Application of thread pool in C++ multi-thread programming

C++ The benefits of using thread pools in multi-threaded programming include: 1) reducing the number of thread creations; 2) load balancing; 3) avoiding resource contention. For example, you can increase the conversion speed of a file conversion application by using a thread pool to distribute image conversion tasks to a thread pool.

Application of thread pool in C++ multi-threaded programming

In modern C++ applications, multi-threaded programming is a key technology to improve performance and execute tasks in parallel . A thread pool is a mechanism for managing and reusing threads that can provide significant efficiency advantages in multi-threaded programming.

Benefits of thread pool

The main benefits of using thread pool include:

• Reduce the number of thread creations: Creating and destroying threads is one Time consuming operation. Thread pools avoid the overhead of frequently creating and destroying threads, thereby improving efficiency.
• Load balancing: The thread pool evenly distributes tasks to available threads, ensuring that all threads are fully utilized.
• Avoid resource contention: By limiting the number of threads running simultaneously, thread pools prevent contention for resources, such as memory and processor time.

How to use thread pools

There are many thread pool libraries available in C++, such as std::thread_pool and Boost.Thread. The following is an example of creating and using a thread pool using std::thread_pool:

#include <iostream>
#include <future>
#include <thread>

// 使用非标准库的线程池版本
using namespace std::experimental;

int main() {
  // 创建一个拥有 4 个线程的线程池
  thread_pool pool(4);

  // 提交任务到线程池
  std::vector<std::future<int>> futures;
  for (int i = 0; i < 10; i++) {
    futures.push_back(pool.submit([i] {
      return i * i;
    }));
  }

  // 等待所有任务完成并收集结果
  int result = 0;
  for (auto& future : futures) {
    result += future.get();
  }

  std::cout << "最终结果：" << result << std::endl;

  return 0;
}

Practical Case

Consider a file conversion application that needs to process a large number of images. Using the thread pool, image conversion tasks can be assigned to the thread pool, thereby increasing the conversion speed.

#include <iostream>
#include <thread>
#include <future>
#include <vector>
#include <algorithm>

using namespace std;

// 定义图像转换函数
void convertImage(const string& inputFile, const string& outputFile) {
  // 在此处添加图像转换逻辑
  std::cout << "Converting image: " << inputFile << std::endl;
}

int main() {
  // 创建线程池（使用非标准库版本）
  thread_pool pool(thread::hardware_concurrency());

  // 获取需要转换的图像列表
  vector<string> imageFiles = {"image1.jpg", "image2.png", "image3.bmp"};

  // 提交图像转换任务到线程池
  vector<future<void>> futures;
  for (const string& imageFile : imageFiles) {
    string outputFile = imageFile + ".converted";
    futures.push_back(pool.submit(convertImage, imageFile, outputFile));
  }

  // 等待所有任务完成
  for (auto& future : futures) {
    future.get();
  }

  std::cout << "图像转换已完成！" << std::endl;
  
  return 0;
}

Conclusion

The thread pool is a powerful tool in C++ multi-threaded programming that can improve performance, simplify code, and prevent resource contention. By understanding the basic principles of thread pools and applying them to real-world problems, you can take full advantage of multi-core processors and develop efficient and scalable applications.

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