Line data    Source code

       1           0 : // Distributed under the MIT License.
       2             : // See LICENSE.txt for details.
       3             : 
       4             : #pragma once
       5             : 
       6             : #include <cstddef>
       7             : #include <type_traits>
       8             : 
       9             : #include "DataStructures/Tensor/IndexType.hpp"
      10             : #include "DataStructures/Tensor/Metafunctions.hpp"
      11             : #include "DataStructures/Tensor/Tensor.hpp"
      12             : #include "DataStructures/VectorImpl.hpp"
      13             : #include "Utilities/Array.hpp"
      14             : #include "Utilities/Gsl.hpp"
      15             : #include "Utilities/StdArrayHelpers.hpp"
      16             : #include "Utilities/TMPL.hpp"
      17             : 
      18             : /// \ingroup TensorGroup
      19             : /// \brief Combines a time component of a tensor with spatial components to
      20             : /// produce a spacetime tensor.
      21             : ///
      22             : /// \details Combines a time component of a tensor with spatial components to
      23             : /// produce a spacetime tensor. Specifically, the components of the result
      24             : /// are views to the inputs. Can do so for a tensor of any rank, but
      25             : /// requires that the new index is the first index of the resulting tensor,
      26             : /// replacing the position of the spatial index in the input spatial tensor.
      27             : /// For instance, it may combine \f$ \phi \f$ with \f$ A^i \f$ into
      28             : /// \f$ A^a = \left(\phi, A^i\right) \f$, or it may combine \f$ A^a{}_b{}_c \f$
      29             : /// with \f$ B_i{}^a{}_b{}_c \f$ into
      30             : /// \f$ C_a{}^b{}_c{}_d = \left(A^b{}_c{}_d, B_i{}^b{}_c{}_d\right)\f$,
      31             : /// but it may not combine \f$ A^i{}_a \f$ with \f$ B^i{}_j{}_a \f$ to produce
      32             : /// a tensor of the form \f$ C^i{}_a{}_b \f$.
      33             : ///
      34             : /// \tparam SpatialDim the number of spatial dimensions in the input and output
      35             : ///         tensors
      36             : /// \tparam Ul whether the new index is covariant or contravariant (must match
      37             : ///         that of the spatial index of the input spatial tensor)
      38             : /// \tparam Frame the frame of the new spacetime index (must match that of the
      39             : ///         spatial index of the input spatial tensor)
      40             : template <size_t SpatialDim, UpLo Ul, typename Frame, typename DataType,
      41             :           typename SymmList, typename IndexList>
      42           1 : void combine_spacetime_view(
      43             :     gsl::not_null<TensorMetafunctions::prepend_spacetime_index<
      44             :         Tensor<DataType, SymmList, IndexList>, SpatialDim, Ul, Frame>*>
      45             :         spacetime_tensor,
      46             :     const Tensor<DataType, SymmList, IndexList>& time_tensor,
      47             :     const TensorMetafunctions::prepend_spatial_index<
      48             :         Tensor<DataType, SymmList, IndexList>, SpatialDim, Ul, Frame>&
      49             :         spatial_tensor) {
      50             :   for (size_t storage_index = 0;
      51             :        storage_index < Tensor<DataVector, SymmList, IndexList>::size();
      52             :        ++storage_index) {
      53             :     const auto u_multi_index =
      54             :         Tensor<DataVector, SymmList,
      55             :                IndexList>::structure::get_canonical_tensor_index(storage_index);
      56             :     if constexpr (std::is_same_v<DataType, DataVector>) {
      57             :       const auto dtu_multi_index = prepend(u_multi_index, 0_st);
      58             :       make_const_view(
      59             :           make_not_null(&std::as_const(spacetime_tensor->get(dtu_multi_index))),
      60             :           time_tensor.get(u_multi_index), 0,
      61             :           time_tensor.get(u_multi_index).size());
      62             :       for (size_t i = 0; i < SpatialDim; i++) {
      63             :         const auto du_multi_index = prepend(u_multi_index, i + 1);
      64             :         const auto diu_multi_index = prepend(u_multi_index, i);
      65             :         make_const_view(make_not_null(&std::as_const(
      66             :                             spacetime_tensor->get(du_multi_index))),
      67             :                         spatial_tensor.get(diu_multi_index), 0,
      68             :                         spatial_tensor.get(diu_multi_index).size());
      69             :       }
      70             :     } else {
      71             :       const auto dtu_multi_index = prepend(u_multi_index, 0_st);
      72             :       spacetime_tensor->get(dtu_multi_index) = time_tensor.get(u_multi_index);
      73             :       for (size_t i = 0; i < SpatialDim; ++i) {
      74             :         const auto du_multi_index = prepend(u_multi_index, i + 1);
      75             :         const auto diu_multi_index = prepend(u_multi_index, i);
      76             :         spacetime_tensor->get(du_multi_index) =
      77             :             spatial_tensor.get(diu_multi_index);
      78             :       }
      79             :     }
      80             :   }
      81             : }