bench.go

package main

import (
	"fmt"
	"math/rand"
	"strings"
	"testing"
)

const alphabet = "abcdefghijklmnopqrstuvwxyz0123456789"
const alphabetSize = 36

func BenchmarkStr(b *testing.B) {
	lengths := []int{1, 10, 100, 1000, 10000, 100000}
	for _, length := range lengths {
		b.Run(fmt.Sprintf("byte array %d", length), func(b *testing.B) {
			random := rand.New(rand.NewSource(0))
			for i := 0; i < b.N; i++ {
				value := make([]byte, length)
				for i := 0; i < length; i++ {
					value[i] = alphabet[random.Intn(alphabetSize)]
				}
				_ = string(value)
			}
		})

		b.Run(fmt.Sprintf("concat %d", length), func(b *testing.B) {
			random := rand.New(rand.NewSource(0))
			for i := 0; i < b.N; i++ {
				value := ""
				for i := 0; i < length; i++ {
					value += string(alphabet[random.Intn(alphabetSize)])
				}
				_ = value
			}
		})

		b.Run(fmt.Sprintf("string builder %d", length), func(b *testing.B) {
			random := rand.New(rand.NewSource(0))
			for i := 0; i < b.N; i++ {
				var sb strings.Builder
				for i := 0; i < length; i++ {
					sb.WriteByte(alphabet[random.Intn(alphabetSize)])
				}
				_ = sb.String()
			}
		})

		b.Run(fmt.Sprintf("string builder + grow %d", length), func(b *testing.B) {
			random := rand.New(rand.NewSource(0))
			for i := 0; i < b.N; i++ {
				var sb strings.Builder
				sb.Grow(length)
				for i := 0; i < length; i++ {
					sb.WriteByte(alphabet[random.Intn(alphabetSize)])
				}
				_ = sb.String()
			}
		})
	}
}

stats.md

	Length	Count	ns/op	ns/op/length	B/op	B/op/length	allocs/op
byte array				17		1.8
	1	38169398	30.2	30	1	1.0	1
	10	6827912	165	17	16	1.6	1
	100	834948	1457	15	224	2.2	2
	1000	85670	13922	14	2048	2.0	2
	10000	8769	136396	14	20480	2.0	2
	100000	832	1369405	14	212999	2.1	2
concat				1847		9834.4
	1	42378474	24.4	24	0	0.0	0
	10	2347600	502	50	64	6.4	9
	100	158595	7071	71	5728	57.3	99
	1000	6658	178428	178	530342	530.3	999
	10000	96	11822332	1182	53164283	5316.4	10001
	100000	2	957450730	9575	5309586624	53095.9	100241
String builder				20		4.1
	1	27875820	39.4	39	8	8.0	1
	10	5805525	205	21	24	2.4	2
	100	707866	1679	17	248	2.5	5
	1000	79156	14888	15	2040	2.0	8
	10000	6871	153444	15	48505	4.9	17
	100000	799	1504200	15	505858	5.1	25
String builder + grow				18		1.1
	1	33155168	33.4	33	1	1.0	1
	10	6849759	175	18	16	1.6	1
	100	720225	1502	15	112	1.1	1
	1000	81234	14903	15	1024	1.0	1
	10000	7467	147579	15	10240	1.0	1
	100000	798	1475910	15	106503	1.1	1