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// -*- 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/set_operations.h

 * @brief Parallel implementations of set operations for random-access

 * iterators.

 *  This file is a GNU parallel extension to the Standard C++ Library.

 */

// Written by Marius Elvert and Felix Bondarenko.

#ifndef _GLIBCXX_PARALLEL_SET_OPERATIONS_H

#define _GLIBCXX_PARALLEL_SET_OPERATIONS_H 1

#include <omp.h>

#include <parallel/settings.h>

#include <parallel/multiseq_selection.h>

namespace __gnu_parallel

{

  template<typename _IIter, typename _OutputIterator>

    _OutputIterator

    __copy_tail(std::pair<_IIter, _IIter> __b,

                std::pair<_IIter, _IIter> __e, _OutputIterator __r)

    {

      if (__b.first != __e.first)

        {

          do

            {

              *__r++ = *__b.first++;

            }

          while (__b.first != __e.first);

        }

      else

        {

          while (__b.second != __e.second)

            *__r++ = *__b.second++;

        }

      return __r;

    }

  template<typename _IIter,

           typename _OutputIterator,

           typename _Compare>

    struct __symmetric_difference_func

    {

      typedef std::iterator_traits<_IIter> _TraitsType;

      typedef typename _TraitsType::difference_type _DifferenceType;

      typedef typename std::pair<_IIter, _IIter> _IteratorPair;

      __symmetric_difference_func(_Compare __comp) : _M_comp(__comp) {}

      _Compare _M_comp;

      _OutputIterator

      _M_invoke(_IIter __a, _IIter __b, _IIter __c, _IIter __d,

                _OutputIterator __r) const

      {

        while (__a != __b && __c != __d)

          {

            if (_M_comp(*__a, *__c))

              {

                *__r = *__a;

                ++__a;

                ++__r;

              }

            else if (_M_comp(*__c, *__a))

              {

                *__r = *__c;

                ++__c;

                ++__r;

              }

            else

              {

                ++__a;

                ++__c;

              }

          }

        return std::copy(__c, __d, std::copy(__a, __b, __r));

      }

      _DifferenceType

      __count(_IIter __a, _IIter __b, _IIter __c, _IIter __d) const

      {

        _DifferenceType __counter = 0;

        while (__a != __b && __c != __d)

          {

            if (_M_comp(*__a, *__c))

              {

                ++__a;

                ++__counter;

              }

            else if (_M_comp(*__c, *__a))

              {

                ++__c;

                ++__counter;

              }

            else

              {

                ++__a;

                ++__c;

              }

          }

        return __counter + (__b - __a) + (__d - __c);

      }

      _OutputIterator

      __first_empty(_IIter __c, _IIter __d, _OutputIterator __out) const

      { return std::copy(__c, __d, __out); }

      _OutputIterator

      __second_empty(_IIter __a, _IIter __b, _OutputIterator __out) const

      { return std::copy(__a, __b, __out); }

    };

  template<typename _IIter,

           typename _OutputIterator,

           typename _Compare>

    struct __difference_func

    {

      typedef std::iterator_traits<_IIter> _TraitsType;

      typedef typename _TraitsType::difference_type _DifferenceType;

      typedef typename std::pair<_IIter, _IIter> _IteratorPair;

      __difference_func(_Compare __comp) : _M_comp(__comp) {}

      _Compare _M_comp;

      _OutputIterator

      _M_invoke(_IIter __a, _IIter __b, _IIter __c, _IIter __d,

                _OutputIterator __r) const

      {

        while (__a != __b && __c != __d)

          {

            if (_M_comp(*__a, *__c))

              {

                *__r = *__a;

                ++__a;

                ++__r;

              }

            else if (_M_comp(*__c, *__a))

              { ++__c; }

            else

              {

                ++__a;

                ++__c;

              }

          }

        return std::copy(__a, __b, __r);

      }

      _DifferenceType

      __count(_IIter __a, _IIter __b,

              _IIter __c, _IIter __d) const

      {

        _DifferenceType __counter = 0;

        while (__a != __b && __c != __d)

          {

            if (_M_comp(*__a, *__c))

              {

                ++__a;

                ++__counter;

              }

            else if (_M_comp(*__c, *__a))

              { ++__c; }

            else

              { ++__a; ++__c; }

          }

        return __counter + (__b - __a);

      }

      _OutputIterator

      __first_empty(_IIter, _IIter, _OutputIterator __out) const

      { return __out; }

      _OutputIterator

      __second_empty(_IIter __a, _IIter __b, _OutputIterator __out) const

      { return std::copy(__a, __b, __out); }

    };

  template<typename _IIter,

           typename _OutputIterator,

           typename _Compare>

    struct __intersection_func

    {

      typedef std::iterator_traits<_IIter> _TraitsType;

      typedef typename _TraitsType::difference_type _DifferenceType;

      typedef typename std::pair<_IIter, _IIter> _IteratorPair;

      __intersection_func(_Compare __comp) : _M_comp(__comp) {}

      _Compare _M_comp;

      _OutputIterator

      _M_invoke(_IIter __a, _IIter __b, _IIter __c, _IIter __d,

                _OutputIterator __r) const

      {

        while (__a != __b && __c != __d)

          {

            if (_M_comp(*__a, *__c))

              { ++__a; }

            else if (_M_comp(*__c, *__a))

              { ++__c; }

            else

              {

                *__r = *__a;

                ++__a;

                ++__c;

                ++__r;

              }

          }

        return __r;

      }

      _DifferenceType

      __count(_IIter __a, _IIter __b, _IIter __c, _IIter __d) const

      {

        _DifferenceType __counter = 0;

        while (__a != __b && __c != __d)

          {

            if (_M_comp(*__a, *__c))

              { ++__a; }

            else if (_M_comp(*__c, *__a))

              { ++__c; }

            else

              {

                ++__a;

                ++__c;

                ++__counter;

              }

          }

        return __counter;

      }

      _OutputIterator

      __first_empty(_IIter, _IIter, _OutputIterator __out) const

      { return __out; }

      _OutputIterator

      __second_empty(_IIter, _IIter, _OutputIterator __out) const

      { return __out; }

    };

  template<class _IIter, class _OutputIterator, class _Compare>

    struct __union_func

    {

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

      _DifferenceType;

      __union_func(_Compare __comp) : _M_comp(__comp) {}

      _Compare _M_comp;

      _OutputIterator

      _M_invoke(_IIter __a, const _IIter __b, _IIter __c,

                const _IIter __d, _OutputIterator __r) const

      {

        while (__a != __b && __c != __d)

          {

            if (_M_comp(*__a, *__c))

              {

                *__r = *__a;

                ++__a;

              }

            else if (_M_comp(*__c, *__a))

              {

                *__r = *__c;

                ++__c;

              }

            else

              {

                *__r = *__a;

                ++__a;

                ++__c;

              }

            ++__r;

          }

        return std::copy(__c, __d, std::copy(__a, __b, __r));

      }

      _DifferenceType

      __count(_IIter __a, _IIter __b, _IIter __c, _IIter __d) const

      {

        _DifferenceType __counter = 0;

        while (__a != __b && __c != __d)

          {

            if (_M_comp(*__a, *__c))

              { ++__a; }

            else if (_M_comp(*__c, *__a))

              { ++__c; }

            else

              {

                ++__a;

                ++__c;

              }

            ++__counter;

          }

        __counter += (__b - __a);

        __counter += (__d - __c);

        return __counter;

      }

      _OutputIterator

      __first_empty(_IIter __c, _IIter __d, _OutputIterator __out) const

      { return std::copy(__c, __d, __out); }

      _OutputIterator

      __second_empty(_IIter __a, _IIter __b, _OutputIterator __out) const

      { return std::copy(__a, __b, __out); }

    };

  template<typename _IIter,

           typename _OutputIterator,

           typename _Operation>

    _OutputIterator

    __parallel_set_operation(_IIter __begin1, _IIter __end1,

                             _IIter __begin2, _IIter __end2,

                             _OutputIterator __result, _Operation __op)

    {

      _GLIBCXX_CALL((__end1 - __begin1) + (__end2 - __begin2))

      typedef std::iterator_traits<_IIter> _TraitsType;

      typedef typename _TraitsType::difference_type _DifferenceType;

      typedef typename std::pair<_IIter, _IIter> _IteratorPair;

      if (__begin1 == __end1)

        return __op.__first_empty(__begin2, __end2, __result);

      if (__begin2 == __end2)

        return __op.__second_empty(__begin1, __end1, __result);

      const _DifferenceType __size = (__end1 - __begin1) + (__end2 - __begin2);

      const _IteratorPair __sequence[2] = { std::make_pair(__begin1, __end1),

                                            std::make_pair(__begin2, __end2) };

      _OutputIterator __return_value = __result;

      _DifferenceType *__borders;

      _IteratorPair *__block_begins;

      _DifferenceType* __lengths;

      _ThreadIndex __num_threads =

          std::min<_DifferenceType>(__get_max_threads(),

              std::min(__end1 - __begin1, __end2 - __begin2));

#     pragma omp parallel num_threads(__num_threads)

      {

#       pragma omp single

        {

          __num_threads = omp_get_num_threads();

          __borders = new _DifferenceType[__num_threads + 2];

          __equally_split(__size, __num_threads + 1, __borders);

          __block_begins = new _IteratorPair[__num_threads + 1];

          // Very __start.

          __block_begins[0] = std::make_pair(__begin1, __begin2);

          __lengths = new _DifferenceType[__num_threads];

        } //single

        _ThreadIndex __iam = omp_get_thread_num();

        // _Result from multiseq_partition.

        _IIter __offset[2];

        const _DifferenceType __rank = __borders[__iam + 1];

        multiseq_partition(__sequence, __sequence + 2,

                           __rank, __offset, __op._M_comp);

        // allowed to read?

        // together

        // *(__offset[ 0 ] - 1) == *__offset[ 1 ]

        if (__offset[ 0 ] != __begin1 && __offset[1] != __end2

            && !__op._M_comp(*(__offset[0] - 1), *__offset[1])

            && !__op._M_comp(*__offset[1], *(__offset[0] - 1)))

          {

            // Avoid split between globally equal elements: move one to

            // front in first sequence.

              --__offset[0];

          }

        _IteratorPair __block_end = __block_begins[__iam + 1] =

          _IteratorPair(__offset[0], __offset[1]);

        // Make sure all threads have their block_begin result written out.

#       pragma omp barrier

        _IteratorPair __block_begin = __block_begins[__iam];

        // Begin working for the first block, while the others except

        // the last start to count.

        if (__iam == 0)

          {

            // The first thread can copy already.

            __lengths[ __iam ] =

              __op._M_invoke(__block_begin.first, __block_end.first,

                             __block_begin.second, __block_end.second,

                             __result) - __result;

          }

        else

          {

            __lengths[ __iam ] =

              __op.__count(__block_begin.first, __block_end.first,

                           __block_begin.second, __block_end.second);

          }

        // Make sure everyone wrote their lengths.

#       pragma omp barrier

        _OutputIterator __r = __result;

        if (__iam == 0)

          {

            // Do the last block.

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

              __r += __lengths[__i];

            __block_begin = __block_begins[__num_threads];

            // Return the result iterator of the last block.

            __return_value =

              __op._M_invoke(__block_begin.first, __end1,

                             __block_begin.second, __end2, __r);

          }

          else

            {

              for (_ThreadIndex __i = 0; __i < __iam; ++__i)

                __r += __lengths[ __i ];

              // Reset begins for copy pass.

              __op._M_invoke(__block_begin.first, __block_end.first,

                             __block_begin.second, __block_end.second, __r);

            }

        }

      return __return_value;

    }

  template<typename _IIter,

           typename _OutputIterator,

           typename _Compare>

    inline _OutputIterator

    __parallel_set_union(_IIter __begin1, _IIter __end1,

                         _IIter __begin2, _IIter __end2,

                         _OutputIterator __result, _Compare __comp)

    {

      return __parallel_set_operation(__begin1, __end1, __begin2, __end2,

                                      __result,

                                      __union_func< _IIter, _OutputIterator,

                                      _Compare>(__comp));

    }

  template<typename _IIter,

           typename _OutputIterator,

           typename _Compare>

    inline _OutputIterator

    __parallel_set_intersection(_IIter __begin1, _IIter __end1,

                                _IIter __begin2, _IIter __end2,

                                _OutputIterator __result, _Compare __comp)

    {

      return __parallel_set_operation(__begin1, __end1, __begin2, __end2,

                                      __result,

                                      __intersection_func<_IIter,

                                      _OutputIterator, _Compare>(__comp));

    }

  template<typename _IIter,

           typename _OutputIterator,

           typename _Compare>

    inline _OutputIterator

    __parallel_set_difference(_IIter __begin1, _IIter __end1,

                              _IIter __begin2, _IIter __end2,

                              _OutputIterator __result, _Compare __comp)

    {

      return __parallel_set_operation(__begin1, __end1, __begin2, __end2,

                                      __result,

                                      __difference_func<_IIter,

                                      _OutputIterator, _Compare>(__comp));

    }

  template<typename _IIter,

           typename _OutputIterator,

           typename _Compare>

    inline _OutputIterator

    __parallel_set_symmetric_difference(_IIter __begin1, _IIter __end1,

                                        _IIter __begin2, _IIter __end2,

                                        _OutputIterator __result,

                                        _Compare __comp)

    {

      return __parallel_set_operation(__begin1, __end1, __begin2, __end2,

                                      __result,

                                      __symmetric_difference_func<_IIter,

                                      _OutputIterator, _Compare>(__comp));

    }

}

#endif /* _GLIBCXX_PARALLEL_SET_OPERATIONS_H */