base.hpp

来自「support vector clustering for vc++」· HPP 代码 · 共 480 行 · 第 1/2 页

#else

template <class T, class NumDims>
struct associated_types
  : value_accessor_generator<T,NumDims>::type
{};

#endif

//
// choose value accessor ends
/////////////////////////////////////////////////////////////////////////



////////////////////////////////////////////////////////////////////////
// multi_array_base
////////////////////////////////////////////////////////////////////////
template <typename T, std::size_t NumDims>
class multi_array_impl_base
  :
#if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
      public mpl::aux::msvc_eti_base<
          typename value_accessor_generator<T,mpl::size_t<NumDims> >::type
       >::type
#else
      public value_accessor_generator<T,mpl::size_t<NumDims> >::type
#endif 
{
  typedef associated_types<T,mpl::size_t<NumDims> > types;
public:
  typedef typename types::index index;
  typedef typename types::size_type size_type;
  typedef typename types::element element;
  typedef typename types::index_range index_range;
  typedef typename types::value_type value_type;
  typedef typename types::reference reference;
  typedef typename types::const_reference const_reference;

  template <std::size_t NDims>
  struct subarray {
    typedef boost::detail::multi_array::sub_array<T,NDims> type;
  };

  template <std::size_t NDims>
  struct const_subarray {
    typedef boost::detail::multi_array::const_sub_array<T,NDims> type;
  };

  template <std::size_t NDims>
  struct array_view {
    typedef boost::detail::multi_array::multi_array_view<T,NDims> type;
  };

  template <std::size_t NDims>
  struct const_array_view {
  public:
    typedef boost::detail::multi_array::const_multi_array_view<T,NDims> type;
  };

  //
  // iterator support
  //
  typedef array_iterator<T,T*,mpl::size_t<NumDims>,reference> iterator;
  typedef array_iterator<T,T const*,mpl::size_t<NumDims>,const_reference> const_iterator;

  typedef ::boost::reverse_iterator<iterator> reverse_iterator;
  typedef ::boost::reverse_iterator<const_iterator> const_reverse_iterator;

  BOOST_STATIC_CONSTANT(std::size_t, dimensionality = NumDims);
protected:

  multi_array_impl_base() { }
  ~multi_array_impl_base() { }

  // Used by operator() in our array classes
  template <typename Reference, typename IndexList, typename TPtr>
  Reference access_element(boost::type<Reference>,
                           const IndexList& indices,
                           TPtr base,
                           const size_type* extents,
                           const index* strides,
                           const index* index_bases) const {

    ignore_unused_variable_warning(index_bases);
    ignore_unused_variable_warning(extents);
#if !defined(NDEBUG) && !defined(BOOST_DISABLE_ASSERTS)
    for (size_type i = 0; i != NumDims; ++i) {
      BOOST_ASSERT(indices[i] - index_bases[i] >= 0);
      BOOST_ASSERT(size_type(indices[i] - index_bases[i]) < extents[i]);
    }
#endif

    index offset = 0;
    for (size_type n = 0; n != NumDims; ++n) 
      offset += indices[n] * strides[n];
    
    return base[offset];
  }

  template <typename StrideList, typename ExtentList>
  void compute_strides(StrideList& stride_list, ExtentList& extent_list,
                       const general_storage_order<NumDims>& storage)
  {
    // invariant: stride = the stride for dimension n
    index stride = 1;
    for (size_type n = 0; n != NumDims; ++n) {
      index stride_sign = +1;
      
      if (!storage.ascending(storage.ordering(n)))
        stride_sign = -1;
      
      // The stride for this dimension is the product of the
      // lengths of the ranks minor to it.
      stride_list[storage.ordering(n)] = stride * stride_sign;
      
      stride *= extent_list[storage.ordering(n)];
    } 
  }

  // This calculates the offset to the array base pointer due to:
  // 1. dimensions stored in descending order
  // 2. non-zero dimension index bases
  template <typename StrideList, typename ExtentList, typename BaseList>
  index
  calculate_origin_offset(const StrideList& stride_list,
                          const ExtentList& extent_list,
                          const general_storage_order<NumDims>& storage,
                          const BaseList& index_base_list)
  {
    return
      calculate_descending_dimension_offset(stride_list,extent_list,
                                            storage) +
      calculate_indexing_offset(stride_list,index_base_list);
  }

  // This calculates the offset added to the base pointer that are
  // caused by descending dimensions
  template <typename StrideList, typename ExtentList>
  index
  calculate_descending_dimension_offset(const StrideList& stride_list,
                                const ExtentList& extent_list,
                                const general_storage_order<NumDims>& storage)
  {
    index offset = 0;
    if (!storage.all_dims_ascending()) 
      for (size_type n = 0; n != NumDims; ++n)
        if (!storage.ascending(n))
          offset -= (extent_list[n] - 1) * stride_list[n];

    return offset;
  }

  // This is used to reindex array_views, which are no longer
  // concerned about storage order (specifically, whether dimensions
  // are ascending or descending) since the viewed array handled it.

  template <typename StrideList, typename BaseList>
  index
  calculate_indexing_offset(const StrideList& stride_list,
                          const BaseList& index_base_list)
  {
    index offset = 0;
    for (size_type n = 0; n != NumDims; ++n)
        offset -= stride_list[n] * index_base_list[n];
    return offset;
  }

  // Slicing using an index_gen.
  // Note that populating an index_gen creates a type that encodes
  // both the number of dimensions in the current Array (NumDims), and 
  // the Number of dimensions for the resulting view.  This allows the 
  // compiler to fail if the dimensions aren't completely accounted
  // for.  For reasons unbeknownst to me, a BOOST_STATIC_ASSERT
  // within the member function template does not work. I should add a 
  // note to the documentation specifying that you get a damn ugly
  // error message if you screw up in your slicing code.
  template <typename ArrayRef, int NDims, typename TPtr>
  ArrayRef
  generate_array_view(boost::type<ArrayRef>,
                      const boost::detail::multi_array::
                      index_gen<NumDims,NDims>& indices,
                      const size_type* extents,
                      const index* strides,
                      const index* index_bases,
                      TPtr base) const {

    boost::array<index,NDims> new_strides;
    boost::array<index,NDims> new_extents;

    index offset = 0;
    size_type dim = 0;
    for (size_type n = 0; n != NumDims; ++n) {
      const index default_start = index_bases[n];
      const index default_finish = default_start+extents[n];
      const index_range& current_range = indices.ranges_[n];
      index start = current_range.get_start(default_start);
      index finish = current_range.get_finish(default_finish);
      index index_factor = current_range.stride();
      index len = (finish - start + (index_factor - 1)) / index_factor;

      BOOST_ASSERT(index_bases[n] <= start &&
                   start <= index_bases[n]+index(extents[n]));
      BOOST_ASSERT(index_bases[n] <= finish &&
                   finish <= index_bases[n]+index(extents[n]));
      BOOST_ASSERT(index_factor > 0);

      // the array data pointer is modified to account for non-zero
      // bases during slicing (see [Garcia] for the math involved)
      offset += start * strides[n];

      if (!current_range.is_degenerate()) {

        // The index_factor for each dimension is included into the
        // strides for the array_view (see [Garcia] for the math involved).
        new_strides[dim] = index_factor * strides[n];
        
        // calculate new extents
        new_extents[dim] = len;
        ++dim;
      }
    }
    BOOST_ASSERT(dim == NDims);

    return
      ArrayRef(base+offset,
               new_extents,
               new_strides);
  }
                     

};

} // namespace multi_array
} // namespace detail

} // namespace boost

#endif // BASE_RG071801_HPP