multithreading

问题 Previously, when I use single-producer mode of disruptor, e.g. new Disruptor<ValueEvent>(ValueEvent.EVENT_FACTORY, 2048, moranContext.getThreadPoolExecutor(), ProducerType.Single, new BlockingWaitStrategy()) the performance is good. Now I am in a situation that multiple threads would write to a single ring buffer. What I found is that ProducerType.Multi make the code several times slower than single producer mode. That poor performance is not going to be accepted by me. So should I use single

问题 Previously, when I use single-producer mode of disruptor, e.g. new Disruptor<ValueEvent>(ValueEvent.EVENT_FACTORY, 2048, moranContext.getThreadPoolExecutor(), ProducerType.Single, new BlockingWaitStrategy()) the performance is good. Now I am in a situation that multiple threads would write to a single ring buffer. What I found is that ProducerType.Multi make the code several times slower than single producer mode. That poor performance is not going to be accepted by me. So should I use single

问题 Currently studying about std::mutex and would love some help. If I've a code that looks like - .... if(returnBoolValue()) { std::lock_guard<std::mutex> lock(mutex_var); .... .... } .... is the std::lock_guard guarding the function returning the value inside if condition? ie. returnBoolValue() And how should I improve it so that function call is inside the guard as well, if possible? std::mutex - http://en.cppreference.com/w/cpp/thread/mutex std::lock_guard - http://en.cppreference.com/w/cpp

问题 I have a java class as below class User { String name; String phone; public String getName() { return name; } public String getPhone() { return phone; } } The way this class is used is, for every thread 1 object of this User class is created. Now since there is one copy of object for every thread, can i call this class as thread safe? Do I need to synchronize these methods? 回答1: The way you presented it, if each thread has its one copy, then it can be called thread-safe, as maximum of

问题 So the syntax for select for update is something like SELECT * //1st query FROM test WHERE id = 4 FOR UPDATE; UPDATE test //2nd query SET parent = 100 WHERE id = 4; I am guessing the locking part is the first line. So when the first set of queries executes, I should not be able to select and modify the row with id = 4 (it is primary key by the way). However, I am still able to select row with id = 4 before I update anything, meaning another thread could probably come in and try to select and

问题 Scenario: I ran into a strange issue while testing out threads in my fragment. I have a fragment written in Kotlin with the following snippet in onResume(): override fun onResume() { super.onResume() val handlerThread = HandlerThread("Stuff") handlerThread.start() val handler = Handler(handlerThread.looper) handler.post { Thread.sleep(2000) tv_name.setText("Something something : " + isMainThread()) } } is MainThread() is a function that checks if the current thread is the main thread like so:

问题 I need a HashMap that is accessible from multiple threads. There are two simple options, using a normal HashMap and synchronizing on it or using a ConcurrentHashMap. Since ConcurrentHashMap does not block on read operations it seems much better suited for my needs (almost exclusively reads, almost never updates). On the other hand, I expect very low concurrency anyway, so there should be no blocking (just the cost of managing the lock). The Map will also be very small (under ten entries), if

问题 I was learning more about threading, and i created a rather simple WPF application with the following code (x64 platform build) public partial class MainWindow : Window { public MainWindow() { InitializeComponent(); for (var i = 0; i <= 20000; i++) { Thread thread = new Thread(Test); thread.IsBackground = true; thread.Start(); } } public void Test() { Thread.Sleep(20000); } } When i run this code, process takes approximately 560MB of RAM while all threads are running / sleeping. Upon it's

问题 basically, I have some code like this: while True: number = int(len(oilrigs)) * 49 number += money time.sleep(1) In front of this I have a start up screen. However because of this while true loop, it blocks it from running the actual start up screen. Instead, it just displays this. So how do you put the code in the background? 回答1: Try multithreading. import threading def background(): while True: number = int(len(oilrigs)) * 49 number += money time.sleep(1) def foreground(): # What you want

问题 I was wondering what's the reasoning of the existance of an empty constructor on Thread class. Since you cant give it a Runnable when it's created, creating a Thread like this: Thread t=new Thread(); Is completely useless. Can you think of a reason why there is not an option of adding a runnable to a thread AFTER CREATION? 回答1: The following works: new Thread() { public void run() { System.out.println("Well you can change the run method."); } } but yes that's not what I'd consider good