LockingTests.swift

//
//  LockingTests.swift
//  LockingTests
//
//  Created by Adlai Holler on 1/18/16.
//  Copyright © 2016 Adlai Holler. All rights reserved.
//
/**
Results in iOS 9.2 simulator (iPhone 6) on my iMac:
'-[LockingTests.LockingTests testDispatchSemaphore]' measured [Time, seconds] average: 1.012, relative standard deviation: 6.997%, values: [1.090330, 1.071983, 1.048037, 0.911319, 1.042073, 0.920707, 1.079228, 0.962281, 0.919077, 1.076169], performanceMetricID:com.apple.XCTPerformanceMetric_WallClockTime, baselineName: "", baselineAverage: , maxPercentRegression: 10.000%, maxPercentRelativeStandardDeviation: 10.000%, maxRegression: 0.100, maxStandardDeviation: 0.100

'-[LockingTests.LockingTests testNSLock]' measured [Time, seconds] average: 4.868, relative standard deviation: 1.557%, values: [4.782288, 4.882415, 4.841834, 4.776851, 4.752024, 4.913981, 4.918518, 4.918231, 4.888296, 5.008807], performanceMetricID:com.apple.XCTPerformanceMetric_WallClockTime, baselineName: "", baselineAverage: , maxPercentRegression: 10.000%, maxPercentRelativeStandardDeviation: 10.000%, maxRegression: 0.100, maxStandardDeviation: 0.100

'-[LockingTests.LockingTests testPthreadMutex]' measured [Time, seconds] average: 4.740, relative standard deviation: 1.924%, values: [4.760173, 4.994403, 4.763439, 4.717273, 4.699853, 4.665326, 4.730564, 4.719830, 4.655418, 4.693427], performanceMetricID:com.apple.XCTPerformanceMetric_WallClockTime, baselineName: "", baselineAverage: , maxPercentRegression: 10.000%, maxPercentRelativeStandardDeviation: 10.000%, maxRegression: 0.100, maxStandardDeviation: 0.100

'-[LockingTests.LockingTests testSpinLock]' measured [Time, seconds] average: 0.462, relative standard deviation: 1.087%, values: [0.469458, 0.462443, 0.459723, 0.451885, 0.462273, 0.468570, 0.465032, 0.461615, 0.463144, 0.456066], performanceMetricID:com.apple.XCTPerformanceMetric_WallClockTime, baselineName: "", baselineAverage: , maxPercentRegression: 10.000%, maxPercentRelativeStandardDeviation: 10.000%, maxRegression: 0.100, maxStandardDeviation: 0.100

*/
import XCTest

final class LockingTests: XCTestCase {
    func testSpinLock() {
        var spinLock = OS_SPINLOCK_INIT
        executeLockTest({
                OSSpinLockLock(&spinLock)
            }, unlock: {
                OSSpinLockUnlock(&spinLock)
        })
    }

    func testDispatchSemaphore() {
        let sem = dispatch_semaphore_create(1)
        executeLockTest({
                dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER)
            }, unlock: {
                dispatch_semaphore_signal(sem)
        })
    }

    func testNSLock() {
        let lock = NSLock()
        executeLockTest({
                lock.lock()
            }, unlock: {
                lock.unlock()
        })
    }

    func testPthreadMutex() {
        var mutex = pthread_mutex_t()
        pthread_mutex_init(&mutex, nil)
        executeLockTest({
                pthread_mutex_lock(&mutex)
            }, unlock: {
                pthread_mutex_unlock(&mutex)
        })
        pthread_mutex_destroy(&mutex);
    }
    
    func disabled_testNoLock() {
        executeLockTest({}, unlock:  {})
    }

    private func executeLockTest(lock: () -> Void, unlock: () -> Void) {
        let dispatchBlockCount = 16
        let iterationCountPerBlock = 100_000
        // This is an example of a performance test case.
        let q = dispatch_get_global_queue(QOS_CLASS_DEFAULT, 0)
        var value = 100
        measureBlock {
            let group = dispatch_group_create()
            for _ in 0..<dispatchBlockCount {
                dispatch_group_enter(group)
                dispatch_async(q) {
                    for _ in 0..<iterationCountPerBlock {
                        lock()
                        value = value + 1
                        value = value - 1
                        unlock()
                    }
                    dispatch_group_leave(group)
                }
            }
            dispatch_group_wait(group, DISPATCH_TIME_FOREVER)
        }
    }
}