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              : 
       8              : #include "Utilities/Gsl.hpp"
       9              : 
      10              : /// \cond
      11              : class DataVector;
      12              : template <size_t Dim>
      13              : class Mesh;
      14              : template <typename TagsList>
      15              : class Variables;
      16              : /// \endcond
      17              : 
      18              : namespace Spectral::filtering {
      19              : /*!
      20              :  * \brief Filters the radial components of tensors stored within a `Variables`
      21              :  * represented by ZernikeB3 basis functions on a filled ball.
      22              :  *
      23              :  * \details Functions on a filled ball with angular degree $\ell$ behave as
      24              :  * $r^\ell$ near the origin, so their radial profile lies in the even or
      25              :  * odd parity ZernikeB3 subspace depending on whether $\ell$ is even or odd. The
      26              :  * combined spectral space is therefore indexed by $(n_\mathrm{jac}, \ell, m)$,
      27              :  * where $n_\mathrm{jac}$ is the radial Jacobi index. The exponential filter
      28              :  * weight for mode $(n_\mathrm{jac}, \ell)$ is
      29              :  *
      30              :  * \f{align*}{
      31              :  *   w = \exp\!\left(-\alpha \left(\frac{n_i}{N_r-1}\right)^{2p}\right),
      32              :  * \f}
      33              :  *
      34              :  * where $n_i = \lfloor (\ell + 2 n_\mathrm{jac}) / 2 \rfloor$ and $N_r$ is the
      35              :  * number of radial grid points.
      36              :  *
      37              :  * The mesh must have basis
      38              :  * `(ZernikeB3, ZernikeB3, ZernikeB3)` with quadrature
      39              :  * `(GaussRadauUpper, Gauss, Equiangular)` and extents
      40              :  * `(n_r, l_max+1, 2*l_max+1)`.
      41              :  *
      42              :  * \see exponential_filter()
      43              :  */
      44              : template <typename VariablesTags>
      45            1 : void zernike_b3_ball_radial_exponential_filter(
      46              :     gsl::not_null<Variables<VariablesTags>*> u, const Mesh<3>& mesh,
      47              :     double alpha, unsigned half_power);
      48              : 
      49              : /*!
      50              :  * \brief Filters the radial components of tensors stored within a `Variables`
      51              :  * represented by ZernikeB3 basis functions on a filled ball.
      52              :  *
      53              :  * \details Overload taking a caller-managed working buffer. Avoids heap
      54              :  * allocations when the filter is applied repeatedly (e.g. every volume call
      55              :  * inside `Filters::Ball`).
      56              :  */
      57              : template <typename VariablesTags>
      58            1 : void zernike_b3_ball_radial_exponential_filter(
      59              :     gsl::not_null<Variables<VariablesTags>*> u, gsl::not_null<DataVector*> buf,
      60              :     const Mesh<3>& mesh, double alpha, unsigned half_power);
      61              : 
      62              : }  // namespace Spectral::filtering