| // Ceres Solver - A fast non-linear least squares minimizer |
| // Copyright 2018 Google Inc. All rights reserved. |
| // http://ceres-solver.org/ |
| // |
| // Redistribution and use in source and binary forms, with or without |
| // modification, are permitted provided that the following conditions are met: |
| // |
| // * Redistributions of source code must retain the above copyright notice, |
| // this list of conditions and the following disclaimer. |
| // * Redistributions in binary form must reproduce the above copyright notice, |
| // this list of conditions and the following disclaimer in the documentation |
| // and/or other materials provided with the distribution. |
| // * Neither the name of Google Inc. nor the names of its contributors may be |
| // used to endorse or promote products derived from this software without |
| // specific prior written permission. |
| // |
| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
| // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| // ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE |
| // LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
| // CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
| // SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
| // INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
| // CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| // ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
| // POSSIBILITY OF SUCH DAMAGE. |
| // |
| // Author: vitus@google.com (Michael Vitus) |
| |
| #include "ceres/thread_pool.h" |
| |
| #include <cmath> |
| #include <limits> |
| |
| #include "ceres/internal/config.h" |
| |
| namespace ceres::internal { |
| namespace { |
| |
| // Constrain the total number of threads to the amount the hardware can support. |
| int GetNumAllowedThreads(int requested_num_threads) { |
| return std::min(requested_num_threads, ThreadPool::MaxNumThreadsAvailable()); |
| } |
| |
| } // namespace |
| |
| int ThreadPool::MaxNumThreadsAvailable() { |
| const int num_hardware_threads = std::thread::hardware_concurrency(); |
| // hardware_concurrency() can return 0 if the value is not well defined or not |
| // computable. |
| return num_hardware_threads == 0 ? std::numeric_limits<int>::max() |
| : num_hardware_threads; |
| } |
| |
| ThreadPool::ThreadPool() = default; |
| |
| ThreadPool::ThreadPool(int num_threads) { Resize(num_threads); } |
| |
| ThreadPool::~ThreadPool() { |
| std::lock_guard<std::mutex> lock(thread_pool_mutex_); |
| // Signal the thread workers to stop and wait for them to finish all scheduled |
| // tasks. |
| Stop(); |
| for (std::thread& thread : thread_pool_) { |
| thread.join(); |
| } |
| } |
| |
| void ThreadPool::Resize(int num_threads) { |
| std::lock_guard<std::mutex> lock(thread_pool_mutex_); |
| |
| const int num_current_threads = thread_pool_.size(); |
| if (num_current_threads >= num_threads) { |
| return; |
| } |
| |
| const int create_num_threads = |
| GetNumAllowedThreads(num_threads) - num_current_threads; |
| |
| for (int i = 0; i < create_num_threads; ++i) { |
| thread_pool_.emplace_back(&ThreadPool::ThreadMainLoop, this); |
| } |
| } |
| |
| void ThreadPool::AddTask(const std::function<void()>& func) { |
| task_queue_.Push(func); |
| } |
| |
| int ThreadPool::Size() { |
| std::lock_guard<std::mutex> lock(thread_pool_mutex_); |
| return thread_pool_.size(); |
| } |
| |
| void ThreadPool::ThreadMainLoop() { |
| std::function<void()> task; |
| while (task_queue_.Wait(&task)) { |
| task(); |
| } |
| } |
| |
| void ThreadPool::Stop() { task_queue_.StopWaiters(); } |
| |
| } // namespace ceres::internal |