ClampTests

ClampTests.swift

// A challenge from https://twitter.com/hanyu_chen_ios/status/1395533041989079045
// Screenshots of performance tests https://twitter.com/ethanhuang13/status/1395577548151541760?s=21

import XCTest

let maxValue = 100
let minValue = 0

final class ClampTests: XCTestCase {
    func testMeasureNaiveCompare() throws {
        measure {
            for _ in 0 ..< 1_000_000 {
                let random = Int.random(in: -100 ... 200)
                let _: Int = {
                    if random > maxValue {
                        return maxValue
                    } else if random < minValue {
                        return minValue
                    } else {
                        return random
                    }
                }()
            }
        }
    }

    func testMeasureFuncMinMax() throws {
        measure {
            for _ in 0 ..< 1_000_000 {
                let random = Int.random(in: -100 ... 200)
                _ = min(max(random, minValue), maxValue)
            }
        }
    }
    
    func testMeasureFuncMaxMin() throws {
        measure {
            for _ in 0 ..< 1_000_000 {
                let random = Int.random(in: -100 ... 200)
                _ = max(min(random, maxValue), minValue)
            }
        }
    }

    func testMeasureSwitch() throws {
        measure {
            for _ in 0 ..< 1_000_000 {
                let random = Int.random(in: -100 ... 200)
                let _: Int = {
                    switch random {
                    case _ where random > maxValue: return maxValue
                    case _ where random < minValue: return minValue
                    default: return random
                    }
                }()
            }
        }
    }
    
    func testMeasureIsThisSlower() throws {
        measure {
            for _ in 0 ..< 1_000_000 {
                let random = Int.random(in: -100 ... 200)
                let _: Int = [minValue, random, maxValue].sorted()[1]
            }
        }
    }
}