mirror of
https://github.com/ceres-solver/ceres-solver.git
synced 2026-08-29 16:40:38 +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
84 lines
3.5 KiB
C++
84 lines
3.5 KiB
C++
// Ceres Solver - A fast non-linear least squares minimizer
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// Copyright 2017 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: yp@photonscore.de (Yury Prokazov)
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#ifndef CERES_INTERNAL_THREAD_TOKEN_PROVIDER_H_
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#define CERES_INTERNAL_THREAD_TOKEN_PROVIDER_H_
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#include "ceres/concurrent_queue.h"
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#include "ceres/internal/config.h"
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#include "ceres/internal/export.h"
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namespace ceres::internal {
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// Helper for C++ thread number identification that is similar to
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// omp_get_thread_num() behaviour. This is necessary to support C++
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// threading with a sequential thread id. This is used to access preallocated
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// resources in the parallelized code parts. The sequence of tokens varies from
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// 0 to num_threads - 1 that can be acquired to identify the thread in a thread
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// pool.
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//
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//
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// Example usage pseudocode:
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//
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// ThreadTokenProvider ttp(N); // allocate N tokens
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// Spawn N threads {
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// int token = ttp.Acquire(); // get unique token
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// ...
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// ... use token to access resources bound to the thread
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// ...
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// ttp.Release(token); // return token to the pool
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// }
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//
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class CERES_NO_EXPORT ThreadTokenProvider {
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public:
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explicit ThreadTokenProvider(int num_threads);
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// Returns the first token from the queue. The acquired value must be
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// given back by Release().
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int Acquire();
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// Makes previously acquired token available for other threads.
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void Release(int thread_id);
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private:
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// This queue initially holds a sequence from 0..num_threads-1. Every
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// Acquire() call the first number is removed from here. When the token is not
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// needed anymore it shall be given back with corresponding Release()
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// call. This concurrent queue is more expensive than TBB's version, so you
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// should not acquire the thread ID on every for loop iteration.
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ConcurrentQueue<int> pool_;
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ThreadTokenProvider(ThreadTokenProvider&) = delete;
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ThreadTokenProvider& operator=(ThreadTokenProvider&) = delete;
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};
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} // namespace ceres::internal
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#endif // CERES_INTERNAL_THREAD_TOKEN_PROVIDER_H_
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