text: // -*- 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/omp_loop.h
   *  @brief Parallelization of embarrassingly parallel execution by
   *  means of an OpenMP for loop.
   *  This file is a GNU parallel extension to the Standard C++ Library.
   */
  
  // Written by Felix Putze.
  
  #ifndef _GLIBCXX_PARALLEL_OMP_LOOP_H
  #define _GLIBCXX_PARALLEL_OMP_LOOP_H 1
  
  #include <omp.h>
  
  #include <parallel/settings.h>
  #include <parallel/basic_iterator.h>
  #include <parallel/base.h>
  
  namespace __gnu_parallel
  {
  /** @brief Embarrassingly parallel algorithm for random access
    * iterators, using an OpenMP for loop.
    *
    *  @param begin Begin iterator of element sequence.
    *  @param end End iterator of element sequence.
    *  @param o User-supplied functor (comparator, predicate, adding
    *  functor, etc.).
    *  @param f Functor to "process" an element with op (depends on
    *  desired functionality, e. g. for std::for_each(), ...).
    *  @param r Functor to "add" a single result to the already
    *  processed elements (depends on functionality).
    *  @param base Base value for reduction.
    *  @param output Pointer to position where final result is written to
    *  @param bound Maximum number of elements processed (e. g. for
    *  std::count_n()).
    *  @return User-supplied functor (that may contain a part of the result).
    */
  template<typename RandomAccessIterator,
  	 typename Op,
  	 typename Fu,
  	 typename Red,
  	 typename Result>
    Op
    for_each_template_random_access_omp_loop(RandomAccessIterator begin,
  					   RandomAccessIterator end,
  					   Op o, Fu& f, Red r, Result base,
  					   Result& output,
  					   typename std::iterator_traits
  					   <RandomAccessIterator>::
  					   difference_type bound)
    {
      typedef typename
          std::iterator_traits<RandomAccessIterator>::difference_type
          difference_type;
  
      difference_type length = end - begin;
      thread_index_t num_threads =
        __gnu_parallel::min<difference_type>(get_max_threads(), length);
  
      Result *thread_results;
  
  #   pragma omp parallel num_threads(num_threads)
        {
  #       pragma omp single
            {
              num_threads = omp_get_num_threads();
              thread_results = new Result[num_threads];
  
              for (thread_index_t i = 0; i < num_threads; ++i)
                thread_results[i] = Result();
            }
  
          thread_index_t iam = omp_get_thread_num();
  
  #      pragma omp for schedule(dynamic, _Settings::get().workstealing_chunk_size)
          for (difference_type pos = 0; pos < length; ++pos)
            thread_results[iam] =
                r(thread_results[iam], f(o, begin+pos));
        } //parallel
  
      for (thread_index_t i = 0; i < num_threads; ++i)
          output = r(output, thread_results[i]);
  
      delete [] thread_results;
  
      // Points to last element processed (needed as return value for
      // some algorithms like transform).
      f.finish_iterator = begin + length;
  
      return o;
    }
  
  } // end namespace
  
  #endif /* _GLIBCXX_PARALLEL_OMP_LOOP_H */
  