Concat

Demo package for Ускорение конкатенации строк в Go своими руками article.

Overview

This package provides simple functions that return concatenation results. Can work faster than Go + operator.

You should not use this package, really. It's just an example.

Benchmarks

BenchmarkConcat2Operator/short-8         	20000000	        84.4 ns/op
BenchmarkConcat2Operator/longer-8        	10000000	       158 ns/op
BenchmarkConcat2Builder/short-8          	20000000	        70.7 ns/op
BenchmarkConcat2Builder/longer-8         	10000000	       127 ns/op
BenchmarkConcat2/short-8                 	30000000	        57.3 ns/op
BenchmarkConcat2/longer-8                	20000000	       106 ns/op
BenchmarkConcat3Operator/short-8         	20000000	       103 ns/op
BenchmarkConcat3Operator/longer-8        	10000000	       217 ns/op
BenchmarkConcat3Builder/short-8          	20000000	        89.9 ns/op
BenchmarkConcat3Builder/longer-8         	 5000000	       249 ns/op
BenchmarkConcat3/short-8                 	20000000	        85.0 ns/op
BenchmarkConcat3/longer-8                	10000000	       189 ns/op

Number one is unsafe concatenation, second is strings.Builder with preallocated buffer and "obvious" concatenation is the slowest one... unless CL123256 is applied.

Using the benchstat, here is the difference between concat and +:

name              old time/op  new time/op  delta
Concat2/short-8   84.4ns ± 2%  64.3ns ± 4%  -23.85%  (p=0.000 n=14+15)
Concat2/longer-8   138ns ± 1%   118ns ± 1%  -14.83%  (p=0.000 n=13+15)
Concat3/short-8    105ns ± 5%    82ns ± 5%  -22.29%  (p=0.000 n=15+14)
Concat3/longer-8   218ns ± 1%   192ns ± 1%  -11.95%  (p=0.000 n=15+15)

If compared with AMD64 asm version for concat2:

name              old time/op  new time/op  delta
Concat2/short-8   84.4ns ± 0%  56.9ns ± 5%  -32.54%  (p=0.000 n=15+15)
Concat2/longer-8   138ns ± 1%   107ns ± 0%  -22.51%  (p=0.000 n=13+15)

As a bonus, asm version also makes empty strings concatenation optimization, just like runtime version of concat would.

Example

package main

import (
	"fmt"

	"github.com/Quasilyte/concat"
)

func main() {
	v := "world!"
	fmt.Println(concat.Strings("hello, ", v)) // => "hello, world!"
}