How to create and use multi-threading in C++ library?

Answer: In C, you can use the std::thread function library to create and use multiple threads to implement concurrent programming. Detailed description: Use std::thread to create a new thread and execute the specified code in the child thread. Use synchronization mechanisms such as mutexes and condition variables to ensure thread-safe access to shared data. A practical case shows parallel array sorting, in which multiple threads sort a subset of the array at the same time, improving efficiency.

C Function Library: Creating and Using Multithreads

Introduction

Multiple Threads are a concurrent programming technology that allows multiple tasks to be performed at the same time. In C, multithreading can be easily created and used by using libraries such as std::thread.

Create thread

To create a thread, you can use std::thread Class:

#include <thread>

using namespace std;

void thread_function() {
  // 要在子线程中执行的代码
}

int main() {
  thread th(thread_function); // 创建新线程
  th.join(); // 等待子线程完成
  return 0;
}

Synchronize thread

In order to ensure that multiple threads can safely access shared data, synchronization mechanisms can be used, such as mutex locks and condition variables:

#include <mutex>
#include <condition_variable>

using namespace std;

mutex mtx; // 互斥锁
condition_variable cv; // 条件变量

int shared_data = 0; // 共享数据

void thread_function() {
  while (true) {
    mtx.lock();
    // 对共享数据进行操作
    mtx.unlock();

    // 通知等待条件变量的线程
    cv.notify_all();
  }
}

int main() {
  thread th(thread_function); // 创建线程

  // 等待条件变量被通知
  unique_lock<mutex> lock(mtx);
  cv.wait(lock);

  // 对共享数据进行操作

  th.join(); // 等待子线程完成
  return 0;
}

Practical case: Parallel array sorting

We can use multi-threading to sort the array in parallel:

#include <thread>
#include <vector>
#include <algorithm>

using namespace std;

void merge(vector<int>& arr, int l, int m, int r) {
  // 对两个子数组进行归并排序
}

void merge_sort(vector<int>& arr, int l, int r) {
  if (l < r) {
    int m = l + (r - l) / 2;
    thread th1(merge_sort, ref(arr), l, m);
    thread th2(merge_sort, ref(arr), m + 1, r);
    th1.join();
    th2.join();
    merge(arr, l, m, r);
  }
}

int main() {
  vector<int> arr = {3, 1, 4, 2, 5};
  merge_sort(arr, 0, arr.size() - 1);
  return 0;
}

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