adaptivestepsizing.hh

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// SPDX-FileCopyrightText: 2021-2025 The Ikarus Developers mueller@ibb.uni-stuttgart.de
// SPDX-License-Identifier: LGPL-3.0-or-later
 
#pragma once
 
#include <ikarus/controlroutines/pathfollowingfunctions.hh>
#include <ikarus/solver/nonlinearsolver/solverinfos.hh>
 
namespace Ikarus::AdaptiveStepSizing {
 
struct NoOp
{
  template <typename F>
  void operator()(const NonLinearSolverInformation& solverInfo, SubsidiaryArgs& subsidiaryArgs, const F& f) {}
 
  [[nodiscard]] int targetIterations() const { return 0; }
 
  void setTargetIterations([[maybe_unused]] int targetIterations) {}
};
 
struct IterationBased
{
  template <typename F>
  void operator()(const NonLinearSolverInformation& solverInfo, SubsidiaryArgs& subsidiaryArgs, const F& f) {
    if (subsidiaryArgs.currentStep == 0)
      return;
    if (targetIterations_ == 0)
      DUNE_THROW(Dune::InvalidStateException,
                 "TargetIterations should not be equal to 0. Try calling "
                 "setTargetIterations(int) first.");
    const auto previousIterations = solverInfo.iterations;
    if (previousIterations > targetIterations_)
      subsidiaryArgs.stepSize =
          sqrt(static_cast<double>(targetIterations_) / previousIterations) * subsidiaryArgs.stepSize;
  }
 
  [[nodiscard]] int targetIterations() const { return targetIterations_; }
 
  void setTargetIterations(int targetIterations) {
    if (targetIterations == 0)
      DUNE_THROW(Dune::InvalidStateException, "TargetIterations should not be equal to 0.");
    targetIterations_ = targetIterations;
  }
 
private:
  int targetIterations_{0};
};
} // namespace Ikarus::AdaptiveStepSizing