Benchmark copy vs append

foo_test.go

package foo

import "testing"

func createSource(b *testing.B) []int {
        source := make([]int, b.N)
        for i := range source {
                source[i] = i
        }
        b.ResetTimer()
        return source
}

func BenchmarkCopyN(b *testing.B) {
        source := createSource(b)
        dest := make([]int, len(source))
        copy(dest, source)
}

func BenchmarkAppendN(b *testing.B) {
        source := createSource(b)
        dest := append([]int(nil), source...)
        _ = dest
}

func BenchmarkAppendSourceN(b *testing.B) {
        source := createSource(b)
        dest := append(source[:0], source...)
        _ = dest
}

func createN(b *testing.B, n int) []int {
        source := make([]int, n)
        for i := range source {
                source[i] = i
        }
        b.ResetTimer()
        return source
}

func BenchmarkCopy1000(b *testing.B) {
        source := createN(b, 1000)
        for i := 0; i < b.N; i++ {
                dest := make([]int, len(source))
                copy(dest, source)
                _ = dest
        }
}

func BenchmarkAppend1000(b *testing.B) {
        source := createN(b, 1000)
        for i := 0; i < b.N; i++ {
                dest := append([]int(nil), source...)
                _ = dest
        }
}

func BenchmarkAppendSource1000(b *testing.B) {
        source := createN(b, 1000)
        for i := 0; i < b.N; i++ {
                dest := append(source[:0], source...)
                _ = dest
        }
}