concurrency

问题 Reading the Java 8 documentation about the java.util.concurrent.locks.Condition interface, the following example is given: class BoundedBuffer { final Lock lock = new ReentrantLock(); final Condition notFull = lock.newCondition(); final Condition notEmpty = lock.newCondition(); final Object[] items = new Object[100]; int putptr, takeptr, count; public void put(Object x) throws InterruptedException { lock.lock(); try { while (count == items.length) notFull.await(); items[putptr] = x; if (+

问题 I'm trying to make client program that communicates with a server using a TcpStream wrapped by a openssl::ssl::SslStream (from crates.io). It should wait for read , and process data sent from the server if it was received without delay . At the same time, it should be able to send messages to the server regardless of reading. I tried some methods such as Passing single stream to both read and write threads. Both read and write methods require a mutable reference, so I couldn't pass a single

问题 I'm trying to find out what is the difference between the SemaphoreSlim use of Wait and WaitAsync, used in this kind of context: private SemaphoreSlim semaphore = new SemaphoreSlim(1); public async Task<string> Get() { // What's the difference between using Wait and WaitAsync here? this.semaphore.Wait(); // await this.semaphore.WaitAsync() string result; try { result = this.GetStringAsync(); } finally { this.semaphore.Release(); } return result; } 回答1: If you have async method - you want to

问题 Is there any performance difference between AtomicInteger and Integer ? 回答1: The choice of these two types should not depend on the performance. The main choice for AtomicInteger is if you want to achieve thread safety with the operations on the integer. However the performace difference might strongly depend on the choosen operating system, as the detailed implementation of atomic operations depend on the operating system. 回答2: AtomicInteger allows some (not all!) operations that would

问题 Is there any performance difference between AtomicInteger and Integer ? 回答1: The choice of these two types should not depend on the performance. The main choice for AtomicInteger is if you want to achieve thread safety with the operations on the integer. However the performace difference might strongly depend on the choosen operating system, as the detailed implementation of atomic operations depend on the operating system. 回答2: AtomicInteger allows some (not all!) operations that would

问题 I am trying to create 86 instances of task.py to run simultaneously. import sys import subprocess for file in range(86): subprocess.call([sys.executable,'task.py',str(file)+'in.csv',str(filen)+'out.csv']) 回答1: subprocess.call waits for command to complete. Use subprocess.Popen instead: import sys import subprocess procs = [] for i in range(86): proc = subprocess.Popen([sys.executable, 'task.py', '{}in.csv'.format(i), '{}out.csv'.format(i)]) procs.append(proc) for proc in procs: proc.wait() 来源

问题 I am trying to create 86 instances of task.py to run simultaneously. import sys import subprocess for file in range(86): subprocess.call([sys.executable,'task.py',str(file)+'in.csv',str(filen)+'out.csv']) 回答1: subprocess.call waits for command to complete. Use subprocess.Popen instead: import sys import subprocess procs = [] for i in range(86): proc = subprocess.Popen([sys.executable, 'task.py', '{}in.csv'.format(i), '{}out.csv'.format(i)]) procs.append(proc) for proc in procs: proc.wait() 来源

问题 I have a mysql table: CREATE TABLE `coupons` ( `id` INT NOT NULL AUTO_INCREMENT, `code` VARCHAR(255), `user_id` INT, UNIQUE KEY `code_idx` (`code`) ) ENGINE=InnoDB; The table consists of thousands/millions of codes and initially user_id is NULL for everyone. Now I have a web application which assigns a unique code to thousands of users visiting the application concurrently. I am not sure what is the correct way to handle this considering very high traffic. The query I have written is: UPDATE

问题 I have a mysql table: CREATE TABLE `coupons` ( `id` INT NOT NULL AUTO_INCREMENT, `code` VARCHAR(255), `user_id` INT, UNIQUE KEY `code_idx` (`code`) ) ENGINE=InnoDB; The table consists of thousands/millions of codes and initially user_id is NULL for everyone. Now I have a web application which assigns a unique code to thousands of users visiting the application concurrently. I am not sure what is the correct way to handle this considering very high traffic. The query I have written is: UPDATE

问题 As per this solution (https://stackoverflow.com/a/18923091/529618) I am using a ConcurrentDictionary<T,byte> as a workaround for the lack of ConcurrentHashSet<T> . However, I'm struggling to see how I can get the original T Key back out of the dictionary in O(1) time. var cache = new ConcurrentDictionary<MyEquatableClass, byte>()); //... if(!cache.TryAdd(classInstance, Byte.MinValue)) return /* Existing cache entry */; return classInstance; Is there any way to get the KeyValuePair<K,V> (or