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37 * \brief Declares MultiDimArray.
39 * \author Christian Blau <cblau@gwdg.de>
40 * \ingroup module_math
41 * \ingroup module_mdspan
44 #ifndef GMX_MATH_MULTIDIMARRAY_H_
45 #define GMX_MATH_MULTIDIMARRAY_H_
47 #include "gromacs/mdspan/mdspan.h"
48 #include "gromacs/utility/arrayref.h"
55 /*! \libinternal \brief
56 * Determine static array size at compile time.
57 * Statically evaluates the product of static array extents.
58 * \tparam Extents Extents of an multidimensional array as in module_mdspan
59 * \returns the product of the static extents
61 template <typename Extents>
62 constexpr typename Extents::index_type staticExtentsProduct(size_t const i = 0)
64 return (i < Extents::rank()) ? Extents::static_extent(i) * staticExtentsProduct<Extents>(i + 1) : 1;
67 /*! \libinternal \brief
68 * Multidimensional array that manages its own memory.
70 * \note No bounds checking when accessing memory
72 * \note That the view holds a valid pointer to the data is a class invariant.
74 * The Container type that stores the data may be resizable (std::vector or similar)
75 * or static (std::array or similar). Copy and move assignment routines as well as
76 * swapping are designed to yield good performances in both cases, notably
77 * foregoing the copy-swap idiom due to the bad performance in swapping std::array.
79 * This class avoids throwing exeptions, apart from the ones that might be thrown
80 * from the containers during resizing an allocation. (bad_malloc from std::vector
81 * is a likely candidate)
84 * Holds as many elements as required by a multidimensional view.
85 * \tparam TContainer Data type container for the data to be stored
86 * as MultiDimArray with random element access and
87 * value_type, refence and const_reference exposed
88 * \tparam Extents An extents class describing the array dimensions
89 * as used in module_mdspan
90 * \tparam LayoutPolicy The data layout as in module_mdspan describes
91 * translation of indices to memory offset.
92 * Defaults to right aligned, so that the right-most index
93 * is contiguous in memory.
95 template <class TContainer, class Extents, class LayoutPolicy = layout_right>
99 //! the type of values that are stored
100 using value_type = typename TContainer::value_type;
101 //! reference type to the stored values
102 using reference = typename TContainer::reference;
103 //! const reference type to the stored values
104 using const_reference = typename TContainer::const_reference;
105 //! the view used to access the data
106 using view_type = basic_mdspan<value_type, Extents, LayoutPolicy>;
107 /*! \brief Iterator type for contiguous iteration over the stored data.
108 * Used, e.g., in free begin and end functions
110 using iterator = typename ArrayRef<value_type>::iterator;
111 /*! \brief Const iterator type for contiguous iteration over the stored data.
112 * used, e.g., in free begin and end functions
114 using const_iterator = const typename ArrayRef<const value_type>::const_iterator;
116 * Allocate dynamic array data and set view with the dynamic extents.
118 * \param[in] dynamicExtent A parameter pack that describes the dynamic
119 * size of the array. Empty if purely static.
121 * \tparam IndexType Parameter pack type holding the dynamic
122 * extents of the multidimensional array
124 template <class ... IndexType>
125 MultiDimArray(IndexType... dynamicExtent)
127 static_assert(Extents::rank_dynamic() != 0,
128 "Resizable container type not allowed in a static MultiDimArray.");
129 resize(dynamicExtent ...);
132 * Construction with fixed sized array for storage if MultiDimArray size
133 * is static and layout policy allows compile time determination of the
136 * Exampe use is MultiDimArray<std::array<float, 9>, extents<3,3>>
137 * \tparam StaticSizeAndLayout Template parameter for activation via SFINAE.
139 template <bool StaticSizeAndLayoutRight = Extents::rank_dynamic() == 0 &&
140 std::is_same<LayoutPolicy, layout_right>::value,
141 typename std::enable_if<StaticSizeAndLayoutRight, int>::type = 0>
142 constexpr MultiDimArray() noexcept : view_(data_.data())
144 // \todo replace staticExtentsProduct by the required_span_size
145 // of the LayoutPolicy, once required_span_size is a constexpr
147 // using tuple_size allows constexpr for this constructor (data_.size() is not available then)
148 static_assert(std::tuple_size<TContainer>() ==
149 detail::staticExtentsProduct<Extents>(),
150 "Non-resizable container type size must match static MultiDimArray size.");
153 * Construction from fixed sized arrays if the array size is static and
154 * layout policy allows compile time determination of the container size.
156 * Enables the expected initialization
157 * MultiDimArray<std::array<float, 9>, extents<3,3>> arr = {{1,2...}}
158 * \tparam StaticSizeAndLayout Template parameter for activation via SFINAE.
160 template <bool StaticSizeAndLayoutRight = Extents::rank_dynamic() == 0 &&
161 std::is_same<LayoutPolicy, layout_right>::value,
162 typename std::enable_if<StaticSizeAndLayoutRight, int>::type = 0>
163 constexpr MultiDimArray(const TContainer &data) noexcept : data_(data), view_(data_.data())
165 // \todo replace staticExtentsProduct by the required_span_size
166 // of the LayoutPolicy, once required_span_size is a constexpr
168 // using tuple_size allows constexpr for this constructor (data_.size() is not available then)
169 static_assert(std::tuple_size<TContainer>() ==
170 detail::staticExtentsProduct<Extents>(),
171 "Non-resizable container type size must match static MultiDimArray size.");
174 constexpr MultiDimArray(const MultiDimArray &o) :
176 view_(data_.data(), o.view_.extents())
179 MultiDimArray(MultiDimArray &&o) noexcept : data_(std::move(o.data_)),
180 view_(data_.data(), o.view_.extents())
183 MultiDimArray &operator=(const MultiDimArray &o) noexcept
186 view_ = view_type(data_.data(), o.view_.extents());
190 MultiDimArray &operator=(MultiDimArray &&o) noexcept
192 data_ = std::move(o.data_);
193 view_ = view_type(data_.data(), o.view_.extents());
196 //! Swaps content with other
197 void swap(MultiDimArray &o)
200 swap(data_, o.data_);
201 swap(view_, o.view_);
204 * Resize the dynamic extents of the array if any and set container size
207 * Invalidates data and views of this array.
209 * \param[in] dynamicExtent A parameter pack that describes the dynamic
210 * size of the array. Empty if purely static.
211 * \tparam IndexType Parameter pack type holding the dynamic
212 * extents of the multidimensional array
214 template <class ... IndexType>
215 void resize(IndexType... dynamicExtent)
217 // use a mapping object to determine the required span size;
218 layout_right::mapping<Extents> map {Extents {dynamicExtent ...}};
219 data_.resize(map.required_span_size());
220 // to construct a valid view on the data, the container has to be resized before
221 // the assignment, so that data_.data() is valid
222 view_ = view_type(data_.data(), dynamicExtent ...);
224 /*! \brief Data access via multidimensional indices.
225 * This allows referencing rank R array elements as array(x_0,x_1,x_2, .., x_R)
227 * \param[in] index multidimensional indices as parameter pack
228 * the number of parameters must match the rank of the array.
230 * \returns reference to array element
232 template< class... IndexType>
233 reference operator()(IndexType ... index) noexcept
235 return view_(index ...);
237 /*! \brief Const data access via multidimensional indices.
238 * This allows referencing rank R array elements as array(x_0,x_1,x_2, .., x_R)
240 * \param[in] index multidimensional indices as parameter pack
241 * the number of parameters must match the rank of the array.
243 * \returns const reference to array element
245 template <class... IndexType>
246 constexpr const_reference operator()(IndexType... index) const noexcept
248 return view_(index ...);
250 /*! \brief Contiguous access to the data.
251 * \returns ArrayRef to stored data.
253 ArrayRef<value_type> toArrayRef()
255 return {data_.data(), data_.data()+data_.size()};
257 /*! \brief Contiguous const access to the data.
258 * \returns ArrayRef to stored data.
260 constexpr ArrayRef<const value_type> toArrayRef() const
262 return {data_.data(), data_.data()+data_.size()};
264 /*! \brief Return the extent.
265 * \param[in] k dimension to query for extent
266 * \returns extent along specified dimension
268 constexpr typename view_type::index_type extent(int k) const noexcept
270 return view_.extent(k);
273 //! The contiguous data that is equipped with multidimensional indexing in this class
275 //! Multidimensional view into data_.
279 //! Free MultiDimArray begin function addressing its contiguous memory.
280 template <class TContainer, class Extents>
281 constexpr typename MultiDimArray<TContainer, Extents>::const_iterator
282 begin(const MultiDimArray<TContainer, Extents> &multiDimArray)
284 return multiDimArray.toArrayRef().begin();
287 //! Free MultiDimArray begin function addressing its contiguous memory.
288 template <class TContainer, class Extents>
289 constexpr typename MultiDimArray<TContainer, Extents>::iterator
290 begin(MultiDimArray<TContainer, Extents> &multiDimArray)
292 return multiDimArray.toArrayRef().begin();
295 //! Free MultiDimArray end function addressing its contiguous memory.
296 template <class TContainer, class Extents>
297 constexpr typename MultiDimArray<TContainer, Extents>::const_iterator
298 end(const MultiDimArray<TContainer, Extents> &multiDimArray)
300 return multiDimArray.toArrayRef().end();
303 //! Free MultiDimArray end function addressing its contiguous memory.
304 template <class TContainer, class Extents>
305 constexpr typename MultiDimArray<TContainer, Extents>::iterator
306 end(MultiDimArray<TContainer, Extents> &multiDimArray)
308 return multiDimArray.toArrayRef().end();
312 template <class TContainer, class Extents>
313 void swap(MultiDimArray<TContainer, Extents> &a, MultiDimArray<TContainer, Extents > &b) noexcept
320 #endif // GMX_MATH_MULTIDIMARRAY_H_