Tensor.hpp

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/* This file is part of OpenKalman, a header-only C++ library for
 * Kalman filters and other recursive filters.
 *
 * Copyright (c) 2023 Christopher Lee Ogden <ogden@gatech.edu>
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 */

#ifndef OPENKALMAN_EIGEN_TRAITS_TENSOR_HPP
#define OPENKALMAN_EIGEN_TRAITS_TENSOR_HPP


namespace OpenKalman::interface
{
  template<typename Scalar, int NumIndices, int options, typename IndexType>
  struct object_traits<Eigen::Tensor<Scalar, NumIndices, options, IndexType>>
    : Eigen3::object_traits_tensor_base<Eigen::Tensor<Scalar, NumIndices, options, IndexType>>
  {
  private:

    using Base = Eigen3::object_traits_tensor_base<Eigen::Tensor<Scalar, NumIndices, options, IndexType>>;

  public:

    template<typename Arg, typename N>
    static constexpr std::size_t get_pattern_collection(const Arg& arg, N n) { return arg.dimension(n); }

    // nested_object() not defined

    // get_constant() not defined

    // get_constant_diagonal() not defined


#ifdef __cpp_lib_concepts
    template<typename Arg, std::convertible_to<IndexType>...I> requires (sizeof...(I) == NumIndices)
#else
    template<typename Arg, typename...I, std::enable_if_t<(stdex::convertible_to<I, IndexType> and ...) and
      (sizeof...(I) == NumIndices), int> = 0>
#endif
    static constexpr decltype(auto) get(Arg&& arg, I...i)
    {
      if constexpr ((Eigen::internal::traits<std::decay_t<Arg>>::Flags & Eigen::LvalueBit) != 0)
        return std::forward<Arg>(arg).coeffRef(static_cast<IndexType>(i)...);
      else
        return std::forward<Arg>(arg).coeff(static_cast<IndexType>(i)...);
    }


#ifdef __cpp_lib_concepts
    template<typename Arg, std::convertible_to<IndexType>...I> requires (sizeof...(I) == NumIndices) and
      ((Eigen::internal::traits<std::decay_t<Arg>>::Flags & Eigen::LvalueBit) != 0x0)
#else
    template<typename Arg, typename...I, std::enable_if_t<(stdex::convertible_to<I, IndexType> and ...) and
      (sizeof...(I) == NumIndices) and ((Eigen::internal::traits<std::decay_t<Arg>>::Flags & Eigen::LvalueBit) != 0x0), int> = 0>
#endif
    static void set(Arg& arg, const scalar_type_of_t<Arg>& s, I...i)
    {
      arg.coeffRef(static_cast<IndexType>(i)...) = s;
    }

    static constexpr bool is_writable = true;

    template<typename Arg>
    static constexpr auto * const
    raw_data(Arg& arg) { return arg.data(); }

    static constexpr data_layout layout = options & Eigen::RowMajor ? data_layout::right : data_layout::left;

  };

}

#endif