LinearDivision.h

/**************************************************************************
 * basf2 (Belle II Analysis Software Framework)                           *
 * Author: The Belle II Collaboration                                     *
 *                                                                        *
 * See git log for contributors and copyright holders.                    *
 * This file is licensed under LGPL-3.0, see LICENSE.md.                  *
 **************************************************************************/
#pragma once
 
#include <tracking/trackFindingCDC/utilities/Product.h>
 
#include <utility>
#include <tuple>
#include <array>
#include <iterator>
#include <cassert>
 
namespace Belle2 {
  namespace TrackFindingCDC {
 
    template<class ABox, std::size_t... divisions>
    class LinearDivision {
 
    public:
      static const std::size_t s_nSubBoxes = Product<divisions...>::value;
 
    private:
      static constexpr std::size_t s_divisions[sizeof...(divisions)] = {divisions...};
 
    public:
      explicit LinearDivision(const typename ABox::Delta& overlaps = typename ABox::Delta())
        : m_overlaps(overlaps)
      {}
 
    public:
      std::array<ABox, s_nSubBoxes> operator()(const ABox& box)
      {
        return makeSubBoxes(box, std::make_index_sequence<s_nSubBoxes>());
      }
 
      template<std::size_t... Is>
 
      std::array<ABox, s_nSubBoxes>
      makeSubBoxes(const ABox& box, std::index_sequence<Is...> /*globalSubBoxIndex*/)
      {
        return {{ makeSubBox(box, Is, std::make_index_sequence<sizeof...(divisions)>())... }};
      }
 
 
      template<std::size_t... Is>
 
      ABox makeSubBox(const ABox& box,
                      std::size_t globalISubBox,
                      std::index_sequence<Is...> /*coordinatesIndex*/)
      {
        std::array<std::size_t, sizeof...(divisions)> indices;
        for (size_t c_Index = 0 ; c_Index <  sizeof...(divisions); ++c_Index) {
          indices[c_Index] = globalISubBox % s_divisions[c_Index];
          globalISubBox /= s_divisions[c_Index];
        }
        assert(globalISubBox == 0);
        return ABox(box.template getDivisionBoundsWithOverlap<Is>(std::get<Is>(m_overlaps),
                                                                  s_divisions[Is],
                                                                  indices[Is]) ...);
      }
 
    private:
      typename ABox::Delta m_overlaps;
 
    };
 
    // Extra mention of the constexpr such that it acquires external linkage.
    template<class ABox, std::size_t... divisions>
    constexpr std::size_t LinearDivision<ABox, divisions...>::s_divisions[sizeof...(divisions)];
  }
}