重构荷兰政府那个非常有效的代码

[utterances-bot]

重构荷兰政府那个非常有效的代码

荷兰政府最近被迫发布其DigiD数字认证iOS应用程序的源代码，好事者在review它的代码时，发现了一段非常有趣的函数:

https://colobu.com/2023/01/20/The-refactoring-of-the-%E2%80%9CVery-efficient-Code%E2%80%9D-from-Dutch-DigiD-App/

[yougg]

还可以试试数组和map方式

var roundsArray = [...]string{
	0: "☆☆☆☆☆☆☆☆☆☆",
	1: "★☆☆☆☆☆☆☆☆☆",
	2: "★★☆☆☆☆☆☆☆☆",
	3: "★★★☆☆☆☆☆☆☆",
	4: "★★★★☆☆☆☆☆☆",
	5: "★★★★★☆☆☆☆☆",
	6: "★★★★★★☆☆☆☆",
	7: "★★★★★★★☆☆☆",
	8: "★★★★★★★★☆☆",
	9: "★★★★★★★★★☆",
}

func getPercentageRoundsArray(percentage float64) string {
	if p := int(percentage * 10); p >= 0 && p < len(roundsArray) {
		return roundsArray[p]
	} else {
		return "★★★★★★★★★★"
	}
}

var roundsMap = map[int]string{
	0: "☆☆☆☆☆☆☆☆☆☆",
	1: "★☆☆☆☆☆☆☆☆☆",
	2: "★★☆☆☆☆☆☆☆☆",
	3: "★★★☆☆☆☆☆☆☆",
	4: "★★★★☆☆☆☆☆☆",
	5: "★★★★★☆☆☆☆☆",
	6: "★★★★★★☆☆☆☆",
	7: "★★★★★★★☆☆☆",
	8: "★★★★★★★★☆☆",
	9: "★★★★★★★★★☆",
}

func getPercentageRoundsMap(percentage float64) string {
    if p, ok := roundsMap[int(percentage * 10)]; ok {
        return p
    } else {
        return "★★★★★★★★★★"
    }
}

[dasheyuan]

结论还是有点区别，substring不是最快的。go 1.19

goos: windows
goarch: amd64
pkg: percent
cpu: Intel Xeon Processor (Skylake, IBRS)
BenchmarkPercentageRounds/original-8            185058242                6.480 ns/op
BenchmarkPercentageRounds/originalOpt-8         1000000000               0.2910 ns/op
BenchmarkPercentageRounds/switch-8              1000000000               0.8603 ns/op
BenchmarkPercentageRounds/tree-8                1000000000               0.2852 ns/op
BenchmarkPercentageRounds/substring-8           877959271                1.370 ns/op
BenchmarkPercentageRounds/concat-8               8593039               137.2 ns/op
BenchmarkPercentageRounds/array-8               1000000000               0.3037 ns/op
BenchmarkPercentageRounds/map-8                 134443492                8.585 ns/op
PASS
ok      percent 8.850s

[PaiGack]

goos: windows
goarch: amd64
pkg: go-rpc/tmp
cpu: Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz
BenchmarkPercentageRounds
BenchmarkPercentageRounds/original
BenchmarkPercentageRounds/original-8            141775195                8.333 ns/op
BenchmarkPercentageRounds/originalOpt
BenchmarkPercentageRounds/originalOpt-8         1000000000               0.3778ns/op
BenchmarkPercentageRounds/originalSwitch
BenchmarkPercentageRounds/originalSwitch-8      1000000000               1.091 ns/op
BenchmarkPercentageRounds/tree
BenchmarkPercentageRounds/tree-8                1000000000               0.3733ns/op
BenchmarkPercentageRounds/substring
BenchmarkPercentageRounds/substring-8           691862770                1.766 ns/op
BenchmarkPercentageRounds/concat
BenchmarkPercentageRounds/concat-8              12225598                97.08 ns/op
BenchmarkPercentageRounds/array
BenchmarkPercentageRounds/array-8               1000000000               0.3699ns/op
BenchmarkPercentageRounds/map
BenchmarkPercentageRounds/map-8                 100000000               11.44 ns/op
PASS

[mengxiaotian]

不能使用percentage * 10的操作，会导致结果有误