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// -*- 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/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 @a process an element with __op (depends on

   *  desired functionality, e. g. for std::for_each(), ...).

   *  @param __r Functor to @a 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 _RAIter,

           typename _Op,

           typename _Fu,

           typename _Red,

           typename _Result>

    _Op

    __for_each_template_random_access_omp_loop(_RAIter __begin, _RAIter __end,

                                               _Op __o, _Fu& __f, _Red __r,

                                               _Result __base,

                                               _Result& __output,

      typename std::iterator_traits<_RAIter>::difference_type __bound)

    {

      typedef typename std::iterator_traits<_RAIter>::difference_type

        _DifferenceType;

      _DifferenceType __length = __end - __begin;

      _ThreadIndex __num_threads = __gnu_parallel::min<_DifferenceType>

        (__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 (_ThreadIndex __i = 0; __i < __num_threads; ++__i)

            __thread_results[__i] = _Result();

        }

        _ThreadIndex __iam = omp_get_thread_num();

#pragma omp for schedule(dynamic, _Settings::get().workstealing_chunk_size)

        for (_DifferenceType __pos = 0; __pos < __length; ++__pos)

          __thread_results[__iam] = __r(__thread_results[__iam],

                                        __f(__o, __begin+__pos));

      } //parallel

      for (_ThreadIndex __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._M_finish_iterator = __begin + __length;

      return __o;

    }

} // end namespace

#endif /* _GLIBCXX_PARALLEL_OMP_LOOP_H */