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- /**
- copy from
- https://softwarerecs.stackexchange.com/questions/11009/c11-thread-pool-implementation
- -> https://github.com/progschj/ThreadPool
- */
- #include <vector>
- #include <queue>
- #include <memory>
- #include <thread>
- #include <mutex>
- #include <condition_variable>
- #include <future>
- #include <functional>
- #include <stdexcept>
- #include <iostream>
- namespace ctpl {
- namespace detail {
- template <typename T>
- class Queue {
- public:
- bool push(T const & value) {
- std::unique_lock<std::mutex> lock(this->mutex);
- this->q.push(value);
- return true;
- }
- // deletes the retrieved element, do not use for non integral types
- bool pop(T & v) {
- std::unique_lock<std::mutex> lock(this->mutex);
- if (this->q.empty())
- return false;
- v = this->q.front();
- this->q.pop();
- return true;
- }
- bool empty() {
- std::unique_lock<std::mutex> lock(this->mutex);
- return this->q.empty();
- }
- private:
- std::queue<T> q;
- std::mutex mutex;
- };
- }
- class thread_pool {
- public:
- thread_pool() { this->init(); }
- thread_pool(int nThreads) { this->init(); this->resize(nThreads); }
- // the destructor waits for all the functions in the queue to be finished
- ~thread_pool() {
- this->stop(true);
- }
- // get the number of running threads in the pool
- int size() { return static_cast<int>(this->threads.size()); }
- // number of idle threads
- int n_idle() { return this->nWaiting; }
- std::thread & get_thread(int i) { return *this->threads[i]; }
- // change the number of threads in the pool
- // should be called from one thread, otherwise be careful to not interleave, also with this->stop()
- // nThreads must be >= 0
- void resize(int nThreads) {
- if (!this->isStop && !this->isDone) {
- int oldNThreads = static_cast<int>(this->threads.size());
- if (oldNThreads <= nThreads) { // if the number of threads is increased
- this->threads.resize(nThreads);
- this->flags.resize(nThreads);
- for (int i = oldNThreads; i < nThreads; ++i) {
- this->flags[i] = std::make_shared<std::atomic<bool>>(false);
- this->set_thread(i);
- }
- }
- else { // the number of threads is decreased
- for (int i = oldNThreads - 1; i >= nThreads; --i) {
- *this->flags[i] = true; // this thread will finish
- this->threads[i]->detach();
- }
- {
- // stop the detached threads that were waiting
- std::unique_lock<std::mutex> lock(this->mutex);
- this->cv.notify_all();
- }
- this->threads.resize(nThreads); // safe to delete because the threads are detached
- this->flags.resize(nThreads); // safe to delete because the threads have copies of shared_ptr of the flags, not originals
- }
- }
- }
- // empty the queue
- void clear_queue() {
- std::function<void(int id)> * _f;
- while (this->q.pop(_f))
- delete _f; // empty the queue
- }
- // pops a functional wrapper to the original function
- std::function<void(int)> pop() {
- std::function<void(int id)> * _f = nullptr;
- this->q.pop(_f);
- std::unique_ptr<std::function<void(int id)>> func(_f); // at return, delete the function even if an exception occurred
- std::function<void(int)> f;
- if (_f)
- f = *_f;
- return f;
- }
- // wait for all computing threads to finish and stop all threads
- // may be called asynchronously to not pause the calling thread while waiting
- // if isWait == true, all the functions in the queue are run, otherwise the queue is cleared without running the functions
- void stop(bool isWait = false) {
- if (!isWait) {
- if (this->isStop)
- return;
- this->isStop = true;
- for (int i = 0, n = this->size(); i < n; ++i) {
- *this->flags[i] = true; // command the threads to stop
- }
- this->clear_queue(); // empty the queue
- }
- else {
- if (this->isDone || this->isStop)
- return;
- this->isDone = true; // give the waiting threads a command to finish
- }
- {
- std::unique_lock<std::mutex> lock(this->mutex);
- this->cv.notify_all(); // stop all waiting threads
- }
- for (int i = 0; i < static_cast<int>(this->threads.size()); ++i) { // wait for the computing threads to finish
- if (this->threads[i]->joinable())
- this->threads[i]->join();
- }
- // if there were no threads in the pool but some functors in the queue, the functors are not deleted by the threads
- // therefore delete them here
- this->clear_queue();
- this->threads.clear();
- this->flags.clear();
- }
- template<typename F, typename... Rest>
- auto push(F && f, Rest&&... rest) ->std::future<decltype(f( 0,rest...))> { //note: me edit
- auto pck = std::make_shared<std::packaged_task<decltype(f( 0,rest...))(int)>>( //note: me edit
- std::bind(std::forward<F>(f), std::placeholders::_1, std::forward<Rest>(rest)...)
- );
- auto _f = new std::function<void(int id)>([pck](int id) {
- (*pck)(id);
- });
- this->q.push(_f);
- std::unique_lock<std::mutex> lock(this->mutex);
- this->cv.notify_one();
- return pck->get_future();
- }
- template<typename F, typename... Rest>
- auto add_immediate(F && f, Rest&&... rest) ->std::future<decltype(f( rest...))> { //note: me edit
- // return push([&](int zerooo,auto restLocal...){
- // return f(restLocal...);
- // },rest...);
- // return push([&](int zerooo){
- // return f(rest...);
- // });
- auto pck = std::make_shared<std::packaged_task<decltype(f( rest...))(int)>>( //note: me edit
- std::bind(std::forward<F>(f), std::forward<Rest>(rest)...)
- );
- auto _f = new std::function<void(int id)>([pck](int id) {
- (*pck)(id);
- });
- this->q.push(_f);
- std::unique_lock<std::mutex> lock(this->mutex);
- this->cv.notify_one();
- return pck->get_future();
- }
- template<typename F>
- auto add_immediate(F && f) ->std::future<decltype(f())> { //note: me edit
- return push([&](int zerooo){
- return f();
- });
- }
- // run the user's function that excepts argument int - id of the running thread. returned value is templatized
- // operator returns std::future, where the user can get the result and rethrow the catched exceptins
- template<typename F>
- auto push(F && f) ->std::future<decltype(f(0))> { //note: me edit
- auto pck = std::make_shared<std::packaged_task<decltype(f(0))(int)>>(std::forward<F>(f)); //note: me edit
- auto _f = new std::function<void(int id)>([pck](int id) {
- (*pck)(id);
- });
- this->q.push(_f);
- std::unique_lock<std::mutex> lock(this->mutex);
- this->cv.notify_one();
- return pck->get_future();
- }
- private:
- // deleted
- thread_pool(const thread_pool &);// = delete;
- thread_pool(thread_pool &&);// = delete;
- thread_pool & operator=(const thread_pool &);// = delete;
- thread_pool & operator=(thread_pool &&);// = delete;
- void set_thread(int i) {
- std::shared_ptr<std::atomic<bool>> flag(this->flags[i]); // a copy of the shared ptr to the flag
- auto f = [this, i, flag/* a copy of the shared ptr to the flag */]() {
- std::atomic<bool> & _flag = *flag;
- std::function<void(int id)> * _f;
- bool isPop = this->q.pop(_f);
- while (true) {
- while (isPop) { // if there is anything in the queue
- std::unique_ptr<std::function<void(int id)>> func(_f); // at return, delete the function even if an exception occurred
- (*_f)(i);
- if (_flag)
- return; // the thread is wanted to stop, return even if the queue is not empty yet
- else
- isPop = this->q.pop(_f);
- }
- // the queue is empty here, wait for the next command
- std::unique_lock<std::mutex> lock(this->mutex);
- ++this->nWaiting;
- this->cv.wait(lock, [this, &_f, &isPop, &_flag](){ isPop = this->q.pop(_f); return isPop || this->isDone || _flag; });
- --this->nWaiting;
- if (!isPop)
- return; // if the queue is empty and this->isDone == true or *flag then return
- }
- };
- this->threads[i].reset(new std::thread(f)); // compiler may not support std::make_unique()
- }
- void init() { this->nWaiting = 0; this->isStop = false; this->isDone = false; }
- std::vector<std::unique_ptr<std::thread>> threads;
- std::vector<std::shared_ptr<std::atomic<bool>>> flags;
- detail::Queue<std::function<void(int id)> *> q;
- std::atomic<bool> isDone;
- std::atomic<bool> isStop;
- std::atomic<int> nWaiting; // how many threads are waiting
- std::mutex mutex;
- std::condition_variable cv;
- };
- }
- //-------------user here
- ctpl::thread_pool pool(4);
- class C{
- public: int d=35;
- };
- class B{
- public: C* c;
- public: void test(){
- std::vector<std::future<void>> cac;
- for(int n=0;n<5;n++){
- cac.push_back(
- pool.push([&](int threadId){
- test2();
- })
- );
- }
- for(auto& ele : cac){
- ele.get();
- }
- };
- public: void test2(){
- std::vector<std::future<void>> cac;
- for(int n=0;n<5;n++){
- cac.push_back(
- pool.push([&](int threadId){
- int accu=0;
- for(int i=0;i<10000;i++){
- accu+=i;
- }
- std::cout<<accu<<" access c="<<c->d<<std::endl;
- })
- );
- }
- for(auto& ele : cac){
- ele.get();
- }
- }
- };
- int main(){
- C c;
- B b; b.c=&c;
- b.test();
- std::cout<<"end"<<std::endl;
- }
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