ypename Comparator>
  RandomAccessIterator3
  multiway_merge_loser_tree_unguarded(
    RandomAccessIteratorIterator seqs_begin,
    RandomAccessIteratorIterator seqs_end,
    RandomAccessIterator3 target,
    const typename std::iterator_traits<typename std::iterator_traits<
      RandomAccessIteratorIterator>::value_type::first_type>::value_type&
        sentinel,
    Comparator comp,
    _DifferenceTp length)
  {
    _GLIBCXX_CALL(length)
    typedef _DifferenceTp difference_type;

    typedef typename std::iterator_traits<RandomAccessIteratorIterator>
      ::value_type::first_type
      RandomAccessIterator1;
    typedef typename std::iterator_traits<RandomAccessIterator1>::value_type
      value_type;

    int k = seqs_end - seqs_begin;

    LT lt(k, sentinel, comp);

    for (int t = 0; t < k; ++t)
      {
#if _GLIBCXX_ASSERTIONS
        _GLIBCXX_PARALLEL_ASSERT(seqs_begin[t].first != seqs_begin[t].second);
#endif
        lt.insert_start(*seqs_begin[t].first, t, false);
      }

    lt.init();

    int source;

#if _GLIBCXX_ASSERTIONS
    difference_type i = 0;
#endif

    RandomAccessIterator3 target_end = target + length;
    while (target < target_end)
      {
        // Take out.
        source = lt.get_min_source();

#if _GLIBCXX_ASSERTIONS
        _GLIBCXX_PARALLEL_ASSERT(0 <= source && source < k);
        _GLIBCXX_PARALLEL_ASSERT(i == 0
            || !comp(*(seqs_begin[source].first), *(target - 1)));
#endif

        // Feed.
        *(target++) = *(seqs_begin[source].first++);

#if _GLIBCXX_ASSERTIONS
        ++i;
#endif
        // Replace from same source.
        lt.delete_min_insert(*seqs_begin[source].first, false);
      }

    return target;
  }


/** @brief Multi-way merging procedure for a high branching factor,
 *         requiring sentinels to exist.
 *
 * @param stable The value must the same as for the used LoserTrees.
 * @param UnguardedLoserTree Loser Tree variant to use for the unguarded
 *   merging.
 * @param GuardedLoserTree Loser Tree variant to use for the guarded
 *   merging.
 *
 * @param seqs_begin Begin iterator of iterator pair input sequence.
 * @param seqs_end End iterator of iterator pair input sequence.
 * @param target Begin iterator out output sequence.
 * @param comp Comparator.
 * @param length Maximum length to merge, less equal than the
 * total number of elements available.
 *
 * @return End iterator of output sequence.
 */
template<
    typename UnguardedLoserTree,
    typename RandomAccessIteratorIterator,
    typename RandomAccessIterator3,
    typename _DifferenceTp,
    typename Comparator>
  RandomAccessIterator3
  multiway_merge_loser_tree_sentinel(
    RandomAccessIteratorIterator seqs_begin,
    RandomAccessIteratorIterator seqs_end,
    RandomAccessIterator3 target,
    const typename std::iterator_traits<typename std::iterator_traits<
      RandomAccessIteratorIterator>::value_type::first_type>::value_type&
        sentinel,
    Comparator comp,
    _DifferenceTp length)
  {
    _GLIBCXX_CALL(length)

    typedef _DifferenceTp difference_type;
    typedef std::iterator_traits<RandomAccessIteratorIterator> traits_type;
    typedef typename std::iterator_traits<RandomAccessIteratorIterator>
      ::value_type::first_type
      RandomAccessIterator1;
    typedef typename std::iterator_traits<RandomAccessIterator1>::value_type
      value_type;

    RandomAccessIterator3 target_end;

    for (RandomAccessIteratorIterator s = seqs_begin; s != seqs_end; ++s)
      // Move the sequends end behind the sentinel spots.  This has the
      // effect that the sentinel appears to be within the sequence. Then,
      // we can use the unguarded variant if we merge out as many
      // non-sentinel elements as we have.
      ++((*s).second);

    target_end = multiway_merge_loser_tree_unguarded
        <UnguardedLoserTree>
      (seqs_begin, seqs_end, target, sentinel, comp, length);

#if _GLIBCXX_ASSERTIONS
    _GLIBCXX_PARALLEL_ASSERT(target_end == target + length);
    _GLIBCXX_PARALLEL_ASSERT(is_sorted(target, target_end, comp));
#endif

    // Restore the sequence ends so the sentinels are not contained in the
    // sequence any more (see comment in loop above).
    for (RandomAccessIteratorIterator s = seqs_begin; s != seqs_end; ++s)
      --((*s).second);

    return target_end;
  }

/**
 * @brief Traits for determining whether the loser tree should
 *   use pointers or copies.
 *
 * The field "use_pointer" is used to determine whether to use pointers in
 * the loser trees or whether to copy the values into the loser tree.
 *
 * The default behavior is to use pointers if the data type is 4 times as
 * big as the pointer to it.
 *
 * Specialize for your data type to customize the behavior.
 *
 * Example:
 *
 *   template<>
 *   struct loser_tree_traits<int>
 *   { static const bool use_pointer = false; };
 *
 *   template<>
 *   struct loser_tree_traits<heavyweight_type>
 *   { static const bool use_pointer = true; };
 *
 * @param T type to give the loser tree traits for.
 */
template <typename T>
struct loser_tree_traits
{
  /**
   * @brief True iff to use pointers instead of values in loser trees.
   *
   * The default behavior is to use pointers if the data type is four
   * times as big as the pointer to it.
   */
  static const bool use_pointer = (sizeof(T) > 4 * sizeof(T*));
};

/**
 * @brief Switch for 3-way merging with sentinels turned off.
 *
 * Note that 3-way merging is always stable!
 */
template<
  bool sentinels /*default == false*/,
  typename RandomAccessIteratorIterator,
  typename RandomAccessIterator3,
  typename _DifferenceTp,
  typename Comparator>
struct multiway_merge_3_variant_sentinel_switch
{
  RandomAccessIterator3 operator()(
      RandomAccessIteratorIterator seqs_begin,
      RandomAccessIteratorIterator seqs_end,
      RandomAccessIterator3 target,
      Comparator comp, _DifferenceTp length)
  {
    return multiway_merge_3_variant<guarded_iterator>(
        seqs_begin, seqs_end, target, comp, length);
  }
};

/**
 * @brief Switch for 3-way merging with sentinels turned on.
 *
 * Note that 3-way merging is always stable!
 */
template<
  typename RandomAccessIteratorIterator,
  typename RandomAccessIterator3,
  typename _DifferenceTp,
  typename Comparator>
struct multiway_merge_3_variant_sentinel_switch
    <true, RandomAccessIteratorIterator, RandomAccessIterator3,
     _DifferenceTp, Comparator>
{
  RandomAccessIterator3 operator()(
      RandomAccessIteratorIterator seqs_begin,
      RandomAccessIteratorIterator seqs_end,
      RandomAccessIterator3 target,
      Comparator comp, _DifferenceTp length)
  {
    return multiway_merge_3_variant<unguarded_iterator>(
        seqs_begin, seqs_end, target, comp, length);
  }
};

/**
 * @brief Switch for 4-way merging with sentinels turned off.
 *
 * Note that 4-way merging is always stable!
 */
template<
  bool sentinels /*default == false*/,
  typename RandomAccessIteratorIterator,
  typename RandomAccessIterator3,
  typename _DifferenceTp,
  typename Comparator>
struct multiway_merge_4_variant_sentinel_switch
{
  RandomAccessIterator3 operator()(
      RandomAccessIteratorIterator seqs_begin,
      RandomAccessIteratorIterator seqs_end,
      RandomAccessIterator3 target,
      Comparator comp, _DifferenceTp length)
  {
    return multiway_merge_4_variant<guarded_iterator>(
        seqs_begin, seqs_end, target, comp, length);
  }
};

/**
 * @brief Switch for 4-way merging with sentinels turned on.
 *
 * Note that 4-way merging is always stable!
 */
template<
  typename RandomAccessIteratorIterator,
  typename RandomAccessIterator3,
  typename _DifferenceTp,
  typename Comparator>
struct multiway_merge_4_variant_sentinel_switch
    <true, RandomAccessIteratorIterator, RandomAccessIterator3,
     _DifferenceTp, Comparator>
{
  RandomAccessIterator3 operator()(
      RandomAccessIteratorIterator seqs_begin,
      RandomAccessIteratorIterator seqs_end,
      RandomAccessIterator3 target,
      Comparator comp, _DifferenceTp length)
  {
    return multiway_merge_4_variant<unguarded_iterator>(
        seqs_begin, seqs_end, target, comp, length);
  }
};

/**
 * @brief Switch for k-way merging with sentinels turned on.
 */
template<
  bool sentinels,
  bool stable,
  typename RandomAccessIteratorIterator,
  typename RandomAccessIterator3,
  typename _DifferenceTp,
  typename Comparator>
struct multiway_merge_k_variant_sentinel_switch
{
  RandomAccessIterator3 operator()(
      RandomAccessIteratorIterator seqs_begin,
      RandomAccessIteratorIterator seqs_end,
      RandomAccessIterator3 target,
      const typename std::iterator_traits<typename std::iterator_traits<
        RandomAccessIteratorIterator>::value_type::first_type>::value_type&
          sentinel,
      Comparator comp, _DifferenceTp length)
  {
    typedef typename std::iterator_traits<RandomAccessIteratorIterator>
      ::value_type::first_type
      RandomAccessIterator1;
    typedef typename std::iterator_traits<RandomAccessIterator1>::value_type
      value_type;

    return multiway_merge_loser_tree_sentinel<
        typename __gnu_cxx::__conditional_type<
            loser_tree_traits<value_type>::use_pointer
          , LoserTreePointerUnguarded<stable, value_type, Comparator>
          , LoserTreeUnguarded<stable, value_type, Comparator>
        >::__type>(seqs_begin, seqs_end, target, sentinel, comp, length);
  }
};

/**
 * @brief Switch for k-way merging with sentinels turned off.
 */
template<
  bool stable,
  typename RandomAccessIteratorIterator,
  typename RandomAccessIterator3,
  typename _DifferenceTp,
  typename Comparator>
struct multiway_merge_k_variant_sentinel_switch
    <false, stable, RandomAccessIteratorIterator, RandomAccessIterator3,
     _DifferenceTp, Comparator>
{
  RandomAccessIterator3 operator()(
      RandomAccessIteratorIterator seqs_begin,
      RandomAccessIteratorIterator seqs_end,
      RandomAccessIterator3 target,
      const typename std::iterator_traits<typename std::iterator_traits<
        RandomAccessIteratorIterator>::value_type::first_type>::value_type&
          sentinel,
      Comparator comp, _DifferenceTp length)
  {
    typedef typename std::iterator_traits<RandomAccessIteratorIterator>
      ::value_type::first_type
      RandomAccessIterator1;
    typedef typename std::iterator_traits<RandomAccessIterator1>::value_type
      value_type;

    return multiway_merge_loser_tree<
        typename __gnu_cxx::__conditional_type<
            loser_tree_traits<value_type>::use_pointer
          , LoserTreePointer<stable, value_type, Comparator>
          , LoserTree<stable, value_type, Comparator>
        >::__type >(seqs_begin, seqs_end, target, comp, length);
  }
};

/** @brief Sequential multi-way merging switch.
 *
 *  The _GLIBCXX_PARALLEL_DECISION is based on the branching factor and
 *  runtime settings.
 *  @param seqs_begin Begin iterator of iterator pair input sequence.
 *  @param seqs_end End iterator of iterator pair input sequence.
 *  @param target Begin iterator out output sequence.
 *  @param comp Comparator.
 *  @param length Maximum length to merge, possibly larger than the
 *  number of elements available.
 *  @param stable Stable merging incurs a performance penalty.
 *  @param sentinel The sequences have a sentinel element.
 *  @return End iterator of output sequence. */
template<
    bool stable,
    bool sentinels,
    typename RandomAccessIteratorIterator,
    typename RandomAccessIterator3,
    typename _DifferenceTp,
    typename Comparator>
  RandomAccessIterator3
  sequential_multiway_merge(
    RandomAccessIteratorIterator seqs_begin,
    RandomAccessIteratorIterator seqs_end,
    RandomAccessIterator3 target,
    const typename std::iterator_traits<typename std::iterator_traits<
      RandomAccessIteratorIterator>::value_type::first_type>::value_type&
        sentinel,
    Comparator comp, _DifferenceTp length)
  {
    _GLIBCXX_CALL(length)

    typedef _DifferenceTp difference_type;
    typedef typename std::iterator_traits<RandomAccessIteratorIterator>
      ::value_type::first_type
      RandomAccessIterator1;
    typedef typename std::iterator_traits<RandomAccessIterator1>::value_type
      value_type;

#if _GLIBCXX_ASSERTIONS
    for (RandomAccessIteratorIterator s = seqs_begin; s != seqs_end; ++s)
      {
        _GLIBCXX_PARALLEL_ASSERT(is_sorted((*s).first, (*s).second, comp));
      }
#endif

    _DifferenceTp total_length = 0;
    for (RandomAccessIteratorIterator s = seqs_begin; s != seqs_end; ++s)
      total_length += _GLIBCXX_PARALLEL_LENGTH(*s);

    length = std::min<_DifferenceTp>(length, total_length);

    if(length == 0)
      return target;

    RandomAccessIterator3 return_target = target;
    int k = static_cast<int>(seqs_end - seqs_begin);

    switch (k)
      {
      case 0:
        break;
      case 1:
        return_target = std::copy(seqs_begin[0].first,
                                  seqs_begin[0].first + length,
                                  target);
        seqs_begin[0].first += length;
        break;
      case 2:
        return_target = merge_advance(seqs_begin[0].first,
                                      seqs_begin[0].second,
                                      seqs_begin[1].first,
                                      seqs_begin[1].second,
                                      target, length, comp);
        break;
      case 3:
        return_target = multiway_merge_3_variant_sentinel_switch<
            sentinels
          , RandomAccessIteratorIterator
          , RandomAccessIterator3
          , _DifferenceTp
          , Comparator>()(seqs_begin, seqs_end, target, comp, length);
        break;
      case 4:
        return_target = multiway_merge_4_variant_sentinel_switch<
            sentinels
          , RandomAccessIteratorIterator
          , RandomAccessIterator3
          , _DifferenceTp
          , Comparator>()(seqs_begin, seqs_end, target, comp, length);
        break;
      default:
          return_target = multiway_merge_k_variant_sentinel_switch<
              sentinels
            , stable
            , RandomAccessIteratorIterator
            , RandomAccessIterator3
            , _DifferenceTp
            , Comparator>()
                (seqs_begin, seqs_end, target, sentinel, comp, length);
          break;
      }
#if _GLIBCXX_ASSERTIONS
    _GLIBCXX_PARALLEL_ASSERT(is_sorted(target, target + length, comp));
#endif

    return return_target;
  }

/**
 * @brief Stable sorting functor.
 *
 * Used to reduce code instanciation in multiway_merge_sampling_splitting.
 */
template<bool stable, class RandomAccessIterator, class StrictWeakOrdering>
struct sampling_sorter
{
  void operator()(RandomAccessIterator first, RandomAccessIterator last,
                  StrictWeakOrdering comp)
  { __gnu_sequential::stable_sort(first, last, comp); }
};

/**
 * @brief Non-stable sorting functor.
 *
 * Used to reduce code instantiation in multiway_merge_sampling_splitting.
 */
template<class RandomAccessIterator, class StrictWeakOrdering>
struct sampling_sorter<false, RandomAccessIterator, StrictWeakOrdering>
{
  void operator()(RandomAccessIterator first, RandomAccessIterator last,
                  StrictWeakOrdering comp)
  { __gnu_sequential::sort(first, last, comp); }
};

/**
 * @brief Sampling based splitting for parallel multiway-merge routine.
 */
template<
    bool stable
  , typename RandomAccessIteratorIterator
  , typename Comparator
  , typename difference_type>
void multiway_merge_sampling_splitting(
    RandomAccessIteratorIterator seqs_begin,
    RandomAccessIteratorIterator seqs_end,
    Comparator comp, difference_type length,
    difference_type total_length,
    std::vector<std::pair<difference_type, difference_type> > *pieces)
{
  typedef typename std::iterator_traits<RandomAccessIteratorIterator>
    ::value_type::first_type
    RandomAccessIterator1;
  typedef typename std::iterator_traits<RandomAccessIterator1>::value_type
    value_type;

  // k sequences.
  int k = static_cast<int>(seqs_end - seqs_begin);

  int num_threads = omp_get_num_threads();

  difference_type num_samples =
      __gnu_parallel::_Settings::get().merge_oversampling * num_threads;

  value_type* samples = static_cast<value_type*>(
    ::operator new(sizeof(value_type) * k * num_samples));
  // Sample.
  for (int s = 0; s < k; ++s)
    for (difference_type i = 0; i < num_samples; ++i)
      {
        difference_type sample_index =
            static_cast<difference_type>(
                _GLIBCXX_PARALLEL_LENGTH(seqs_begin[s])
                    * (double(i + 1) / (num_samples + 1))
                    * (double(length) / total_length));
        new(&(samples[s * num_samples + i]))
            value_type(seqs_begin[s].first[sample_index]);
      }

  // Sort stable or non-stable, depending on value of template parameter
  // "stable".
  sampling_sorter<stable, value_type*, Comparator>()(
      samples, samples + (num_samples * k), comp);

  for (int slab = 0; slab < num_threads; ++slab)
    // For each slab / processor.
    for (int seq = 0; seq < k; ++seq)
      {
        // For each sequence.
        if (slab > 0)
          pieces[slab][seq].first =
              std::upper_bound(
                seqs_begin[seq].first,
                seqs_begin[seq].second,
                samples[num_samples * k * slab / num_threads],
                  comp)
              - seqs_begin[seq].first;
        else
          // Absolute beginning.
          pieces[slab][seq].first = 0;
        if ((slab + 1) < num_threads)
          pieces[slab][seq].second =
              std::upper_bound(
                  seqs_begin[seq].first,
                  seqs_begin[seq].second,
                  samples[num_samples * k * (slab + 1) /
                      num_threads], comp)
              - seqs_begin[seq].first;
        else
            // Absolute end.
          pieces[slab][seq].second = _GLIBCXX_PARALLEL_LENGTH(seqs_begin[seq]);
      }
    ::operator delete(samples);
}

/**
 * @brief Exact splitting for parallel multiway-merge routine.
 *
 * None of the passed sequences may be empty.
 */
template<
    bool stable
  , typename RandomAccessIteratorIterator
  , typename Comparator
  , typename difference_type>
void multiway_merge_exact_splitting(
    RandomAccessIteratorIterator seqs_begin,
    RandomAccessIteratorIterator seqs_end,
    Comparator comp,
    difference_type length,
    difference_type total_length,
    std::vector<std::pair<difference_type, difference_type> > *pieces)
{
  typedef typename std::iterator_traits<RandomAccessIteratorIterator>
    ::value_type::first_type
    RandomAccessIterator1;

  const bool tight = (total_length == length);

  // k sequences.
  const int k = static_cast<int>(seqs_end - seqs_begin);

  const int num_threads = omp_get_num_threads();

  // (Settings::multiway_merge_splitting == __gnu_parallel::_Settings::EXACT).
  std::vector<RandomAccessIterator1>* offsets =
      new std::vector<RandomAccessIterator1>[num_threads];
  std::vector<
      std::pair<RandomAccessIterator1, RandomAccessIterator1>
      > se(k);

  copy(seqs_begin, seqs_end, se.begin());

  difference_type* borders =
      new difference_type[num_threads + 1];
  equally_split(length, num_threads, borders);

  for (int s = 0; s < (num_threads - 1); ++s)
    {
      offsets[s].resize(k);
      multiseq_partition(
          se.begin(), se.end(), borders[s + 1],
          offsets[s].begin(), comp);

      // Last one also needed and available.
      if (!tight)
        {
          offsets[num_threads - 1].resize(k);
          multiseq_partition(se.begin(), se.end(),
                difference_type(length),
                offsets[num_threads - 1].begin(),  comp);
        }
    }


  for (int slab = 0; slab < num_threads; ++slab)
    {
      // For each slab / processor.
      for (int seq = 0; seq < k; ++seq)
        {
          // For each sequence.
          if (slab == 0)
            {
              // Absolute beginning.
              pieces[slab][seq].first = 0;
            }
          else
            pieces[slab][seq].first =
                pieces[slab - 1][seq].second;
          if (!tight || slab < (num_threads - 1))
            pieces[slab][seq].second =
                offsets[slab][seq] - seqs_begin[seq].first;
          else
            {
              // slab == num_threads - 1
              pieces[slab][seq].second =
                  _GLIBCXX_PARALLEL_LENGTH(seqs_begin[seq]);
            }
        }
    }
  delete[] offsets;
}

/** @brief Parallel multi-way merge routine.
 *
 * The _GLIBCXX_PARALLEL_DECISION is based on the branching factor
 * and runtime settings.
 *
 * Must not be called if the number of sequences is 1.
 *
 * @param Splitter functor to split input (either exact or sampling based)
 *
 * @param seqs_begin Begin iterator of iterator pair input sequence.
 * @param seqs_end End iterator of iterator pair input sequence.
 * @param target Begin iterator out output sequence.
 * @param comp Comparator.
 * @param length Maximum length to merge, possibly larger than the
 * number of elements available.
 * @param stable Stable merging incurs a performance penalty.
 * @param sentinel Ignored.
 * @return End iterator of output sequence.
 */
template<
    bool stable,
    bool sentinels,
    typename RandomAccessIteratorIterator,
    typename RandomAccessIterator3,
    typename _DifferenceTp,
    typename Splitter,
    typename Comparator
    >
  RandomAccessIterator3
  parallel_multiway_merge(RandomAccessIteratorIterator seqs_begin,
                          RandomAccessIteratorIterator seqs_end,
                          RandomAccessIterator3 target,
                          Comparator comp,
                          Splitter splitter,
                          _DifferenceTp length)
    {
#if _GLIBCXX_ASSERTIONS
      _GLIBCXX_PARALLEL_ASSERT(seqs_end - seqs_begin > 1);
#endif

      _GLIBCXX_CALL(length)

      typedef _DifferenceTp difference_type;
      typedef typename std::iterator_traits<RandomAccessIteratorIterator>
        ::value_type::first_type
        RandomAccessIterator1;
      typedef typename
        std::iterator_traits<RandomAccessIterator1>::value_type value_type;

      // Leave only non-empty sequences.
      std::pair<RandomAccessIterator1, RandomAccessIterator1>* ne_seqs =
        static_cast<std::pair<RandomAccessIterator1, RandomAccessIterator1>*>(
        ::operator new(
            sizeof(std::pair<RandomAccessIterator1, RandomAccessIterator1>)
              * (seqs_end - seqs_begin)));
      int k = 0;
      difference_type total_length = 0;
      for (RandomAccessIteratorIterator raii = seqs_begin;
           raii != seqs_end; ++raii)
        {
          _DifferenceTp seq_length = _GLIBCXX_PARALLEL_LENGTH(*raii);
          if(seq_length > 0)
            {
              total_length += seq_length;
              //ne_seqs[k] = *raii;
              new(&(ne_seqs[k++]))
                std::pair<RandomAccessIterator1, RandomAccessIterator1>(*raii);
            }
        }

      _GLIBCXX_CALL(total_length)

      length = std::min<_DifferenceTp>(length, total_length);

      if (total_length == 0 || k == 0)
      {
        ::operator delete(ne_seqs);
        return target;
      }

      std::vector<std::pair<difference_type, difference_type> >* pieces;

      thread_index_t num_threads = static_cast<thread_index_t>
        (std::min<difference_type>(get_max_threads(), total_length));

#     pragma omp parallel num_threads (num_threads)
        {
#         pragma omp single
            {
              num_threads = omp_get_num_threads();
              // Thread t will have to merge pieces[iam][0..k - 1]
              pieces = new std::vector<
                  std::pair<difference_type, difference_type> >[num_threads];
              for (int s = 0; s < num_threads; ++s)
                pieces[s].resize(k);

              difference_type num_samples =
                  __gnu_parallel::_Settings::get().merge_oversampling *
                    num_threads;

              splitter(ne_seqs, ne_seqs + k, comp, length, total_length,
                       pieces);
            } //single

          thread_index_t iam = omp_get_thread_num();

          difference_type target_position = 0;

          for (int c = 0; c < k; ++c)
            target_position += pieces[iam][c].first;

          std::pair<RandomAccessIterator1, RandomAccessIterator1>* chunks
            = new std::pair<RandomAccessIterator1, RandomAccessIterator1>[k];

          for (int s = 0; s < k; ++s)
            {
              chunks[s] = std::make_pair(
                ne_seqs[s].first + pieces[iam][s].first,
                ne_seqs[s].first + pieces[iam][s].second);
            }

          if(length > target_position)
            sequential_multiway_merge<stable, sentinels>(
              chunks, chunks + k, target + target_position,
              *(seqs_begin->second), comp, length - target_position);

          delete[] chunks;
        } // parallel

#if _GLIBCXX_ASSERTIONS
      _GLIBCXX_PARALLEL_ASSERT(is_sorted(target, target + length, comp));
#endif

      k = 0;
      // Update ends of sequences.
      for (RandomAccessIteratorIterator raii = seqs_begin;
           raii != seqs_end; ++raii)
        {
          _DifferenceTp length = _GLIBCXX_PARALLEL_LENGTH(*raii);
          if(length > 0)
            (*raii).first += pieces[num_threads - 1][k++].second;
        }

      delete[] pieces;

      return target + length;
    }

/**
 * @brief Multiway Merge Frontend.
 *
 * Merge the sequences specified by seqs_begin and seqs_end into
 * target.  seqs_begin and seqs_end must point to a sequence of
 * pairs.  These pairs must contain an iterator to the beginning
 * of a sequence in their first entry and an iterator the end of
 * the same sequence in their second entry.
 *
 * Ties are broken arbitrarily.  See stable_multiway_merge for a variant
 * that breaks ties by sequence number but is slower.
 *
 * The first entries of the pairs (i.e. the begin iterators) will be moved
 * forward.
 *
 * The output sequence has to provide enough space for all elements
 * that are written to it.
 *
 * This function will merge the input sequences:
 *
 * - not stable
 * - parallel, depending on the input size and Settings
 * - using sampling for splitting
 * - not using sentinels
 *
 * Example:
 *
 * <pre>
 *   int sequences[10][10];
 *   for (int i = 0; i < 10; ++i)
 *     for (int j = 0; i < 10; ++j)
 *       sequences[i][j] = j;
 *
 *   int out[33];
 *   std::vector<std::pair<int*> > seqs;
 *   for (int i = 0; i < 10; ++i)
 *     { seqs.push(std::make_pair<int*>(sequences[i], sequences[i] + 10)) }
 *
 *   multiway_merge(seqs.begin(), seqs.end(), target, std::less<int>(), 33);
 * </pre>
 *
 * @see stable_multiway_merge
 *
 * @pre All input sequences must be sorted.
 * @pre Target must provide enough space to merge out length elements or
 *    the number of elements in all sequences, whichever is smaller.
 *
 * @post [target, return value) contains merged elements from the
 *    input sequences.
 * @post return value - target = min(length, number of elements in all
 *    sequences).
 *
 * @param RandomAccessIteratorPairIterator iterator over sequence
 *    of pairs of iterators
 * @param RandomAccessIteratorOut iterator over target sequence
 * @param _DifferenceTp difference type for the sequence
 * @param Comparator strict weak ordering type to compare elements
 *    in sequences
 *
 * @param seqs_begin  begin of sequence sequence
 * @param seqs_end    end of sequence sequence
 * @param target      target sequence to merge to.
 * @param comp        strict weak ordering to use for element comparison.
 * @param length Maximum length to merge, possibly larger than the
 * number of elements available.
 *
 * @return end iterator of output sequence
 */
// public interface
template<
    typename RandomAccessIteratorPairIterator
  , typename RandomAccessIteratorOut
  , typename _DifferenceTp
  , typename Comparator>
RandomAccessIteratorOut
multiway_merge(RandomAccessIteratorPairIterator seqs_begin
    , RandomAccessIteratorPairIterator seqs_end
    , RandomAccessIteratorOut target
    , Comparator comp, _DifferenceTp length)
{
  typedef _DifferenceTp difference_type;
  _GLIBCXX_CALL(seqs_end - seqs_begin)

  // catch special case: no sequences
  if (seqs_begin == seqs_end)
    return target;

  // Execute merge; maybe parallel, depending on the number of merged
  // elements and the number of sequences and global thresholds in
  // Settings.
  if ((seqs_end - seqs_begin > 1) &&
        _GLIBCXX_PARALLEL_CONDITION(
        ((seqs_end - seqs_begin) >=
        __gnu_parallel::_Settings::get().multiway_merge_minimal_k)
        && ((sequence_index_t)length >=
        __gnu_parallel::_Settings::get().multiway_merge_minimal_n)))
    return parallel_multiway_merge
      </* stable = */ false, /* sentinels = */ false>
        (seqs_begin, seqs_end, target, comp,
        multiway_merge_sampling_splitting</* stable = */ false,
          typename std::iterator_traits<RandomAccessIteratorPairIterator>
            ::value_type*, Comparator, _DifferenceTp>,
        static_cast<difference_type>(length));
  else
    return sequential_multiway_merge
      </* stable = */false, /* sentinels = */ false>(
        seqs_begin, seqs_end,
        target, *(seqs_begin->second), comp, length);
}

// public interface
template<
    typename RandomAccessIteratorPairIterator
  , typename RandomAccessIteratorOut
  , typename _DifferenceTp
  , typename Comparator>
RandomAccessIteratorOut
multiway_merge(RandomAccessIteratorPairIterator seqs_begin
    , RandomAccessIteratorPairIterator seqs_end
    , RandomAccessIteratorOut target
    , Comparator comp, _DifferenceTp length
    , __gnu_parallel::sequential_tag)
{
  typedef _DifferenceTp difference_type;
  _GLIBCXX_CALL(seqs_end - seqs_begin)

  // catch special case: no sequences
  if (seqs_begin == seqs_end)
    return target;

  // Execute multiway merge *sequentially*.
  return sequential_multiway_merge
    </* stable = */ false, /* sentinels = */ false>
      (seqs_begin, seqs_end, target, *(seqs_begin->second), comp, length);
}

//public interface
template<
    typename RandomAccessIteratorPairIterator
  , typename RandomAccessIteratorOut
  , typename _DifferenceTp
  , typename Comparator>
RandomAccessIteratorOut
multiway_merge(RandomAccessIteratorPairIterator seqs_begin
    , RandomAccessIteratorPairIterator seqs_end
    , RandomAccessIteratorOut target
    , Comparator comp, _DifferenceTp length
    , __gnu_parallel::exact_tag)
{
    typedef _DifferenceTp difference_type;
    _GLIBCXX_CALL(seqs_end - seqs_begin)

    // catch special case: no sequences
    if (seqs_begin == seqs_end)
      return target;

    // Execute merge; maybe parallel, depending on the number of merged
    // elements and the number of sequences and global thresholds in
    // Settings.
    if ((seqs_end - seqs_begin > 1) &&
          _GLIBCXX_PARALLEL_CONDITION(
          ((seqs_end - seqs_begin) >=
             __gnu_parallel::_Settings::get().multiway_merge_minimal_k)
          && ((sequence_index_t)length >=
            __gnu_parallel::_Settings::get().multiway_merge_minimal_n)))
      return parallel_multiway_merge
                    </* stable = */ false, /* sentinels = */ false>(
          seqs_begin, seqs_end,
          target, comp,
          multiway_merge_exact_splitting</* stable = */ false,
            typename std::iterator_traits<RandomAccessIteratorPairIterator>
              ::value_type*, Comparator, _DifferenceTp>,
          static_cast<difference_type>(length));
    else
      return sequential_multiway_merge
                      </* stable = */ false, /* sentinels = */ false>(
          seqs_begin, seqs_end,
          target, *(seqs_begin->second), comp, length);
}

// public interface
template<
    typename RandomAccessIteratorPairIterator
  , typename RandomAccessIteratorOut
  , typename _DifferenceTp
  , typename Comparator>
RandomAccessIteratorOut
stable_multiway_merge(RandomAccessIteratorPairIterator seqs_begin
    , RandomAccessIteratorPairIterator seqs_end
    , RandomAccessIteratorOut target
    , Comparator comp, _DifferenceTp length)
{
    typedef _DifferenceTp difference_type;
    _GLIBCXX_CALL(seqs_end - seqs_begin)

    // catch special case: no sequences
    if (seqs_begin == seqs_end)
      return target;

    // Execute merge; maybe parallel, depending on the number of merged
    // elements and the number of sequences and global thresholds in
    // Settings.
    if ((seqs_end - seqs_begin > 1) &&
          _GLIBCXX_PARALLEL_CONDITION(
          ((seqs_end - seqs_begin) >=
            __gnu_parallel::_Settings::get().multiway_merge_minimal_k)
          && ((sequence_index_t)length >=
            __gnu_parallel::_Settings::get().multiway_merge_minimal_n)))
      return parallel_multiway_merge
        </* stable = */ true, /* sentinels = */ false>(
          seqs_begin, seqs_end,
          target, comp,
          multiway_merge_sampling_splitting</* stable = */ true,
            typename std::iterator_traits<RandomAccessIteratorPairIterator>
              ::value_type*, Comparator, _DifferenceTp>,
          static_cast<difference_type>(length));
    else
      return sequential_multiway_merge
        </* stable = */ true, /* sentinels = */ false>(
          seqs_begin, seqs_end,
          target, *(seqs_begin->second), comp, length);
}

// public interface
template<
    typename RandomAccessIteratorPairIterator
  , typename RandomAccessIteratorOut
  , typename _DifferenceTp
  , typename Comparator>
RandomAccessIteratorOut
stable_multiway_merge(RandomAccessIteratorPairIterator seqs_begin
    , RandomAccessIteratorPairIterator seqs_end
    , RandomAccessIteratorOut target
    , Comparator comp, _DifferenceTp length
    , __gnu_parallel::sequential_tag)
{
    typedef _DifferenceTp difference_type;
    _GLIBCXX_CALL(seqs_end - seqs_begin)

    // catch special case: no sequences
    if (seqs_begin == seqs_end)
      return target;

    // Execute multiway merge *sequentially*.
    return sequential_multiway_merge
      </* stable = */ true, /* sentinels = */ false>
        (seqs_begin, seqs_end, target, *(seqs_begin->second), comp, length);
}

// public interface
template<
    typename RandomAccessIteratorPairIterator
  , typename RandomAccessIteratorOut
  , typename _DifferenceTp
  , typename Comparator>
RandomAccessIteratorOut
stable_multiway_merge(RandomAccessIteratorPairIterator seqs_begin
    , RandomAccessIteratorPairIterator seqs_end
    , RandomAccessIteratorOut target
    , Comparator comp, _DifferenceTp length
    , __gnu_parallel::exact_tag)
{
    typedef _DifferenceTp difference_type;
    _GLIBCXX_CALL(seqs_end - seqs_begin)

    // catch special case: no sequences
    if (seqs_begin == seqs_end)
      return target;

    // Execute merge; maybe parallel, depending on the number of merged
    // elements and the number of sequences and global thresholds in
    // Settings.
    if ((seqs_end - seqs_begin > 1) &&
          _GLIBCXX_PARALLEL_CONDITION(
          ((seqs_end - seqs_begin) >=
            __gnu_parallel::_Settings::get().multiway_merge_minimal_k)
          && ((sequence_index_t)length >=
            __gnu_parallel::_Settings::get().multiway_merge_minimal_n)))
      return parallel_multiway_merge
        </* stable = */ true, /* sentinels = */ false>(
          seqs_begin, seqs_end,
          target, comp, 
          multiway_merge_exact_splitting
            </* stable = */ true,
              typename std::iterator_traits<RandomAccessIteratorPairIterator>
                ::value_type*, Comparator, _DifferenceTp>,
          static_cast<difference_type>(length));
    else
      return sequential_multiway_merge</* stable = */ true,
        /* sentinels = */ false>(
          seqs_begin, seqs_end,
          target, *(seqs_begin->second), comp, length);
}

/**
 * @brief Multiway Merge Frontend.
 *
 * Merge the sequences specified by seqs_begin and seqs_end into
 * target.  seqs_begin and seqs_end must point to a sequence of
 * pairs.  These pairs must contain an iterator to the beginning
 * of a sequence in their first entry and an iterator the end of
 * the same sequence in their second entry.
 *
 * Ties are broken arbitrarily.  See stable_multiway_merge for a variant
 * that breaks ties by sequence number but is slower.
 *
 * The first entries of the pairs (i.e. the begin iterators) will be moved
 * forward accordingly.
 *
 * The output sequence has to provide enough space for all elements
 * that are written to it.
 *
 * This function will merge the input sequences:
 *
 * - not stable
 * - parallel, depending on the input size and Settings
 * - using sampling for splitting
 * - using sentinels
 *
 * You have to take care that the element the end iterator points to is
 * readable and contains a value that is greater than any other non-sentinel
 * value in all sequences.
 *
 * Example:
 *
 * <pre>
 *   int sequences[10][11];
 *   for (int i = 0; i < 10; ++i)
 *     for (int j = 0; i < 11; ++j)
 *       sequences[i][j] = j; // last one is sentinel!
 *
 *   int out[33];
 *   std::vector<std::pair<int*> > seqs;
 *   for (int i = 0; i < 10; ++i)
 *     { seqs.push(std::make_pair<int*>(sequences[i], sequences[i] + 10)) }
 *
 *   multiway_merge(seqs.begin(), seqs.end(), target, std::less<int>(), 33);
 * </pre>
 *
 * @pre All input sequences must be sorted.
 * @pre Target must provide enough space to merge out length elements or
 *    the number of elements in all sequences, whichever is smaller.
 * @pre For each @c i, @c seqs_begin[i].second must be the end
 *    marker of the sequence, but also reference the one more sentinel
 *    element.
 *
 * @post [target, return value) contains merged elements from the
 *    input sequences.
 * @post return value - target = min(length, number of elements in all
 *    sequences).
 *
 * @see stable_multiway_merge_sentinels
 *
 * @param RandomAccessIteratorPairIterator iterator over sequence
 *    of pairs of iterators
 * @param RandomAccessIteratorOut iterator over target sequence
 * @param _DifferenceTp difference type for the sequence
 * @param Comparator strict weak ordering type to compare elements
 *    in sequences
 *
 * @param seqs_begin  begin of sequence sequence
 * @param seqs_end    end of sequence sequence
 * @param target      target sequence to merge to.
 * @param comp        strict weak ordering to use for element comparison.
 * @param length Maximum length to merge, possibly larger than the
 * number of elements available.
 *
 * @return end iterator of output sequence
 */
// public interface
template<
    typename RandomAccessIteratorPairIterator
  , typename RandomAccessIteratorOut
  , typename _DifferenceTp
  , typename Comparator>
RandomAccessIteratorOut
multiway_merge_sentinels(RandomAccessIteratorPairIterator seqs_begin
    , RandomAccessIteratorPairIterator seqs_end
    , RandomAccessIteratorOut target
    , Comparator comp, _DifferenceTp length)
{
    typedef _DifferenceTp difference_type;
    _GLIBCXX_CALL(seqs_end - seqs_begin)

    // catch special case: no sequences
    if (seqs_begin == seqs_end)
      return target;

    // Execute merge; maybe parallel, depending on the number of merged
    // elements and the number of sequences and global thresholds in
    // Settings.
    if ((seqs_end - seqs_begin > 1) &&
          _GLIBCXX_PARALLEL_CONDITION(
          ((seqs_end - seqs_begin) >=
            __gnu_parallel::_Settings::get().multiway_merge_minimal_k)
          && ((sequence_index_t)length >=
            __gnu_parallel::_Settings::get().multiway_merge_minimal_n)))
      return parallel_multiway_merge
        </* stable = */ false, /* sentinels = */ true>
          (seqs_begin, seqs_end, target, comp,
          multiway_merge_sampling_splitting
            </* stable = */ false,
              typename std::iterator_traits<RandomAccessIteratorPairIterator>
                ::value_type*, Comparator, _DifferenceTp>,
          static_cast<difference_type>(length));
    else
      return sequential_multiway_merge
        </* stable = */false, /* sentinels = */ true>(
          seqs_begin, seqs_end,
          target, *(seqs_begin->second), comp, length);
}

//public interface
template<
    typename RandomAccessIteratorPairIterator
  , typename RandomAccessIteratorOut
  , typename _DifferenceTp
  , typename Comparator>
RandomAccessIteratorOut
multiway_merge_sentinels(RandomAccessIteratorPairIterator seqs_begin
    , RandomAccessIteratorPairIterator seqs_end
    , RandomAccessIteratorOut target
    , Comparator comp, _DifferenceTp length
    , __gnu_parallel::sequential_tag)
{
    typedef _DifferenceTp difference_type;
    _GLIBCXX_CALL(seqs_end - seqs_begin)

    // catch special case: no sequences
    if (seqs_begin == seqs_end)
      return target;

    // Execute multiway merge *sequentially*.
    return sequential_multiway_merge
      </* stable = */ false, /* sentinels = */ true>
        (seqs_begin, seqs_end, target, *(seqs_begin->second), comp, length);
}

// public interface
template<
    typename RandomAccessIteratorPairIterator
  , typename RandomAccessIteratorOut
  , typename _DifferenceTp
  , typename Comparator>
RandomAccessIteratorOut
multiway_merge_sentinels(RandomAccessIteratorPairIterator seqs_begin
    , RandomAccessIteratorPairIterator seqs_end
    , RandomAccessIteratorOut target
    , Comparator comp, _DifferenceTp length
    , __gnu_parallel::exact_tag)
{
    typedef _DifferenceTp difference_type;
    _GLIBCXX_CALL(seqs_end - seqs_begin)

    // catch special case: no sequences
    if (seqs_begin == seqs_end)
      return target;

    // Execute merge; maybe parallel, depending on the number of merged
    // elements and the number of sequences and global thresholds in
    // Settings.
    if ((seqs_end - seqs_begin > 1) &&
          _GLIBCXX_PARALLEL_CONDITION(
          ((seqs_end - seqs_begin) >=
            __gnu_parallel::_Settings::get().multiway_merge_minimal_k)
          && ((sequence_index_t)length >=
            __gnu_parallel::_Settings::get().multiway_merge_minimal_n)))
      return parallel_multiway_merge
        </* stable = */ false, /* sentinels = */ true>(
          seqs_begin, seqs_end,
          target, comp,
          multiway_merge_exact_splitting
            </* stable = */ false,
              typename std::iterator_traits<RandomAccessIteratorPairIterator>
                ::value_type*, Comparator, _DifferenceTp>,
          static_cast<difference_type>(length));
    else
      return sequential_multiway_merge
        </* stable = */ false, /* sentinels = */ true>(
          seqs_begin, seqs_end,
          target, *(seqs_begin->second), comp, length);
}

// public interface
template<
    typename RandomAccessIteratorPairIterator
  , typename RandomAccessIteratorOut
  , typename _DifferenceTp
  , typename Comparator>
RandomAccessIteratorOut
stable_multiway_merge_sentinels(RandomAccessIteratorPairIterator seqs_begin
    , RandomAccessIteratorPairIterator seqs_end
    , RandomAccessIteratorOut target
    , Comparator comp, _DifferenceTp length)
{
    typedef _DifferenceTp difference_type;
    _GLIBCXX_CALL(seqs_end - seqs_begin)

    // catch special case: no sequences
    if (seqs_begin == seqs_end)
      return target;

    // Execute merge; maybe parallel, depending on the number of merged
    // elements and the number of sequences and global thresholds in
    // Settings.
    if ((seqs_end - seqs_begin > 1) &&
          _GLIBCXX_PARALLEL_CONDITION(
          ((seqs_end - seqs_begin) >=
            __gnu_parallel::_Settings::get().multiway_merge_minimal_k)
          && ((sequence_index_t)length >=
            __gnu_parallel::_Settings::get().multiway_merge_minimal_n)))
      return parallel_multiway_merge
        </* stable = */ true, /* sentinels = */ true>(
          seqs_begin, seqs_end,
          target, comp,
          multiway_merge_sampling_splitting
            </* stable = */ true,
              typename std::iterator_traits<RandomAccessIteratorPairIterator>
                ::value_type*, Comparator, _DifferenceTp>,
          static_cast<difference_type>(length));
    else
      return sequential_multiway_merge
        </* stable = */ true, /* sentinels = */ true>(
          seqs_begin, seqs_end,
          target, *(seqs_begin->second), comp, length);
}

// public interface
template<
    typename RandomAccessIteratorPairIterator
  , typename RandomAccessIteratorOut
  , typename _DifferenceTp
  , typename Comparator>
RandomAccessIteratorOut
stable_multiway_merge_sentinels(RandomAccessIteratorPairIterator seqs_begin
    , RandomAccessIteratorPairIterator seqs_end
    , RandomAccessIteratorOut target
    , Comparator comp, _DifferenceTp length
    , __gnu_parallel::sequential_tag)
{
    typedef _DifferenceTp difference_type;
    _GLIBCXX_CALL(seqs_end - seqs_begin)

    // catch special case: no sequences
    if (seqs_begin == seqs_end)
      return target;

    // Execute multiway merge *sequentially*.
    return sequential_multiway_merge
      </* stable = */ true, /* sentinels = */ true>
        (seqs_begin, seqs_end, target, *(seqs_begin->second), comp, length);
}

// public interface
template<
    typename RandomAccessIteratorPairIterator
  , typename RandomAccessIteratorOut
  , typename _DifferenceTp
  , typename Comparator>
RandomAccessIteratorOut
stable_multiway_merge_sentinels(RandomAccessIteratorPairIterator seqs_begin
    , RandomAccessIteratorPairIterator seqs_end
    , RandomAccessIteratorOut target
    , Comparator comp, _DifferenceTp length
    , __gnu_parallel::exact_tag)
{
    typedef _DifferenceTp difference_type;
    _GLIBCXX_CALL(seqs_end - seqs_begin)

    // catch special case: no sequences
    if (seqs_begin == seqs_end)
      return target;

    // Execute merge; maybe parallel, depending on the number of merged
    // elements and the number of sequences and global thresholds in
    // Settings.
    if ((seqs_end - seqs_begin > 1) &&
          _GLIBCXX_PARALLEL_CONDITION(
          ((seqs_end - seqs_begin) >=
          __gnu_parallel::_Settings::get().multiway_merge_minimal_k)
          && ((sequence_index_t)length >=
          __gnu_parallel::_Settings::get().multiway_merge_minimal_n)))
      return parallel_multiway_merge
        </* stable = */ true, /* sentinels = */ true>(
          seqs_begin, seqs_end,
          target, comp, 
          multiway_merge_exact_splitting
            </* stable = */ true,
              typename std::iterator_traits<RandomAccessIteratorPairIterator>
                ::value_type*, Comparator, _DifferenceTp>,
          static_cast<difference_type>(length));
    else
      return sequential_multiway_merge
        </* stable = */ true, /* sentinels = */ true>(
          seqs_begin, seqs_end,
          target, *(seqs_begin->second), comp, length);
}

}; // namespace __gnu_parallel

#endif
// -*- C++ -*-

// Copyright (C) 2007, 2008 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 2, 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.

// You should have received a copy of the GNU General Public License
// along with this library; see the file COPYING.  If not, write to
// the Free Software Foundation, 59 Temple Place - Suite 330, Boston,
// MA 02111-1307, USA.

// As a special exception, you may use this file as part of a free
// software library without restriction.  Specifically, if other files
// instantiate templates or use macros or inline functions from this
// file, or you compile this file and link it with other files to
// produce an executable, this file does not by itself cause the
// resulting executable to be covered by the GNU General Public
// License.  This exception does not however invalidate any other
// reasons why the executable file might be covered by the GNU General
// Public License.

/** @file parallel/algo.h
 *  @brief Parallel STL function calls corresponding to the stl_algo.h header.
 *
 *  The functions defined here mainly do case switches and
 *  call the actual parallelized versions in other files.
 *  Inlining policy: Functions that basically only contain one function call,
 *  are declared inline.
 *  This file is a GNU parallel extension to the Standard C++ Library.
 */

// Written by Johannes Singler and Felix Putze.

#ifndef _GLIBCXX_PARALLEL_ALGO_H
#define _GLIBCXX_PARALLEL_ALGO_H 1

#include <parallel/algorithmfwd.h>
#include <bits/stl_algobase.h>
#include <bits/stl_algo.h>
#include <parallel/iterator.h>
#include <parallel/base.h>
#include <parallel/sort.h>
#include <parallel/workstealing.h>
#include <parallel/par_loop.h>
#include <parallel/omp_loop.h>
#include <parallel/omp_loop_static.h>
#include <parallel/for_each_selectors.h>
#include <parallel/for_each.h>
#include <parallel/find.h>
#include <parallel/find_selectors.h>
#include <parallel/search.h>
#include <parallel/random_shuffle.h>
#include <parallel/partition.h>
#include <parallel/merge.h>
#include <parallel/unique_copy.h>
#include <parallel/set_operations.h>

namespace std
{
namespace __parallel
{
  // Sequential fallback
  template<typename InputIterator, typename Function>
    inline Function
    for_each(InputIterator begin, InputIterator end, Function f, 
	     __gnu_parallel::sequential_tag)
    { return _GLIBCXX_STD_P::for_each(begin, end, f); }

  // Sequential fallback for input iterator case
  template<typename InputIterator, typename Function, typename IteratorTag>
    inline Function
    for_each_switch(InputIterator begin, InputIterator end, Function f, 
		    IteratorTag)
    { return for_each(begin, end, f, __gnu_parallel::sequential_tag()); }

  // Parallel algorithm for random access iterators
  template<typename RandomAccessIterator, typename Function>
    Function
    for_each_switch(RandomAccessIterator begin, RandomAccessIterator end, 
		    Function f, random_access_iterator_tag, 
		    __gnu_parallel::_Parallelism parallelism_tag
		    = __gnu_parallel::parallel_balanced)
    {
      if (_GLIBCXX_PARALLEL_CONDITION(
	    static_cast<__gnu_parallel::sequence_index_t>(end - begin)
	    >= __gnu_parallel::_Settings::get().for_each_minimal_n
	    && __gnu_parallel::is_parallel(parallelism_tag)))
	{
	  bool dummy;
	  __gnu_parallel::for_each_selector<RandomAccessIterator> functionality;

	  return __gnu_parallel::
	    for_each_template_random_access(begin, end, f, functionality,
					    __gnu_parallel::dummy_reduct(),
					    true, dummy, -1, parallelism_tag);
	}
      else
	return for_each(begin, end, f, __gnu_parallel::sequential_tag());
    }

  // Public interface
  template<typename Iterator, typename Function>
    inline Function
    for_each(Iterator begin, Iterator end, Function f, 
	     __gnu_parallel::_Parallelism parallelism_tag)
    {
      typedef std::iterator_traits<Iterator> iterator_traits;
      typedef typename iterator_traits::iterator_category iterator_category;
      return for_each_switch(begin, end, f, iterator_category(), 
			     parallelism_tag);
    }

  template<typename Iterator, typename Function>
    inline Function
    for_each(Iterator begin, Iterator end, Function f) 
    {
      typedef std::iterator_traits<Iterator> iterator_traits;
      typedef typename iterator_traits::iterator_category iterator_category;
      return for_each_switch(begin, end, f, iterator_category());
    }


  // Sequential fallback
  template<typename InputIterator, typename T>
    inline InputIterator
    find(InputIterator begin, InputIterator end, const T& val, 
	 __gnu_parallel::sequential_tag)
    { return _GLIBCXX_STD_P::find(begin, end, val); }

  // Sequential fallback for input iterator case
  template<typename InputIterator, typename T, typename IteratorTag>
    inline InputIterator
    find_switch(InputIterator begin, InputIterator end, const T& val,
		IteratorTag)
    { return _GLIBCXX_STD_P::find(begin, end, val); }

  // Parallel find for random access iterators
  template<typename RandomAccessIterator, typename T>
    RandomAccessIterator
    find_switch(RandomAccessIterator begin, RandomAccessIterator end,
		const T& val, random_access_iterator_tag)
    {
      typedef iterator_traits<RandomAccessIterator> traits_type;
      typedef typename traits_type::value_type value_type;

      if (_GLIBCXX_PARALLEL_CONDITION(true))
	{
	  binder2nd<__gnu_parallel::equal_to<value_type, T> >
	    comp(__gnu_parallel::equal_to<value_type, T>(), val);
	  return __gnu_parallel::find_template(begin, end, begin, comp,
					       __gnu_parallel::
					       find_if_selector()).first;
	}
      else
	return _GLIBCXX_STD_P::find(begin, end, val);
    }

  // Public interface
  template<typename InputIterator, typename T>
    inline InputIterator
    find(InputIterator begin, InputIterator end, const T& val)
    {
      typedef std::iterator_traits<InputIterator> iterator_traits;
      typedef typename iterator_traits::iterator_category iterator_category;
      return find_switch(begin, end, val, iterator_category());
    }

  // Sequential fallback
  template<typename InputIterator, typename Predicate>
    inline InputIterator
    find_if(InputIterator begin, InputIterator end, Predicate pred, 
	    __gnu_parallel::sequential_tag)
    { return _GLIBCXX_STD_P::find_if(begin, end, pred); }

  // Sequential fallback for input iterator case
  template<typename InputIterator, typename Predicate, typename IteratorTag>
    inline InputIterator
    find_if_switch(InputIterator begin, InputIterator end, Predicate pred, 
		   IteratorTag)
    { return _GLIBCXX_STD_P::find_if(begin, end, pred); }

  // Parallel find_if for random access iterators
  template<typename RandomAccessIterator, typename Predicate>
    RandomAccessIterator
    find_if_switch(RandomAccessIterator begin, RandomAccessIterator end, 
		   Predicate pred, random_access_iterator_tag)
    {
      if (_GLIBCXX_PARALLEL_CONDITION(true))
	return __gnu_parallel::find_template(begin, end, begin, pred, 
					     __gnu_parallel::
					     find_if_selector()).first;
      else
	return _GLIBCXX_STD_P::find_if(begin, end, pred);
    }

  // Public interface
  template<typename InputIterator, typename Predicate>
    inline InputIterator
    find_if(InputIterator begin, InputIterator end, Predicate pred)
    {
      typedef std::iterator_traits<InputIterator> iterator_traits;
      typedef typename iterator_traits::iterator_category iterator_category;
      return find_if_switch(begin, end, pred, iterator_category());
    }

  // Sequential fallback
  template<typename InputIterator, typename ForwardIterator>
    inline InputIterator
    find_first_of(InputIterator begin1, InputIterator end1, 
		  ForwardIterator begin2, ForwardIterator end2, 
		  __gnu_parallel::sequential_tag)
    { return _GLIBCXX_STD_P::find_first_of(begin1, end1, begin2, end2); }

  // Sequential fallback
  template<typename InputIterator, typename ForwardIterator,
	   typename BinaryPredicate>
    inline InputIterator
    find_first_of(InputIterator begin1, InputIterator end1,
		  ForwardIterator begin2, ForwardIterator end2,
		  BinaryPredicate comp, __gnu_parallel::sequential_tag)
  { return _GLIBCXX_STD_P::find_first_of(begin1, end1, begin2, end2, comp); }

  // Sequential fallback for input iterator type
  template<typename InputIterator, typename ForwardIterator,
	   typename IteratorTag1, typename IteratorTag2>
    inline InputIterator
    find_first_of_switch(InputIterator begin1, InputIterator end1,
			 ForwardIterator begin2, ForwardIterator end2, 
			 IteratorTag1, IteratorTag2)
    { return find_first_of(begin1, end1, begin2, end2, 
			   __gnu_parallel::sequential_tag()); }

  // Parallel algorithm for random access iterators
  template<typename RandomAccessIterator, typename ForwardIterator,
	   typename BinaryPredicate, typename IteratorTag>
    inline RandomAccessIterator
    find_first_of_switch(RandomAccessIterator begin1,
			 RandomAccessIterator end1,
			 ForwardIterator begin2, ForwardIterator end2, 
			 BinaryPredicate comp, random_access_iterator_tag, 
			 IteratorTag)
    {
      return __gnu_parallel::
	find_template(begin1, end1, begin1, comp,
		      __gnu_parallel::find_first_of_selector
		      <ForwardIterator>(begin2, end2)).first;
    }

  // Sequential fallback for input iterator type
  template<typename InputIterator, typename ForwardIterator,
	   typename BinaryPredicate, typename IteratorTag1,
	   typename IteratorTag2>
    inline InputIterator
    find_first_of_switch(InputIterator begin1, InputIterator end1,
			 ForwardIterator begin2, ForwardIterator end2, 
			 BinaryPredicate comp, IteratorTag1, IteratorTag2)
    { return find_first_of(begin1, end1, begin2, end2, comp, 
			   __gnu_parallel::sequential_tag()); }

  // Public interface
  template<typename InputIterator, typename ForwardIterator,
	   typename BinaryPredicate>
    inline InputIterator
    find_first_of(InputIterator begin1, InputIterator end1,
		  ForwardIterator begin2, ForwardIterator end2, 
		  BinaryPredicate comp)
    {
      typedef std::iterator_traits<InputIterator> iteratori_traits;
      typedef std::iterator_traits<ForwardIterator> iteratorf_traits;
      typedef typename iteratori_traits::iterator_category iteratori_category;
      typedef typename iteratorf_traits::iterator_category iteratorf_category;

      return find_first_of_switch(begin1, end1, begin2, end2, comp,
				  iteratori_category(), iteratorf_category());
    }

  // Public interface, insert default comparator
  template<typename InputIterator, typename ForwardIterator>
    inline InputIterator
    find_first_of(InputIterator begin1, InputIterator end1, 
		  ForwardIterator begin2, ForwardIterator end2)
    {
      typedef std::iterator_traits<InputIterator> iteratori_traits;
      typedef std::iterator_traits<ForwardIterator> iteratorf_traits;
      typedef typename iteratori_traits::value_type valuei_type;
      typedef typename iteratorf_traits::value_type valuef_type;

      return find_first_of(begin1, end1, begin2, end2, __gnu_parallel::
			   equal_to<valuei_type, valuef_type>());
    }

  // Sequential fallback
  template<typename InputIterator, typename OutputIterator>
    inline OutputIterator
    unique_copy(InputIterator begin1, InputIterator end1, OutputIterator out,
		__gnu_parallel::sequential_tag)
    { return _GLIBCXX_STD_P::unique_copy(begin1, end1, out); }

  // Sequential fallback
  template<typename InputIterator, typename OutputIterator,
	   typename Predicate>
    inline OutputIterator
    unique_copy(InputIterator begin1, InputIterator end1, OutputIterator out,
		Predicate pred, __gnu_parallel::sequential_tag)
    { return _GLIBCXX_STD_P::unique_copy(begin1, end1, out, pred); }

  // Sequential fallback for input iterator case
  templatû#ü#ý#þ#ÿ#$
$$$$$$$$	$
$$$
$$$$$$$$$$$$$$$$$$$ $!$"$#$$$%$&$'$($)$*$+$,$-$.$/$0$1$2$3$4$5$6$7$8$9$:$;$<$=$>$?$@$A$B$C$e<typename InputIterator, typename OutputIterator,
	   typename Predicate, typename IteratorTag1, typename IteratorTag2>
    inline OutputIterator
    unique_copy_switch(InputIterator begin, InputIterator last, 
		       OutputIterator out, Predicate pred, 
		       IteratorTag1, IteratorTag2)
    { return _GLIBCXX_STD_P::unique_copy(begin, last, out, pred); }

  // Parallel unique_copy for random access iterators
  template<typename RandomAccessIterator, typename RandomAccessOutputIterator,
	   typename Predicate>
    RandomAccessOutputIterator
    unique_copy_switch(RandomAccessIterator begin, RandomAccessIterator last, 
		       RandomAccessOutputIterator out, Predicate pred, 
		       random_access_iterator_tag, random_access_iterator_tag)
    {
      if (_GLIBCXX_PARALLEL_CONDITION(
	    static_cast<__gnu_parallel::sequence_index_t>(last - begin)
	    > __gnu_parallel::_Settings::get().unique_copy_minimal_n))
	return __gnu_parallel::parallel_unique_copy(begin, last, out, pred);
      else
	return _GLIBCXX_STD_P::unique_copy(begin, last, out, pred);
    }

  // Public interface
  template<typename InputIterator, typename OutputIterator>
    inline OutputIterator
    unique_copy(InputIterator begin1, InputIterator end1, OutputIterator out)
    {
      typedef std::iterator_traits<InputIterator> iteratori_traits;
      typedef std::iterator_traits<OutputIterator> iteratoro_traits;
      typedef typename iteratori_traits::iterator_category iteratori_category;
      typedef typename iteratori_traits::value_type value_type;
      typedef typename iteratoro_traits::iterator_category iteratoro_category;

      return unique_copy_switch(begin1, end1, out, equal_to<value_type>(),
				iteratori_category(), iteratoro_category());
    }

  // Public interface
  template<typename InputIterator, typename OutputIterator, typename Predicate>
    inline OutputIterator
    unique_copy(InputIterator begin1, InputIterator end1, OutputIterator out,
		Predicate pred)
    {
      typedef std::iterator_traits<InputIterator> iteratori_traits;
      typedef std::iterator_traits<OutputIterator> iteratoro_traits;
      typedef typename iteratori_traits::iterator_category iteratori_category;
      typedef typename iteratoro_traits::iterator_category iteratoro_category;

      return unique_copy_switch(begin1, end1, out, pred, iteratori_category(), 
				iteratoro_category());
    }

  // Sequential fallback
  template<typename InputIterator1, typename InputIterator2,
	   typename OutputIterator>
    inline OutputIterator
    set_union(InputIterator1 begin1, InputIterator1 end1,
	      InputIterator2 begin2, InputIterator2 end2,
	      OutputIterator out, __gnu_parallel::sequential_tag)
    { return _GLIBCXX_STD_P::set_union(begin1, end1, begin2, end2, out); }

  // Sequential fallback
  template<typename InputIterator1, typename InputIterator2,
	   typename OutputIterator, typename Predicate>
    inline OutputIterator
    set_union(InputIterator1 begin1, InputIterator1 end1,
	      InputIterator2 begin2, InputIterator2 end2,
	      OutputIterator out, Predicate pred,
	      __gnu_parallel::sequential_tag)
    { return _GLIBCXX_STD_P::set_union(begin1, end1,
				       begin2, end2, out, pred); }

  // Sequential fallback for input iterator case
  template<typename InputIterator1, typename InputIterator2,
	   typename Predicate, typename OutputIterator,
	   typename IteratorTag1, typename IteratorTag2, typename IteratorTag3>
    inline OutputIterator
    set_union_switch(InputIterator1 begin1, InputIterator1 end1, 
		     InputIterator2 begin2, InputIterator2 end2, 
		     OutputIterator result, Predicate pred, IteratorTag1,
		     IteratorTag2, IteratorTag3)
    { return _GLIBCXX_STD_P::set_union(begin1, end1,
				       begin2, end2, result, pred); }

  // Parallel set_union for random access iterators
  template<typename RandomAccessIterator1, typename RandomAccessIterator2,
	   typename OutputRandomAccessIterator, typename Predicate>
    OutputRandomAccessIterator
    set_union_switch(RandomAccessIterator1 begin1, RandomAccessIterator1 end1, 
		     RandomAccessIterator2 begin2, RandomAccessIterator2 end2, 
		     OutputRandomAccessIterator result, Predicate pred,
		     random_access_iterator_tag, random_access_iterator_tag, 
		     random_access_iterator_tag)
    {
      if (_GLIBCXX_PARALLEL_CONDITION(
	    static_cast<__gnu_parallel::sequence_index_t>(end1 - begin1)
	    >= __gnu_parallel::_Settings::get().set_union_minimal_n
	    || static_cast<__gnu_parallel::sequence_index_t>(end2 - begin2)
	    >= __gnu_parallel::_Settings::get().set_union_minimal_n))
	return __gnu_parallel::parallel_set_union(begin1, end1,
						  begin2, end2, result, pred);
      else
	return _GLIBCXX_STD_P::set_union(begin1, end1,
					 begin2, end2, result, pred);
    }

  // Public interface
  template<typename InputIterator1, typename InputIterator2,
	   typename OutputIterator>
    inline OutputIterator 
    set_union(InputIterator1 begin1, InputIterator1 end1,
	      InputIterator2 begin2, InputIterator2 end2, OutputIterator out)
    {
      typedef std::iterator_