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