Measuring performance of three different algorithms for calculating the average for an array of doubles

Measuring_average_performance.swift

import Foundation


extension Array where Element: FloatingPoint {

    func average() -> Element {
        // one addition and one division per array item
        return reduce(0) { result, value in result + value / Element(count) }
    }
    
    func average2() -> Element {
        // number of items minus one additions and one division.
        return reduce(0, +)/Element(count)
    }

    func average3() -> Element {
        var average: Element = 0
        forEach() { e in
            average += e
        }
        return average / Element(count)
    }
 }

func measureTime(_ block: (() -> Void)) {
        let start = DispatchTime.now()
        block()
        let end = DispatchTime.now()
        let nanoTime = end.uptimeNanoseconds - start.uptimeNanoseconds
        let timeInterval = Double(nanoTime) / 1_000_000_000
        print("Time: \(timeInterval) seconds")

    }

// uses 80 MB of memory
let longList: [Double] = (1...1_000_0000).map { _ in Double.random(in: (0...1.0e23)) } 
measureTime() {
    print("average")
    let average = longList.average()
    print("average: \(average)")
}
measureTime() {
    print("average2")
    let average = longList.average2()
    print("average2: \(average)")
}
measureTime() {
    print("average3")
    let average = longList.average3()
    print("average3: \(average)")
}