Benchmarking string concatenation written to a buffer in Go

README.md

This module benchmarks joining 5 strings with colons and writing the resulting string to a buffer. The result shows that concatenating with + is ~3-4x faster and performs fewer allocations. Fprintf and friends require 1 allocation per formatting operator.

golang/go#8618

go test -bench=.

goos: darwin
goarch: arm64
pkg: bench-strings
BenchmarkFprintf-10    	 5534516	       216.9 ns/op	     192 B/op	       7 allocs/op
BenchmarkConcat-10     	19905655	        60.62 ns/op	      64 B/op	       1 allocs/op
PASS
ok  	bench-strings	2.827s

go.mod

module bench-strings

go 1.19

main_test.go

package main

import (
	"bytes"
	"fmt"
	"testing"
)

var (
	testData = []string{"a", "b", "c", "d", "e"}
)

func BenchmarkFprintf(b *testing.B) {
	b.ReportAllocs()

	for i := 0; i < b.N; i++ {
		buf := &bytes.Buffer{}
		fmt.Fprintf(buf, "%s:%s:%s:%s:%s", testData[0], testData[1], testData[2], testData[3], testData[4])
	}
}

func BenchmarkConcat(b *testing.B) {
	b.ReportAllocs()

	for i := 0; i < b.N; i++ {
		buf := &bytes.Buffer{}
		buf.WriteString(testData[0] + ":" + testData[1] + ":" + testData[2] + ":" + testData[3] + ":" + testData[4])
	}
}