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36 * \brief Declares gmx::ArrayRefWithPadding that refers to memory whose
37 * size includes padding for SIMD operations.
39 * \author Mark Abraham <mark.j.abraham@gmail.com>
42 * \ingroup module_math
44 #ifndef GMX_MATH_ARRAYREFWITHPADDING_H
45 #define GMX_MATH_ARRAYREFWITHPADDING_H
49 #include "gromacs/utility/arrayref.h"
50 #include "gromacs/utility/basedefinitions.h"
51 #include "gromacs/utility/gmxassert.h"
56 /*! \brief Interface to a C array of T (or part of a std container of
57 * T), that includes padding that is suitable for the kinds of SIMD
58 * operations GROMACS uses.
60 * High level code e.g. in the force calculation routines need to hold
61 * a non-owning view of memory and be able to create ArrayRef objects
62 * that view padded or unpadded memory, suitable for the various
63 * component routines. This class implements that non-owning view,
64 * and the only available functionality refers to its size, and the
65 * methods to create such ArrayRef objects.
69 * \ingroup module_math
72 class ArrayRefWithPadding
75 //! Type of values stored in the reference.
77 //! Type for representing size of the reference.
78 using size_type = index;
79 //! Const pointer to an element.
80 using const_pointer = const T*;
81 //! Const iterator type to an element.
82 using const_iterator = const T*;
83 //! Pointer to an element.
85 //! Iterator type to an element.
89 * Constructs an empty reference.
92 : begin_(nullptr), end_(nullptr), paddedEnd_(nullptr) {}
94 * Constructs an empty reference.
96 * This is provided for convenience, such that EmptyArrayRef can be
97 * used to initialize any ArrayRefWithPadding, without specifying the template
98 * type. It is not explicit to enable that usage.
100 ArrayRefWithPadding(const EmptyArrayRef & /*unused*/)
101 : begin_(nullptr), end_(nullptr), paddedEnd_(nullptr) {}
103 * Constructs a reference to a particular range.
105 * \param[in] begin Pointer to the beginning of a range.
106 * \param[in] end Pointer to the end of a range without padding.
107 * \param[in] paddedEnd Pointer to the end of a range including padding.
109 * Passed pointers must remain valid for the lifetime of this object.
111 ArrayRefWithPadding(pointer begin, pointer end, pointer paddedEnd)
112 : begin_(begin), end_(end), paddedEnd_(paddedEnd)
114 GMX_ASSERT(end >= begin, "Invalid range");
115 GMX_ASSERT(paddedEnd >= end, "Invalid range");
118 ArrayRefWithPadding(const ArrayRefWithPadding &o)
119 : begin_(o.begin_), end_(o.end_), paddedEnd_(o.paddedEnd_) {}
121 ArrayRefWithPadding(ArrayRefWithPadding &&o) noexcept
122 : begin_(std::move(o.begin_)), end_(std::move(o.end_)), paddedEnd_(std::move(o.paddedEnd_)) {}
123 //! Copy assignment operator
124 ArrayRefWithPadding &operator=(ArrayRefWithPadding const &o)
130 paddedEnd_ = o.paddedEnd_;
134 //! Move assignment operator
135 ArrayRefWithPadding &operator=(ArrayRefWithPadding &&o) noexcept
139 begin_ = std::move(o.begin_);
140 end_ = std::move(o.end_);
141 paddedEnd_ = std::move(o.paddedEnd_);
146 //! Return the size of the view, i.e with the padding.
147 size_type size() const { return paddedEnd_ - begin_; }
148 //! Whether the reference refers to no memory.
149 bool empty() const { return begin_ == end_; }
151 //! Returns an ArrayRef of elements that does not include the padding region.
152 ArrayRef<T> unpaddedArrayRef()
154 return {begin_, end_};
156 //! Returns an ArrayRef of const elements that does not include the padding region.
157 ArrayRef<const T> unpaddedConstArrayRef() const
159 return {begin_, end_};
161 //! Returns an ArrayRef of elements that does include the padding region.
162 ArrayRef<T> paddedArrayRef()
164 return {begin_, paddedEnd_};
166 //! Returns an ArrayRef of const elements that does include the padding region.
167 ArrayRef<const T> paddedConstArrayRef() const
169 return {begin_, paddedEnd_};
172 * Swaps referenced memory with the other object.
174 * The actual memory areas are not modified, only the references are
177 void swap(ArrayRefWithPadding<T> &other)
179 std::swap(begin_, other.begin_);
180 std::swap(end_, other.end_);