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Add Barrier.h.
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unsupported/Eigen/CXX11/src/ThreadPool/Barrier.h
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67
unsupported/Eigen/CXX11/src/ThreadPool/Barrier.h
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// This file is part of Eigen, a lightweight C++ template library
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// for linear algebra.
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//
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// Copyright (C) 2018 Rasmus Munk Larsen <rmlarsen@google.com>
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//
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// This Source Code Form is subject to the terms of the Mozilla
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// Public License v. 2.0. If a copy of the MPL was not distributed
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// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
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// Barrier is an object that allows one or more threads to wait until
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// Notify has been called a specified number of times.
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#ifndef EIGEN_CXX11_THREADPOOL_BARRIER_H
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#define EIGEN_CXX11_THREADPOOL_BARRIER_H
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namespace Eigen {
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class Barrier {
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public:
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Barrier(unsigned int count) : state_(count << 1), notified_(false) {
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eigen_assert(((count << 1) >> 1) == count);
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}
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~Barrier() {
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eigen_assert((state_>>1) == 0);
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}
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void Notify() {
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unsigned int v = state_.fetch_sub(2, std::memory_order_acq_rel) - 2;
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if (v != 1) {
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eigen_assert(((v + 2) & ~1) != 0);
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return; // either count has not dropped to 0, or waiter is not waiting
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}
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std::unique_lock<std::mutex> l(mu_);
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eigen_assert(!notified_);
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notified_ = true;
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cv_.notify_all();
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}
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void Wait() {
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unsigned int v = state_.fetch_or(1, std::memory_order_acq_rel);
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if ((v >> 1) == 0) return;
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std::unique_lock<std::mutex> l(mu_);
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while (!notified_) {
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cv_.wait(l);
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}
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}
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private:
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std::mutex mu_;
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std::condition_variable cv_;
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std::atomic<unsigned int> state_; // low bit is waiter flag
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bool notified_;
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};
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// Notification is an object that allows a user to to wait for another
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// thread to signal a notification that an event has occurred.
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//
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// Multiple threads can wait on the same Notification object,
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// but only one caller must call Notify() on the object.
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struct Notification : Barrier {
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Notification() : Barrier(1) {};
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};
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} // namespace Eigen
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#endif // EIGEN_CXX11_THREADPOOL_BARRIER_H
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