How does a thread pool in C++ work?

The idea behind a C++ thread pool is to distribute tasks to a group of pre-existing threads in order to enhance concurrency performance and reduce the overhead of creating and tearing down threads.

The main principle of a thread pool is as follows:

1. Creating a thread pool: When initialized, a thread pool creates a group of threads that typically remain active and wait for tasks to arrive.
2. Task queue: The thread pool maintains a task queue for storing tasks that need to be executed.
3. Task distribution: When a task needs to be executed, the thread pool will add the task to the task queue.
4. Thread execution of tasks: idle threads will retrieve tasks from the task queue and then perform the tasks. After completing the task, the thread will return to a waiting state until a new task arrives.
5. Thread Pool Management: The thread pool will put the threads back into the pool after the tasks are completed, for future use.

By utilizing a thread pool, the overhead of frequently creating and destroying threads can be avoided, enhancing the performance of the program. Additionally, thread pools can also regulate the number of threads and limit the concurrent execution of tasks to prevent excessive resource consumption.