multithreading

问题 There is a wonderful article about a lightweight notification system built in Swift, by Mike Ash: (https://www.mikeash.com/pyblog/friday-qa-2015-01-23-lets-build-swift-notifications.html). The basic idea is you create objects that you can "listen" to i.e. invoke a callback on when there is some state change. To make it thread-safe, each object created holds its own dispatch_queue. The dispatch_queue is simply used to gate critical sections: dispatch_sync(self.myQueue) { // modify critical

问题 There is a wonderful article about a lightweight notification system built in Swift, by Mike Ash: (https://www.mikeash.com/pyblog/friday-qa-2015-01-23-lets-build-swift-notifications.html). The basic idea is you create objects that you can "listen" to i.e. invoke a callback on when there is some state change. To make it thread-safe, each object created holds its own dispatch_queue. The dispatch_queue is simply used to gate critical sections: dispatch_sync(self.myQueue) { // modify critical

问题 Here's what's been puzzling me: When you schedule a sequence of tasks that are homogenous in terms of content but heterogenous in terms of processing time (not known ex ante) using foreach, how exactly does foreach process these embarrassingly parallel tasks sequentially? For instance, I registered 4 threads registerDoMC(cores=4) and I have 10 tasks and the 4th and the 5th each turned out to be longer than all others combine. Then the first batch is obviously the 1st, 2nd, 3rd and 4th. When

问题 If you declare a member variable as volatile in Java, does this mean that all the object's data is stored in volatile memory, or that the reference to the object is stored in volatile memory? For example if I have the following class: class C{ int i = 0; char c = 'c'; } If I declare an instance of it as follows: private volatile C obj; does that store the reference to obj in volatile memory, or obj 's data ( obj.i and obj.c ) in volatile memory? Does it make obj.c and obj.i thread safe or not

问题 I was just very confused by some code that I wrote. I was surprised to discover that: with concurrent.futures.ThreadPoolExecutor(max_workers=4) as executor: results = list(executor.map(f, iterable)) and with concurrent.futures.ThreadPoolExecutor(max_workers=4) as executor: results = list(map(lambda x: executor.submit(f, x), iterable)) produce different results. The first one produces a list of whatever type f returns, the second produces a list of concurrent.futures.Future objects that then

问题 I am trying to make a program in C++ to process a lot of packets in the fastest way possible. All the packets come from the standard should be read as fast as possible, sent to one thread from a pool to do the processing and then handled to an output thread that will write the packet to the standard output. When you are using the standard input and output in C++, it's recommended that before any input or output you call to the std::ios_base::sync_with_stdio(false) function. In some

问题 I've read that wait-free causes all threads to finish independently and lock-free ensures the program as a whole completes. I couldn't quite get it. Can anyone give an example (java) illustrating this. EDIT: Does lock-free mean a program without deadlock? 回答1: If a program is lock-free, it basically means that at least one of its threads is guaranteed to make progress over an arbitrary period of time. If a program deadlocks, none of its threads (and therefore the program as a whole) cannot

问题 I know that a java thread cannot be restarted. So when I submit more than one tasks to newSingleThreadExecutor, then how does it perform all tasks using single thread? My understanding is that newSingleThreadExecutor will use maximum one thread at a time to process any submitted tasks. I guess same for newFixedThreadPool. If a Thread cannot be restarted then for performing n tasks, n threads should be spawned. I think newSingleThreadExecutor, newFixedThreadPool will make sure that not many

问题 I'm having some trouble using Parallel.ForEach. I need to simulate a couple of hardware components, that wait for an incoming connection, and reply to it. My current code is as follows: Task.Factory.StartNew(() => components, (component) => { var listener = new TcpListener(component.Ip, component.Port); while(true) { using(var socket = listener.AcceptSocket()) { //Read out socket and send a reply socket.Close(); } } }); The problem I'm having is: Not every component will get his own thread

问题 I'm having some trouble using Parallel.ForEach. I need to simulate a couple of hardware components, that wait for an incoming connection, and reply to it. My current code is as follows: Task.Factory.StartNew(() => components, (component) => { var listener = new TcpListener(component.Ip, component.Port); while(true) { using(var socket = listener.AcceptSocket()) { //Read out socket and send a reply socket.Close(); } } }); The problem I'm having is: Not every component will get his own thread