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Diffstat (limited to 'extern/ceres/internal/ceres/thread_token_provider.h')
| -rw-r--r-- | extern/ceres/internal/ceres/thread_token_provider.h | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/extern/ceres/internal/ceres/thread_token_provider.h b/extern/ceres/internal/ceres/thread_token_provider.h new file mode 100644 index 00000000000..06dc0438572 --- /dev/null +++ b/extern/ceres/internal/ceres/thread_token_provider.h @@ -0,0 +1,97 @@ +// Ceres Solver - A fast non-linear least squares minimizer +// Copyright 2017 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: yp@photonscore.de (Yury Prokazov) + +#ifndef CERES_INTERNAL_THREAD_TOKEN_PROVIDER_H_ +#define CERES_INTERNAL_THREAD_TOKEN_PROVIDER_H_ + +#include "ceres/internal/config.h" +#include "ceres/internal/port.h" + +#ifdef CERES_USE_CXX_THREADS +#include "ceres/concurrent_queue.h" +#endif + +namespace ceres { +namespace internal { + +// Helper for C++ thread number identification that is similar to +// omp_get_thread_num() behaviour. This is necessary to support C++ +// threading with a sequential thread id. This is used to access preallocated +// resources in the parallelized code parts. The sequence of tokens varies from +// 0 to num_threads - 1 that can be acquired to identify the thread in a thread +// pool. +// +// If CERES_NO_THREADS is defined, Acquire() always returns 0 and Release() +// takes no action. +// +// If CERES_USE_OPENMP, omp_get_thread_num() is used to Acquire() with no action +// in Release() +// +// +// Example usage pseudocode: +// +// ThreadTokenProvider ttp(N); // allocate N tokens +// Spawn N threads { +// int token = ttp.Acquire(); // get unique token +// ... +// ... use token to access resources bound to the thread +// ... +// ttp.Release(token); // return token to the pool +// } +// +class ThreadTokenProvider { + public: + ThreadTokenProvider(int num_threads); + + // Returns the first token from the queue. The acquired value must be + // given back by Release(). + int Acquire(); + + // Makes previously acquired token available for other threads. + void Release(int thread_id); + + private: +#ifdef CERES_USE_CXX_THREADS + // This queue initially holds a sequence from 0..num_threads-1. Every + // Acquire() call the first number is removed from here. When the token is not + // needed anymore it shall be given back with corresponding Release() + // call. This concurrent queue is more expensive than TBB's version, so you + // should not acquire the thread ID on every for loop iteration. + ConcurrentQueue<int> pool_; +#endif + + ThreadTokenProvider(ThreadTokenProvider&); + ThreadTokenProvider& operator=(ThreadTokenProvider&); +}; + +} // namespace internal +} // namespace ceres + +#endif // CERES_INTERNAL_THREAD_TOKEN_PROVIDER_H_ |