How to Efficiently Implement a Thread Pool in C 11 to Avoid Repeated Thread Creation and Deletion Overhead?

Thread Pooling in C 11

Issue: Creating and deleting threads repeatedly is expensive. How can we establish a persistent thread pool to handle tasks without incurring this overhead?

Solution:

Implementing the ThreadPool Class

To create an efficient thread pool, we first define the ThreadPool class:

class ThreadPool {
public:
    void Start();
    void QueueJob(const std::function<void()>& job);
    void Stop();
    bool busy();

private:
    void ThreadLoop();
    bool should_terminate = false;
    std::mutex queue_mutex;
    std::condition_variable mutex_condition;
    std::vector<std::thread> threads;
    std::queue<std::function<void()>> jobs;
};

1. ThreadPool::Start:

Creates a fixed number of threads based on system capabilities:

void ThreadPool::Start() {
    const uint32_t num_threads = std::thread::hardware_concurrency();
    for (uint32_t ii = 0; ii < num_threads; ++ii) {
        threads.emplace_back(std::thread(&ThreadPool::ThreadLoop,this))
    }
}

2. ThreadPool::ThreadLoop:

Endless loop that waits for new tasks:

void ThreadPool::ThreadLoop() {
    while (true) {
        std::function<void()> job;
        {
            std::unique_lock<std::mutex> lock(queue_mutex);
            mutex_condition.wait(lock, [this] {
                return !jobs.empty() || should_terminate;
            });
            if (should_terminate) {
                return;
            }
            job = jobs.front();
            jobs.pop();
        }
        job();
    }
}

3. ThreadPool::QueueJob:

Adds a new task to the pool:

void ThreadPool::QueueJob(const std::function<void()>& job) {
    {
        std::unique_lock<std::mutex> lock(queue_mutex);
        jobs.push(job);
    }
    mutex_condition.notify_one();
}

4. ThreadPool::busy:

Checks if the pool has active jobs:

bool ThreadPool::busy() {
    bool poolbusy;
    {
        std::unique_lock<std::mutex> lock(queue_mutex);
        poolbusy = !jobs.empty();
    }
    return poolbusy;
}

5. ThreadPool::Stop:

Gracefully stops the pool:

void ThreadPool::Stop() {
    {
        std::unique_lock<std::mutex> lock(queue_mutex);
        should_terminate = true;
    }
    mutex_condition.notify_all();
    for (std::thread& active_thread : threads) {
        active_thread.join();
    }
    threads.clear();
}

Usage:

thread_pool->QueueJob([] { /* ... */ });

This implementation provides a dynamic thread pool where threads persistently run and wait for tasks to be added.

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