Testing non-branching alternatives to ternary expressions (array-based vectorized expression vs. inline bitwise operation v. ternary conditional expressions). The vectorized expression narrowly beat the ternary; the bitwise operation lags twice over.

Non-Branching Alternatives to Ternary Expressions.swift

import CoreFoundation
import Foundation

var a = 3
var b = 7
var c = 5
var d = 10

func measureTime(for expression: () -> Void, iterations: Int) -> Double {
	var totalTime: CFAbsoluteTime = 0
	for _ in 0 ..< iterations {
		let start = CFAbsoluteTimeGetCurrent()
		expression()
		let end = CFAbsoluteTimeGetCurrent()
		totalTime += (end - start)
	}
	return totalTime / Double(iterations)
}

// Measure time for the array-based vectorized expression
let arrayAverageTime = measureTime(
	for: {
		let aVec = [a, a]
		let bVec = [b, b]
		let cVec = [c, c]
		let dVec = [d, d]

		let diff = zip(aVec, bVec).map { $0 - $1 }
		let wordBit = Int.bitWidth
		let sign = diff.map { $0 >> (wordBit - 1) }
		let xorCD = zip(cVec, dVec).map { $0 ^ $1 }
		let resultVec = zip(sign, xorCD).map { ($0 & $1) ^ d }
		_ = resultVec[0]
	}, iterations: 1_000_000
)

print("Average time for the array-based vectorized expression: \(arrayAverageTime) seconds")

// Measure time for the inline bitwise expression
let bitwiseAverageTime = measureTime(
	for: {
		let wordBit = Int.bitWidth
		let diff = a - b
		let sign = diff >> (wordBit - 1)
		let xorCD = c ^ d
		let result = (sign & xorCD) ^ d
		_ = result
	}, iterations: 1_000_000
)

print("Average time for the inline bitwise expression: \(bitwiseAverageTime) seconds")

// Measure time for the conditional expression
let conditionalAverageTime = measureTime(
	for: {
		_ = (a < b) ? c : d
	}, iterations: 1_000_000
)

print("Average time for the conditional expression: \(conditionalAverageTime) seconds")