73 lines
2.7 KiB
C++
73 lines
2.7 KiB
C++
/*
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* Copyright © 2004 Ondra Kamenik
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* Copyright © 2019 Dynare Team
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*
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* This file is part of Dynare.
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*
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* Dynare is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Dynare is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Dynare. If not, see <https://www.gnu.org/licenses/>.
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*/
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#include <algorithm>
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#include "sthread.hh"
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namespace sthread
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{
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/* We set the default value for ‘max_parallel_threads’ to half the number of
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logical CPUs */
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int
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default_threads_number()
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{
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return std::max(1, static_cast<int>(std::thread::hardware_concurrency()) / 2);
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}
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int detach_thread_group::max_parallel_threads = default_threads_number();
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/* We cycle through all threads in the group, and in each cycle we wait for
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the change in the ‘counter’. If the counter indicates less than maximum
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parallel threads running, then a new thread is run, and the iterator in
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the list is moved.
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At the end we have to wait for all thread to finish. */
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void
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detach_thread_group::run()
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{
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std::unique_lock<std::mutex> lk{mut_cv};
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auto it = tlist.begin();
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while (it != tlist.end())
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{
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counter++;
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std::thread th{[&, it] {
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// The ‘it’ variable is captured by value, because otherwise the iterator may move
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(*it)->operator()(mut_threads);
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std::unique_lock<std::mutex> lk2{mut_cv};
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counter--;
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/* First notify the thread waiting on the condition variable, then
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unlock the mutex. We must do these two operations in that order,
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otherwise there is a possibility of having the main process
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destroying the condition variable before the thread tries to
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notify it (if all other threads terminate at the same time and
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bring the counter down to zero).
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For that reason, we cannot use std::notify_all_at_thread_exit() */
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cv.notify_one();
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lk2.unlock();
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}};
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th.detach();
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++it;
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cv.wait(lk, [&] { return counter < max_parallel_threads; });
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}
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cv.wait(lk, [&] { return counter == 0; });
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}
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}
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