--- /dev/null
+// -*- C++ -*-
+
+// Copyright (C) 2007, 2008, 2009, 2010, 2011 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/partial_sum.h
+ * @brief Parallel implementation of std::partial_sum(), i.e. prefix
+* sums.
+ * This file is a GNU parallel extension to the Standard C++ Library.
+ */
+
+// Written by Johannes Singler.
+
+#ifndef _GLIBCXX_PARALLEL_PARTIAL_SUM_H
+#define _GLIBCXX_PARALLEL_PARTIAL_SUM_H 1
+
+#include <omp.h>
+#include <new>
+#include <bits/stl_algobase.h>
+#include <parallel/parallel.h>
+#include <parallel/numericfwd.h>
+
+namespace __gnu_parallel
+{
+ // Problem: there is no 0-element given.
+
+ /** @brief Base case prefix sum routine.
+ * @param __begin Begin iterator of input sequence.
+ * @param __end End iterator of input sequence.
+ * @param __result Begin iterator of output sequence.
+ * @param __bin_op Associative binary function.
+ * @param __value Start value. Must be passed since the neutral
+ * element is unknown in general.
+ * @return End iterator of output sequence. */
+ template<typename _IIter,
+ typename _OutputIterator,
+ typename _BinaryOperation>
+ _OutputIterator
+ __parallel_partial_sum_basecase(_IIter __begin, _IIter __end,
+ _OutputIterator __result,
+ _BinaryOperation __bin_op,
+ typename std::iterator_traits <_IIter>::value_type __value)
+ {
+ if (__begin == __end)
+ return __result;
+
+ while (__begin != __end)
+ {
+ __value = __bin_op(__value, *__begin);
+ *__result = __value;
+ ++__result;
+ ++__begin;
+ }
+ return __result;
+ }
+
+ /** @brief Parallel partial sum implementation, two-phase approach,
+ no recursion.
+ * @param __begin Begin iterator of input sequence.
+ * @param __end End iterator of input sequence.
+ * @param __result Begin iterator of output sequence.
+ * @param __bin_op Associative binary function.
+ * @param __n Length of sequence.
+ * @return End iterator of output sequence.
+ */
+ template<typename _IIter,
+ typename _OutputIterator,
+ typename _BinaryOperation>
+ _OutputIterator
+ __parallel_partial_sum_linear(_IIter __begin, _IIter __end,
+ _OutputIterator __result,
+ _BinaryOperation __bin_op,
+ typename std::iterator_traits<_IIter>::difference_type __n)
+ {
+ typedef std::iterator_traits<_IIter> _TraitsType;
+ typedef typename _TraitsType::value_type _ValueType;
+ typedef typename _TraitsType::difference_type _DifferenceType;
+
+ if (__begin == __end)
+ return __result;
+
+ _ThreadIndex __num_threads =
+ std::min<_DifferenceType>(__get_max_threads(), __n - 1);
+
+ if (__num_threads < 2)
+ {
+ *__result = *__begin;
+ return __parallel_partial_sum_basecase(__begin + 1, __end,
+ __result + 1, __bin_op,
+ *__begin);
+ }
+
+ _DifferenceType* __borders;
+ _ValueType* __sums;
+
+ const _Settings& __s = _Settings::get();
+
+# pragma omp parallel num_threads(__num_threads)
+ {
+# pragma omp single
+ {
+ __num_threads = omp_get_num_threads();
+
+ __borders = new _DifferenceType[__num_threads + 2];
+
+ if (__s.partial_sum_dilation == 1.0f)
+ __equally_split(__n, __num_threads + 1, __borders);
+ else
+ {
+ _DifferenceType __first_part_length =
+ std::max<_DifferenceType>(1,
+ __n / (1.0f + __s.partial_sum_dilation * __num_threads));
+ _DifferenceType __chunk_length =
+ (__n - __first_part_length) / __num_threads;
+ _DifferenceType __borderstart =
+ __n - __num_threads * __chunk_length;
+ __borders[0] = 0;
+ for (_ThreadIndex __i = 1; __i < (__num_threads + 1); ++__i)
+ {
+ __borders[__i] = __borderstart;
+ __borderstart += __chunk_length;
+ }
+ __borders[__num_threads + 1] = __n;
+ }
+
+ __sums = static_cast<_ValueType*>(::operator new(sizeof(_ValueType)
+ * __num_threads));
+ _OutputIterator __target_end;
+ } //single
+
+ _ThreadIndex __iam = omp_get_thread_num();
+ if (__iam == 0)
+ {
+ *__result = *__begin;
+ __parallel_partial_sum_basecase(__begin + 1,
+ __begin + __borders[1],
+ __result + 1,
+ __bin_op, *__begin);
+ ::new(&(__sums[__iam])) _ValueType(*(__result + __borders[1] - 1));
+ }
+ else
+ {
+ ::new(&(__sums[__iam]))
+ _ValueType(__gnu_parallel::accumulate(
+ __begin + __borders[__iam] + 1,
+ __begin + __borders[__iam + 1],
+ *(__begin + __borders[__iam]),
+ __bin_op,
+ __gnu_parallel::sequential_tag()));
+ }
+
+# pragma omp barrier
+
+# pragma omp single
+ __parallel_partial_sum_basecase(__sums + 1, __sums + __num_threads,
+ __sums + 1, __bin_op, __sums[0]);
+
+# pragma omp barrier
+
+ // Still same team.
+ __parallel_partial_sum_basecase(__begin + __borders[__iam + 1],
+ __begin + __borders[__iam + 2],
+ __result + __borders[__iam + 1],
+ __bin_op, __sums[__iam]);
+ } //parallel
+
+ for (_ThreadIndex __i = 0; __i < __num_threads; ++__i)
+ __sums[__i].~_ValueType();
+ ::operator delete(__sums);
+
+ delete[] __borders;
+
+ return __result + __n;
+ }
+
+ /** @brief Parallel partial sum front-__end.
+ * @param __begin Begin iterator of input sequence.
+ * @param __end End iterator of input sequence.
+ * @param __result Begin iterator of output sequence.
+ * @param __bin_op Associative binary function.
+ * @return End iterator of output sequence. */
+ template<typename _IIter,
+ typename _OutputIterator,
+ typename _BinaryOperation>
+ _OutputIterator
+ __parallel_partial_sum(_IIter __begin, _IIter __end,
+ _OutputIterator __result, _BinaryOperation __bin_op)
+ {
+ _GLIBCXX_CALL(__begin - __end)
+
+ typedef std::iterator_traits<_IIter> _TraitsType;
+ typedef typename _TraitsType::value_type _ValueType;
+ typedef typename _TraitsType::difference_type _DifferenceType;
+
+ _DifferenceType __n = __end - __begin;
+
+ switch (_Settings::get().partial_sum_algorithm)
+ {
+ case LINEAR:
+ // Need an initial offset.
+ return __parallel_partial_sum_linear(__begin, __end, __result,
+ __bin_op, __n);
+ default:
+ // Partial_sum algorithm not implemented.
+ _GLIBCXX_PARALLEL_ASSERT(0);
+ return __result + __n;
+ }
+ }
+}
+
+#endif /* _GLIBCXX_PARALLEL_PARTIAL_SUM_H */
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