在Swift中测量经过时间 [英] Measure elapsed time in Swift

问题描述

我们如何测量在Swift中运行一个函数所花费的时间?我试图以这种方式显示经过的时间:经过的时间为.05秒".看到在Java中，我们可以使用System.nanoTime()，Swift中是否有等效的方法可以完成此任务?

How can we measure the time elapsed for running a function in Swift? I am trying to display the elapsed time like this: "Elapsed time is .05 seconds". Saw that in Java, we can use System.nanoTime(), is there any equivalent methods are available in Swift to accomplish this?

请查看示例程序:

func isPrime(var number:Int) ->Bool {
    var i = 0;
    for i=2; i<number; i++ {
        if(number % i == 0 && i != 0) {
            return false;
        }
    }
    return true;
}

var number = 5915587277;

if(isPrime(number)) {
    println("Prime number");
} else {
    println("NOT a prime number");
}

推荐答案

这是我编写的用于测量 Project Euler 的Swift函数. a> Swift中的问题

Here's a Swift function I wrote to measure Project Euler problems in Swift

从Swift 3开始，Grand Central Dispatch现在有一个精简版"版本.因此，正确的答案可能是使用 DispatchTime API .

As of Swift 3, there is now a version of Grand Central Dispatch that is "swiftified". So the correct answer is probably to use the DispatchTime API.

我的功能如下:

// Swift 3
func evaluateProblem(problemNumber: Int, problemBlock: () -> Int) -> Answer
{
    print("Evaluating problem \(problemNumber)")

    let start = DispatchTime.now() // <<<<<<<<<< Start time
    let myGuess = problemBlock()
    let end = DispatchTime.now()   // <<<<<<<<<<   end time

    let theAnswer = self.checkAnswer(answerNum: "\(problemNumber)", guess: myGuess)

    let nanoTime = end.uptimeNanoseconds - start.uptimeNanoseconds // <<<<< Difference in nano seconds (UInt64)
    let timeInterval = Double(nanoTime) / 1_000_000_000 // Technically could overflow for long running tests

    print("Time to evaluate problem \(problemNumber): \(timeInterval) seconds")
    return theAnswer
}

---

旧答案

对于Swift 1和2，我的函数使用NSDate:

---

Old answer

For Swift 1 and 2, my function uses NSDate:

// Swift 1
func evaluateProblem(problemNumber: Int, problemBlock: () -> Int) -> Answer
{
    println("Evaluating problem \(problemNumber)")

    let start = NSDate() // <<<<<<<<<< Start time
    let myGuess = problemBlock()
    let end = NSDate()   // <<<<<<<<<<   end time

    let theAnswer = self.checkAnswer(answerNum: "\(problemNumber)", guess: myGuess)

    let timeInterval: Double = end.timeIntervalSinceDate(start) // <<<<< Difference in seconds (double)

    println("Time to evaluate problem \(problemNumber): \(timeInterval) seconds")
    return theAnswer
}

_{请注意，建议不要将NSdate用于计时功能:"由于与外部时间参考同步或由于用户明确更改了时钟，系统时间可能会减少."./sub>}

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