RiddersPropagator.hpp

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// This file is part of the Acts project.
//
// Copyright (C) 2017-2019 CERN for the benefit of the Acts project
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

#pragma once

#include "Acts/Propagator/Propagator.hpp"
#include "Acts/Surfaces/Surface.hpp"

namespace Acts {

template <typename propagator_t>
class RiddersPropagator {
  using Jacobian = BoundMatrix;
  using Covariance = BoundSquareMatrix;


  template <typename parameters_t, typename action_list_t>
  struct result_type_helper {
    template <typename... args>
    using this_result_type = PropagatorResult<parameters_t, args...>;

    using type = typename action_list_t::template result_type<this_result_type>;
  };

  template <typename parameters_t, typename action_list_t>
  using action_list_t_result_t =
      typename result_type_helper<parameters_t, action_list_t>::type;

 public:
  struct Config {
    std::vector<double> deviations = {-4e-4, -2e-4, 2e-4, 4e-4};
    std::vector<double> deviationsDisc = {-3e-5, -1e-5, 1e-5, 3e-5};
  };

  RiddersPropagator(propagator_t& propagator, Config config = {})
      : m_propagator(propagator), m_config(std::move(config)) {}

  template <typename stepper_t, typename navigator_t = detail::VoidNavigator>
  RiddersPropagator(stepper_t stepper, navigator_t navigator = navigator_t(),
                    Config config = {})
      : m_propagator(Propagator(stepper, navigator)),
        m_config(std::move(config)) {}

  template <typename parameters_t, typename propagator_options_t>
  Result<
      action_list_t_result_t<CurvilinearTrackParameters,
                             typename propagator_options_t::action_list_type>>
  propagate(const parameters_t& start,
            const propagator_options_t& options) const;

  template <typename parameters_t, typename propagator_options_t>
  Result<action_list_t_result_t<
      BoundTrackParameters, typename propagator_options_t::action_list_type>>
  propagate(const parameters_t& start, const Surface& target,
            const propagator_options_t& options) const;

 private:
  template <typename propagator_options_t, typename parameters_t,
            typename result_t>
  Jacobian wiggleAndCalculateJacobian(const propagator_options_t& options,
                                      const parameters_t& start,
                                      result_t& nominalResult) const;

  static bool inconsistentDerivativesOnDisc(
      const std::vector<BoundVector>& derivatives);

  template <typename propagator_options_t, typename parameters_t>
  std::vector<BoundVector> wiggleParameter(
      const propagator_options_t& options, const parameters_t& start,
      unsigned int param, const Surface& target, const BoundVector& nominal,
      const std::vector<double>& deviations) const;

  static Jacobian calculateJacobian(
      const std::vector<double>& deviations,
      const std::array<std::vector<BoundVector>, eBoundSize>& derivatives);

  static BoundVector fitLinear(const std::vector<double>& deviations,
                               const std::vector<BoundVector>& derivatives);

  propagator_t m_propagator;
  Config m_config;
};
}  // namespace Acts

#include "Acts/Propagator/RiddersPropagator.ipp"