Tempus_StepperTrapezoidal_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_StepperTrapezoidal_impl_hpp
#define Tempus_StepperTrapezoidal_impl_hpp

#include "Tempus_StepperTrapezoidalModifierDefault.hpp"
#include "Tempus_WrapperModelEvaluatorBasic.hpp"


namespace Tempus {


template<class Scalar>
StepperTrapezoidal<Scalar>::StepperTrapezoidal()
{
  this->setStepperName(        "Trapezoidal Method");
  this->setStepperType(        "Trapezoidal Method");
  this->setUseFSAL(            true);
  this->setICConsistency(      "Consistent");
  this->setICConsistencyCheck( false);
  this->setZeroInitialGuess(   false);

  this->setAppAction(Teuchos::null);
  this->setDefaultSolver();
}


template<class Scalar>
StepperTrapezoidal<Scalar>::StepperTrapezoidal(
  const Teuchos::RCP<const Thyra::ModelEvaluator<Scalar> >& appModel,
  const Teuchos::RCP<Thyra::NonlinearSolverBase<Scalar> >& solver,
  bool useFSAL,
  std::string ICConsistency,
  bool ICConsistencyCheck,
  bool zeroInitialGuess,
  const Teuchos::RCP<StepperTrapezoidalAppAction<Scalar> >& stepperTrapAppAction)
{
  this->setStepperName(        "Trapezoidal Method");
  this->setStepperType(        "Trapezoidal Method");
  this->setUseFSAL(            useFSAL);
  this->setICConsistency(      ICConsistency);
  this->setICConsistencyCheck( ICConsistencyCheck);
  this->setZeroInitialGuess(   zeroInitialGuess);

  this->setAppAction(stepperTrapAppAction);
  this->setSolver(solver);

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


template<class Scalar>
void StepperTrapezoidal<Scalar>::setAppAction(
  Teuchos::RCP<StepperTrapezoidalAppAction<Scalar> > appAction)
{
  if (appAction == Teuchos::null) {
    // Create default appAction
    stepperTrapAppAction_ =
    Teuchos::rcp(new StepperTrapezoidalModifierDefault<Scalar>());
  } else {
  stepperTrapAppAction_ = appAction;
  }
  this->isInitialized_ = false;
}


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

  StepperImplicit<Scalar>::setInitialConditions(solutionHistory);

  TEUCHOS_TEST_FOR_EXCEPTION( !(this->getUseFSAL()), std::logic_error,
    "Error - The First-Same-As-Last (FSAL) principle is required\n"
    "        for the Trapezoidal Stepper (i.e., useFSAL=true)!\n");
//   There are at least two ways around this, but are not implemented.
//    - Do a solve for xDotOld, xDot_{n-1}, at each time step as for the
//      initial conditions.  This is expensive since you would be doing
//      two solves every time step.
//    - Use evaluateExplicitODE to get xDot_{n-1} if the application
//      provides it.  Explicit evaluations are cheaper but requires the
//      application to implement xDot = f(x,t).
}


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

  using Teuchos::RCP;

  TEMPUS_FUNC_TIME_MONITOR("Tempus::StepperTrapezoidal::takeStep()");
  {
    TEUCHOS_TEST_FOR_EXCEPTION(solutionHistory->getNumStates() < 2,
      std::logic_error,
      "Error - StepperTrapezoidal<Scalar>::takeStep(...)\n"
      "Need at least two SolutionStates for Trapezoidal.\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<StepperTrapezoidal<Scalar> > thisStepper = Teuchos::rcpFromRef(*this);
    stepperTrapAppAction_->execute(solutionHistory, thisStepper,
      StepperTrapezoidalAppAction<Scalar>::ACTION_LOCATION::BEGIN_STEP);

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

    RCP<const Thyra::VectorBase<Scalar> > xOld    = currentState->getX();
    RCP<const Thyra::VectorBase<Scalar> > xDotOld = currentState->getXDot();
    RCP<Thyra::VectorBase<Scalar> > x    = workingState->getX();
    if (workingState->getXDot() != Teuchos::null)
      this->setStepperXDot(workingState->getXDot());
    RCP<Thyra::VectorBase<Scalar> > xDot = this->getStepperXDot();

    const Scalar time  = workingState->getTime();
    const Scalar dt    = workingState->getTimeStep();
    const Scalar alpha = getAlpha(dt);
    const Scalar beta  = getBeta (dt);

    // Setup TimeDerivative
    Teuchos::RCP<TimeDerivative<Scalar> > timeDer =
      Teuchos::rcp(new StepperTrapezoidalTimeDerivative<Scalar>(
        alpha, xOld, xDotOld));

    auto p = Teuchos::rcp(new ImplicitODEParameters<Scalar>(
      timeDer, dt, alpha, beta));
    stepperTrapAppAction_->execute(solutionHistory, thisStepper,
      StepperTrapezoidalAppAction<Scalar>::ACTION_LOCATION::BEFORE_SOLVE);

    const Thyra::SolveStatus<Scalar> sStatus =
      this->solveImplicitODE(x, xDot, time, p);
    stepperTrapAppAction_->execute(solutionHistory, thisStepper,
      StepperTrapezoidalAppAction<Scalar>::ACTION_LOCATION::AFTER_SOLVE);

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

    workingState->setSolutionStatus(sStatus);  // Converged --> pass.
    workingState->setOrder(this->getOrder());
    workingState->computeNorms(currentState);
    stepperTrapAppAction_->execute(solutionHistory, thisStepper,
      StepperTrapezoidalAppAction<Scalar>::ACTION_LOCATION::END_STEP);
  }
  return;
}


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


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

  out << "--- StepperTrapezoidal ---\n";
  out << "  stepperTrapAppAction_ = " << stepperTrapAppAction_ << std::endl;
  out << "--------------------------" << std::endl;
}


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

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

  if (stepperTrapAppAction_ == Teuchos::null) {
    isValidSetup = false;
    out << "The Trapezoidal AppAction is not set!\n";
  }

  return isValidSetup;
}


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

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

  return stepper;
}


} // namespace Tempus
#endif // Tempus_StepperTrapezoidal_impl_hpp