What are the strategies and principles of thread scheduling in C++ multi-threaded programming?

C++ Thread scheduling strategies in multi-threaded programming include time slice rotation and priority scheduling. Time slice rotation allocates CPU time equally, while priority scheduling allocates CPU time based on thread priority. The principles of thread scheduling include: ready queue, scheduling algorithm, context switching, execution and time slice exhaustion.

Strategies and principles of thread scheduling in C++ multi-threaded programming

Introduction
Multi-threading Programming is an important technology that allows us to create and manage multiple tasks or threads that execute concurrently. Thread scheduling is a key part of multi-threaded programming because it determines how CPU resources are allocated to different threads. This article will explore the strategies and principles of thread scheduling in C++.

Thread scheduling strategy
In C++, there are two common thread scheduling strategies:

• Time slice rotation (Round- robin): This is the most basic strategy, allocating CPU time equally to all runnable threads. Each thread is assigned a time slice during which it can execute. When the time slice runs out, the operating system switches the context to another runnable thread.
• Priority Scheduling: This policy allocates CPU time based on the priority of each thread. Threads with higher priority get more CPU time than threads with lower priority. This allows important tasks to be prioritized over less important tasks.

The principle of thread scheduling
The role of the thread scheduler is to determine which thread gets the CPU at a given point in time. The following steps describe the basic principles of thread scheduling in C++:

1. Ready Queue: All runnable threads are kept in the ready queue.
2. Scheduling algorithm: Based on the selected scheduling policy, the scheduling algorithm selects the next thread to execute.
3. Context switch: The operating system performs a context switch to transfer CPU control from the current thread to a selected thread.
4. Execution: The selected thread begins executing its code.
5. Time slice runs out: If the scheduling policy is time slice rotation and the time slice runs out, the execution context switches to another runnable thread.
6. Thread termination: Each thread will perform its task and terminate.

Practical Case
To demonstrate thread scheduling in C++, let us create a simple program that creates two threads, one with higher priority and the other With lower priority:

#include <iostream>
#include <thread>

using namespace std;

// 线程函数
void task(int priority) {
    // 执行线程任务
    for (int i = 0; i < 10; i++) {
        cout << "Thread " << priority << ": Iteration " << i << endl;
    }
}

int main() {
    // 创建两个线程
    thread thread1(task, 1);
    thread thread2(task, 5);

    // 设置线程优先级
    thread1.join();
    thread2.join();

    return 0;
}

In this example, thread1 has higher priority (1), while thread2 has lower priority (1 5). We use the join() function to wait for the thread to complete execution. Due to priority scheduling, thread1 will get more time to perform its tasks than thread2.

Conclusion
Thread scheduling is an important part of C++ multi-threaded programming. It decides how to allocate CPU time to different threads by using different strategies and principles. By understanding these strategies and principles, you can optimize the performance and reliability of multi-threaded applications.

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