performance.swift

#!/usr/bin/env swift -Ounchecked

/*
   Performance testing of imperative and declarative solutions to the same problem.
   Example from "Practical Declarative Programming" presented at 360 iDev in 2015.
*/

import func CoreFoundation.CFAbsoluteTimeGetCurrent

func imperativeMap() {
  let groups = [
    ["Kyle", "Katie"],
    ["André", "Maxine", "Ash"],
  ]

  var counts = [Int]()

  for group in groups {
    let people = group.count
    counts.append(people)
  }
}

func declarativeMap() {
  let groups = [
    ["Kyle", "Katie"],
    ["André", "Maxine", "Ash"],
  ]

  groups.map { $0.count }
}

let amount = 1_000_0000

func time(closure:(() -> ())) -> Double {
  let start = CFAbsoluteTimeGetCurrent()

  for _ in (0..<amount) {
    closure()
  }

  let end = CFAbsoluteTimeGetCurrent()

  return end - start
}

let declarativeTime = time(declarativeMap)
let imperativeTime = time(imperativeMap)

print("Total time taken for 1 million iterations.")
print("Declarative: \(declarativeTime)s")
print("Imperative:  \(imperativeTime)s")