C++11下的线程池以及灵活的functional + bind + lamda

利用boost的thread实现一个线程类，维护一个任务队列，以便可以承载非常灵活的调用。这个线程类可以方便的为后面的线程池打好基础。线程池还是动态均衡，没有什么别的。由于minGW 4.7 对 C++11 thread 不支持，所以采用 boost 代替，linux 下是支持的，只是名字空间不同而已，套路都一样。先上代码： [cpp] view plaincopy #include #include <boost/thread/thread.hpp> #include <boost/thread/mutex.hpp> #include #include #include #include #include #include #include #include //This class defines a class contains a thread, a task queue class cpp11_thread { public: cpp11_thread() :m_b_is_finish(false) ,m_pthread(nullptr) { } ~cpp11_thread() { if (m_pthread != nullptr) delete m_pthread; m_list_tasks.clear(); } public: //wait until this thread is terminated; void join() { terminate(); if (m_pthread!=nullptr) m_pthread->join(); } //wait until this thread has no tasks pending. void wait_for_idle() { while(load()) boost::this_thread::sleep(boost::posix_time::milliseconds(200)); } //set the mask to termminiate void terminate() {m_b_is_finish = true; m_cond_incoming_task.notify_one();} //return the current load of this thread size_t load() { size_t sz = 0; m_list_tasks_mutex.lock(); sz = m_list_tasks.size(); m_list_tasks_mutex.unlock(); return sz; } //Append a task to do size_t append(std::function< void (void) > func) { if (m_pthread==nullptr) m_pthread = new boost::thread(std::bind(&cpp11_thread::run,this)); size_t sz = 0; m_list_tasks_mutex.lock(); m_list_tasks.push_back(func); sz = m_list_tasks.size(); //if there were no tasks before, we should notidy the thread to do next job. if (sz==1) m_cond_incoming_task.notify_one(); m_list_tasks_mutex.unlock(); return sz; } protected: std::atomic< bool> m_b_is_finish; //atomic bool var to mark the thread the next loop will be terminated. std::list<std::function< void (void)> > m_list_tasks; //The Task List contains function objects boost::mutex m_list_tasks_mutex; //The mutex with which we protect task list boost::thread *m_pthread; //inside the thread, a task queue will be maintained. boost::mutex m_cond_mutex; //condition mutex used by m_cond_locker boost::condition_variable m_cond_incoming_task; //condition var with which we notify the thread for incoming tasks protected: void run() { // loop wait while (!m_b_is_finish) { std::function< void (void)> curr_task ; bool bHasTasks = false; m_list_tasks_mutex.lock(); if (m_list_tasks.empty()==false) { bHasTasks = true; curr_task = *m_list_tasks.begin(); } m_list_tasks_mutex.unlock(); //doing task if (bHasTasks) { curr_task(); m_list_tasks_mutex.lock(); m_list_tasks.pop_front(); m_list_tasks_mutex.unlock(); } if (!load()) { boost::unique_lock< boost::mutex> m_cond_locker(m_cond_mutex); boost::system_time const timeout=boost::get_system_time()+ boost::posix_time::milliseconds(5000); if (m_cond_locker.mutex()) m_cond_incoming_task.timed_wait(m_cond_locker,timeout);//m_cond_incoming_task.wait(m_cond_locker); } } } }; //the thread pool class class cpp11_thread_pool { public: cpp11_thread_pool(int nThreads) :m_n_threads(nThreads) { assert(nThreads>0 && nThreads<=512); for (int i = 0; i< nThreads ;i++) m_vec_threads.push_back(std::shared_ptr<cpp11_thread>(new cpp11_thread())); } ~cpp11_thread_pool() { } public: //total threads; size_t count(){return m_vec_threads.size();} //wait until all threads is terminated; void join() { for_each(m_vec_threads.begin(),m_vec_threads.end(),[this](std::shared_ptr<cpp11_thread> & item) { item->terminate(); item->join(); }); } //wait until this thread has no tasks pending. void wait_for_idle() { int n_tasks = 0; do { if (n_tasks) boost::this_thread::sleep(boost::posix_time::milliseconds(200)); n_tasks = 0; for_each(m_vec_threads.begin(),m_vec_threads.end(),[this,&n_tasks](std::shared_ptr<cpp11_thread> & item) { n_tasks += item->load(); }); }while (n_tasks); } //set the mask to termminiate void terminate() { for_each(m_vec_threads.begin(),m_vec_threads.end(),[this](std::shared_ptr<cpp11_thread> & item) { item->terminate(); }); } //return the current load of this thread size_t load(int n) { return (n>=m_vec_threads.size())?0:m_vec_threads[n]->load(); } //Append a task to do void append(std::function< void (void) > func) { int nIdx = -1; unsigned int nMinLoad = -1; for (unsigned int i=0;i<m_n_threads;i++) { if (nMinLoad> m_vec_threads[i]->load()) { nMinLoad = m_vec_threads[i]->load(); nIdx = i; } } assert(nIdx>=0 && nIdx<m_n_threads); m_vec_threads[nIdx]->append(func); } protected: //NO. threads int m_n_threads; //vector contains all the threads std::vector<std::shared_ptr<cpp11_thread> > m_vec_threads; }; //a function which will be executed in sub thread. void hello() { //sleep for a while boost::this_thread::sleep(boost::posix_time::milliseconds(rand()%900+100)); std::cout << "Hello world, I'm a function runing in a thread!" << std::endl; } //a class has a method, which will be called in a thread different from the main thread. class A { private: int m_n; public: A(int n) :m_n(n) {} ~A(){} public: void foo (int k) { //sleep for a while boost::this_thread::sleep(boost::posix_time::milliseconds(rand()%900+100)); std::cout <<"n*k = "<<k*m_n<<std::endl; m_n++; } }; //let's test the thread. int main() { cpp11_thread_pool thread(2); srand((unsigned int)time(0)); A a(1),b(2),c(3); int nsleep = rand()%900+100; //append a simple function task thread.append(&hello); //append lamda thread.append ( [&nsleep]() { boost::this_thread::sleep(boost::posix_time::milliseconds(nsleep)); std::cout<<"I'm a lamda runing in a thread"<<std::endl; } ); //append object method with copy-constructor(value-assignment) thread.append(std::bind(&A::foo,a,10)); thread.append(std::bind(&A::foo,b,11)); thread.append(std::bind(&A::foo,c,12)); thread.append(std::bind(&A::foo,a,100)); //append object method with address assignment, will cause the objects' member increase. thread.append(std::bind(&A::foo,&a,10)); thread.append(std::bind(&A::foo,&b,11)); thread.append(std::bind(&A::foo,&c,12)); thread.append(std::bind(&A::foo,&a,100)); //wait for all tasks done. thread.wait_for_idle(); //kill thread.terminate(); //wait for killed thread.join(); //test function std::function < void (void) > func1 = &hello; std::function < void (void) > func2 = &hello; if (func1.target()!=func2.target()) return 0; else return 1; } 程序输出: [plain] view plaincopy Hello world, I'm a function runing in a thread! I'm a lamda runing in a thread n*k = 22 n*k = 10 n*k = 36 n*k = 100 n*k = 22 n*k = 10 n*k = 36 n*k = 200 Process returned 0 (0x0) execution time : 2.891 s Press any key to continue. 下面来看看代码。首先是线程类。 第13-99行是线程类。该类实现了一个带任务队列的线程模型。关键部件是62行的std::list<std::function< void (void)> > m_list_tasks; ，这个fifo 用来承载顺序在子线程运行的任务。任务通过48行的append方法进行追加，64行m_list_tasks_mutex是一个mutex，来保护队列的进出。65行定义的线程对象boost::thread在构造函数中初始化并运行，绑定了本对象的run方法。线程得以运行的关键是run方法，在71-99行定义。该方法首先判断是否有pending的任务，有的话就弹出来执行。如果任务做完了，则使用67行定义的条件变量m_cond_incoming_task 进行wait, 直到新的任务到来，在第56行触发条件，激活队列。 线程类还提供了一些方法，比如load()返回队列的大小，以及terminate终止线程。而后，转到线程池。线程池采用最简单的策略，即直接分配给最空闲的线程。 有了上述封装，main函数就简单多了。可以append几乎所有的东西到线程池，这是以前简单的利用 virtual function 很难做到的。