Swift Array<T> count performance test comparison

ArrayCountPerformanceTests.swift

import XCTest

// # Setup
// Big array size: 1_000_000_000 (1 billion elements of 12345)
// Small array size: 2 [12345, 12345]
// Loop: 1_000_000 (1 million) times.
// Machine: Macbook Pro 2023 16" M2 Max 32gb

// # Results
// TLDR: Stored: 3% faster
// Baseline (no operation, just the loop): 0.204s
// Small array Computed: 0.211s | Stored: 0.204s
// Big array: Computed: 0.213s | Stored: 0.203s (funny)


class ArrayCountPerformanceTests: XCTestCase {
    let bigArray = Array(repeating: 12345, count: 1_000_000_000)
    let smallArray = Array(repeating: 12345, count: 2)
    let numnberOfLoops = 1_000_000

    func test_baselinePerformance() {
        measure {
            for _ in 0...numnberOfLoops {
                let _ = 1
            }
        }
    }

    func test_smallArray_computedCountPerformance() {
        measure {
            for _ in 0...numnberOfLoops {
                let _ = smallArray.count
            }
        }
    }

    func test_smallArray_storedCountPerformance() {
        measure {
            let count = smallArray.count
            for _ in 0...numnberOfLoops {
                let _ = count
            }
        }
    }

    func test_bigArray_computedCountPerformance() {
        measure {
            for _ in 0...numnberOfLoops {
                let _ = bigArray.count
            }
        }
    }

    func test_bigArray_storedCountPerformance() {
        measure {
            let count = bigArray.count
            for _ in 0...numnberOfLoops {
                let _ = count
            }
        }
    }
}