Benchmarking functions

main_test.go

package main

import (
  "fmt"
  "testing"
)

func BenchmarkAnonymousFunction(b *testing.B) {
  var t int64
  for i := 0; i < b.N; i++ {
    f := func(j int64) (r int64) {
      r = j * 2
      return
    }
    t = f(int64(i))
  }
  fmt.Sprintln(t)
}

func BenchmarkClosure(b *testing.B) {
  var t int64
  for i := 0; i < b.N; i++ {
    f := func() (r int64) {
      r = int64(i) * 2
      return
    }
    t = f()
  }
  fmt.Sprintln(t)
}

func BenchmarkNormalFunction(b *testing.B) {
  var t int64
  for i := 0; i < b.N; i++ {
    t = multiple2(int64(i))
  }
  fmt.Sprintln(t)
}

func BenchmarkNormalFunctionNotInline(b *testing.B) {
  var t int64
  for i := 0; i < b.N; i++ {
    t = multiple2NoInline(int64(i))
  }
  fmt.Sprintln(t)
}

func BenchmarkReturnedFunction(b *testing.B) {
  var t int64
  f := getFunc()
  for i := 0; i < b.N; i++ {
    t = f(int64(i))
  }
  fmt.Sprintln(t)
}

func multiple2(i int64) int64 {
  return i * 2
}

//go:noinline
func multiple2NoInline(i int64) int64 {
  return i * 2
}

func getFunc() func(int64) int64 {
  return func(i int64) int64 {
    return i * 2
  }
}

Results on go 1.10.1 amd64

$ go test -bench=.
goos: linux
goarch: amd64
pkg: foo
BenchmarkAnonymousFunction-32           2000000000               0.86 ns/op
BenchmarkClosure-32                     1000000000               2.26 ns/op
BenchmarkNormalFunction-32              2000000000               0.78 ns/op
BenchmarkNormalFunctionNotInline-32     500000000                2.34 ns/op
BenchmarkReturnedFunction-32            1000000000               2.36 ns/op
PASS
ok      foo     10.284s