|
| 1 | +#ifndef THREAD_POOL_H |
| 2 | +#define THREAD_POOL_H |
| 3 | + |
| 4 | +#include <vector> |
| 5 | +#include <deque> |
| 6 | +#include <memory> |
| 7 | +#include <thread> |
| 8 | +#include <mutex> |
| 9 | +#include <condition_variable> |
| 10 | + |
| 11 | +class ThreadPool; |
| 12 | + |
| 13 | +// our worker thread objects |
| 14 | +class Worker { |
| 15 | +public: |
| 16 | + Worker(ThreadPool &s) : pool(s) { } |
| 17 | + void operator()(); |
| 18 | +private: |
| 19 | + ThreadPool &pool; |
| 20 | +}; |
| 21 | + |
| 22 | +template<class T> |
| 23 | +class Result { |
| 24 | + struct ResultImpl { |
| 25 | + ResultImpl() : value(T()), available(false) { } |
| 26 | + T value; |
| 27 | + bool available; |
| 28 | + std::mutex lock; |
| 29 | + std::condition_variable cond; |
| 30 | + }; |
| 31 | +public: |
| 32 | + Result() : impl(new ResultImpl()) { } |
| 33 | + bool available() const |
| 34 | + { |
| 35 | + std::unique_lock<std::mutex> ul(impl->lock); |
| 36 | + return impl->available; |
| 37 | + } |
| 38 | + void wait() |
| 39 | + { |
| 40 | + if(!impl) |
| 41 | + return; |
| 42 | + std::unique_lock<std::mutex> ul(impl->lock); |
| 43 | + if(impl->available) |
| 44 | + return; |
| 45 | + impl->cond.wait(ul); |
| 46 | + } |
| 47 | + void signal() const |
| 48 | + { |
| 49 | + std::unique_lock<std::mutex> ul(impl->lock); |
| 50 | + impl->available = true; impl->cond.notify_all(); |
| 51 | + } |
| 52 | + bool valid() const |
| 53 | + { |
| 54 | + std::unique_lock<std::mutex> ul(impl->lock); |
| 55 | + return static_cast<bool>(impl); |
| 56 | + } |
| 57 | + |
| 58 | + T& get() |
| 59 | + { |
| 60 | + wait(); |
| 61 | + return impl->value; |
| 62 | + } |
| 63 | + void set(T v) const |
| 64 | + { |
| 65 | + std::unique_lock<std::mutex> ul(impl->lock); |
| 66 | + impl->value = v; |
| 67 | + } |
| 68 | + |
| 69 | +private: |
| 70 | + std::shared_ptr<ResultImpl> impl; |
| 71 | +}; |
| 72 | + |
| 73 | +template<> |
| 74 | +class Result<void> { |
| 75 | + struct ResultImpl { |
| 76 | + ResultImpl() : available(false) { } |
| 77 | + bool available; |
| 78 | + std::mutex lock; |
| 79 | + std::condition_variable cond; |
| 80 | + }; |
| 81 | +public: |
| 82 | + Result() : impl(new ResultImpl()) { } |
| 83 | + |
| 84 | + bool available() const |
| 85 | + { |
| 86 | + std::unique_lock<std::mutex> ul(impl->lock); |
| 87 | + return impl->available; |
| 88 | + } |
| 89 | + void wait() |
| 90 | + { |
| 91 | + if(!impl) |
| 92 | + return; |
| 93 | + std::unique_lock<std::mutex> ul(impl->lock); |
| 94 | + if(impl->available) |
| 95 | + return; |
| 96 | + impl->cond.wait(ul); |
| 97 | + } |
| 98 | + void signal() const |
| 99 | + { |
| 100 | + std::unique_lock<std::mutex> ul(impl->lock); |
| 101 | + impl->available = true; impl->cond.notify_all(); |
| 102 | + } |
| 103 | + bool valid() const |
| 104 | + { |
| 105 | + std::unique_lock<std::mutex> ul(impl->lock); |
| 106 | + return static_cast<bool>(impl); |
| 107 | + } |
| 108 | +private: |
| 109 | + std::shared_ptr<ResultImpl> impl; |
| 110 | +}; |
| 111 | + |
| 112 | +// the actual thread pool |
| 113 | +class ThreadPool { |
| 114 | +public: |
| 115 | + ThreadPool(size_t); |
| 116 | + template<class T, class F> |
| 117 | + Result<T> enqueue(F f); |
| 118 | + ~ThreadPool(); |
| 119 | +private: |
| 120 | + friend class Worker; |
| 121 | + |
| 122 | + // need to keep track of threads so we can join them |
| 123 | + std::vector< std::thread > workers; |
| 124 | + // the task queue |
| 125 | + std::deque< std::function<void()> > tasks; |
| 126 | + |
| 127 | + // synchronization |
| 128 | + std::mutex queue_mutex; |
| 129 | + std::condition_variable condition; |
| 130 | + bool stop; |
| 131 | +}; |
| 132 | + |
| 133 | +void Worker::operator()() |
| 134 | +{ |
| 135 | + std::function<void()> task; |
| 136 | + while(true) |
| 137 | + { |
| 138 | + { |
| 139 | + std::unique_lock<std::mutex> lock(pool.queue_mutex); |
| 140 | + while(!pool.stop && pool.tasks.empty()) |
| 141 | + pool.condition.wait(lock); |
| 142 | + if(pool.stop) |
| 143 | + return; |
| 144 | + task = pool.tasks.front(); |
| 145 | + pool.tasks.pop_front(); |
| 146 | + } |
| 147 | + task(); |
| 148 | + } |
| 149 | +} |
| 150 | + |
| 151 | +// the constructor just launches some amount of workers |
| 152 | +ThreadPool::ThreadPool(size_t threads) |
| 153 | + : stop(false) |
| 154 | +{ |
| 155 | + for(size_t i = 0;i<threads;++i) |
| 156 | + workers.push_back(std::thread(Worker(*this))); |
| 157 | +} |
| 158 | + |
| 159 | +template<class T, class F> |
| 160 | +struct CallAndSet { |
| 161 | + void operator()(const Result<T> &res, const F f) |
| 162 | + { |
| 163 | + res.set(f()); |
| 164 | + res.signal(); |
| 165 | + } |
| 166 | +}; |
| 167 | + |
| 168 | +template<class F> |
| 169 | +struct CallAndSet<void,F> { |
| 170 | + void operator()(const Result<void> &res, const F &f) |
| 171 | + { |
| 172 | + f(); |
| 173 | + res.signal(); |
| 174 | + } |
| 175 | +}; |
| 176 | + |
| 177 | +// add new work item to the pool |
| 178 | +template<class T, class F> |
| 179 | +Result<T> ThreadPool::enqueue(F f) |
| 180 | +{ |
| 181 | + Result<T> res; |
| 182 | + { |
| 183 | + std::unique_lock<std::mutex> lock(queue_mutex); |
| 184 | + tasks.push_back(std::function<void()>( |
| 185 | + [f,res]() |
| 186 | + { |
| 187 | + CallAndSet<T,F>()(res, f); |
| 188 | + })); |
| 189 | + } |
| 190 | + condition.notify_one(); |
| 191 | + return res; |
| 192 | +} |
| 193 | + |
| 194 | +// the destructor joins all threads |
| 195 | +ThreadPool::~ThreadPool() |
| 196 | +{ |
| 197 | + stop = true; |
| 198 | + condition.notify_all(); |
| 199 | + for(size_t i = 0;i<workers.size();++i) |
| 200 | + workers[i].join(); |
| 201 | +} |
| 202 | + |
| 203 | +#endif |
0 commit comments