benchmark.swift

import Foundation

func randomString(_ length: Int) -> String {
	let letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
	return String((0..<length).map{ _ in letters.randomElement()! })
}

func bm<R>(_ title:String, operation: () -> R) {
	var totalTime = 0.0
	for _ in (0..<10) {
		let startTime = CFAbsoluteTimeGetCurrent()
		_ = operation()
		let timeElapsed = CFAbsoluteTimeGetCurrent() - startTime
		totalTime += timeElapsed
	}
	let meanTime = totalTime / 1000
	print("Mean time for \(title): \(meanTime) s")
}

func method1<T: Hashable>(_ array: Array<T>) -> Array<T> {
	return Array(Set(array))
}

func method2<T: Equatable>(_ array: Array<T>) -> Array<T>{
	return array
	.enumerated()
	.filter{ array.firstIndex(of: $0.1) == $0.0 }
	.map{ $0.1 }
}

// Alain T.'s answer (adapted)
func method3<T: Hashable>(_ array: Array<T>) -> Array<T> {
	var uniqueKeys = Set<T>()
	return array.filter{uniqueKeys.insert($0).inserted}
}

func method4<T: Hashable>(_ array: Array<T>) -> Array<T> {
	var uniqueKeys = Set<T>()
	uniqueKeys.reserveCapacity(array.count)
	return array.filter{uniqueKeys.insert($0).inserted}
}

let shortIntList = (0..<100).map{_ in Int.random(in: 0..<100) }
let longIntList = (0..<10000).map{_ in Int.random(in: 0..<10000) }
let longIntListManyRepetitions = (0..<10000).map{_ in Int.random(in: 0..<100) }
let longStringList = (0..<10000).map{_ in randomString(1000)}
let longMegaStringList = (0..<10000).map{_ in randomString(10000)}

print("Finished generated test data")

bm("method1 shortIntList") { method1(shortIntList) }
bm("method2 shortIntList") { method2(shortIntList) }
bm("method3 shortIntList") { method3(shortIntList) }
bm("method4 shortIntList") { method4(shortIntList) }

bm("method1 longIntList") { method1(longIntList) }
bm("method2 longIntList") { method2(longIntList) }
bm("method3 longIntList") { method3(longIntList) }
bm("method4 longIntList") { method4(longIntList) }

bm("method1 longIntListManyRepetitions") { method1(longIntListManyRepetitions) }
bm("method2 longIntListManyRepetitions") { method2(longIntListManyRepetitions) }
bm("method3 longIntListManyRepetitions") { method3(longIntListManyRepetitions) }
bm("method4 longIntListManyRepetitions") { method4(longIntListManyRepetitions) }

bm("method1 longStringList") { method1(longStringList) }
bm("method2 longStringList") { method2(longStringList) }
bm("method3 longStringList") { method3(longStringList) }
bm("method4 longStringList") { method4(longStringList) }

bm("method1 longMegaStringList") { method1(longMegaStringList) }
bm("method2 longMegaStringList") { method2(longMegaStringList) }
bm("method3 longMegaStringList") { method3(longMegaStringList) }
bm("method4 longMegaStringList") { method4(longMegaStringList) }