A quick test to compare performance of different dictionary lookups in Swift

DictBench.swift

// A quick test to compare performance of different dictionary lookups in Swift.
// Note: Results recorded on a 2020 M1 MBP. be sure to run with "Optimize for Speed [-O]

import Foundation

let iterations = 1000000

var dictionary = [Int: Int]()
for i in 0 ..< iterations {
    dictionary[i] = Int.random(in: 0 ..< 1000)
}

let start = CFAbsoluteTimeGetCurrent()

for i in 0 ..< iterations {
    if !dictionary.keys.contains(i) {
        print("uh...?")
    }
}

let mid = CFAbsoluteTimeGetCurrent()

for i in 0 ..< iterations {
    if dictionary[i] == nil {
        print("uh...?")
    }
}

let end = CFAbsoluteTimeGetCurrent()

print("keys.contains", mid - start) // 0.02835094928741455
print("subscript", end - mid) // 0.038653016090393066