atomic-snippet.swift

class Atomic<Value> {
  /// ...  

	/// Atomically modifies the variable.
	///
	/// Returns the old value.
	public func modify(@noescape action: (inout Value) throws -> Void) rethrows -> Value {
		return try withValue { value in
			try action(&_value)
			return value
		}
	}

	/// Atomically modifies the variable.
	///
	/// Returns the old value.
	public func _prev_modify(@noescape action: (Value) throws -> Value) rethrows -> Value {
		return try withValue { value in
			_value = try action(value)
			return value
		}
	}

  /// ...
}

atomicSpeedTestCase.swift

import XCTest

class AtomicSpeedTestCase: XCTestCase {

	func test_ModifyBeforeChange_10000() {
		let number = Atomic(1)
		measureBlock {
			/// 10000 itrs
			for _ in 1 ... 10000 {
				number._prev_modify { $0 + 1 }
			}
		}
	}

	func test_ModifyBeforeChange_500000() {
		let number = Atomic(1)
		measureBlock {
			/// 500000 itrs
			for _ in 1 ... 500000 {
				number._prev_modify { $0 + 1 }
			}
		}
	}

	func test_ModifyBeforeChange_5000000() {
		let number = Atomic(1)
		measureBlock {
			/// 5000000 itrs
			for _ in 1 ... 5000000 {
				number._prev_modify { $0 + 1 }
			}
		}
	}

	func test_ModifyAfterChange_10000() {
		let number = Atomic(1)
		measureBlock {
			for _ in 1 ... 10000 {
				number.modify { $0 += 1 }
			}
		}
	}

	func test_ModifyAfterChange_500000() {
		let number = Atomic(1)
		measureBlock {
			for _ in 1 ... 500000 {
				number.modify { $0 += 1 }
			}
		}
	}

	func test_ModifyAfterChange_5000000() {
		let number = Atomic(1)
		measureBlock {
			for _ in 1 ... 5000000 {
				number.modify { $0 += 1 }
			}
		}
	}
}