map_test.go

package main

import (
	"errors"
	"testing"
)

func coreFunc(t int) error {
	return nil
}

var (
	errNotFound = errors.New("not found")
	funcMap     = map[int]func(int) error{
		1: coreFunc,
		2: coreFunc,
		3: coreFunc,
		4: coreFunc,
		5: coreFunc,
	}
)

func fMap(selector int) error {
	return funcMap[selector](selector)
}

func fSwitch(selector int) error {
	switch selector {
	case 1:
		return coreFunc(100)
	case 2:
		return coreFunc(100)
	case 3:
		return coreFunc(100)
	case 4:
		return coreFunc(100)
	case 5:
		return coreFunc(100)
	}
	return errNotFound
}

func BenchmarkMapFirst(b *testing.B) {
	for i := 0; i < b.N; i++ {
		fMap(1)
	}
}

func BenchmarkMapLast(b *testing.B) {
	for i := 0; i < b.N; i++ {
		fMap(5)
	}
}

func BenchmarkSwitchFirst(b *testing.B) {
	for i := 0; i < b.N; i++ {
		fSwitch(1)
	}
}

func BenchmarkSwitchLast(b *testing.B) {
	for i := 0; i < b.N; i++ {
		fSwitch(5)
	}
}

// Results
// goos: darwin
// goarch: arm64
// pkg: sw1
// BenchmarkMapFirst-10            309510448                3.683 ns/op
// BenchmarkMapLast-10             195455868                6.138 ns/op
// BenchmarkSwitchFirst-10         1000000000               0.4093 ns/op
// BenchmarkSwitchLast-10          1000000000               0.4091 ns/op
// PASS
// ok      sw1     4.702s

Remaping switch with cases to map implementation. Switch has const access time to any case path. Map is slower.