How to benchmark Swift code execution?

If you just want a standalone timing function for a block of code, I use the following Swift helper functions:

func printTimeElapsedWhenRunningCode(title:String, operation:()->()) {    let startTime = CFAbsoluteTimeGetCurrent()    operation()    let timeElapsed = CFAbsoluteTimeGetCurrent() - startTime    print("Time elapsed for \(title): \(timeElapsed) s.")}func timeElapsedInSecondsWhenRunningCode(operation: ()->()) -> Double {    let startTime = CFAbsoluteTimeGetCurrent()    operation()    let timeElapsed = CFAbsoluteTimeGetCurrent() - startTime    return Double(timeElapsed)}

The former will log out the time required for a given section of code, with the latter returning that as a float. As an example of the first variant:

printTimeElapsedWhenRunningCode(title:"map()") {    let resultArray1 = randoms.map { pow(sin(CGFloat($0)), 10.0) }}

will log out something like:

Time elapsed for map(): 0.0617449879646301 s

Be aware that Swift benchmarks will vary heavily based on the level of optimization you select, so this may only be useful for relative comparisons of Swift execution time. Even that may change on a per-beta-version basis.

If you want to get insight into performance of a certain block of code and make sure performance doesn't hurt when you make edits, best thing would be using XCTest's measuring performance functions, like measure(_ block: () -> Void).

Write a unit test that executes method you want to benchmark, and that unit test will run it multiple times giving you time needed and deviation of results

func testExample() {    self.measure {        //do something you want to measure    }}

You can find more info in apple docs under Testing with Xcode -> Performance Testing

You can use this function to measure asynchronous as well as synchronous code:

import Foundationfunc measure(_ title: String, block: (@escaping () -> ()) -> ()) {    let startTime = CFAbsoluteTimeGetCurrent()    block {        let timeElapsed = CFAbsoluteTimeGetCurrent() - startTime        print("\(title):: Time: \(timeElapsed)")    }}

So basically you pass a block that accepts a function as a parameter, which you use to tell measure when to finish.

For example to measure how long some call called "myAsyncCall" takes, you would call it like this:

measure("some title") { finish in    myAsyncCall {        finish()    }    // ...}

For synchronous code:

measure("some title") { finish in     // code to benchmark     finish()     // ...}

This should be similar to measureBlock from XCTest, though I don't know how exactly it's implemented there.