Function assemble_matrix0

cpp/demo/custom_kernel/main.cpp:73–93

/// @return Frobenius norm squared of the matrix.
template <std::floating_point T>
double assemble_matrix0(std::shared_ptr<const fem::FunctionSpace<T>> V,
                        auto kernel, const std::vector<std::int32_t>& cells)
{
  // Kernel data (ID, kernel function, cell indices to execute over)
  std::map integrals{
      std::pair{std::tuple{fem::IntegralType::cell, 0, 0},
                fem::integral_data<T>(kernel, cells, std::vector<int>{})}};

  fem::Form<T, T> a({V, V}, integrals, V->mesh(), {}, {}, false, {});
  auto dofmap = V->dofmap();
  auto sp = la::SparsityPattern(
      V->mesh()->comm(), {dofmap->index_map, dofmap->index_map},
      {dofmap->index_map_bs(), dofmap->index_map_bs()});
  fem::sparsitybuild::cells(sp, std::pair{cells, cells}, {*dofmap, *dofmap});
  sp.finalize();
  la::MatrixCSR<T> A(sp);
  common::Timer timer("Assembler0 std::function (matrix)");
  assemble_matrix(A.mat_add_values(), a, {});
  A.scatter_rev();
  return A.squared_norm();
}

/// @brief Assemble a RHS vector using a `std::function` kernel
/// function.