dml-benchmark.swift

// See this Swift bug for more info: https://bugs.swift.org/browse/SR-9323

import Benchmark

struct User {
  var name = "Blob"
  var age = 42
}

@dynamicMemberLookup
struct UserWrapper {
  var user: User

  subscript<Value>(dynamicMember keyPath: WritableKeyPath<User, Value>) -> Value {
    get { self.user[keyPath: keyPath] }
    set { self.user[keyPath: keyPath] = newValue }
  }
}

benchmark("Dynamic member lookup: setter only") {
  (1...100_000).forEach { _ in
    var user = UserWrapper(user: .init())
    user.name = "Blob Jr."
    user.age = 21
  }
}
benchmark("Dynamic member lookup: getter and setter") {
  (1...100_000).forEach { _ in
    var user = UserWrapper(user: .init())
    user.name = "Blob Jr."
    user.age = 21
    precondition(user.name == "Blob Jr.")
    precondition(user.age == 21)
  }
}
benchmark("Direct Access: setter only") {
  (1...100_000).forEach { _ in
    var user = UserWrapper(user: .init())
    user.user.name = "Blob Jr."
    user.user.age = 21
  }
}
benchmark("Direct Access: getter and setter") {
  (1...100_000).forEach { _ in
    var user = UserWrapper(user: .init())
    user.user.name = "Blob Jr."
    user.user.age = 21
    precondition(user.name == "Blob Jr.")
    precondition(user.age == 21)
  }
}

Benchmark.main()

/*

running Dynamic member lookup: setter only... done! (83.95 ms)
running Dynamic member lookup: getter and setter... done! (1355.41 ms)
running Direct Access: setter only... done! (76.52 ms)
running Direct Access: getter and setter... done! (73.11 ms)

name                                     time       std         iterations
--------------------------------------------------------------------------
Dynamic member lookup: setter only        30.000 ns ± 232.94 %     1000000
Dynamic member lookup: getter and setter 987.000 ns ± 142.01 %     1000000
Direct Access: setter only                26.000 ns ± 1021.99 %    1000000
Direct Access: getter and setter          26.000 ns ± 916.78 %     1000000
Program ended with exit code: 0

*/