Dune::Std::mdarray< Element, Extents, LayoutPolicy, Container > Class Template Reference

An owning multi-dimensional array analog of mdspan. More...

#include <dune/common/std/mdarray.hh>

Public Member Functions
constexpr const mapping_type &	mapping () const noexcept
	Index mapping of a layout policy.
constexpr const container_type &	container () const noexcept
	The underlying storage container.
constexpr container_type &&	extract_container () &&noexcept
	Move the container out of the mdarray. More...

Related Functions
(Note that these are not member functions.)
constexpr const extents_type &	extents () const noexcept
	Number of elements in all dimensions of the array,.

Conversion into mdspan
container_type	container_
DUNE_NO_UNIQUE_ADDRESS mapping_type	mapping_
template<class V , class E , class L , class A , std::enable_if_t< std::is_assignable_v< mdspan< V, E, L, A >, mdspan_type >, int > = 0>
constexpr	operator mdspan< V, E, L, A > ()
	Conversion operator to mdspan.
template<class V , class E , class L , class A , std::enable_if_t< std::is_assignable_v< mdspan< V, E, L, A >, const_mdspan_type >, int > = 0>
constexpr	operator mdspan< V, E, L, A > () const
	Conversion operator to mdspan.
template<class AccessorPolicy = Std::default_accessor<element_type>, std::enable_if_t< std::is_assignable_v< mdspan_type, mdspan< element_type, extents_type, layout_type, AccessorPolicy > >, int > = 0>
constexpr mdspan< element_type, extents_type, layout_type, AccessorPolicy >	to_mdspan (const AccessorPolicy &a=AccessorPolicy{})
	Conversion function to mdspan.
template<class AccessorPolicy = Std::default_accessor<const element_type>, std::enable_if_t< std::is_assignable_v< const_mdspan_type, mdspan< const element_type, extents_type, layout_type, AccessorPolicy > >, int > = 0>
constexpr mdspan< const element_type, extents_type, layout_type, AccessorPolicy >	to_mdspan (const AccessorPolicy &a=AccessorPolicy{}) const
	Conversion function to mdspan.

mdarray constructors
template<class E = extents_type, class C = container_type, class M = mapping_type, std::enable_if_t<(E::rank_dynamic() !=0), int > = 0, std::enable_if_t< std::is_default_constructible_v< C >, int > = 0, std::enable_if_t< std::is_default_constructible_v< M >, int > = 0>
constexpr	mdarray ()
	A default constructor; needed only if the constructor for dynamic extents does not apply.
template<class... IndexTypes, std::enable_if_t<(... &&std::is_convertible_v< IndexTypes, index_type >), int > = 0, std::enable_if_t< std::is_constructible_v< extents_type, IndexTypes... >, int > = 0, std::enable_if_t<(... &&std::is_nothrow_constructible_v< index_type, IndexTypes >), int > = 0>
constexpr	mdarray (IndexTypes... exts)
	Construct from the dynamic extents.
constexpr	mdarray (const extents_type &e)
	Construct from the extents of the array.
template<class C = container_type, decltype(construct_container< C >(std::declval< std::size_t >()), bool{}) = true>
constexpr	mdarray (const mapping_type &m)
	Construct from the layout mapping of the array.
constexpr	mdarray (const extents_type &e, const value_type &v)
	Construct from extents and initial value.
template<class C = container_type, decltype(construct_container< C >(std::declval< std::size_t >(), std::declval< const value_type & >()), bool{}) = true>
constexpr	mdarray (const mapping_type &m, const value_type &v)
	Construct from layout mapping and initial value.
template<class E = extents_type, std::enable_if_t< std::is_constructible_v< mapping_type, const E & >, int > = 0>
constexpr	mdarray (const E &e, const container_type &c)
	Construct from extents and the storage container.
template<class E = extents_type, std::enable_if_t< std::is_constructible_v< mapping_type, const E & >, int > = 0>
constexpr	mdarray (const E &e, container_type &&c)
	Construct from extents and the storage container.
constexpr	mdarray (const mapping_type &m, const container_type &c)
	Construct from layout mapping and the storage container.
constexpr	mdarray (const mapping_type &m, container_type &&c)
	Construct from layout mapping and the storage container.
template<class OtherElementType , class OtherExtents , class OtherLayoutPolicy , class OtherContainer , std::enable_if_t< std::is_constructible_v< Container, const OtherContainer & >, int > = 0, std::enable_if_t< std::is_constructible_v< extents_type, OtherExtents >, int > = 0, std::enable_if_t< std::is_constructible_v< mapping_type, const typename OtherLayoutPolicy::template mapping< OtherExtents > & >, int > = 0>
constexpr	mdarray (const mdarray< OtherElementType, OtherExtents, OtherLayoutPolicy, OtherContainer > &other)
	Converting constructor from other mdarray.
template<class OtherElementType , class OtherExtents , class OtherLayoutPolicy , class Accessor , std::enable_if_t< std::is_constructible_v< value_type, typename Accessor::reference >, int > = 0, std::enable_if_t< std::is_assignable_v< typename Accessor::reference, value_type >, int > = 0, std::enable_if_t< std::is_constructible_v< mapping_type, const typename OtherLayoutPolicy::template mapping< OtherExtents > & >, int > = 0, decltype(construct_container< container_type >(std::declval< std::size_t >()), bool{}) = true>
constexpr	mdarray (const mdspan< OtherElementType, OtherExtents, OtherLayoutPolicy, Accessor > &other)
	Converting constructor from mdspan.
template<class Alloc , std::enable_if_t< std::is_constructible_v< container_type, std::size_t, Alloc >, int > = 0>
constexpr	mdarray (const extents_type &e, const Alloc &a)
	Construct from the extents of the array and allocator.
template<class Alloc , std::enable_if_t< std::is_constructible_v< container_type, std::size_t, Alloc >, int > = 0>
constexpr	mdarray (const mapping_type &m, const Alloc &a)
	Construct from the layout mapping of the array and allocator.
template<class Alloc >
constexpr	mdarray (const extents_type &e, const value_type &v, const Alloc &a)
	Construct from extents, initial value and allocator.
template<class Alloc , std::enable_if_t< std::is_constructible_v< container_type, std::size_t, value_type, Alloc >, int > = 0>
constexpr	mdarray (const mapping_type &m, const value_type &v, const Alloc &a)
	Construct from layout mapping, initial value and allocator.
template<class Alloc , std::enable_if_t< std::is_constructible_v< container_type, container_type, Alloc >, int > = 0>
constexpr	mdarray (const extents_type &e, const container_type &c, const Alloc &a)
	Construct from extents, container and allocator.
template<class Alloc , std::enable_if_t< std::is_constructible_v< container_type, container_type, Alloc >, int > = 0>
constexpr	mdarray (const extents_type &e, container_type &&c, const Alloc &a)
	Construct from extents, container and allocator.
template<class Alloc , std::enable_if_t< std::is_constructible_v< container_type, container_type, Alloc >, int > = 0>
constexpr	mdarray (const mapping_type &m, const container_type &c, const Alloc &a)
	Construct from layout mapping, container and allocator.
template<class Alloc , std::enable_if_t< std::is_constructible_v< container_type, container_type, Alloc >, int > = 0>
constexpr	mdarray (const mapping_type &m, container_type &&c, const Alloc &a)
	Construct from layout mapping, container and allocator.
template<class V , class E , class L , class C , class Alloc , std::enable_if_t< std::is_constructible_v< container_type, C, Alloc >, int > = 0>
constexpr	mdarray (const mdarray< V, E, L, C > &other, const Alloc &a) noexcept
	Converting constructor with alternative allocator.
template<class V , class E , class L , class A , class Alloc , class C = container_type, class Al = typename C::allocator_type, std::enable_if_t< std::is_constructible_v< C, std::size_t, Alloc >, int > = 0>
constexpr	mdarray (const mdspan< V, E, L, A > &other, const Alloc &a)
	Converting constructor from mdspan.

Multi index access
template<class... Indices, std::enable_if_t<(sizeof...(Indices)==extents_type::rank()), int > = 0, std::enable_if_t<(... &&std::is_convertible_v< Indices, index_type >), int > = 0>
constexpr reference	operator() (Indices... indices)
	Access element at position (i0,i1,...) More...
template<class... Indices, std::enable_if_t<(sizeof...(Indices)==extents_type::rank()), int > = 0, std::enable_if_t<(... &&std::is_convertible_v< Indices, index_type >), int > = 0>
constexpr const_reference	operator() (Indices... indices) const
	Access element at position (i0,i1,...) More...
template<class Index , class E = extents_type, std::enable_if_t< std::is_convertible_v< Index, index_type >, int > = 0, std::enable_if_t<(E::rank()==1), int > = 0>
constexpr reference	operator[] (Index index)
	Access specified element at position [i0] For a rank one mdarray, the operator[i] is added to support bracket access before __cpp_multidimensional_subscript is supported.
template<class Index , class E = extents_type, std::enable_if_t< std::is_convertible_v< Index, index_type >, int > = 0, std::enable_if_t<(E::rank()==1), int > = 0>
constexpr const_reference	operator[] (Index index) const
	Access specified element at position [i0] For a rank one mdarray, the operator[i] is added to support bracket access before __cpp_multidimensional_subscript is supported.
template<class Index , std::enable_if_t< std::is_convertible_v< const Index &, index_type >, int > = 0>
constexpr reference	operator[] (Std::span< Index, extents_type::rank()> indices)
	Access element at position [{i0,i1,...}].
template<class Index , std::enable_if_t< std::is_convertible_v< const Index &, index_type >, int > = 0>
constexpr const_reference	operator[] (Std::span< Index, extents_type::rank()> indices) const
	Access element at position [{i0,i1,...}].
template<class Index , std::enable_if_t< std::is_convertible_v< const Index &, index_type >, int > = 0>
constexpr reference	operator[] (const std::array< Index, extents_type::rank()> &indices)
	Access element at position [{i0,i1,...}].
template<class Index , std::enable_if_t< std::is_convertible_v< const Index &, index_type >, int > = 0>
constexpr const_reference	operator[] (const std::array< Index, extents_type::rank()> &indices) const
	Access element at position [{i0,i1,...}].

Size information
constexpr index_type	extent (rank_type r) const noexcept
	Number of elements in the r'th dimension of the tensor.
constexpr size_type	size () const noexcept
	Size of the multi-dimensional index space.
constexpr std::size_t	container_size () const
	Size of the underlying container.
constexpr bool	empty () const noexcept
	Check whether the index space is empty.
constexpr index_type	stride (rank_type r) const
	The stride along the specified dimension.
static constexpr rank_type	rank () noexcept
	Number of dimensions of the array.
static constexpr rank_type	rank_dynamic () noexcept
	Number of dimension with dynamic size.
static constexpr std::size_t	static_extent (rank_type r) noexcept
	Number of elements in the r'th dimension of the tensor.

Direct access to the data
constexpr pointer	container_data () noexcept
	Direct access to the underlying data in the container.
constexpr const_pointer	container_data () const noexcept
	Direct access to the underlying const data in the container.

Detailed Description

template<class Element, class Extents, class LayoutPolicy = Std::layout_right, class Container = std::vector<Element>>
class Dune::Std::mdarray< Element, Extents, LayoutPolicy, Container >

An owning multi-dimensional array analog of mdspan.

The implementation is inspired by the mdarray c++ standard proposals P1684R5.

Example:

// two-dimensional array with 2 rows and 6 columns of static shape
Dune::Std::mdarray<double, Dune::Std::extents<std::size_t,2,6>> m1{};
 
// same two-dimensional array but with dynamic shape
Dune::Std::mdarray<double, Dune::Std::dextents<std::size_t,2>> m2{2,6};
 
// storage type similar to the Dune::FieldMatrix
template <class T, int m, int n>
using FieldMatrix = Dune::Std::mdarray<T,
  Dune::Std::extents<int,m,n>, Dune::Std::layout_right, std::array<T,m*n>>;
 
// store data into the array using two indices
for (std::size_t i = 0; i != m1.extent(0); i++)
    for (std::size_t j = 0; j != m1.extent(1); j++)
        m1(i, j) = i + j;  // or m1[i, j]

Note

The interface of Std::mdarray provides the operator[] with multiple indices overload only if available in c++23. For older c++ versions the operator() overload is implemented.

Template Parameters

Element	The element type; a complete object type that is neither an abstract class type nor an array type.
Extents	Specifies number of dimensions, their sizes, and which are known at compile time. Must be a specialization of Std::extents.
LayoutPolicy	Specifies how to convert multi-dimensional index to underlying flat index.
Container	A container type accessible by a single index provided by the layout mapping.

Member Function Documentation

extract_container()

template<class Element , class Extents , class LayoutPolicy = Std::layout_right, class Container = std::vector<Element>>

constexpr container_type && Dune::Std::mdarray< Element, Extents, LayoutPolicy, Container >::extract_container ( ) &&

inlineconstexprnoexcept

Move the container out of the mdarray.

Note that after moving out the container the mdarray remains in a valid but an unspecified state. One can destruct it or move-assign to it (i.e. restore the container in some way).

operator()() [1/2]

template<class Element , class Extents , class LayoutPolicy = Std::layout_right, class Container = std::vector<Element>>

template<class... Indices, std::enable_if_t<(sizeof...(Indices)==extents_type::rank()), int > = 0, std::enable_if_t<(... &&std::is_convertible_v< Indices, index_type >), int > = 0>

constexpr reference Dune::Std::mdarray< Element, Extents, LayoutPolicy, Container >::operator() ( Indices...  indices )

inlineconstexpr

Access element at position (i0,i1,...)

Note

The operator() is not in the std proposal, but is provided for using mdspan without c++23. For compatibility reasons it should only be used if the macro DUNE_HAVE_CXX_STD_MDARRAY is explicitly set to 0.

operator()() [2/2]

template<class Element , class Extents , class LayoutPolicy = Std::layout_right, class Container = std::vector<Element>>

template<class... Indices, std::enable_if_t<(sizeof...(Indices)==extents_type::rank()), int > = 0, std::enable_if_t<(... &&std::is_convertible_v< Indices, index_type >), int > = 0>

constexpr const_reference Dune::Std::mdarray< Element, Extents, LayoutPolicy, Container >::operator() ( Indices...  indices ) const

inlineconstexpr

Access element at position (i0,i1,...)

Note

The operator() is not in the std proposal, but is provided for using mdspan without c++23.

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The documentation for this class was generated from the following file:

• dune/common/std/mdarray.hh