Tempus_TimeStepControlStrategyConstant.hpp

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//@HEADER
// *****************************************************************************
//          Tempus: Time Integration and Sensitivity Analysis Package
//
// Copyright 2017 NTESS and the Tempus contributors.
// SPDX-License-Identifier: BSD-3-Clause
// *****************************************************************************
//@HEADER

#ifndef Tempus_TimeStepControlStrategy_Constant_hpp
#define Tempus_TimeStepControlStrategy_Constant_hpp

#include "Tempus_config.hpp"
#include "Tempus_TimeStepControlStrategy.hpp"
#include "Tempus_SolutionState.hpp"
#include "Tempus_SolutionHistory.hpp"
#include "Tempus_StepperState.hpp"

namespace Tempus {

template <class Scalar>
class TimeStepControlStrategyConstant
  : virtual public TimeStepControlStrategy<Scalar> {
 public:
  TimeStepControlStrategyConstant() : constantTimeStep_(0.0)
  {
    this->setStrategyType("Constant");
    this->setStepType("Constant");
    this->setName("Constant");
    this->initialize();
  }

  TimeStepControlStrategyConstant(Scalar constantTimeStep,
                                  std::string name = "Constant")
    : constantTimeStep_(constantTimeStep)
  {
    this->setStrategyType("Constant");
    this->setStepType("Constant");
    this->setName(name);
    this->initialize();
  }

  virtual ~TimeStepControlStrategyConstant() {}

  virtual void setNextTimeStep(
      const TimeStepControl<Scalar> &tsc,
      Teuchos::RCP<SolutionHistory<Scalar> > solutionHistory,
      Status &integratorStatus) override
  {
    using Teuchos::RCP;

    this->checkInitialized();

    RCP<SolutionState<Scalar> > workingState =
        solutionHistory->getWorkingState();
    const Scalar errorAbs = workingState->getErrorAbs();
    const Scalar errorRel = workingState->getErrorRel();
    Scalar dt             = workingState->getTimeStep();

    RCP<Teuchos::FancyOStream> out = tsc.getOStream();
    Teuchos::OSTab ostab(out, 1, "setNextTimeStep");
    out->setOutputToRootOnly(0);

    // Check constant time step
    if (dt != tsc.getInitTimeStep()) {
      tsc.printDtChanges(workingState->getIndex(), dt, tsc.getInitTimeStep(),
                         "Resetting constant dt.");
      dt = tsc.getInitTimeStep();
    }

    // Stepper failure
    if (workingState->getSolutionStatus() == Status::FAILED) {
      *out << "Failure - Stepper failed and can not change time step size!\n"
           << "    Time step type == CONSTANT_STEP_SIZE\n"
           << std::endl;
      integratorStatus = FAILED;
      return;
    }

    // Absolute error failure
    if (errorAbs > tsc.getMaxAbsError()) {
      *out << "Failure - Absolute error failed and can not change time step!\n"
           << "  Time step type == CONSTANT_STEP_SIZE\n"
           << "  (errorAbs =" << errorAbs
           << ") > (errorMaxAbs =" << tsc.getMaxAbsError() << ")" << std::endl;
      integratorStatus = FAILED;
      return;
    }

    // Relative error failure
    if (errorRel > tsc.getMaxRelError()) {
      *out << "Failure - Relative error failed and can not change time step!\n"
           << "  Time step type == CONSTANT_STEP_SIZE\n"
           << "  (errorRel =" << errorRel
           << ") > (errorMaxRel =" << tsc.getMaxRelError() << ")" << std::endl;
      integratorStatus = FAILED;
      return;
    }

    // update dt
    workingState->setTimeStep(dt);

    // Set time from initial time, dt, and index to avoid numerical roundoff.
    const Scalar initTime = tsc.getInitTime();
    const int initIndex   = tsc.getInitIndex();
    const int index       = workingState->getIndex();
    const Scalar time     = (index - initIndex) * dt + initTime;
    workingState->setTime(time);
  }


  std::string description() const override
  {
    return "Tempus::TimeStepControlStrategyConstant";
  }

  void describe(Teuchos::FancyOStream &out,
                const Teuchos::EVerbosityLevel verbLevel) const override
  {
    auto l_out = Teuchos::fancyOStream(out.getOStream());
    Teuchos::OSTab ostab(*l_out, 2, this->description());
    l_out->setOutputToRootOnly(0);

    *l_out << "\n--- " << this->description() << " ---" << std::endl;

    if (Teuchos::as<int>(verbLevel) >= Teuchos::as<int>(Teuchos::VERB_MEDIUM)) {
      *l_out << "  Strategy Type = " << this->getStrategyType() << std::endl
             << "  Step Type     = " << this->getStepType() << std::endl
             << "  Time Step     = " << getConstantTimeStep() << std::endl;

      *l_out << std::string(this->description().length() + 8, '-') << std::endl;
    }
  }

  virtual Teuchos::RCP<const Teuchos::ParameterList> getValidParameters()
      const override
  {
    Teuchos::RCP<Teuchos::ParameterList> pl =
        Teuchos::parameterList("Time Step Control Strategy");

    pl->set<std::string>("Strategy Type", this->getStrategyType(), "Constant");
    pl->set<double>("Time Step", getConstantTimeStep());

    return pl;
  }

  virtual void initialize() const override
  {
    this->isInitialized_ = true;  // Only place where this is set to true!
  }

  virtual Scalar getConstantTimeStep() const { return constantTimeStep_; }

  virtual void setConstantTimeStep(Scalar dt)
  {
    constantTimeStep_    = dt;
    this->isInitialized_ = false;
  }

 private:
  Scalar constantTimeStep_;  
};

template <class Scalar>
Teuchos::RCP<TimeStepControlStrategyConstant<Scalar> >
createTimeStepControlStrategyConstant(
    const Teuchos::RCP<Teuchos::ParameterList> &pList,
    std::string name = "Constant")
{
  auto tscs = Teuchos::rcp(new TimeStepControlStrategyConstant<Scalar>());
  if (pList == Teuchos::null || pList->numParams() == 0) return tscs;

  TEUCHOS_TEST_FOR_EXCEPTION(
      pList->get<std::string>("Strategy Type") != "Constant", std::logic_error,
      "Error - Strategy Type != 'Constant'.  (='" +
          pList->get<std::string>("Strategy Type") + "')\n");

  pList->validateParametersAndSetDefaults(*tscs->getValidParameters());

  tscs->setConstantTimeStep(pList->get<double>("Time Step"));

  tscs->setName(name);
  tscs->initialize();

  return tscs;
}

template <class Scalar>
Teuchos::RCP<Teuchos::ParameterList> getTimeStepControlStrategyConstantPL()
{
  auto t = rcp(new Tempus::TimeStepControlStrategyConstant<Scalar>());
  return Teuchos::rcp_const_cast<Teuchos::ParameterList>(
      t->getValidParameters());
}

}  // namespace Tempus
#endif  // Tempus_TimeStepControlStrategy_Constant_hpp