grand-central-dispatch

问题 import Dispatch class SynchronizedArray<T> { private var array: [T] = [] private let accessQueue = DispatchQueue(label: "SynchronizedArrayAccess", attributes: .concurrent) var get: [T] { accessQueue.sync { array } } func append(newElement: T) { accessQueue.async(flags: .barrier) { self.array.append(newElement) } } } If I run the following code, 10,000 elements are appended to the array as expected even if I am reading concurrently: DispatchQueue.concurrentPerform(iterations: 10000) { i in _

问题 For example, there is a 1000 times loop. What's the max value to make it fast, effective, and not lead to a deadlock? let group = DispatchGroup() let queue = DispatchQueue(label: "com.num.loop", attributes: .concurrent) let semaphore = DispatchSemaphore(value: 4) for i in 1...1000 { semaphore.wait() group.enter() queue.async(group: group, execute: { doWork(i) group.leave() semaphore.signal() }) } group.notify(queue: DispatchQueue.main) { // go on... } 回答1: A couple of observations: You never

问题 For example, there is a 1000 times loop. What's the max value to make it fast, effective, and not lead to a deadlock? let group = DispatchGroup() let queue = DispatchQueue(label: "com.num.loop", attributes: .concurrent) let semaphore = DispatchSemaphore(value: 4) for i in 1...1000 { semaphore.wait() group.enter() queue.async(group: group, execute: { doWork(i) group.leave() semaphore.signal() }) } group.notify(queue: DispatchQueue.main) { // go on... } 回答1: A couple of observations: You never

问题 I am a rookie in Swift, and there is such misunderstandings what is the difference how to create dispatch queue sample 1 let backgroundQueue = DispatchQueue(label: "com.app.queue", qos: .background, target: nil) backgroundQueue.async { print("Dispatched to background queue") } sample 2 let backgroundQueue = DispatchQueue.global() backgroundQueue.async { print("Dispatched to background queue") } as far as I understand this two approaches do the same or for example this approach DispatchQueue

问题 DispatchQueue.global(qos: .background).async { //This will run on the background queue self.writeValue(tag: GlobalData.WRITE_DATA, data: getDataForWrite(1) ) self.writeValue(tag: GlobalData.WRITE_DATA, data: getDataForWrite(2) ) self.writeValue(tag: GlobalData.WRITE_DATA, data: getDataForWrite(3) ) self.writeValue(tag: GlobalData.WRITE_DATA, data: getDataForWrite(4) ) self.writeValue(tag: GlobalData.WRITE_DATA, data: getDataForWrite(5) ) // ..... DispatchQueue.main.async { //This will run on

问题 DispatchQueue.global(qos: .background).async { //This will run on the background queue self.writeValue(tag: GlobalData.WRITE_DATA, data: getDataForWrite(1) ) self.writeValue(tag: GlobalData.WRITE_DATA, data: getDataForWrite(2) ) self.writeValue(tag: GlobalData.WRITE_DATA, data: getDataForWrite(3) ) self.writeValue(tag: GlobalData.WRITE_DATA, data: getDataForWrite(4) ) self.writeValue(tag: GlobalData.WRITE_DATA, data: getDataForWrite(5) ) // ..... DispatchQueue.main.async { //This will run on

问题 Am trying on coding game MineSweeper, the following code is to set the numbers around landmines. For a test, I choose the minimum level 9 x 9 with 10 landmines. For a faster performance, I tried to use more threads when setting numbers, but one day I found that it doesn't always give the correct number arrangements, I made a loop to create it 1000 times and found that 20 ~ 40 out of 1000 are wrong. Here are several wrong results, "*" represents landmine, "0" means no landmine around wrong

来源： https://stackoverflow.com/questions/50791315/can-i-call-on-semaphore-wait-main-thread

来源： https://stackoverflow.com/questions/61452583/too-many-files-open-while-monitoring-file-changes

来源： https://stackoverflow.com/questions/57826691/how-to-limit-gcd-queue-buffer-size