Swiftで実行時間計測

2017/10/04 - Swift4での動作確認済み

この記事について

関数の実行時間を求めるのにいちいち

let start = NSDate()
// someMethod
let timeElapsed = -startTime.timeIntervalSinceNow
print(timeElapsed)

などと毎回書いていくのがめんどくさかったので調べてみました。

1. タイトル付きで表示

func printTimeElapsedWhenRunningCode <T> (title: String, operation: @autoclosure () -> T) {
    let startTime = CFAbsoluteTimeGetCurrent()
    operation()
    let timeElapsed = CFAbsoluteTimeGetCurrent() - startTime
    print("Time elapsed for \(title): \(timeElapsed) seconds")
}

使い方

以下のような関数があるとしたら、

func isEven(x: Int) -> Bool {
    return x % 2 == 0
}

printTimeElapsedWhenRunningCode("isEven", operation: isEven(1))
// Time elapsed for isEven: 0.000578999519348145 seconds

2. 返り値が実行時間

func timeElapsedInSecondsWhenRunningCode <T> (operation: @autoclosure () -> T)  -> Double {
    let startTime = CFAbsoluteTimeGetCurrent()
    operation()
    let timeElapsed = CFAbsoluteTimeGetCurrent() - startTime
    return Double(timeElapsed)
}

使い方

print(timeElapsedInSecondsWhenRunningCode(isEven(1)))
// 0.000547945499420166

3.1 関数の返り値と実行時間のメッセージ

func measure <T> (_ f: @autoclosure () -> T) -> (result: T, duration: String) {
    let startTime = CFAbsoluteTimeGetCurrent()
    let result = f()
    let timeElapsed = CFAbsoluteTimeGetCurrent() - startTime
    return (result, "Elapsed time is \(timeElapsed) seconds.")
}

使い方

print(measure(isEven(1)))
// (false, "Elapsed time is 0.000652015209197998 seconds.")

print(measure(isEven(1)).result)
// false

print(measure(isEven(1)).duration)
// Elapsed time is 0.000642001628875732 seconds.

3.2 関数の返り値と実行時間

func measure <T> (_ f: @autoclosure () -> T) -> (result: T, duration: Double) {
    let startTime = CFAbsoluteTimeGetCurrent()
    let result = f()
    let timeElapsed = CFAbsoluteTimeGetCurrent() - startTime
    return (result, Double(timeElapsed))
}

使い方

print(measure(isEven(1)))
// (false, 0.000528991222381592)

print(measure(isEven(1)).result)
// false

print(measure(isEven(1)).duration)
// 0.000581979751586914

おわりに

お好みのものが見つかれば幸いです。

参考

How to log a method's execution time exactly in milliseconds?
Measure elapsed time in swift
How to benchmark Swift code execution?