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37 * \brief Declares MultiDimArray.
39 * \author Christian Blau <cblau@gwdg.de>
40 * \ingroup module_math
41 * \ingroup module_mdspan
45 #ifndef GMX_MATH_MULTIDIMARRAY_H_
46 #define GMX_MATH_MULTIDIMARRAY_H_
48 #include "gromacs/mdspan/mdspan.h"
49 #include "gromacs/utility/arrayref.h"
56 //! Same as std::void_t from C++17
60 template<typename T, typename = void>
61 struct is_resizable : std::false_type
66 struct is_resizable<T, void_t<decltype(std::declval<T>().resize(size_t()))>> : std::true_type
70 //! Type has a resize member function callable with size_t argument
72 // NOLINTNEXTLINE misc-definitions-in-headers
73 constexpr bool is_resizable_v = is_resizable<T>::value;
76 /*! \libinternal \brief
77 * Multidimensional array that manages its own memory.
79 * \note No bounds checking when accessing memory
81 * \note That the view holds a valid pointer to the data is a class invariant.
83 * The Container type that stores the data may be resizable (std::vector or similar)
84 * or static (std::array or similar). Copy and move assignment routines as well as
85 * swapping are designed to yield good performances in both cases, notably
86 * foregoing the copy-swap idiom due to the bad performance in swapping std::array.
88 * This class avoids throwing exeptions, apart from the ones that might be thrown
89 * from the containers during resizing an allocation. (bad_malloc from std::vector
90 * is a likely candidate)
93 * Holds as many elements as required by a multidimensional view.
94 * \tparam TContainer Data type container for the data to be stored
95 * as MultiDimArray with random element access and
96 * value_type, refence and const_reference exposed
97 * \tparam Extents An extents class describing the array dimensions
98 * as used in module_mdspan
99 * \tparam LayoutPolicy The data layout as in module_mdspan describes
100 * translation of indices to memory offset.
101 * Defaults to right aligned, so that the right-most index
102 * is contiguous in memory.
104 template<class TContainer, class Extents, class LayoutPolicy = layout_right>
108 //! the type of values that are stored
109 using value_type = typename TContainer::value_type;
110 //! reference type to the stored values
111 using reference = typename TContainer::reference;
112 //! const reference type to the stored values
113 using const_reference = typename TContainer::const_reference;
114 //! the view used to access the data
115 using view_type = basic_mdspan<value_type, Extents, LayoutPolicy>;
116 //! const view on the data
117 using const_view_type = basic_mdspan<const value_type, Extents, LayoutPolicy>;
118 /*! \brief Iterator type for contiguous iteration over the stored data.
119 * Used, e.g., in free begin and end functions
121 using iterator = typename ArrayRef<value_type>::iterator;
122 /*! \brief Const iterator type for contiguous iteration over the stored data.
123 * used, e.g., in free begin and end functions
125 using const_iterator = const typename ArrayRef<const value_type>::const_iterator;
127 static_assert(detail::is_resizable_v<TContainer> == (Extents::rank_dynamic() > 0),
128 "Resizable container (e.g. std::vector) requires at least one dynamic rank. "
129 "Non-resizable container (e.g. std::array) requires zero dynamic ranks.");
132 * Allocate dynamic array data and set view with the dynamic extents.
134 * \param[in] dynamicExtent A parameter pack that describes the dynamic
135 * size of the array. Empty if purely static.
137 * \tparam IndexType Parameter pack type holding the dynamic
138 * extents of the multidimensional array
140 template<class... IndexType, typename T = TContainer, typename = typename std::enable_if_t<detail::is_resizable_v<T>>>
141 MultiDimArray(IndexType... dynamicExtent)
143 resize(dynamicExtent...);
146 * Construction from fixed sized arrays if the array size is static and
147 * layout policy allows compile time determination of the container size.
149 * Enables the expected initialization
150 * MultiDimArray<std::array<float, 9>, extents<3,3>> arr = {{1,2...}}
151 * \tparam T Template parameter for activation via SFINAE.
153 // SFINAE required because std::vector::size isn't constexpr and is_constexpr doesn't exist.
154 template<typename T = TContainer, typename = typename std::enable_if_t<!detail::is_resizable_v<T>>>
155 constexpr MultiDimArray(const TContainer& data = {}) noexcept : data_(data), view_(data_.data())
157 static_assert(TContainer().size() == typename view_type::mapping_type().required_span_size(),
158 "Non-resizable container type size must match static MultiDimArray size.");
161 constexpr MultiDimArray(const MultiDimArray& o) :
162 data_(o.data_), view_(data_.data(), o.view_.extents())
166 MultiDimArray(MultiDimArray&& o) noexcept :
167 data_(std::move(o.data_)), view_(data_.data(), o.view_.extents())
171 MultiDimArray& operator=(const MultiDimArray& o)
174 view_ = view_type(data_.data(), o.view_.extents());
178 MultiDimArray& operator=(MultiDimArray&& o) noexcept
180 data_ = std::move(o.data_);
181 view_ = view_type(data_.data(), o.view_.extents());
184 //! Swaps content with other
185 void swap(MultiDimArray& o)
188 swap(data_, o.data_);
189 // swap(view_, o.view_) also swaps the pointer to the data and thus does not work
190 // instead, restore the view as class invariant after the data swapping operation
191 o.view_ = view_type(o.data_.data(), view_.extents());
192 view_ = view_type(data_.data(), o.view_.extents());
195 * Resize the dynamic extents of the array if any and set container size
198 * Invalidates data and views of this array.
200 * \param[in] dynamicExtent A parameter pack that describes the dynamic
201 * size of the array. Empty if purely static.
202 * \tparam IndexType Parameter pack type holding the dynamic
203 * extents of the multidimensional array
205 template<class... IndexType>
206 void resize(IndexType... dynamicExtent)
208 // use a mapping object to determine the required span size;
209 layout_right::mapping<Extents> map{ Extents{ dynamicExtent... } };
210 data_.resize(map.required_span_size());
211 // to construct a valid view on the data, the container has to be resized before
212 // the assignment, so that data_.data() is valid
213 view_ = view_type(data_.data(), dynamicExtent...);
215 /*! \brief Data access via multidimensional indices.
216 * This allows referencing rank R array elements as array(x_0,x_1,x_2, .., x_R)
218 * \param[in] index multidimensional indices as parameter pack
219 * the number of parameters must match the rank of the array.
221 * \returns reference to array element
223 template<class... IndexType>
224 reference operator()(IndexType... index) noexcept
226 return view_(index...);
228 /*! \brief Const data access via multidimensional indices.
229 * This allows referencing rank R array elements as array(x_0,x_1,x_2, .., x_R)
231 * \param[in] index multidimensional indices as parameter pack
232 * the number of parameters must match the rank of the array.
234 * \returns const reference to array element
236 template<class... IndexType>
237 constexpr const_reference operator()(IndexType... index) const noexcept
239 return view_(index...);
241 /*! \brief Contiguous access to the data.
242 * \returns ArrayRef to stored data.
244 ArrayRef<value_type> toArrayRef() { return { data_.data(), data_.data() + data_.size() }; }
245 /*! \brief Contiguous const access to the data.
246 * \returns ArrayRef to stored data.
248 constexpr ArrayRef<const value_type> toArrayRef() const
250 return { data_.data(), data_.data() + data_.size() };
252 /*! \brief Return the extent.
253 * \param[in] k dimension to query for extent
254 * \returns extent along specified dimension
256 constexpr typename view_type::index_type extent(int k) const noexcept
258 return view_.extent(k);
260 //! Conversion to multidimensional view on the data
261 constexpr view_type asView() noexcept { return view_; }
262 //! Conversion to const multidimensional view on the data
263 constexpr const_view_type asConstView() const noexcept
265 return { data_.data(), view_.mapping() };
269 //! The contiguous data that is equipped with multidimensional indexing in this class
271 //! Multidimensional view into data_.
275 //! Free MultiDimArray begin function addressing its contiguous memory.
276 template<class TContainer, class Extents>
277 constexpr typename MultiDimArray<TContainer, Extents>::const_iterator
278 begin(const MultiDimArray<TContainer, Extents>& multiDimArray)
280 return multiDimArray.toArrayRef().begin();
283 //! Free MultiDimArray begin function addressing its contiguous memory.
284 template<class TContainer, class Extents>
285 constexpr typename MultiDimArray<TContainer, Extents>::iterator begin(MultiDimArray<TContainer, Extents>& multiDimArray)
287 return multiDimArray.toArrayRef().begin();
290 //! Free MultiDimArray end function addressing its contiguous memory.
291 template<class TContainer, class Extents>
292 constexpr typename MultiDimArray<TContainer, Extents>::const_iterator
293 end(const MultiDimArray<TContainer, Extents>& multiDimArray)
295 return multiDimArray.toArrayRef().end();
298 //! Free MultiDimArray end function addressing its contiguous memory.
299 template<class TContainer, class Extents>
300 constexpr typename MultiDimArray<TContainer, Extents>::iterator end(MultiDimArray<TContainer, Extents>& multiDimArray)
302 return multiDimArray.toArrayRef().end();
306 template<class TContainer, class Extents>
307 void swap(MultiDimArray<TContainer, Extents>& a, MultiDimArray<TContainer, Extents>& b) noexcept
314 #endif // GMX_MATH_MULTIDIMARRAY_H_