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Check out http://www.gromacs.org. 34 */ 35 /*! \libinternal 36 * \file 37 * \brief Declares MultiDimArray. 38 * 39 * \author Christian Blau <cblau@gwdg.de> 40 * \ingroup module_math 41 * \ingroup module_mdspan 42 * \inlibraryapi 43 */ 44 45 #ifndef GMX_MATH_MULTIDIMARRAY_H_ 46 #define GMX_MATH_MULTIDIMARRAY_H_ 47 48 #include "gromacs/mdspan/mdspan.h" 49 #include "gromacs/utility/arrayref.h" 50 51 namespace gmx 52 { 53 54 namespace detail 55 { 56 //! Same as std::void_t from C++17 57 template<class...> 58 using void_t = void; 59 60 template<typename T, typename = void> 61 struct is_resizable : std::false_type 62 { 63 }; 64 65 template<typename T> 66 struct is_resizable<T, void_t<decltype(std::declval<T>().resize(size_t()))>> : std::true_type 67 { 68 }; 69 70 //! Type has a resize member function callable with size_t argument 71 template<typename T> 72 // NOLINTNEXTLINE misc-definitions-in-headers 73 constexpr bool is_resizable_v = is_resizable<T>::value; 74 } // namespace detail 75 76 /*! \libinternal \brief 77 * Multidimensional array that manages its own memory. 78 * 79 * \note No bounds checking when accessing memory 80 * 81 * \note That the view holds a valid pointer to the data is a class invariant. 82 * 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. 87 * 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) 91 * 92 * 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. 103 */ 104 template<class TContainer, class Extents, class LayoutPolicy = layout_right> 105 class MultiDimArray 106 { 107 public: 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 120 */ 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 124 */ 125 using const_iterator = const typename ArrayRef<const value_type>::const_iterator; 126 127 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."); 130 131 /*! \brief 132 * Allocate dynamic array data and set view with the dynamic extents. 133 * 134 * \param[in] dynamicExtent A parameter pack that describes the dynamic 135 * size of the array. Empty if purely static. 136 * 137 * \tparam IndexType Parameter pack type holding the dynamic 138 * extents of the multidimensional array 139 */ 140 template<class... IndexType, typename T = TContainer, typename = typename std::enable_if_t<detail::is_resizable_v<T>>> 141 MultiDimArray(IndexType... dynamicExtent) 142 { 143 resize(dynamicExtent...); 144 } 145 /*! \brief 146 * Construction from fixed sized arrays if the array size is static and 147 * layout policy allows compile time determination of the container size. 148 * 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. 152 */ 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()) 156 { 157 static_assert(TContainer().size() == typename view_type::mapping_type().required_span_size(), 158 "Non-resizable container type size must match static MultiDimArray size."); 159 } 160 //! Copy constructor 161 constexpr MultiDimArray(const MultiDimArray& o) : 162 data_(o.data_), 163 view_(data_.data(), o.view_.extents()) 164 { 165 } 166 //! Move constructor 167 MultiDimArray(MultiDimArray&& o) noexcept : 168 data_(std::move(o.data_)), 169 view_(data_.data(), o.view_.extents()) 170 { 171 } 172 //! Copy assignment 173 MultiDimArray& operator=(const MultiDimArray& o) 174 { 175 data_ = o.data_; 176 view_ = view_type(data_.data(), o.view_.extents()); 177 return *this; 178 } 179 //! Move assignment 180 MultiDimArray& operator=(MultiDimArray&& o) noexcept 181 { 182 data_ = std::move(o.data_); 183 view_ = view_type(data_.data(), o.view_.extents()); 184 return *this; 185 } 186 //! Swaps content with other 187 void swap(MultiDimArray& o) 188 { 189 using std::swap; 190 swap(data_, o.data_); 191 // swap(view_, o.view_) also swaps the pointer to the data and thus does not work 192 // instead, restore the view as class invariant after the data swapping operation 193 o.view_ = view_type(o.data_.data(), view_.extents()); 194 view_ = view_type(data_.data(), o.view_.extents()); 195 } 196 /*! \brief 197 * Resize the dynamic extents of the array if any and set container size 198 * accordingly. 199 * 200 * Invalidates data and views of this array. 201 * 202 * \param[in] dynamicExtent A parameter pack that describes the dynamic 203 * size of the array. Empty if purely static. 204 * \tparam IndexType Parameter pack type holding the dynamic 205 * extents of the multidimensional array 206 */ 207 template<class... IndexType> 208 void resize(IndexType... dynamicExtent) 209 { 210 // use a mapping object to determine the required span size; 211 layout_right::mapping<Extents> map{ Extents{ dynamicExtent... } }; 212 data_.resize(map.required_span_size()); 213 // to construct a valid view on the data, the container has to be resized before 214 // the assignment, so that data_.data() is valid 215 view_ = view_type(data_.data(), dynamicExtent...); 216 } 217 /*! \brief Data access via multidimensional indices. 218 * This allows referencing rank R array elements as array(x_0,x_1,x_2, .., x_R) 219 * 220 * \param[in] index multidimensional indices as parameter pack 221 * the number of parameters must match the rank of the array. 222 * 223 * \returns reference to array element 224 */ 225 template<class... IndexType> 226 reference operator()(IndexType... index) noexcept 227 { 228 return view_(index...); 229 } 230 /*! \brief Const data access via multidimensional indices. 231 * This allows referencing rank R array elements as array(x_0,x_1,x_2, .., x_R) 232 * 233 * \param[in] index multidimensional indices as parameter pack 234 * the number of parameters must match the rank of the array. 235 * 236 * \returns const reference to array element 237 */ 238 template<class... IndexType> 239 constexpr const_reference operator()(IndexType... index) const noexcept 240 { 241 return view_(index...); 242 } 243 /*! \brief Contiguous access to the data. 244 * \returns ArrayRef to stored data. 245 */ 246 ArrayRef<value_type> toArrayRef() { return { data_.data(), data_.data() + data_.size() }; } 247 /*! \brief Contiguous const access to the data. 248 * \returns ArrayRef to stored data. 249 */ 250 constexpr ArrayRef<const value_type> toArrayRef() const 251 { 252 return { data_.data(), data_.data() + data_.size() }; 253 } 254 /*! \brief Return the extent. 255 * \param[in] k dimension to query for extent 256 * \returns extent along specified dimension 257 */ 258 constexpr typename view_type::index_type extent(int k) const noexcept 259 { 260 return view_.extent(k); 261 } 262 //! Conversion to multidimensional view on the data 263 constexpr view_type asView() noexcept { return view_; } 264 //! Conversion to const multidimensional view on the data 265 constexpr const_view_type asConstView() const noexcept 266 { 267 return { data_.data(), view_.mapping() }; 268 } 269 270 private: 271 //! The contiguous data that is equipped with multidimensional indexing in this class 272 TContainer data_; 273 //! Multidimensional view into data_. 274 view_type view_; 275 }; 276 277 //! Free MultiDimArray begin function addressing its contiguous memory. 278 template<class TContainer, class Extents> 279 constexpr typename MultiDimArray<TContainer, Extents>::const_iterator 280 begin(const MultiDimArray<TContainer, Extents>& multiDimArray) 281 { 282 return multiDimArray.toArrayRef().begin(); 283 } 284 285 //! Free MultiDimArray begin function addressing its contiguous memory. 286 template<class TContainer, class Extents> 287 constexpr typename MultiDimArray<TContainer, Extents>::iterator begin(MultiDimArray<TContainer, Extents>& multiDimArray) 288 { 289 return multiDimArray.toArrayRef().begin(); 290 } 291 292 //! Free MultiDimArray end function addressing its contiguous memory. 293 template<class TContainer, class Extents> 294 constexpr typename MultiDimArray<TContainer, Extents>::const_iterator 295 end(const MultiDimArray<TContainer, Extents>& multiDimArray) 296 { 297 return multiDimArray.toArrayRef().end(); 298 } 299 300 //! Free MultiDimArray end function addressing its contiguous memory. 301 template<class TContainer, class Extents> 302 constexpr typename MultiDimArray<TContainer, Extents>::iterator end(MultiDimArray<TContainer, Extents>& multiDimArray) 303 { 304 return multiDimArray.toArrayRef().end(); 305 } 306 307 //! Swap function 308 template<class TContainer, class Extents> 309 void swap(MultiDimArray<TContainer, Extents>& a, MultiDimArray<TContainer, Extents>& b) noexcept 310 { 311 a.swap(b); 312 } 313 314 } // namespace gmx 315 316 #endif // GMX_MATH_MULTIDIMARRAY_H_ 317