adaptivestepsizing.hh

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// SPDX-FileCopyrightText: 2021-2024 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 NonLinearOperator>
    void operator()(const NonLinearSolverInformation& solverInfo, SubsidiaryArgs& subsidiaryArgs,
                    const NonLinearOperator& nonLinearOperator) {}
 
    [[nodiscard]] int targetIterations() const { return 0; }
 
    void setTargetIterations([[maybe_unused]] int targetIterations) {}
  };
 
  struct IterationBased {
    template <typename NonLinearOperator>
    void operator()(const NonLinearSolverInformation& solverInfo, SubsidiaryArgs& subsidiaryArgs,
                    const NonLinearOperator&) {
      if (subsidiaryArgs.currentStep == 0) return;
      if (targetIterations_ == 0)
        DUNE_THROW(Dune::InvalidStateException,
                   "For IterationBased, 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) { targetIterations_ = targetIterations; }
 
  private:
    int targetIterations_{0};
  };
}  // namespace Ikarus::AdaptiveStepSizing