aboutsummaryrefslogtreecommitdiffstats
path: root/gcc-4.4.3/libstdc++-v3/include/parallel/queue.h
diff options
context:
space:
mode:
Diffstat (limited to 'gcc-4.4.3/libstdc++-v3/include/parallel/queue.h')
-rw-r--r--gcc-4.4.3/libstdc++-v3/include/parallel/queue.h149
1 files changed, 149 insertions, 0 deletions
diff --git a/gcc-4.4.3/libstdc++-v3/include/parallel/queue.h b/gcc-4.4.3/libstdc++-v3/include/parallel/queue.h
new file mode 100644
index 000000000..9686a9ac2
--- /dev/null
+++ b/gcc-4.4.3/libstdc++-v3/include/parallel/queue.h
@@ -0,0 +1,149 @@
+// -*- C++ -*-
+
+// Copyright (C) 2007, 2008, 2009 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 T Contained element type. */
+ template<typename T>
+ class RestrictedBoundedConcurrentQueue
+ {
+ private:
+ /** @brief Array of elements, seen as cyclic buffer. */
+ T* base;
+
+ /** @brief Maximal number of elements contained at the same time. */
+ sequence_index_t max_size;
+
+ /** @brief Cyclic begin and end pointers contained in one
+ atomically changeable value. */
+ _GLIBCXX_VOLATILE lcas_t borders;
+
+ public:
+ /** @brief Constructor. Not to be called concurrent, of course.
+ * @param max_size Maximal number of elements to be contained. */
+ RestrictedBoundedConcurrentQueue(sequence_index_t max_size)
+ {
+ this->max_size = max_size;
+ base = new T[max_size];
+ borders = encode2(0, 0);
+#pragma omp flush
+ }
+
+ /** @brief Destructor. Not to be called concurrent, of course. */
+ ~RestrictedBoundedConcurrentQueue()
+ { delete[] base; }
+
+ /** @brief Pushes one element into the queue at the front end.
+ * Must not be called concurrently with pop_front(). */
+ void
+ push_front(const T& t)
+ {
+ lcas_t former_borders = borders;
+ int former_front, former_back;
+ decode2(former_borders, former_front, former_back);
+ *(base + former_front % max_size) = t;
+#if _GLIBCXX_ASSERTIONS
+ // Otherwise: front - back > max_size eventually.
+ _GLIBCXX_PARALLEL_ASSERT(((former_front + 1) - former_back)
+ <= max_size);
+#endif
+ fetch_and_add(&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(T& t)
+ {
+ int former_front, former_back;
+#pragma omp flush
+ decode2(borders, former_front, former_back);
+ while (former_front > former_back)
+ {
+ // Chance.
+ lcas_t former_borders = encode2(former_front, former_back);
+ lcas_t new_borders = encode2(former_front - 1, former_back);
+ if (compare_and_swap(&borders, former_borders, new_borders))
+ {
+ t = *(base + (former_front - 1) % max_size);
+ return true;
+ }
+#pragma omp flush
+ decode2(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(T& t) //queue behavior
+ {
+ int former_front, former_back;
+#pragma omp flush
+ decode2(borders, former_front, former_back);
+ while (former_front > former_back)
+ {
+ // Chance.
+ lcas_t former_borders = encode2(former_front, former_back);
+ lcas_t new_borders = encode2(former_front, former_back + 1);
+ if (compare_and_swap(&borders, former_borders, new_borders))
+ {
+ t = *(base + former_back % max_size);
+ return true;
+ }
+#pragma omp flush
+ decode2(borders, former_front, former_back);
+ }
+ return false;
+ }
+ };
+} //namespace __gnu_parallel
+
+#undef _GLIBCXX_VOLATILE
+
+#endif /* _GLIBCXX_PARALLEL_QUEUE_H */