Add replacements for pbc enumerations

[gromacs.git] / src / gromacs / math / multidimarray.h

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/*! \libinternal
 * \file
 * \brief Declares MultiDimArray.
 *
 * \author Christian Blau <cblau@gwdg.de>
 * \ingroup module_math
 * \ingroup module_mdspan
 */

#ifndef GMX_MATH_MULTIDIMARRAY_H_
#define GMX_MATH_MULTIDIMARRAY_H_

#include "gromacs/mdspan/mdspan.h"
#include "gromacs/utility/arrayref.h"

namespace gmx
{

namespace detail
{
//! Same as std::void_t from C++17
template< class ... >
using void_t = void;

template<typename T, typename = void>
struct is_resizable : std::false_type {};

template<typename T>
struct is_resizable<T, void_t<decltype(std::declval<T>().resize(size_t()))> > : std::true_type {};

//! Type has a resize member function callable with size_t argument
template<typename T>
constexpr bool is_resizable_v = is_resizable<T>::value;
}   //namespace detail

/*! \libinternal \brief
 * Multidimensional array that manages its own memory.
 *
 * \note No bounds checking when accessing memory
 *
 * \note That the view holds a valid pointer to the data is a class invariant.
 *
 * The Container type that stores the data may be resizable (std::vector or similar)
 * or static (std::array or similar). Copy and move assignment routines as well as
 * swapping are designed to yield good performances in both cases, notably
 * foregoing the copy-swap idiom due to the bad performance in swapping std::array.
 *
 * This class avoids throwing exeptions, apart from the ones that might be thrown
 * from the containers during resizing an allocation. (bad_malloc from std::vector
 * is a likely candidate)
 *
 *
 * Holds as many elements as required by a multidimensional view.
 * \tparam TContainer   Data type container for the data to be stored
 *                      as MultiDimArray with random element access and
 *                      value_type, refence and const_reference exposed
 * \tparam Extents      An extents class describing the array dimensions
 *                      as used in module_mdspan
 * \tparam LayoutPolicy The data layout as in module_mdspan describes
 *                      translation of indices to memory offset.
 *                      Defaults to right aligned, so that the right-most index
 *                      is contiguous in memory.
 */
template <class TContainer, class Extents, class LayoutPolicy = layout_right>
class MultiDimArray
{
    public:
        //! the type of values that are stored
        using value_type = typename TContainer::value_type;
        //! reference type to the stored values
        using reference = typename TContainer::reference;
        //! const reference type to the stored values
        using const_reference = typename TContainer::const_reference;
        //! the view used to access the data
        using view_type = basic_mdspan<value_type, Extents, LayoutPolicy>;
        //! const view on the data
        using const_view_type = basic_mdspan<const value_type, Extents, LayoutPolicy>;
        /*! \brief Iterator type for contiguous iteration over the stored data.
         * Used, e.g., in free begin and end functions
         */
        using iterator = typename ArrayRef<value_type>::iterator;
        /*! \brief Const iterator type for contiguous iteration over the stored data.
         *  used, e.g., in free begin and end functions
         */
        using const_iterator = const typename ArrayRef<const value_type>::const_iterator;

        static_assert(detail::is_resizable_v<TContainer> == (Extents::rank_dynamic() > 0),
                      "Resizable container (e.g. std::vector) requires at least one dynamic rank. "
                      "Non-resizable container (e.g. std::array) requires zero dynamic ranks.");

        /*! \brief
         * Allocate dynamic array data and set view with the dynamic extents.
         *
         * \param[in] dynamicExtent A parameter pack that describes the dynamic
         *                          size of the array. Empty if purely static.
         *
         * \tparam IndexType        Parameter pack type holding the dynamic
         *                          extents of the multidimensional array
         */
        template <class ... IndexType, typename T = TContainer,
                  typename = typename std::enable_if_t<detail::is_resizable_v<T> > >
        MultiDimArray(IndexType... dynamicExtent)
        {
            resize(dynamicExtent ...);
        }
        /*! \brief
         * Construction from fixed sized arrays if the array size is static and
         * layout policy allows compile time determination of the container size.
         *
         * Enables the expected initialization
         * MultiDimArray<std::array<float, 9>, extents<3,3>> arr = {{1,2...}}
         * \tparam T Template parameter for activation via SFINAE.
         */
        // SFINAE required because std::vector::size isn't constexpr and is_constexpr doesn't exist.
        template <typename T = TContainer,
                  typename   = typename std::enable_if_t<!detail::is_resizable_v<T> > >
        constexpr MultiDimArray(const TContainer &data = {}
                                ) noexcept : data_(data), view_(data_.data())
        {
            static_assert(TContainer().size() == typename view_type::mapping_type().required_span_size(),
                          "Non-resizable container type size must match static MultiDimArray size.");
        }
        //! Copy constructor
        constexpr MultiDimArray(const MultiDimArray &o) :
            data_(o.data_),
            view_(data_.data(), o.view_.extents())
        {}
        //! Move constructor
        MultiDimArray(MultiDimArray &&o) noexcept : data_(std::move(o.data_)),
                                                    view_(data_.data(), o.view_.extents())
        {}
        //! Copy assignment
        MultiDimArray &operator=(const MultiDimArray &o)
        {
            data_ = o.data_;
            view_ = view_type(data_.data(), o.view_.extents());
            return *this;
        }
        //! Move assignment
        MultiDimArray &operator=(MultiDimArray &&o) noexcept
        {
            data_ = std::move(o.data_);
            view_ = view_type(data_.data(), o.view_.extents());
            return *this;
        }
        //! Swaps content with other
        void swap(MultiDimArray &o)
        {
            using std::swap;
            swap(data_, o.data_);
            // swap(view_, o.view_) also swaps the pointer to the data and thus does not work
            // instead, restore the view as class invariant after the data swapping operation
            o.view_ = view_type(o.data_.data(), view_.extents());
            view_   = view_type(data_.data(), o.view_.extents());
        }
        /*! \brief
         * Resize the dynamic extents of the array if any and set container size
         * accordingly.
         *
         * Invalidates data and views of this array.
         *
         * \param[in] dynamicExtent A parameter pack that describes the dynamic
         *                          size of the array. Empty if purely static.
         * \tparam IndexType        Parameter pack type holding the dynamic
         *                          extents of the multidimensional array
         */
        template <class ... IndexType>
        void resize(IndexType... dynamicExtent)
        {
            // use a mapping object to determine the required span size;
            layout_right::mapping<Extents> map {Extents {dynamicExtent ...}};
            data_.resize(map.required_span_size());
            // to construct a valid view on the data, the container has to be resized before
            // the assignment, so that data_.data() is valid
            view_ = view_type(data_.data(), dynamicExtent ...);
        }
        /*! \brief Data access via multidimensional indices.
         * This allows referencing rank R array elements as array(x_0,x_1,x_2, .., x_R)
         *
         * \param[in] index multidimensional indices as parameter pack
         *                  the number of parameters must match the rank of the array.
         *
         * \returns reference to array element
         */
        template< class... IndexType>
        reference operator()(IndexType ... index) noexcept
        {
            return view_(index ...);
        }
        /*! \brief Const data access via multidimensional indices.
         * This allows referencing rank R array elements as array(x_0,x_1,x_2, .., x_R)
         *
         * \param[in] index multidimensional indices as parameter pack
         *                  the number of parameters must match the rank of the array.
         *
         * \returns const reference to array element
         */
        template <class... IndexType>
        constexpr const_reference operator()(IndexType... index) const noexcept
        {
            return view_(index ...);
        }
        /*! \brief Contiguous access to the data.
         * \returns ArrayRef to stored data.
         */
        ArrayRef<value_type> toArrayRef()
        {
            return {data_.data(), data_.data()+data_.size()};
        }
        /*! \brief Contiguous const access to the data.
         * \returns ArrayRef to stored data.
         */
        constexpr ArrayRef<const value_type> toArrayRef() const
        {
            return {data_.data(), data_.data()+data_.size()};
        }
        /*! \brief Return the extent.
         * \param[in] k dimension to query for extent
         * \returns extent along specified dimension
         */
        constexpr typename view_type::index_type extent(int k) const noexcept
        {
            return view_.extent(k);
        }
        //! Conversion to multidimensional view on the data
        constexpr view_type asView() noexcept
        {
            return view_;
        }
        //! Conversion to const multidimensional view on the data
        constexpr const_view_type asConstView() const noexcept
        {
            return {data_.data(), view_.mapping()};
        }
    private:
        //! The contiguous data that is equipped with multidimensional indexing in this class
        TContainer data_;
        //! Multidimensional view into data_.
        view_type  view_;
};

//! Free MultiDimArray begin function addressing its contiguous memory.
template <class TContainer, class Extents>
constexpr typename MultiDimArray<TContainer, Extents>::const_iterator
begin(const MultiDimArray<TContainer, Extents> &multiDimArray)
{
    return multiDimArray.toArrayRef().begin();
}

//! Free MultiDimArray begin function addressing its contiguous memory.
template <class TContainer, class Extents>
constexpr typename MultiDimArray<TContainer, Extents>::iterator
begin(MultiDimArray<TContainer, Extents> &multiDimArray)
{
    return multiDimArray.toArrayRef().begin();
}

//! Free MultiDimArray end function addressing its contiguous memory.
template <class TContainer, class Extents>
constexpr typename MultiDimArray<TContainer, Extents>::const_iterator
end(const MultiDimArray<TContainer, Extents> &multiDimArray)
{
    return multiDimArray.toArrayRef().end();
}

//! Free MultiDimArray end function addressing its contiguous memory.
template <class TContainer, class Extents>
constexpr typename MultiDimArray<TContainer, Extents>::iterator
end(MultiDimArray<TContainer, Extents> &multiDimArray)
{
    return multiDimArray.toArrayRef().end();
}

//! Swap function
template <class TContainer, class Extents>
void swap(MultiDimArray<TContainer, Extents> &a, MultiDimArray<TContainer, Extents > &b) noexcept
{
    a.swap(b);
}

}      // namespace gmx

#endif // GMX_MATH_MULTIDIMARRAY_H_