The use and selection of C++ concurrent programming modes

C++ has a variety of concurrent programming modes, including threads, mutexes, condition variables, atomic operations and asynchronous processing. Choosing the appropriate mode depends on application requirements such as synchronous data access, conditional waits, atomic operations, and improved responsiveness. By understanding pattern purpose and selection criteria, developers can build efficient and maintainable concurrent applications.

The use and selection of C++ concurrent programming modes

Concurrent programming is crucial in modern software development, and C++ provides a wealth of Concurrent programming model to meet the needs of different scenarios. This article explores the use and selection of these modes.

Concurrent programming mode

• Threads: Independently executed code blocks, allowing multiple tasks to be executed simultaneously.
• Mutex: Ensure that a critical section is accessed by at most one thread at any time.
• Condition variable: A thread can wait on it until a specific condition is true.
• Atomic operations: Ensure the atomicity of execution, that is, either all operations succeed or all fail.
• Asynchronous processing: Allows tasks to be executed without blocking the calling thread.

Mode Selection

Choosing the correct concurrency mode depends on the needs of your specific application:

• Data Access Synchronization: Mutexes can be used to synchronize access to shared data to ensure data integrity.
• Conditional waiting: Condition variables are used for threads to wait before specific conditions are met, such as waiting for resources to be available.
• Atomic operations: Atomic operations ensure that reading and writing shared data such as counters or flags are atomic.
• Asynchronous processing: Asynchronous tasks can be executed asynchronously, such as network I/O or file reading and writing, to improve application response speed.

Practical case

Mutex protects shared variables

// 定义互斥体
std::mutex m;

// 使用锁保护临界区
std::lock_guard<std::mutex> lock(m);
// 在临界区中对共享变量进行操作
...

Conditional variables wait for resources to be available

// 定义条件变量
std::condition_variable cv;

// 线程等待条件成立
std::unique_lock<std::mutex> lock(m);
cv.wait(lock, []{ return resource_available; });

// 条件成立后继续执行任务
...

Atomic operation update counter

// 原子计数器
std::atomic<int> counter;

// 原子更新计数器
counter.fetch_add(1);

Asynchronous processing of file reading and writing

// 异步文件读写
std::async(std::launch::async, [](const std::string& filename) {
  // 在单独的线程中读取文件的内容
  std::ifstream file(filename);
  std::string contents;
  std::getline(file, contents);
  ...
}, "file.txt");

Conclusion

C++ provides various concurrent programming modes to meet different application needs. By understanding the purpose and selection criteria of different patterns, developers can efficiently build concurrent applications, improving performance and maintainability.

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