http://blog.shenwei.me/map-is-not-the-fastest-in-go

checkLetter_test.go

// run:
//
//     go test -test.bench="." -test.cpuprofile=prof.out
//     go tool pprof ./gist.test prof.out
package main

import (
	"bytes"
	"testing"
)

var alphabet string
var subject []byte

var queryMap map[byte]bool
var querySlice []byte

func init() {
	alphabet = "acgtryswkmbdhvnACGTRYSWKMBDHVN -"

	// map
	queryMap = make(map[byte]bool, len(alphabet))
	for i := 0; i < len(alphabet); i++ {
		queryMap[alphabet[i]] = true
	}
	// fmt.Println("queryMap:", queryMap)

	// slice
	max := -1
	for i := 0; i < len(alphabet); i++ {
		j := int(alphabet[i])
		if max < j {
			max = j
		}
	}
	querySlice = make([]byte, max+1)
	for i := 0; i < len(alphabet); i++ {
		querySlice[int(alphabet[i])] = alphabet[i]
	}
	// fmt.Println("querySlice: ", querySlice)

	text := `
GCCTGTCTCAGACTCTTGGGGGCCTTGCAGCCTCCACCCCTACAGTGCTGCCATCTGGCT
TCTCAGCAGGGACCGAGTGATGCCCCTCTCCCCTCTACTACCCCCCACCCCTCTACTTCC
TGGTGTCACGTGGAAGGCAGCTGCCCGGGTTTGCCTGTGACTCCACACCCAGCATGTCTG
TCCCCTGCCCCAGGTCAGGGTGGGGCCTCGGCTTCCGCAGGAAGTGGTCTTGGTGCCAGC
CCTGCTGCCCTGGCTTTGAGCTGGGGCCCAGTGCCCTCTGGGTCCTGCTGGCTGCAGCTG
GCCCTCGGGGAACCCGCACACACAGCAGGAGGGGCCTGCCCAGGCCCAGTGCTGACTCTC
TCCTGCCATGCTCTCGGGCCCAGAGGTGCCATCCAGCCCCTGCCGTCTATCCACCCATCT
GTTCCTCGTCCCCCAGGCTGCAGGGCTCCCCACGCCACTGCTGTGGCCGCCTCACCTGCT
CCCCCTGTCTCTTTGGTCTTGCAGTCGGCTTCTCTATGGCCACAGCCTACTTTTAGAAGT
GCAGCTCTGTTAGGAGCCTTGAAGGTACCCGGTGCGCGGGACAGTGCGGCCCGCCGCCCC
TGCATGCCCAGGCCGCACCCCATTAGCATCCATGATTCCTGGTAGCATTTGGAGACTGTC
GCTCATGTGACGTGGATCATGACATGGCTCCGGGGGCCCTGGCCATCCCCAGCCATAGTG
GCATTTACGAGGCAGATCCAGGGTTCAGCTGGGTGGCCGCCTTCTCACTGGCCTCTCCTC
CCCTCccctccctcagtcctccctcccctccctcagtcctccctcccctccctcagtcct
ccctcccctccctcagtcctccctcccctccctcAGCCCCTTCCCTGGCGGGCAGCCCGC
TGGAGCCCCCACTGTGCCCCTCCTATCCCCCTCCTTCTCTCTCCTGCCCCCATCTCGGAC
CCTCAGGCTGTTGGTTCTGAGTTCGCCTCCCACTCCCTCC
`
	subject = []byte{}
	for i := 0; i < len(text); i++ {
		switch text[i] {
		case '\r', '\n', ' ':
		default:
			subject = append(subject, text[i])
		}
	}
	subject = bytes.Repeat(subject, 10000)

	// fmt.Println(len(subject))
}

// BenchmarkMap uses map
func BenchmarkCheckLetterWithMap(t *testing.B) {
	var ok bool
	for i, letter := range subject {
		if _, ok = queryMap[letter]; !ok {
			t.Errorf("invalid letter: %s in %d\n", []byte{letter}, i)
			return
		}
	}
}

// BenchmarkMap uses switch
func BenchmarkCheckLetterWithSwitch(t *testing.B) {
	for i, letter := range subject {
		switch letter {
		case 'a', 'A':
		case 'c', 'C':
		case 'g', 'G':
		case 't', 'T':
		case ' ':
		case '-':
		default:
			t.Errorf("invalid letter: %s in %d\n", []byte{letter}, i)
			return
		}
	}
}

func BenchmarkCheckLetterWithSwitchWithLargerAlphabetSize(t *testing.B) {
	for i, letter := range subject {
		switch letter {
		case 'a', 'A':
		case 'c', 'C':
		case 'g', 'G':
		case 't', 'T':
		case 'r', 'R':
		case 'y', 'Y':
		case 's', 'S':
		case 'w', 'W':
		case 'k', 'K':
		case 'm', 'M':
		case 'b', 'B':
		case 'd', 'D':
		case 'h', 'H':
		case 'v', 'V':
		case 'n', 'N':
		case ' ':
		case '-':
		default:
			t.Errorf("invalid letter: %s in %d\n", []byte{letter}, i)
			return
		}
	}
}

// BenchmarkSlice uses slice
func BenchmarkCheckLetterWithSlice(t *testing.B) {
	var value byte
	var j int
	var sliceSize = len(querySlice)
	for i, letter := range subject {
		j = int(letter)
		if j >= sliceSize {
			t.Errorf("invalid letter: %s in %d\n", []byte{letter}, i)
			return
		}
		value = querySlice[int(letter)]
		if value == 0 {
			t.Errorf("invalid letter: %s in %d\n", []byte{letter}, i)
			return
		}
	}
}

result

BenchmarkCheckLetterWithMap-4                           2000000000               0.18 ns/op
BenchmarkCheckLetterWithSwitch-4                        1000000000               0.02 ns/op
BenchmarkCheckLetterWithSwitchWithLargerAlphabetSize-4  1000000000               0.03 ns/op
BenchmarkCheckLetterWithSlice-4                         2000000000               0.01 ns/op