SPAR/AIModule/BWTA/vendors/CGAL/CGAL/Multiscale_sort.h

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// Copyright (c) 2007  INRIA Sophia-Antipolis (France).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org); you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public License as
// published by the Free Software Foundation; version 2.1 of the License.
// See the file LICENSE.LGPL distributed with CGAL.
//
// Licensees holding a valid commercial license may use this file in
// accordance with the commercial license agreement provided with the software.
//
// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
//
// $URL: svn+ssh://scm.gforge.inria.fr/svn/cgal/branches/CGAL-3.5-branch/Spatial_sorting/include/CGAL/Multiscale_sort.h $
// $Id: Multiscale_sort.h 47102 2008-11-28 09:07:23Z spion $
//
// Author(s)     : Christophe Delage

#ifndef CGAL_MULTISCALE_SORT_H
#define CGAL_MULTISCALE_SORT_H

#include <CGAL/basic.h>
#include <iterator>
#include <cstddef>

CGAL_BEGIN_NAMESPACE

template <class Sort>
class Multiscale_sort
{
    Sort _sort;
    std::ptrdiff_t _threshold;
    double _ratio;

public:
    Multiscale_sort (const Sort &sort = Sort(), std::ptrdiff_t threshold = 1, double ratio = 0.5)
        : _sort (sort), _threshold (threshold), _ratio (ratio)
    {
        CGAL_precondition (0. <= ratio && ratio <= 1.);
    }

    template <class RandomAccessIterator>
    void operator() (RandomAccessIterator begin, RandomAccessIterator end) const
    {
        typedef typename std::iterator_traits<RandomAccessIterator>::difference_type difference_type;
        RandomAccessIterator middle = begin;
        if (end - begin >= _threshold) {
            middle = begin + difference_type ((end - begin) * _ratio);
            this->operator() (begin, middle);
        }
        _sort (middle, end);
    }
};

CGAL_END_NAMESPACE

#endif // CGAL_MULTISCALE_SORT_H