mirror of
https://github.com/ceres-solver/ceres-solver.git
synced 2026-08-30 00:50:37 +08:00
Sameer Agarwal
06bfe6ffac
Since c++11, we can depend on C++ threads always being available. With the recent work on the performance of CXX threading, the additional complexity of maintaining multiple backends for some minor performance delta is not worth it https://github.com/ceres-solver/ceres-solver/issues/886 Change-Id: Idee480b22a498daec9c4366da8589aa58eaf36a1
105 lines
3.5 KiB
C++
105 lines
3.5 KiB
C++
// Ceres Solver - A fast non-linear least squares minimizer
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// Copyright 2018 Google Inc. All rights reserved.
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// http://ceres-solver.org/
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are met:
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//
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// * Redistributions of source code must retain the above copyright notice,
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// this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above copyright notice,
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// this list of conditions and the following disclaimer in the documentation
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// and/or other materials provided with the distribution.
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// * Neither the name of Google Inc. nor the names of its contributors may be
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// used to endorse or promote products derived from this software without
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// specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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// 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
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// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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// POSSIBILITY OF SUCH DAMAGE.
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//
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// Author: vitus@google.com (Michael Vitus)
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#include "ceres/thread_pool.h"
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#include <cmath>
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#include <limits>
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#include "ceres/internal/config.h"
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namespace ceres::internal {
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namespace {
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// Constrain the total number of threads to the amount the hardware can support.
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int GetNumAllowedThreads(int requested_num_threads) {
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return std::min(requested_num_threads, ThreadPool::MaxNumThreadsAvailable());
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}
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} // namespace
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int ThreadPool::MaxNumThreadsAvailable() {
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const int num_hardware_threads = std::thread::hardware_concurrency();
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// hardware_concurrency() can return 0 if the value is not well defined or not
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// computable.
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return num_hardware_threads == 0 ? std::numeric_limits<int>::max()
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: num_hardware_threads;
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}
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ThreadPool::ThreadPool() = default;
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ThreadPool::ThreadPool(int num_threads) { Resize(num_threads); }
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ThreadPool::~ThreadPool() {
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std::lock_guard<std::mutex> lock(thread_pool_mutex_);
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// Signal the thread workers to stop and wait for them to finish all scheduled
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// tasks.
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Stop();
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for (std::thread& thread : thread_pool_) {
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thread.join();
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}
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}
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void ThreadPool::Resize(int num_threads) {
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std::lock_guard<std::mutex> lock(thread_pool_mutex_);
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const int num_current_threads = thread_pool_.size();
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if (num_current_threads >= num_threads) {
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return;
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}
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const int create_num_threads =
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GetNumAllowedThreads(num_threads) - num_current_threads;
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for (int i = 0; i < create_num_threads; ++i) {
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thread_pool_.emplace_back(&ThreadPool::ThreadMainLoop, this);
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}
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}
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void ThreadPool::AddTask(const std::function<void()>& func) {
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task_queue_.Push(func);
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}
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int ThreadPool::Size() {
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std::lock_guard<std::mutex> lock(thread_pool_mutex_);
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return thread_pool_.size();
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}
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void ThreadPool::ThreadMainLoop() {
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std::function<void()> task;
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while (task_queue_.Wait(&task)) {
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task();
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}
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}
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void ThreadPool::Stop() { task_queue_.StopWaiters(); }
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} // namespace ceres::internal
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