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Diffstat (limited to 'libstdc++-v3/include/parallel/queue.h')
| -rw-r--r-- | libstdc++-v3/include/parallel/queue.h | 155 |
1 files changed, 155 insertions, 0 deletions
diff --git a/libstdc++-v3/include/parallel/queue.h b/libstdc++-v3/include/parallel/queue.h new file mode 100644 index 000000000..03c1c78bb --- /dev/null +++ b/libstdc++-v3/include/parallel/queue.h @@ -0,0 +1,155 @@ +// -*- C++ -*- + +// Copyright (C) 2007, 2008, 2009, 2010 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the terms +// of the GNU General Public License as published by the Free Software +// Foundation; either version 3, or (at your option) any later +// version. + +// This library is distributed in the hope that it will be useful, but +// WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +// General Public License for more details. + +// Under Section 7 of GPL version 3, you are granted additional +// permissions described in the GCC Runtime Library Exception, version +// 3.1, as published by the Free Software Foundation. + +// You should have received a copy of the GNU General Public License and +// a copy of the GCC Runtime Library Exception along with this program; +// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see +// <http://www.gnu.org/licenses/>. + +/** @file parallel/queue.h + * @brief Lock-free double-ended queue. + * This file is a GNU parallel extension to the Standard C++ Library. + */ + +// Written by Johannes Singler. + +#ifndef _GLIBCXX_PARALLEL_QUEUE_H +#define _GLIBCXX_PARALLEL_QUEUE_H 1 + +#include <parallel/types.h> +#include <parallel/base.h> +#include <parallel/compatibility.h> + +/** @brief Decide whether to declare certain variable volatile in this file. */ +#define _GLIBCXX_VOLATILE volatile + +namespace __gnu_parallel +{ + /**@brief Double-ended queue of bounded size, allowing lock-free + * atomic access. push_front() and pop_front() must not be called + * concurrently to each other, while pop_back() can be called + * concurrently at all times. + * @c empty(), @c size(), and @c top() are intentionally not provided. + * Calling them would not make sense in a concurrent setting. + * @param _Tp Contained element type. */ + template<typename _Tp> + class _RestrictedBoundedConcurrentQueue + { + private: + /** @brief Array of elements, seen as cyclic buffer. */ + _Tp* _M_base; + + /** @brief Maximal number of elements contained at the same time. */ + _SequenceIndex _M_max_size; + + /** @brief Cyclic __begin and __end pointers contained in one + atomically changeable value. */ + _GLIBCXX_VOLATILE _CASable _M_borders; + + public: + /** @brief Constructor. Not to be called concurrent, of course. + * @param _M_max_size Maximal number of elements to be contained. */ + _RestrictedBoundedConcurrentQueue(_SequenceIndex __max_size) + { + _M_max_size = __max_size; + _M_base = new _Tp[__max_size]; + _M_borders = __encode2(0, 0); +#pragma omp flush + } + + /** @brief Destructor. Not to be called concurrent, of course. */ + ~_RestrictedBoundedConcurrentQueue() + { delete[] _M_base; } + + /** @brief Pushes one element into the queue at the front end. + * Must not be called concurrently with pop_front(). */ + void + push_front(const _Tp& __t) + { + _CASable __former_borders = _M_borders; + int __former_front, __former_back; + __decode2(__former_borders, __former_front, __former_back); + *(_M_base + __former_front % _M_max_size) = __t; +#if _GLIBCXX_ASSERTIONS + // Otherwise: front - back > _M_max_size eventually. + _GLIBCXX_PARALLEL_ASSERT(((__former_front + 1) - __former_back) + <= _M_max_size); +#endif + __fetch_and_add(&_M_borders, __encode2(1, 0)); + } + + /** @brief Pops one element from the queue at the front end. + * Must not be called concurrently with pop_front(). */ + bool + pop_front(_Tp& __t) + { + int __former_front, __former_back; +#pragma omp flush + __decode2(_M_borders, __former_front, __former_back); + while (__former_front > __former_back) + { + // Chance. + _CASable __former_borders = __encode2(__former_front, + __former_back); + _CASable __new_borders = __encode2(__former_front - 1, + __former_back); + if (__compare_and_swap(&_M_borders, __former_borders, + __new_borders)) + { + __t = *(_M_base + (__former_front - 1) % _M_max_size); + return true; + } +#pragma omp flush + __decode2(_M_borders, __former_front, __former_back); + } + return false; + } + + /** @brief Pops one element from the queue at the front end. + * Must not be called concurrently with pop_front(). */ + bool + pop_back(_Tp& __t) //queue behavior + { + int __former_front, __former_back; +#pragma omp flush + __decode2(_M_borders, __former_front, __former_back); + while (__former_front > __former_back) + { + // Chance. + _CASable __former_borders = __encode2(__former_front, + __former_back); + _CASable __new_borders = __encode2(__former_front, + __former_back + 1); + if (__compare_and_swap(&_M_borders, __former_borders, + __new_borders)) + { + __t = *(_M_base + __former_back % _M_max_size); + return true; + } +#pragma omp flush + __decode2(_M_borders, __former_front, __former_back); + } + return false; + } + }; +} //namespace __gnu_parallel + +#undef _GLIBCXX_VOLATILE + +#endif /* _GLIBCXX_PARALLEL_QUEUE_H */ |