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              : }