11.2.0/parallel/queue.h

// -*- C++ -*-

// Copyright (C) 2007-2021 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 __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_PARALLEL_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 */
Revision:	1166
Committed:	Tue Oct 26 14:22:36 2021 UTC (4 years ago) by rossy
Content type:	text/x-chdr
File size:	5542 byte(s)
Log Message:	Daodan: Replace MinGW build env with an up-to-date MSYS2 env
#	Content
1	// -- C++ --
2
3	// Copyright (C) 2007-2021 Free Software Foundation, Inc.
4	//
5	// This file is part of the GNU ISO C++ Library. This library is free
6	// software; you can redistribute it and/or modify it under the terms
7	// of the GNU General Public License as published by the Free Software
8	// Foundation; either version 3, or (at your option) any later
9	// version.
10
11	// This library is distributed in the hope that it will be useful, but
12	// WITHOUT ANY WARRANTY; without even the implied warranty of
13	// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14	// General Public License for more details.
15
16	// Under Section 7 of GPL version 3, you are granted additional
17	// permissions described in the GCC Runtime Library Exception, version
18	// 3.1, as published by the Free Software Foundation.
19
20	// You should have received a copy of the GNU General Public License and
21	// a copy of the GCC Runtime Library Exception along with this program;
22	// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23	// <http://www.gnu.org/licenses/>.
24
25	/** @file parallel/queue.h
26	* @brief Lock-free double-ended queue.
27	* This file is a GNU parallel extension to the Standard C++ Library.
28	*/
29
30	// Written by Johannes Singler.
31
32	#ifndef _GLIBCXX_PARALLEL_QUEUE_H
33	#define _GLIBCXX_PARALLEL_QUEUE_H 1
34
35	#include <parallel/types.h>
36	#include <parallel/base.h>
37	#include <parallel/compatibility.h>
38
39	/** @brief Decide whether to declare certain variable volatile in this file. */
40	#define _GLIBCXX_VOLATILE volatile
41
42	namespace __gnu_parallel
43	{
44	/**@brief Double-ended queue of bounded size, allowing lock-free
45	* atomic access. push_front() and pop_front() must not be called
46	* concurrently to each other, while pop_back() can be called
47	* concurrently at all times.
48	* @c empty(), @c size(), and @c top() are intentionally not provided.
49	* Calling them would not make sense in a concurrent setting.
50	* @param _Tp Contained element type. */
51	template<typename _Tp>
52	class _RestrictedBoundedConcurrentQueue
53	{
54	private:
55	/** @brief Array of elements, seen as cyclic buffer. */
56	_Tp* _M_base;
57
58	/** @brief Maximal number of elements contained at the same time. */
59	_SequenceIndex _M_max_size;
60
61	/** @brief Cyclic __begin and __end pointers contained in one
62	atomically changeable value. */
63	_GLIBCXX_VOLATILE _CASable _M_borders;
64
65	public:
66	/** @brief Constructor. Not to be called concurrent, of course.
67	* @param __max_size Maximal number of elements to be contained. */
68	_RestrictedBoundedConcurrentQueue(_SequenceIndex __max_size)
69	{
70	_M_max_size = __max_size;
71	_M_base = new _Tp[__max_size];
72	_M_borders = __encode2(0, 0);
73	#pragma omp flush
74	}
75
76	/** @brief Destructor. Not to be called concurrent, of course. */
77	~_RestrictedBoundedConcurrentQueue()
78	{ delete[] _M_base; }
79
80	/** @brief Pushes one element into the queue at the front end.
81	* Must not be called concurrently with pop_front(). */
82	void
83	push_front(const _Tp& __t)
84	{
85	_CASable __former_borders = _M_borders;
86	int __former_front, __former_back;
87	__decode2(__former_borders, __former_front, __former_back);
88	*(_M_base + __former_front % _M_max_size) = __t;
89	#if _GLIBCXX_PARALLEL_ASSERTIONS
90	// Otherwise: front - back > _M_max_size eventually.
91	_GLIBCXX_PARALLEL_ASSERT(((__former_front + 1) - __former_back)
92	<= _M_max_size);
93	#endif
94	__fetch_and_add(&_M_borders, __encode2(1, 0));
95	}
96
97	/** @brief Pops one element from the queue at the front end.
98	* Must not be called concurrently with pop_front(). */
99	bool
100	pop_front(_Tp& __t)
101	{
102	int __former_front, __former_back;
103	#pragma omp flush
104	__decode2(_M_borders, __former_front, __former_back);
105	while (__former_front > __former_back)
106	{
107	// Chance.
108	_CASable __former_borders = __encode2(__former_front,
109	__former_back);
110	_CASable __new_borders = __encode2(__former_front - 1,
111	__former_back);
112	if (__compare_and_swap(&_M_borders, __former_borders,
113	__new_borders))
114	{
115	__t = *(_M_base + (__former_front - 1) % _M_max_size);
116	return true;
117	}
118	#pragma omp flush
119	__decode2(_M_borders, __former_front, __former_back);
120	}
121	return false;
122	}
123
124	/** @brief Pops one element from the queue at the front end.
125	* Must not be called concurrently with pop_front(). */
126	bool
127	pop_back(_Tp& __t) //queue behavior
128	{
129	int __former_front, __former_back;
130	#pragma omp flush
131	__decode2(_M_borders, __former_front, __former_back);
132	while (__former_front > __former_back)
133	{
134	// Chance.
135	_CASable __former_borders = __encode2(__former_front,
136	__former_back);
137	_CASable __new_borders = __encode2(__former_front,
138	__former_back + 1);
139	if (__compare_and_swap(&_M_borders, __former_borders,
140	__new_borders))
141	{
142	__t = *(_M_base + __former_back % _M_max_size);
143	return true;
144	}
145	#pragma omp flush
146	__decode2(_M_borders, __former_front, __former_back);
147	}
148	return false;
149	}
150	};
151	} //namespace __gnu_parallel
152
153	#undef _GLIBCXX_VOLATILE
154
155	#endif /* _GLIBCXX_PARALLEL_QUEUE_H */