vvsqrtf performance tests

main.swift

// swift -O main.swift

import Foundation
import Accelerate

let N = 100_000_000

let x = (0...N).map { _ in Float(drand48() * 1_000_000) }

func test(_ f: () -> [Float], name: String) {
    let start = CFAbsoluteTimeGetCurrent()
    let y = f()
    let end = CFAbsoluteTimeGetCurrent()
    print(name, end - start, y.last!)
}

func testMap() -> [Float] {
    return x.map { sqrtf($0) }
}

func testVV() -> [Float] {
    var n = Int32(x.count)
    var y = [Float](repeating: 0, count: x.count)
    vvsqrtf(&y, x, &n)
    return y
}

func testForIn() -> [Float] {
    var y: [Float] = []
    for val in x {
        y.append(sqrtf(val))
    }
    return y
}

test(testMap, name: "map")
test(testVV, name:  "vv ")
test(testForIn, name: "for")

testTests.swift

// As a unit test; don't forget to set the scheme to test in Release
import XCTest
import Accelerate

class testTests: XCTestCase {

    var x: [Float] = []

    override func setUp() {
        super.setUp()
        for _ in 0...10_000_000 {
            x.append(Float(drand48() * 1_000_000))
        }
    }

    func testMap() {
        var y: [Float] = []
        self.measure {
            y = x.map { sqrtf($0) }
        }
        print(y.last!)
    }
    
    func testPerformanceVV() {
        var y: [Float] = []
        self.measure {
            var n = Int32(x.count)
            y = [Float](repeating: 0, count: x.count)
            vvsqrtf(&y, x, &n)
        }
        print(y.last!)
    }

    func testPerformanceForIn() {
        var y: [Float] = []
        self.measure {
            for val in x {
                y.append(sqrtf(val))
            }
        }
        print(y.last!)
    }
}