cpp-taskflow/taskflow/threadpool/threadpool_cxx14.hpp at master · DerThorsten/cpp-taskflow · GitHub

Repository navigation

History

402 lines (324 loc) · 11 KB

Raw

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

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

203

204

205

206

207

208

209

210

211

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

234

235

236

237

238

239

240

241

242

243

244

245

246

247

248

249

250

251

252

253

254

255

256

257

258

259

260

261

262

263

264

265

266

267

268

269

270

271

272

273

274

275

276

277

278

279

280

281

282

283

284

285

286

287

288

289

290

291

292

293

294

295

296

297

298

299

300

301

302

303

304

305

306

307

308

309

310

311

312

313

314

315

316

317

318

319

320

321

322

323

324

325

326

327

328

329

330

331

332

333

334

335

336

337

338

339

340

341

342

343

344

345

346

347

348

349

350

351

352

353

354

355

356

357

358

359

360

361

362

363

364

365

366

367

368

369

370

371

372

373

374

375

376

377

378

379

380

381

382

383

384

385

386

387

388

389

390

391

392

393

394

395

396

397

398

399

400

401

402

// A C++-14 based threadpool implementation inspired by Taskflow Threadpool.

// 2018/09/02 - contributed by Glen Fraser

// - added wait_for_all method

// 2018/08/27 - contributed by Glen Fraser

// taskflow.hpp was modified by Glen Fraser to produce this file

// (threadpool_cxx14.hpp), which is a "light" version of the library with

// restricted functionality -- it only exposes the tf::Threadpool class.

// However, it has also been reworked to support compilation with C++14

// (instead of requiring C++17, as the main Taskflow library does).

// It is designed to be used in cases where only the Threadpool

// functionality is required, in projects that are reliant on a (slightly)

// older version of C++.

// NOTE: if you are using a fully C++17-compliant compiler, you should

// be including "taskflow.hpp" rather than this file!

#pragma once

#include <deque>

#include <vector>

#include <thread>

#include <future>

#include <unordered_set>

#include <type_traits>

#include <utility>

//-------------------------------------------------------------------------------------------------

// C++14 implementation of C++17's std::invoke_result, taken from:

// https://en.cppreference.com/w/cpp/types/result_of

//-------------------------------------------------------------------------------------------------

namespace std {

namespace detail {

template <class T>

struct is_reference_wrapper : std::false_type {};

template <class U>

struct is_reference_wrapper<std::reference_wrapper<U>> : std::true_type {};

template<class T>

struct invoke_impl {

template<class F, class... Args>

static auto call(F&& f, Args&&... args)

-> decltype(std::forward<F>(f)(std::forward<Args>(args)...));

};

template<class B, class MT>

struct invoke_impl<MT B::*> {

template<class T, class Td = typename std::decay<T>::type,

class = typename std::enable_if<std::is_base_of<B, Td>::value>::type

static auto get(T&& t)->T&&;

template<class T, class Td = typename std::decay<T>::type,

class = typename std::enable_if<is_reference_wrapper<Td>::value>::type

static auto get(T&& t) -> decltype(t.get());

template<class T, class Td = typename std::decay<T>::type,

class = typename std::enable_if<!std::is_base_of<B, Td>::value>::type,

class = typename std::enable_if<!is_reference_wrapper<Td>::value>::type

static auto get(T&& t) -> decltype(*std::forward<T>(t));

template<class T, class... Args, class MT1,

class = typename std::enable_if<std::is_function<MT1>::value>::type

static auto call(MT1 B::*pmf, T&& t, Args&&... args)

-> decltype((invoke_impl::get(std::forward<T>(t)).*pmf)(std::forward<Args>(args)...));

template<class T>

static auto call(MT B::*pmd, T&& t)

-> decltype(invoke_impl::get(std::forward<T>(t)).*pmd);

};

template<class F, class... Args, class Fd = typename std::decay<F>::type>

auto INVOKE(F&& f, Args&&... args)

-> decltype(invoke_impl<Fd>::call(std::forward<F>(f), std::forward<Args>(args)...));

} // namespace detail

// Conforming C++14 implementation (is also a valid C++11 implementation):

namespace detail {

template <typename AlwaysVoid, typename, typename...>

struct invoke_result { };

template <typename F, typename...Args>

struct invoke_result<decltype(void(detail::INVOKE(std::declval<F>(), std::declval<Args>()...))),

F, Args...> {

using type = decltype(detail::INVOKE(std::declval<F>(), std::declval<Args>()...));

};

} // namespace detail

template <class F, class... ArgTypes>

struct invoke_result : detail::invoke_result<void, F, ArgTypes...> {};

template< class F, class... ArgTypes>

using invoke_result_t = typename invoke_result<F, ArgTypes...>::type;

}

// ------------------------------------------------------------------------------------------------

namespace tf {

//-------------------------------------------------------------------------------------------------

// Utility

//-------------------------------------------------------------------------------------------------

// Struct: MoC

template <typename T>

struct MoC {

MoC(T&& rhs) : object(std::move(rhs)) {}

MoC(const MoC& other) : object(std::move(other.object)) {}

T& get() { return object; }

mutable T object;

};

//-------------------------------------------------------------------------------------------------

// Threadpool definition

//-------------------------------------------------------------------------------------------------

// Class: Threadpool

class Threadpool {

enum class Signal {

STANDARD,

SHUTDOWN

};

public:

inline Threadpool(unsigned);

inline ~Threadpool();

template<typename C>

std::enable_if_t<

std::is_same<void, std::invoke_result_t<C>>::value,

std::future<std::invoke_result_t<C>>

async(C&&, Signal = Signal::STANDARD);

template<typename C>

std::enable_if_t<

!std::is_same<void, std::invoke_result_t<C>>::value,

std::future<std::invoke_result_t<C>>

async(C&&, Signal = Signal::STANDARD);

template <typename C>

auto silent_async(C&&, Signal = Signal::STANDARD);

inline void shutdown();

inline void spawn(unsigned);

inline void wait_for_all();

inline size_t num_tasks() const;

inline size_t num_workers() const;

inline bool is_worker() const;

private:

mutable std::mutex _mutex;

std::condition_variable _worker_signal;

std::deque<std::function<Signal()>> _task_queue;

std::vector<std::thread> _threads;

std::unordered_set<std::thread::id> _worker_ids;

};

// Constructor

inline Threadpool::Threadpool(unsigned N) {

spawn(N);

}

// Destructor

inline Threadpool::~Threadpool() {

shutdown();

}

// Function: num_tasks

// Return the number of "unfinished" tasks. Notice that this value is not necessary equal to

// the size of the task_queue since the task can be popped out from the task queue while

// not yet finished.

inline size_t Threadpool::num_tasks() const {

return _task_queue.size();

}

inline size_t Threadpool::num_workers() const {

return _threads.size();

}

inline bool Threadpool::is_worker() const {

std::lock_guard<std::mutex> lock(_mutex);

return _worker_ids.find(std::this_thread::get_id()) != _worker_ids.end();

}

// Procedure: spawn

// The procedure spawns "n" threads monitoring the task queue and executing each task. After the

// task is finished, the thread reacts to the returned signal.

inline void Threadpool::spawn(unsigned N) {

if(is_worker()) {

throw std::runtime_error("Worker thread cannot spawn threads");

}

for(size_t i=0; i<N; ++i) {

_threads.emplace_back([this] () -> void {

{ // Acquire lock

std::lock_guard<std::mutex> lock(_mutex);

_worker_ids.insert(std::this_thread::get_id());

}

bool stop {false};

while(!stop) {

decltype(_task_queue)::value_type task;

{ // Acquire lock. --------------------------------

std::unique_lock<std::mutex> lock(_mutex);

_worker_signal.wait(lock, [this] () { return _task_queue.size() != 0; });

task = std::move(_task_queue.front());

_task_queue.pop_front();

} // Release lock. --------------------------------

// Execute the task and react to the returned signal.

switch(task()) {

case Signal::SHUTDOWN:

stop = true;

break;

default:

break;

};

} // End of worker loop.

{ // Acquire lock

std::lock_guard<std::mutex> lock(_mutex);

_worker_ids.erase(std::this_thread::get_id());

}

});

}

// Function: silent_async

// Insert a task without giving future.

template <typename C>

auto Threadpool::silent_async(C&& c, Signal sig) {

// No worker, do this right away.

if(num_workers() == 0) {

c();

}

// Dispatch this to a thread.

else {

{

std::lock_guard<std::mutex> lock(_mutex);

_task_queue.emplace_back(

[c=std::forward<C>(c), ret=sig] () mutable {

c();

return ret;

}

);

}

_worker_signal.notify_one();

}

// Function: async

// Insert a callable task and return a future representing the task.

// Version for tasks returning void.

template<typename C>

std::enable_if_t<

std::is_same<void, std::invoke_result_t<C>>::value,

std::future<std::invoke_result_t<C>>

> Threadpool::async(C&& c, Signal sig) {

using R = std::invoke_result_t<C>;

std::promise<R> p;

auto fu = p.get_future();

// No worker, do this immediately.

if(_threads.empty()) {

c();

p.set_value();

}

// Schedule a thread to do this.

else {

{

std::lock_guard<std::mutex> lock(_mutex);

_task_queue.emplace_back(

[p = MoC<decltype(p)>(std::move(p)), c = std::forward<C>(c), ret = sig]() mutable {

c();

p.get().set_value();

return ret;

}

);

}

_worker_signal.notify_one();

}

return fu;

}

// Function: async

// Version for tasks returning anything other than void.

template<typename C>

std::enable_if_t<

!std::is_same<void, std::invoke_result_t<C>>::value,

std::future<std::invoke_result_t<C>>

> Threadpool::async(C&& c, Signal sig) {

using R = std::invoke_result_t<C>;

std::promise<R> p;

auto fu = p.get_future();

// No worker, do this immediately.

if (_threads.empty()) {

p.set_value(c());

}

// Schedule a thread to do this.

else {

{

std::lock_guard<std::mutex> lock(_mutex);

_task_queue.emplace_back(

[p=MoC<decltype(p)>(std::move(p)), c=std::forward<C>(c), ret=sig]() mutable {

p.get().set_value(c());

return ret;

}

);

}

_worker_signal.notify_one();

}

return fu;

}

// Procedure: wait_for_all

// After this method returns, all previously-scheduled tasks in the pool

// will have been executed.

inline void Threadpool::wait_for_all() {

if(is_worker()) {

throw std::runtime_error("Worker thread cannot wait for all");

}

std::mutex barrier_mutex;

std::condition_variable barrier_cv;

auto threads_to_sync{_threads.size()};

std::vector<std::future<void>> futures;

auto barrier_task = [&] {

std::unique_lock<std::mutex> lock(barrier_mutex);

if (--threads_to_sync == 0) {

barrier_cv.notify_all();

}

else {

barrier_cv.wait(lock, [&threads_to_sync] {

return threads_to_sync == 0;

});

}

};

for(size_t i=0; i<_threads.size(); ++i) {

futures.emplace_back(async(barrier_task));

}

// Wait for all threads to have finished synchronization

for (auto& fu : futures) {

fu.get();

}

// Procedure: shutdown

// Remove a given number of workers. Notice that only the master can call this procedure.

inline void Threadpool::shutdown() {

if(is_worker()) {

throw std::runtime_error("Worker thread cannot shut down the thread pool");

}

for(size_t i=0; i<_threads.size(); ++i) {

silent_async([](){}, Signal::SHUTDOWN);

}

for(auto& t : _threads) {

t.join();

}

_threads.clear();

}

}; // end of namespace tf. ---------------------------------------------------

cpp-taskflow/taskflow/threadpool/threadpool_cxx14.hpp at master · DerThorsten/cpp-taskflow · GitHub

Repository navigation

Expand file tree

Breadcrumbs

threadpool_cxx14.hpp

Latest commit

History

Breadcrumbs

threadpool_cxx14.hpp

File metadata and controls