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 <ostream>
       8             : 
       9             : /// \cond
      10             : class DataVector;
      11             : template <size_t>
      12             : class Mesh;
      13             : /// \endcond
      14             : 
      15             : namespace Limiters::Weno_detail {
      16             : 
      17             : // Denote different schemes for computing related oscillation indicators by
      18             : // changing the relative weight given to each derivative of the input data.
      19             : // - Unity: l'th derivative has weight 1
      20             : // - PowTwoEll: l'th derivative has weight 2^(2 l - 1)
      21             : //   This penalizes higher derivatives more strongly: w(l=4) = 128
      22             : // - PowTwoEllOverEllFactorial: l'th derivative has weight 2^(2 l - 1) / (l!)^2
      23             : //   This penalizes the 1st and 2nd derivatives most strongly, but then higher
      24             : //   derivatives have decreasing weights so are weakly penalized: w(l=4) = 0.222
      25             : enum class DerivativeWeight { Unity, PowTwoEll, PowTwoEllOverEllFactorial };
      26             : 
      27             : std::ostream& operator<<(std::ostream& os, DerivativeWeight derivative_weight);
      28             : 
      29             : // Compute the WENO oscillation indicator (also called the smoothness indicator)
      30             : //
      31             : // The oscillation indicator measures the amount of variation in the input data,
      32             : // with larger indicator values corresponding to a larger amount of variation
      33             : // (either from large monotonic slopes or from oscillations).
      34             : //
      35             : // Implements an indicator similar to that of Eq. 23 of Dumbser2007, but with
      36             : // the necessary adaptations for use on square/cube grids. We favor this
      37             : // indicator because it is formulated in the reference coordinates, which we
      38             : // use for the WENO reconstruction, and because it lends itself to an efficient
      39             : // implementation.
      40             : template <size_t VolumeDim>
      41             : double oscillation_indicator(DerivativeWeight derivative_weight,
      42             :                              const DataVector& data,
      43             :                              const Mesh<VolumeDim>& mesh);
      44             : 
      45             : }  // namespace Limiters::Weno_detail