Swiftで実行時間計測 ref: http://qiita.com/ken0nek/items/7577d26143a6fe4355f9

file0.swift

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

file1.swift

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

file2.swift

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

file3.swift

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

file4.swift

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

file5.swift

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

file6.swift

func time <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.")
}

file7.swift

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

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

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

file8.swift

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

file9.swift

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

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

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