| Line | Branch | Exec | Source |
|---|---|---|---|
| 1 | // | ||
| 2 | // Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com) | ||
| 3 | // | ||
| 4 | // Distributed under the Boost Software License, Version 1.0. (See accompanying | ||
| 5 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | ||
| 6 | // | ||
| 7 | // Official repository: https://github.com/boostorg/capy | ||
| 8 | // | ||
| 9 | |||
| 10 | #ifndef BOOST_CAPY_EX_THREAD_POOL_HPP | ||
| 11 | #define BOOST_CAPY_EX_THREAD_POOL_HPP | ||
| 12 | |||
| 13 | #include <boost/capy/detail/config.hpp> | ||
| 14 | #include <boost/capy/ex/any_coro.hpp> | ||
| 15 | #include <boost/capy/ex/execution_context.hpp> | ||
| 16 | #include <cstddef> | ||
| 17 | |||
| 18 | namespace boost { | ||
| 19 | namespace capy { | ||
| 20 | |||
| 21 | /** A pool of threads for executing work concurrently. | ||
| 22 | |||
| 23 | Use this when you need to run coroutines on multiple threads | ||
| 24 | without the overhead of creating and destroying threads for | ||
| 25 | each task. Work items are distributed across the pool using | ||
| 26 | a shared queue. | ||
| 27 | |||
| 28 | @par Thread Safety | ||
| 29 | Distinct objects: Safe. | ||
| 30 | Shared objects: Unsafe. | ||
| 31 | |||
| 32 | @par Example | ||
| 33 | @code | ||
| 34 | thread_pool pool(4); // 4 worker threads | ||
| 35 | auto ex = pool.get_executor(); | ||
| 36 | ex.post(some_coroutine); | ||
| 37 | // pool destructor waits for all work to complete | ||
| 38 | @endcode | ||
| 39 | */ | ||
| 40 | class BOOST_CAPY_DECL | ||
| 41 | thread_pool | ||
| 42 | : public execution_context | ||
| 43 | { | ||
| 44 | class impl; | ||
| 45 | impl* impl_; | ||
| 46 | |||
| 47 | public: | ||
| 48 | class executor_type; | ||
| 49 | |||
| 50 | /** Destroy the thread pool. | ||
| 51 | |||
| 52 | Signals all worker threads to stop, waits for them to | ||
| 53 | finish, and destroys any pending work items. | ||
| 54 | */ | ||
| 55 | ~thread_pool(); | ||
| 56 | |||
| 57 | /** Construct a thread pool. | ||
| 58 | |||
| 59 | Creates a pool with the specified number of worker threads. | ||
| 60 | If `num_threads` is zero, the number of threads is set to | ||
| 61 | the hardware concurrency, or one if that cannot be determined. | ||
| 62 | |||
| 63 | @param num_threads The number of worker threads, or zero | ||
| 64 | for automatic selection. | ||
| 65 | */ | ||
| 66 | explicit | ||
| 67 | thread_pool(std::size_t num_threads = 0); | ||
| 68 | |||
| 69 | thread_pool(thread_pool const&) = delete; | ||
| 70 | thread_pool& operator=(thread_pool const&) = delete; | ||
| 71 | |||
| 72 | /** Request all worker threads to stop. | ||
| 73 | |||
| 74 | Signals all threads to exit via stop token. Threads will | ||
| 75 | finish their current work item before exiting. Does not | ||
| 76 | wait for threads to exit. | ||
| 77 | */ | ||
| 78 | void | ||
| 79 | stop() noexcept; | ||
| 80 | |||
| 81 | /** Return an executor for this thread pool. | ||
| 82 | |||
| 83 | @return An executor associated with this thread pool. | ||
| 84 | */ | ||
| 85 | executor_type | ||
| 86 | get_executor() const noexcept; | ||
| 87 | }; | ||
| 88 | |||
| 89 | //------------------------------------------------------------------------------ | ||
| 90 | |||
| 91 | /** An executor that submits work to a thread_pool. | ||
| 92 | |||
| 93 | Executors are lightweight handles that can be copied and stored. | ||
| 94 | All copies refer to the same underlying thread pool. | ||
| 95 | |||
| 96 | @par Thread Safety | ||
| 97 | Distinct objects: Safe. | ||
| 98 | Shared objects: Safe. | ||
| 99 | */ | ||
| 100 | class thread_pool::executor_type | ||
| 101 | { | ||
| 102 | friend class thread_pool; | ||
| 103 | |||
| 104 | thread_pool* pool_ = nullptr; | ||
| 105 | |||
| 106 | explicit | ||
| 107 | 51 | executor_type(thread_pool& pool) noexcept | |
| 108 | 51 | : pool_(&pool) | |
| 109 | { | ||
| 110 | 51 | } | |
| 111 | |||
| 112 | public: | ||
| 113 | /// Default construct a null executor. | ||
| 114 | executor_type() = default; | ||
| 115 | |||
| 116 | /// Return the underlying thread pool. | ||
| 117 | thread_pool& | ||
| 118 | 27 | context() const noexcept | |
| 119 | { | ||
| 120 | 27 | return *pool_; | |
| 121 | } | ||
| 122 | |||
| 123 | /// Notify that work has started (no-op for thread pools). | ||
| 124 | void | ||
| 125 | 4 | on_work_started() const noexcept | |
| 126 | { | ||
| 127 | 4 | } | |
| 128 | |||
| 129 | /// Notify that work has finished (no-op for thread pools). | ||
| 130 | void | ||
| 131 | 4 | on_work_finished() const noexcept | |
| 132 | { | ||
| 133 | 4 | } | |
| 134 | |||
| 135 | /** Dispatch a coroutine for execution. | ||
| 136 | |||
| 137 | Posts the coroutine to the thread pool and returns | ||
| 138 | immediately. The caller should suspend after calling | ||
| 139 | this function. | ||
| 140 | |||
| 141 | @param h The coroutine handle to execute. | ||
| 142 | |||
| 143 | @return A noop coroutine handle to resume. | ||
| 144 | */ | ||
| 145 | any_coro | ||
| 146 | 3 | dispatch(any_coro h) const | |
| 147 | { | ||
| 148 | 3 | post(h); | |
| 149 | 3 | return std::noop_coroutine(); | |
| 150 | } | ||
| 151 | |||
| 152 | /** Post a coroutine to the thread pool. | ||
| 153 | |||
| 154 | The coroutine will be resumed on one of the pool's | ||
| 155 | worker threads. | ||
| 156 | |||
| 157 | @param h The coroutine handle to execute. | ||
| 158 | */ | ||
| 159 | BOOST_CAPY_DECL | ||
| 160 | void | ||
| 161 | post(any_coro h) const; | ||
| 162 | |||
| 163 | /// Return true if two executors refer to the same thread pool. | ||
| 164 | bool | ||
| 165 | 16 | operator==(executor_type const& other) const noexcept | |
| 166 | { | ||
| 167 | 16 | return pool_ == other.pool_; | |
| 168 | } | ||
| 169 | }; | ||
| 170 | |||
| 171 | //------------------------------------------------------------------------------ | ||
| 172 | |||
| 173 | inline | ||
| 174 | auto | ||
| 175 | 51 | thread_pool:: | |
| 176 | get_executor() const noexcept -> | ||
| 177 | executor_type | ||
| 178 | { | ||
| 179 | 51 | return executor_type(const_cast<thread_pool&>(*this)); | |
| 180 | } | ||
| 181 | |||
| 182 | } // capy | ||
| 183 | } // boost | ||
| 184 | |||
| 185 | #endif | ||
| 186 |