Slices vs. Array performance in golang.

benchmark_test.go

package main

import "testing"

var gs = make([]byte, 1000)
var ga [1000]byte

func BenchmarkSliceGlobal(b *testing.B) {
	for i := 0; i < b.N; i++ {
		for j, v := range gs {
			gs[j]++
			gs[j] = gs[j] + v + 10
			gs[j] += v
		}
	}
}

func BenchmarkArrayGlobal(b *testing.B) {
	for i := 0; i < b.N; i++ {
		for j, v := range ga {
			ga[j]++
			ga[j] = ga[j] + v + 10
			ga[j] += v
		}
	}
}

func BenchmarkSliceLocal(b *testing.B) {
	var s = make([]byte, 1000)
	for i := 0; i < b.N; i++ {
		for j, v := range s {
			s[j]++
			s[j] = s[j] + v + 10
			s[j] += v
		}
	}
}

func BenchmarkArrayLocal(b *testing.B) {
	var a [1000]byte
	for i := 0; i < b.N; i++ {
		for j, v := range a {
			a[j]++
			a[j] = a[j] + v + 10
			a[j] += v
		}
	}
}

go test -bench=. -benchmem

goos: darwin
goarch: arm64
pkg: scratch
BenchmarkSliceGlobal-10           758868              1574 ns/op               0 B/op          0 allocs/op
BenchmarkArrayGlobal-10          2258762               532.8 ns/op             0 B/op          0 allocs/op
BenchmarkSliceLocal-10           2263557               528.1 ns/op             0 B/op          0 allocs/op
BenchmarkArrayLocal-10           1946401               615.5 ns/op             0 B/op          0 allocs/op
PASS
ok      scratch 7.511s