results testing linear search vs. binary search

Big O notation

import Foundation
var array = [Int]()

for i in 1 ..< 10000000 {
	array.append(i)
}
//let numberList = array

extension Array where Element: Comparable {

	 mutating func linearSearch(forElement key: Element) -> Bool {
		//check all possible values
		for number in self {
			if number == key {
				return true
			}
		}
		return false
	}

 	func binarySearch(forElement key: Element) -> Bool {
//		print("check")
			var result = false

			//establish indices
			let min = self.startIndex
			let max = self.endIndex - 1
			let mid = self.midIndex()

			//check bounds
			if key > self[max] || key < self[min] {
				 print("search value \(key) not found..")
				 return false
			}

			//evaluate chosen number..
			let n = self[mid]

			if n > key {
				 var slice = Array(self[min...mid - 1])
				 result = slice.binarySearch(forElement: key)
			}

			else if n < key {
				 var slice = Array(self[mid + 1...max])
				 result = slice.binarySearch(forElement: key)
			}

			else {
				 //print("search value \(key) found..")
				 result = true
			}

			return result
	  }

	 //returns middle index
	 func midIndex() -> Index {
		  return startIndex + (count / 2)
	 }
}


	//execute search
let date = NSDate()
var isFound: Bool = array.linearSearch(forElement: 9000000)
print(date.timeIntervalSinceNow) //-0.01704

let date2 = NSDate()
isFound = array.binarySearch(forElement: 9000000)
print(date2.timeIntervalSinceNow) //-0.03014

I also tried this without binarySearch function being mutating, changing internal methods to
var slice = ... to let slice = ...
it was basically the same result

I compiled on CodeRunner 2 with -O flag,