Go Interface conversion benchmarks

bench_test.go

package example

import (
	"testing"
)

type foo struct {
	name string
}

const (
	stringConst = "omg"
)

var (
	pointer = &foo{"foo"}
)

func nop(_ interface{}) {}

func BenchmarkInterfaceConversion(b *testing.B) {
	b.Run("pointer", func(b *testing.B) {
		var f interface{}
		for i := 0; i < b.N; i++ {
			f = interface{}(pointer)
		}
		nop(f)
	})

	b.Run("not a pointer", func(b *testing.B) {
		var f interface{}
		for i := 0; i < b.N; i++ {
			f = interface{}(foo{"foo"})
		}
		nop(f)
	})

	b.Run("const string", func(b *testing.B) {
		var f interface{}
		for i := 0; i < b.N; i++ {
			f = interface{}(stringConst)
		}
		nop(f)
	})

	b.Run("string", func(b *testing.B) {
		var k string = "foo"
		var f interface{}
		for i := 0; i < b.N; i++ {
			f = interface{}(k)
		}
		nop(f)
	})

	b.Run("int8", func(b *testing.B) {
		var k int8 = 100
		var f interface{}
		for i := 0; i < b.N; i++ {
			f = interface{}(k)
		}
		nop(f)
	})

	b.Run("int16", func(b *testing.B) {
		var k int16 = 1024
		var f interface{}
		for i := 0; i < b.N; i++ {
			f = interface{}(k)
		}
		nop(f)
	})

	b.Run("float32", func(b *testing.B) {
		var k float32 = 1
		var f interface{}
		for i := 0; i < b.N; i++ {
			f = interface{}(k)
		}
		nop(f)
	})

	b.Run("slice", func(b *testing.B) {
		k := make([]int, 10000)
		for i := 0; i < len(k); i++ {
			k[i] = i
		}

		var f interface{}
		for i := 0; i < b.N; i++ {
			f = interface{}(k)
		}
		nop(f)
	})

	b.Run("map", func(b *testing.B) {
		k := map[int]string{1: "fooo"}
		var f interface{}
		for i := 0; i < b.N; i++ {
			f = interface{}(k)
		}
		nop(f)
	})
}

results

go test -benchmem -bench .

goos: darwin
goarch: amd64
BenchmarkInterfaceConversion/pointer-4         	2000000000	         0.53 ns/op	       0 B/op	       0 allocs/op
BenchmarkInterfaceConversion/not_a_pointer-4   	50000000	        29.5 ns/op	      16 B/op	       1 allocs/op
BenchmarkInterfaceConversion/const_string-4    	2000000000	         0.27 ns/op	       0 B/op	       0 allocs/op
BenchmarkInterfaceConversion/string-4          	50000000	        24.0 ns/op	      16 B/op	       1 allocs/op
BenchmarkInterfaceConversion/int8-4            	2000000000	         0.26 ns/op	       0 B/op	       0 allocs/op
BenchmarkInterfaceConversion/int16-4           	100000000	        11.0 ns/op	       2 B/op	       1 allocs/op
BenchmarkInterfaceConversion/float32-4         	100000000	        11.0 ns/op	       4 B/op	       1 allocs/op
BenchmarkInterfaceConversion/slice-4           	50000000	        29.6 ns/op	      32 B/op	       1 allocs/op
BenchmarkInterfaceConversion/map-4             	2000000000	         0.26 ns/op	       0 B/op	       0 allocs/op
PASS
ok  	_/var/folders/_b/d1934m9s587_8t_6ngv3hnc00000gp/T/tmp.kFulmEtK	9.275s