144 lines
4.2 KiB
C++
144 lines
4.2 KiB
C++
// Copyright (c) 2014-2017, The Monero Project, The Danicoin Project
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//
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without modification, are
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// permitted provided that the following conditions are met:
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//
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// 1. Redistributions of source code must retain the above copyright notice, this list of
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// conditions and the following disclaimer.
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//
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// 2. Redistributions in binary form must reproduce the above copyright notice, this list
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// of conditions and the following disclaimer in the documentation and/or other
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// materials provided with the distribution.
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//
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// 3. Neither the name of the copyright holder nor the names of its contributors may be
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// used to endorse or promote products derived from this software without specific
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// prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
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// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
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// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
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// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#pragma once
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#include <boost/optional/optional.hpp>
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#include <boost/thread/condition_variable.hpp>
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#include <boost/thread/mutex.hpp>
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#include <boost/thread/thread.hpp>
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#include <cstddef>
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#include <functional>
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#include <thread>
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#include <utility>
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#include <vector>
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namespace tools
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{
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//! Manages zero or more threads for work dispatching.
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class thread_group
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{
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public:
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//! \return `get_max_concurrency() ? get_max_concurrency() - 1 : 0`
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static std::size_t optimal();
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//! \return `count ? min(count - 1, optimal()) : 0`
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static std::size_t optimal_with_max(std::size_t count);
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//! Create an optimal number of threads.
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explicit thread_group() : thread_group(optimal()) {}
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//! Create exactly `count` threads.
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explicit thread_group(std::size_t count);
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thread_group(thread_group const&) = delete;
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thread_group(thread_group&&) = delete;
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//! Joins threads, but does not necessarily run all dispatched functions.
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~thread_group() = default;
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thread_group& operator=(thread_group const&) = delete;
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thread_group& operator=(thread_group&&) = delete;
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//! \return Number of threads owned by `this` group.
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std::size_t count() const noexcept {
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if (internal) {
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return internal->count();
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}
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return 0;
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}
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//! \return True iff a function was available and executed (on `this_thread`).
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bool try_run_one() noexcept {
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if (internal) {
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return internal->try_run_one();
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}
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return false;
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}
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/*! `f` is invoked immediately if `count() == 0`, otherwise execution of `f`
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is queued for next available thread. If `f` is queued, any exception leaving
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that function will result in process termination. Use std::packaged_task if
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exceptions need to be handled. */
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template<typename F>
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void dispatch(F&& f) {
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if (internal) {
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internal->dispatch(std::forward<F>(f));
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}
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else {
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f();
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}
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}
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private:
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class data {
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public:
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data(std::size_t count);
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~data() noexcept;
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std::size_t count() const noexcept {
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return threads.size();
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}
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bool try_run_one() noexcept;
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void dispatch(std::function<void()> f);
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private:
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struct work;
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struct node {
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std::unique_ptr<work> ptr;
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};
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struct work {
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std::function<void()> f;
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node next;
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};
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//! Requires lock on `mutex`.
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std::unique_ptr<work> get_next() noexcept;
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//! Blocks until destructor is invoked, only call from thread.
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void run() noexcept;
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private:
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std::vector<boost::thread> threads;
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node head;
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node* last;
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boost::condition_variable has_work;
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boost::mutex mutex;
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bool stop;
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};
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private:
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// optionally construct elements, without separate heap allocation
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boost::optional<data> internal;
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};
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}
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