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_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>
StepperTrapezoidal<Scalar>::StepperTrapezoidal()
{
  this->setStepperType(        "Trapezoidal Method");
  this->setUseFSAL(            this->getUseFSALDefault());
  this->setICConsistency(      this->getICConsistencyDefault());
  this->setICConsistencyCheck( this->getICConsistencyCheckDefault());
  this->setZeroInitialGuess(   false);

  this->setObserver();
}


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

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

  this->setObserver(obs);

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


template<class Scalar>
void StepperTrapezoidal<Scalar>::setObserver(
  Teuchos::RCP<StepperObserver<Scalar> > obs)
{
  if (obs == Teuchos::null) {
    // Create default observer, otherwise keep current observer.
    if (this->stepperObserver_ == Teuchos::null) {
      stepperTrapObserver_ =
        Teuchos::rcp(new StepperTrapezoidalObserver<Scalar>());
      this->stepperObserver_ =
        Teuchos::rcp_dynamic_cast<StepperObserver<Scalar> >
          (stepperTrapObserver_, true);
     }
  } else {
    this->stepperObserver_ = obs;
    stepperTrapObserver_ =
      Teuchos::rcp_dynamic_cast<StepperTrapezoidalObserver<Scalar> >
        (this->stepperObserver_, true);
  }
}


template<class Scalar>
void StepperTrapezoidal<Scalar>::initialize()
{
  TEUCHOS_TEST_FOR_EXCEPTION(
    this->wrapperModel_ == Teuchos::null, std::logic_error,
    "Error - Need to set the model, setModel(), before calling "
    "StepperTrapezoidal::initialize()\n");
}


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());

  StepperImplicit<Scalar>::setInitialConditions(solutionHistory);

  TEUCHOS_TEST_FOR_EXCEPTION( !(this->getUseFSAL()), std::logic_error,
    "Error - The First-Step-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)
{
  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");

    this->stepperObserver_->observeBeginTakeStep(solutionHistory, *this);
    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();
    RCP<Thyra::VectorBase<Scalar> > xDot = workingState->getXDot();

    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));

    stepperTrapObserver_->observeBeforeSolve(solutionHistory, *this);

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

    stepperTrapObserver_->observeAfterSolve(solutionHistory, *this);

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

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


/** \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> >
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 << this->getStepperType() << "::describe:" << std::endl
      << "wrapperModel_ = " << this->wrapperModel_->description() << std::endl;
}


template<class Scalar>
Teuchos::RCP<const Teuchos::ParameterList>
StepperTrapezoidal<Scalar>::getValidParameters() const
{
  Teuchos::RCP<Teuchos::ParameterList> pl = Teuchos::parameterList();
  getValidParametersBasic(pl, this->getStepperType());
  pl->set<bool>       ("Use FSAL", this->getUseFSALDefault());
  pl->set<std::string>("Initial Condition Consistency",
                       this->getICConsistencyDefault());
  pl->set<std::string>("Solver Name", "Default Solver");
  pl->set<bool>       ("Zero Initial Guess", false);
  Teuchos::RCP<Teuchos::ParameterList> solverPL = defaultSolverParameters();
  pl->set("Default Solver", *solverPL);

  return pl;
}


} // namespace Tempus
#endif // Tempus_StepperTrapezoidal_impl_hpp