reference, declarationdefinition
definition → references, declarations, derived classes, virtual overrides
reference to multiple definitions → definitions
unreferenced
    1
    2
    3
    4
    5
    6
    7
    8
    9
   10
   11
   12
   13
   14
   15
   16
   17
   18
   19
   20
   21
   22
   23
   24
   25
   26
   27
   28
   29
   30
   31
   32
   33
   34
   35
   36
   37
   38
   39
   40
   41
   42
   43
   44
   45
   46
   47
   48
   49
   50
   51
   52
   53
   54
   55
   56
   57
   58
   59
   60
   61
   62
   63
   64
   65
   66
   67
   68
   69
   70
   71
   72
   73
   74
   75
   76
   77
   78
   79
   80
   81
   82
   83
   84
   85
   86
   87
   88
   89
   90
   91
   92
   93
   94
   95
   96
   97
   98
   99
  100
  101
  102
  103
  104
  105
  106
  107
  108
  109
  110
  111
  112
  113
  114
  115
  116
  117
  118
  119
  120
  121
  122
  123
  124
  125
  126
  127
  128
  129
  130
  131
  132
  133
  134
  135
  136
  137
  138
  139
  140
  141
  142
  143
  144
  145
  146
  147
  148
  149
  150
  151
  152
#include <cstdint>
#include <thread>
#include <vector>
#include <queue>
#include <functional>
#include <future>
#include <iostream>
#include <cassert>

class TaskPoolImpl
{
public:
    TaskPoolImpl(uint32_t num_threads) :
        m_stop(false)
    {
        for (uint32_t i = 0; i < num_threads; ++i)
            m_threads.emplace_back(Worker, this);
    }

    ~TaskPoolImpl()
    {
        Stop();
    }

    template<typename F, typename... Args>
    std::future<typename std::result_of<F(Args...)>::type>
    AddTask(F&& f, Args&&... args)
    {
        auto task = std::make_shared<std::packaged_task<typename std::result_of<F(Args...)>::type()>>(
            std::bind(std::forward<F>(f), std::forward<Args>(args)...));

        std::unique_lock<std::mutex> lock(m_tasks_mutex);
        assert(!m_stop && "Can't add task to TaskPool after it is stopped");
        m_tasks.emplace([task](){ (*task)(); });
        lock.unlock();
        m_tasks_cv.notify_one();

        return task->get_future();
    }

    void
    Stop()
    {
        std::unique_lock<std::mutex> lock(m_tasks_mutex);
        m_stop = true;
        m_tasks_mutex.unlock();
        m_tasks_cv.notify_all();
        for (auto& t : m_threads)
            t.join();
    }

private:
    static void
    Worker(TaskPoolImpl* pool)
    {
        while (true)
        {
            std::unique_lock<std::mutex> lock(pool->m_tasks_mutex);
            if (pool->m_tasks.empty())
                pool->m_tasks_cv.wait(lock, [pool](){ return !pool->m_tasks.empty() || pool->m_stop; });
            if (pool->m_tasks.empty())
                break;

            std::function<void()> f = pool->m_tasks.front();
            pool->m_tasks.pop();
            lock.unlock();

            f();
        }
    }

    std::queue<std::function<void()>> m_tasks;
    std::mutex                        m_tasks_mutex;
    std::condition_variable           m_tasks_cv;
    bool                              m_stop;
    std::vector<std::thread>          m_threads;
};

class TaskPool
{
public:
    // Add a new task to the thread pool and return a std::future belongs for the newly created task.
    // The caller of this function have to wait on the future for this task to complete.
    template<typename F, typename... Args>
    static std::future<typename std::result_of<F(Args...)>::type>
    AddTask(F&& f, Args&&... args)
    {
        return GetImplementation().AddTask(std::forward<F>(f), std::forward<Args>(args)...);
    }

    // Run all of the specified tasks on the thread pool and wait until all of them are finished
    // before returning
    template<typename... T>
    static void
    RunTasks(T&&... t)
    {
        RunTaskImpl<T...>::Run(std::forward<T>(t)...);
    }

private:
    static TaskPoolImpl&
    GetImplementation()
    {
        static TaskPoolImpl g_task_pool_impl(std::thread::hardware_concurrency());
        return g_task_pool_impl;
    }

    template<typename... T>
    struct RunTaskImpl;
};

template<typename H, typename... T>
struct TaskPool::RunTaskImpl<H, T...>
{
    static void
    Run(H&& h, T&&... t)
    {
        auto f = AddTask(std::forward<H>(h));
        RunTaskImpl<T...>::Run(std::forward<T>(t)...);
        f.wait();
    }
};

template<>
struct TaskPool::RunTaskImpl<>
{
    static void
    Run() {}
};

int main()
{
    std::vector<std::future<uint32_t>> tasks;
    for (int i = 0; i < 100000; ++i)
    {
        tasks.emplace_back(TaskPool::AddTask([](int i){
            uint32_t s = 0;
            for (int j = 0; j <= i; ++j)
                s += j;
            return s;
        },
        i));
    }

    for (auto& it : tasks)  // Set breakpoint here
        it.wait();

    TaskPool::RunTasks(
        []() { return 1; },
        []() { return "aaaa"; }
    );
}