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