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?
Please have a look at the sample program:
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");
}
Here's a Swift function I wrote to measure Project Euler problems in Swift
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.
My function would look something like:
// 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
}
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
}
Note that using NSdate for timing functions is discouraged: "The system time may decrease due to synchronization with external time references or due to an explicit user change of the clock.".