Tempus_StepperBDF2_impl.hpp

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// @HEADER
// ****************************************************************************
//                Tempus: Copyright (2017) Sandia Corporation
//
// Distributed under BSD 3-clause license (See accompanying file Copyright.txt)
// ****************************************************************************
// @HEADER

#ifndef Tempus_StepperBDF2_impl_hpp
#define Tempus_StepperBDF2_impl_hpp

#include "Tempus_config.hpp"
#include "Tempus_StepperFactory.hpp"
#include "Tempus_WrapperModelEvaluatorBasic.hpp"
#include "Teuchos_VerboseObjectParameterListHelpers.hpp"
#include "NOX_Thyra.H"


namespace Tempus {

// Forward Declaration for recursive includes (this Stepper <--> StepperFactory)
template<class Scalar> class StepperFactory;


template<class Scalar>
StepperBDF2<Scalar>::StepperBDF2()
{
  this->setStepperType(        "BDF2");
  this->setUseFSAL(            this->getUseFSALDefault());
  this->setICConsistency(      this->getICConsistencyDefault());
  this->setICConsistencyCheck( this->getICConsistencyCheckDefault());
  this->setZeroInitialGuess(   false);

  this->setObserver();
  this->setDefaultSolver();
  this->setStartUpStepper("DIRK 1 Stage Theta Method");
}


template<class Scalar>
StepperBDF2<Scalar>::StepperBDF2(
  const Teuchos::RCP<const Thyra::ModelEvaluator<Scalar> >& appModel,
  const Teuchos::RCP<StepperObserver<Scalar> >& obs,
  const Teuchos::RCP<Thyra::NonlinearSolverBase<Scalar> >& solver,
  const Teuchos::RCP<Stepper<Scalar> >& startUpStepper,
  bool useFSAL,
  std::string ICConsistency,
  bool ICConsistencyCheck,
  bool zeroInitialGuess)

{
  this->setStepperType(        "BDF2");
  this->setUseFSAL(            useFSAL);
  this->setICConsistency(      ICConsistency);
  this->setICConsistencyCheck( ICConsistencyCheck);
  this->setZeroInitialGuess(   zeroInitialGuess);

  this->setObserver(obs);
  this->setSolver(solver);
  this->setStartUpStepper(startUpStepper);

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


template<class Scalar>
void StepperBDF2<Scalar>::setModel(
  const Teuchos::RCP<const Thyra::ModelEvaluator<Scalar> >& appModel)
{
  StepperImplicit<Scalar>::setModel(appModel);
  if (startUpStepper_->getModel() == Teuchos::null) {
    startUpStepper_->setModel(appModel);
    startUpStepper_->initialize();
  }

  this->isInitialized_ = false;
}


/// Set the startup stepper to a default stepper.
template<class Scalar>
void StepperBDF2<Scalar>::setStartUpStepper(std::string startupStepperType)
{
  using Teuchos::RCP;
  RCP<StepperFactory<Scalar> > sf = Teuchos::rcp(new StepperFactory<Scalar>());
  if (this->wrapperModel_ != Teuchos::null &&
      this->wrapperModel_->getAppModel() != Teuchos::null) {
    startUpStepper_ =
      sf->createStepper(startupStepperType, this->wrapperModel_->getAppModel());
  } else {
    startUpStepper_ = sf->createStepper(startupStepperType);
  }

  this->isInitialized_ = false;
}


/// Set the start up stepper.
template<class Scalar>
void StepperBDF2<Scalar>::setStartUpStepper(
  Teuchos::RCP<Stepper<Scalar> > startUpStepper)
{
  startUpStepper_ = startUpStepper;

  if (this->wrapperModel_ != Teuchos::null) {
    TEUCHOS_TEST_FOR_EXCEPTION(
      this->wrapperModel_->getAppModel() == Teuchos::null, std::logic_error,
      "Error - Can not set the startUpStepper to Teuchos::null.\n");

    if (startUpStepper->getModel() == Teuchos::null  &&
        this->wrapperModel_->getAppModel() != Teuchos::null) {
      startUpStepper_->setModel(this->wrapperModel_->getAppModel());
      startUpStepper_->initialize();
    }
  }

  this->isInitialized_ = false;
}


template<class Scalar>
void StepperBDF2<Scalar>::setObserver(
  Teuchos::RCP<StepperObserver<Scalar> > obs)
{
  if (this->stepperObserver_ == Teuchos::null)
    this->stepperObserver_  =
      Teuchos::rcp(new StepperObserverComposite<Scalar>());

  if (obs == Teuchos::null) {
    if (stepperBDF2Observer_ == Teuchos::null)
      stepperBDF2Observer_ = Teuchos::rcp(new StepperBDF2Observer<Scalar>());
    if (this->stepperObserver_->getSize() == 0)
      this->stepperObserver_->addObserver(stepperBDF2Observer_);
  } else {
    stepperBDF2Observer_ =
      Teuchos::rcp_dynamic_cast<StepperBDF2Observer<Scalar> >(obs,true);
    this->stepperObserver_->addObserver(stepperBDF2Observer_);
  }

  this->isInitialized_ = false;
}


template<class Scalar>
void StepperBDF2<Scalar>::initialize()
{
  StepperImplicit<Scalar>::initialize();
}


template<class Scalar>
void StepperBDF2<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());

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


template<class Scalar>
void StepperBDF2<Scalar>::takeStep(
  const Teuchos::RCP<SolutionHistory<Scalar> >& solutionHistory)
{
  this->checkInitialized();

  using Teuchos::RCP;

  TEMPUS_FUNC_TIME_MONITOR("Tempus::StepperBDF2::takeStep()");
  {
    int numStates = solutionHistory->getNumStates();

    RCP<Thyra::VectorBase<Scalar> > xOld;
    RCP<Thyra::VectorBase<Scalar> > xOldOld;

    // If there are less than 3 states (e.g., first time step), call
    // startup stepper and return.
    if (numStates < 3) {
      computeStartUp(solutionHistory);
      return;
    }
    TEUCHOS_TEST_FOR_EXCEPTION( (numStates < 3), std::logic_error,
      "Error in Tempus::StepperBDF2::takeStep(): numStates after \n"
        << "startup stepper must be at least 3, whereas numStates = "
        << numStates <<"!\n" << "If running with Storage Type = Static, "
        << "make sure Storage Limit > 2.\n");

    //IKT, FIXME: add error checking regarding states being consecutive and
    //whether interpolated states are OK to use.

    //this->stepperObserver_->observeBeginTakeStep(solutionHistory, *this);

    RCP<SolutionState<Scalar> > workingState=solutionHistory->getWorkingState();
    RCP<SolutionState<Scalar> > currentState=solutionHistory->getCurrentState();

    RCP<Thyra::VectorBase<Scalar> > x    = workingState->getX();
    RCP<Thyra::VectorBase<Scalar> > xDot = this->getStepperXDot(workingState);

    //get time, dt and dtOld
    const Scalar time  = workingState->getTime();
    const Scalar dt    = workingState->getTimeStep();
    const Scalar dtOld = currentState->getTimeStep();

    xOld    = solutionHistory->getStateTimeIndexNM1()->getX();
    xOldOld = solutionHistory->getStateTimeIndexNM2()->getX();
    order_ = Scalar(2.0);

    // Setup TimeDerivative
    Teuchos::RCP<TimeDerivative<Scalar> > timeDer =
      Teuchos::rcp(new StepperBDF2TimeDerivative<Scalar>(dt, dtOld, xOld, xOldOld));

    const Scalar alpha = getAlpha(dt, dtOld);
    const Scalar beta  = getBeta (dt);

    auto p = Teuchos::rcp(new ImplicitODEParameters<Scalar>(
      timeDer, dt, alpha, beta));

    if (!Teuchos::is_null(stepperBDF2Observer_))
      stepperBDF2Observer_->observeBeforeSolve(solutionHistory, *this);

    const Thyra::SolveStatus<Scalar> sStatus =
      this->solveImplicitODE(x, xDot, time, p);

    if (!Teuchos::is_null(stepperBDF2Observer_))
      stepperBDF2Observer_->observeAfterSolve(solutionHistory, *this);

    if (workingState->getXDot() != Teuchos::null)
      timeDer->compute(x, xDot);

    workingState->setSolutionStatus(sStatus);  // Converged --> pass.
    workingState->setOrder(getOrder());
    workingState->computeNorms(currentState);
    //this->stepperObserver_->observeEndTakeStep(solutionHistory, *this);
  }
  return;
}

template<class Scalar>
void StepperBDF2<Scalar>::computeStartUp(
      const Teuchos::RCP<SolutionHistory<Scalar> >& solutionHistory)
{
  Teuchos::RCP<Teuchos::FancyOStream> out = this->getOStream();
  Teuchos::OSTab ostab(out,1,"StepperBDF2::computeStartUp()");
  *out << "Warning -- Taking a startup step for BDF2 using '"
       << startUpStepper_->getStepperType()<<"'!" << std::endl;

  //Take one step using startUpStepper_
  startUpStepper_->takeStep(solutionHistory);

  order_ = startUpStepper_->getOrder();
}

/** \brief Provide a StepperState to the SolutionState.
 *  This Stepper does not have any special state data,
 *  so just provide the base class StepperState with the
 *  Stepper description.  This can be checked to ensure
 *  that the input StepperState can be used by this Stepper.
 */
template<class Scalar>
Teuchos::RCP<Tempus::StepperState<Scalar> >
StepperBDF2<Scalar>::
getDefaultStepperState()
{
  Teuchos::RCP<Tempus::StepperState<Scalar> > stepperState =
    rcp(new StepperState<Scalar>(this->getStepperType()));
  return stepperState;
}


template<class Scalar>
void StepperBDF2<Scalar>::describe(
  Teuchos::FancyOStream               &out,
  const Teuchos::EVerbosityLevel      verbLevel ) const
{
  out << std::endl;
  Stepper<Scalar>::describe(out, verbLevel);
  StepperImplicit<Scalar>::describe(out, verbLevel);

  out << "--- StepperBDF2 ---\n";
  if (startUpStepper_ != Teuchos::null) {
    out << "  startup stepper type             = "
        << startUpStepper_->description() << std::endl;
  }
  out << "  startUpStepper_                  = "
      << startUpStepper_ << std::endl;
  out << "  startUpStepper_->isInitialized() = "
      << Teuchos::toString(startUpStepper_->isInitialized()) << std::endl;
  out << "  stepperBDF2Observer_             = "
      << stepperBDF2Observer_ << std::endl;
  out << "  order_                           = " << order_ << std::endl;
  out << "-------------------" << std::endl;
}


template<class Scalar>
bool StepperBDF2<Scalar>::isValidSetup(Teuchos::FancyOStream & out) const
{
  bool isValidSetup = true;

  if ( !Stepper<Scalar>::isValidSetup(out) ) isValidSetup = false;
  if ( !StepperImplicit<Scalar>::isValidSetup(out) ) isValidSetup = false;

  if ( !this->startUpStepper_->isInitialized() ) {
    isValidSetup = false;
    out << "The startup stepper is not initialized!\n";
  }

  if (stepperBDF2Observer_ == Teuchos::null) {
    isValidSetup = false;
    out << "The BDF2 observer is not set!\n";
  }

  return isValidSetup;
}


template<class Scalar>
Teuchos::RCP<const Teuchos::ParameterList>
StepperBDF2<Scalar>::getValidParameters() const
{
  Teuchos::RCP<Teuchos::ParameterList> pl = Teuchos::parameterList();
  getValidParametersBasic(pl, this->getStepperType());
  pl->set<bool>("Initial Condition Consistency Check",
                this->getICConsistencyCheckDefault());
  pl->set<std::string>("Solver Name", "Default Solver");
  pl->set<bool>("Zero Initial Guess", false);
  pl->set<std::string>("Start Up Stepper Type", "DIRK 1 Stage Theta Method");
  Teuchos::RCP<Teuchos::ParameterList> solverPL = defaultSolverParameters();
  pl->set("Default Solver", *solverPL);

  return pl;
}


} // namespace Tempus
#endif // Tempus_StepperBDF2_impl_hpp