Line data    Source code

       1           0 : // Distributed under the MIT License.
       2             : // See LICENSE.txt for details.
       3             : 
       4             : #pragma once
       5             : 
       6             : #include <array>
       7             : #include <cstddef>
       8             : #include <deque>
       9             : 
      10             : namespace fd {
      11             : /*!
      12             :  * \ingroup FiniteDifferenceGroup
      13             :  * \brief Returns the weights for a 1D non-uniform finite difference stencil.
      14             :  *
      15             :  * These weights are for the Lagrange interpolation polynomial and its
      16             :  * derivatives evaluated at `times[0]`. If the number of times is not the same
      17             :  * as `StencilSize`, then an error will occur.
      18             :  *
      19             :  * The reason that `times` was chosen to be monotonically decreasing is because
      20             :  * the intended use of this function is with data that is stored in a
      21             :  * `std::deque` where the zeroth element is the "most recent" in time and then
      22             :  * later elements are further in the "past".
      23             :  *
      24             :  * \param times A monotonically *decreasing* sequence of times
      25             :  * \return A 2D array of all finite difference weights that correspond to the
      26             :  * input times. The outer dimension is the Nth derivative, and the inner
      27             :  * dimension loops over the weights for each of the times.
      28             :  *
      29             :  * \note Only stencil sizes 2, 3, and 4 are implemented right now. If you need
      30             :  * more, you'll either need to add it yourself or generalize the algorithm.
      31             :  */
      32             : template <size_t StencilSize>
      33           1 : std::array<std::array<double, StencilSize>, StencilSize> non_uniform_1d_weights(
      34             :     const std::deque<double>& times);
      35             : }  // namespace fd