 2025

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👍

for _, s := range ss {
for _, v := range s {
if members.Add(v) {
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104 changes: 104 additions & 0 deletions gslice/gslice_bench_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@ import (
"strconv"
"testing"

"github.com/bytedance/gg/collection/set"
"github.com/bytedance/gg/internal/iter"
)

Expand Down Expand Up @@ -107,3 +108,106 @@ func BenchmarkShuffle_Parallel(b *testing.B) {
})
})
}

func oldUnion[S ~[]T, T comparable](ss ...S) S {
if len(ss) == 0 {
return S{}
}
if len(ss) == 1 {
return Uniq(ss[0])
}
members := set.New[T]()
ret := S{} // TODO: Guess a cap.
for _, s := range ss {
for _, v := range s {
if members.Add(v) {
ret = append(ret, v)
}
}
}
return ret
}

func BenchmarkUnion(b *testing.B) {
// 1. all different
ss1 := [][]int{
Range(0, 10),
Range(10, 20),
}
b.Run("new-union-diff-2-10", func(b *testing.B) {
for i := 0; i < b.N; i++ {
Union(ss1...)
}
})
b.Run("old-union-diff-2-10", func(b *testing.B) {
for i := 0; i < b.N; i++ {
oldUnion(ss1...)
}
})
ss2 := [][]int{
Range(0, 100),
Range(100, 200),
Range(200, 300),
Range(300, 400),
Range(400, 500),
}
b.Run("new-union-diff-5-100", func(b *testing.B) {
for i := 0; i < b.N; i++ {
Union(ss2...)
}
})
b.Run("old-union-diff-5-100", func(b *testing.B) {
for i := 0; i < b.N; i++ {
oldUnion(ss2...)
}
})

// 2. all same
ss3 := [][]int{
Repeat(0, 10),
Repeat(0, 10),
}
b.Run("new-union-same-2-10", func(b *testing.B) {
for i := 0; i < b.N; i++ {
Union(ss3...)
}
})
b.Run("old-union-same-2-10", func(b *testing.B) {
for i := 0; i < b.N; i++ {
oldUnion(ss3...)
}
})
ss4 := [][]int{
Repeat(0, 100),
Repeat(0, 100),
Repeat(0, 100),
Repeat(0, 100),
Repeat(0, 100),
}
b.Run("new-union-same-5-100", func(b *testing.B) {
for i := 0; i < b.N; i++ {
Union(ss4...)
}
})
b.Run("old-union-same-5-100", func(b *testing.B) {
for i := 0; i < b.N; i++ {
oldUnion(ss4...)
}
})

// 3. half different
ss5 := [][]int{
Range(0, 100),
Range(50, 150),
}
b.Run("new-union-half-2-100", func(b *testing.B) {
for i := 0; i < b.N; i++ {
Union(ss5...)
}
})
b.Run("old-union-half-2-100", func(b *testing.B) {
for i := 0; i < b.N; i++ {
oldUnion(ss5...)
}
})
}
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