Tempus_StepperForwardEuler_impl.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_StepperForwardEuler_impl_hpp
#define Tempus_StepperForwardEuler_impl_hpp

#include "Thyra_VectorStdOps.hpp"

#include "Tempus_StepperForwardEulerModifierDefault.hpp"

namespace Tempus {

template <class Scalar>
StepperForwardEuler<Scalar>::StepperForwardEuler()
{
  this->setStepperName("Forward Euler");
  this->setStepperType("Forward Euler");
  this->setUseFSAL(true);
  this->setICConsistency("Consistent");
  this->setICConsistencyCheck(false);
  this->setAppAction(Teuchos::null);
}

template <class Scalar>
StepperForwardEuler<Scalar>::StepperForwardEuler(
    const Teuchos::RCP<const Thyra::ModelEvaluator<Scalar> >& appModel,
    bool useFSAL, std::string ICConsistency, bool ICConsistencyCheck,
    const Teuchos::RCP<StepperForwardEulerAppAction<Scalar> >&
        stepperFEAppAction)
{
  this->setStepperName("Forward Euler");
  this->setStepperType("Forward Euler");
  this->setUseFSAL(useFSAL);
  this->setICConsistency(ICConsistency);
  this->setICConsistencyCheck(ICConsistencyCheck);

  this->setAppAction(stepperFEAppAction);
  if (appModel != Teuchos::null) {
    this->setModel(appModel);
    this->initialize();
  }
}

template <class Scalar>
void StepperForwardEuler<Scalar>::setAppAction(
    Teuchos::RCP<StepperForwardEulerAppAction<Scalar> > appAction)
{
  if (appAction == Teuchos::null) {
    // Create default appAction
    stepperFEAppAction_ =
        Teuchos::rcp(new StepperForwardEulerModifierDefault<Scalar>());
  }
  else {
    stepperFEAppAction_ = appAction;
  }
}

template <class Scalar>
void StepperForwardEuler<Scalar>::setInitialConditions(
    const Teuchos::RCP<SolutionHistory<Scalar> >& solutionHistory)
{
  using Teuchos::RCP;

  RCP<SolutionState<Scalar> > initialState = solutionHistory->getCurrentState();

  // Check if we need Stepper storage for xDot
  if (initialState->getXDot() == Teuchos::null)
    this->setStepperXDot(initialState->getX()->clone_v());
  else
    this->setStepperXDot(initialState->getXDot());

  StepperExplicit<Scalar>::setInitialConditions(solutionHistory);
}

template <class Scalar>
void StepperForwardEuler<Scalar>::takeStep(
    const Teuchos::RCP<SolutionHistory<Scalar> >& solutionHistory)
{
  this->checkInitialized();

  using Teuchos::RCP;

  TEMPUS_FUNC_TIME_MONITOR("Tempus::StepperForwardEuler::takeStep()");
  {
    TEUCHOS_TEST_FOR_EXCEPTION(
        solutionHistory->getNumStates() < 2, std::logic_error,
        "Error - StepperForwardEuler<Scalar>::takeStep(...)\n"
            << "Need at least two SolutionStates for Forward Euler.\n"
            << "  Number of States = " << solutionHistory->getNumStates()
            << "\n Try setting in \"Solution History\" \"Storage Type\" = "
            << "\"Undo\"\n or \"Storage Type\" = \"Static\" and \"Storage Limit\" = "
            << "\"2\"\n");

    RCP<StepperForwardEuler<Scalar> > thisStepper = Teuchos::rcpFromRef(*this);
    stepperFEAppAction_->execute(
        solutionHistory, thisStepper,
        StepperForwardEulerAppAction<Scalar>::ACTION_LOCATION::BEGIN_STEP);

    RCP<SolutionState<Scalar> > currentState =
        solutionHistory->getCurrentState();
    RCP<SolutionState<Scalar> > workingState =
        solutionHistory->getWorkingState();
    if (currentState->getXDot() != Teuchos::null)
      this->setStepperXDot(currentState->getXDot());
    RCP<Thyra::VectorBase<Scalar> > xDot = this->getStepperXDot();
    const Scalar dt                      = workingState->getTimeStep();

    if (!(this->getUseFSAL()) || workingState->getNConsecutiveFailures() != 0) {
      // Need to compute XDotOld.
      stepperFEAppAction_->execute(
          solutionHistory, thisStepper,
          StepperForwardEulerAppAction<
              Scalar>::ACTION_LOCATION::BEFORE_EXPLICIT_EVAL);

      auto p = Teuchos::rcp(new ExplicitODEParameters<Scalar>(dt));

      // Evaluate xDot = f(x,t).
      this->evaluateExplicitODE(xDot, currentState->getX(),
                                currentState->getTime(), p);

      // For UseFSAL=false, x and xDot are now sync'ed or consistent
      // at the same time level for the currentState.
      currentState->setIsSynced(true);
    }

    // Forward Euler update, x^n = x^{n-1} + dt^n * xDot^{n-1}
    Thyra::V_VpStV(Teuchos::outArg(*(workingState->getX())),
                   *(currentState->getX()), dt, *(xDot));

    if (workingState->getXDot() != Teuchos::null)
      this->setStepperXDot(workingState->getXDot());
    xDot = this->getStepperXDot();

    if (this->getUseFSAL()) {
      // Get consistent xDot^n.
      stepperFEAppAction_->execute(
          solutionHistory, thisStepper,
          StepperForwardEulerAppAction<
              Scalar>::ACTION_LOCATION::BEFORE_EXPLICIT_EVAL);

      auto p = Teuchos::rcp(new ExplicitODEParameters<Scalar>(dt));

      // Evaluate xDot = f(x,t).
      this->evaluateExplicitODE(xDot, workingState->getX(),
                                workingState->getTime(), p);

      // For UseFSAL=true, x and xDot are now sync'ed or consistent
      // for the workingState.
      workingState->setIsSynced(true);
    }
    else {
      assign(xDot.ptr(), Teuchos::ScalarTraits<Scalar>::zero());
      workingState->setIsSynced(false);
    }

    workingState->setSolutionStatus(Status::PASSED);
    workingState->setOrder(this->getOrder());
    workingState->computeNorms(currentState);
    stepperFEAppAction_->execute(
        solutionHistory, thisStepper,
        StepperForwardEulerAppAction<Scalar>::ACTION_LOCATION::END_STEP);
  }
  return;
}

template <class Scalar>
Teuchos::RCP<Tempus::StepperState<Scalar> >
StepperForwardEuler<Scalar>::getDefaultStepperState()
{
  Teuchos::RCP<Tempus::StepperState<Scalar> > stepperState =
      rcp(new StepperState<Scalar>(this->getStepperType()));
  return stepperState;
}

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

  *l_out << std::endl;
  Stepper<Scalar>::describe(*l_out, verbLevel);
  StepperExplicit<Scalar>::describe(*l_out, verbLevel);
  *l_out << "  stepperFEAppAction_ = " << stepperFEAppAction_ << std::endl
         << "----------------------------" << std::endl;
}

template <class Scalar>
bool StepperForwardEuler<Scalar>::isValidSetup(Teuchos::FancyOStream& out) const
{
  out.setOutputToRootOnly(0);

  bool isValidSetup = true;

  if (!Stepper<Scalar>::isValidSetup(out)) isValidSetup = false;
  if (!StepperExplicit<Scalar>::isValidSetup(out)) isValidSetup = false;
  if (stepperFEAppAction_ == Teuchos::null) {
    isValidSetup = false;
    out << "The Forward Euler AppAction is not set!\n";
  }
  return isValidSetup;
}

// Nonmember constructor - ModelEvaluator and ParameterList
// ------------------------------------------------------------------------
template <class Scalar>
Teuchos::RCP<StepperForwardEuler<Scalar> > createStepperForwardEuler(
    const Teuchos::RCP<const Thyra::ModelEvaluator<Scalar> >& model,
    Teuchos::RCP<Teuchos::ParameterList> pl)
{
  auto stepper = Teuchos::rcp(new StepperForwardEuler<Scalar>());
  stepper->setStepperExplicitValues(pl);

  if (model != Teuchos::null) {
    stepper->setModel(model);
    stepper->initialize();
  }

  return stepper;
}

}  // namespace Tempus
#endif  // Tempus_StepperForwardEuler_impl_hpp