Tempus_StepperBackwardEuler_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_StepperBackwardEuler_impl_hpp
#define Tempus_StepperBackwardEuler_impl_hpp
 
#include "Tempus_StepperBackwardEulerModifierDefault.hpp"
#include "Tempus_WrapperModelEvaluatorBasic.hpp"
#include "Tempus_StepperFactory.hpp"
 
namespace Tempus {
 
template <class Scalar>
StepperBackwardEuler<Scalar>::StepperBackwardEuler()
{
  this->setStepperName("Backward Euler");
  this->setStepperType("Backward Euler");
  this->setUseFSAL(false);
  this->setICConsistency("None");
  this->setICConsistencyCheck(false);
  this->setZeroInitialGuess(false);
 
  this->setAppAction(Teuchos::null);
  this->setDefaultSolver();
  this->setPredictor();
}
 
template <class Scalar>
StepperBackwardEuler<Scalar>::StepperBackwardEuler(
    const Teuchos::RCP<const Thyra::ModelEvaluator<Scalar> >& appModel,
    const Teuchos::RCP<Thyra::NonlinearSolverBase<Scalar> >& solver,
    const Teuchos::RCP<Stepper<Scalar> >& predictorStepper, bool useFSAL,
    std::string ICConsistency, bool ICConsistencyCheck, bool zeroInitialGuess,
    const Teuchos::RCP<StepperBackwardEulerAppAction<Scalar> >&
        stepperBEAppAction)
{
  this->setStepperName("Backward Euler");
  this->setStepperType("Backward Euler");
  this->setUseFSAL(useFSAL);
  this->setICConsistency(ICConsistency);
  this->setICConsistencyCheck(ICConsistencyCheck);
  this->setZeroInitialGuess(zeroInitialGuess);
 
  this->setAppAction(stepperBEAppAction);
  this->setSolver(solver);
  this->setPredictor(predictorStepper);
 
  if (appModel != Teuchos::null) {
    this->setModel(appModel);
    this->initialize();
  }
}
 
template <class Scalar>
void StepperBackwardEuler<Scalar>::setPredictor(std::string predictorType)
{
  if (predictorType == "None") {
    predictorStepper_ = Teuchos::null;
    return;
  }
 
  auto sf = Teuchos::rcp(new StepperFactory<Scalar>());
  if (this->wrapperModel_ != Teuchos::null &&
      this->wrapperModel_->getAppModel() != Teuchos::null) {
    predictorStepper_ =
        sf->createStepper(predictorType, this->wrapperModel_->getAppModel());
  }
  else {
    predictorStepper_ = sf->createStepper(predictorType);
  }
 
  this->isInitialized_ = false;
}

template <class Scalar>
void StepperBackwardEuler<Scalar>::setPredictor(
    Teuchos::RCP<Stepper<Scalar> > predictorStepper)
{
  predictorStepper_ = predictorStepper;
  if (predictorStepper_ == Teuchos::null) return;
 
  TEUCHOS_TEST_FOR_EXCEPTION(
      predictorStepper_->getModel() == Teuchos::null &&
          this->wrapperModel_->getAppModel() == Teuchos::null,
      std::logic_error,
      "Error - Need to set the model, setModel(), before calling "
      "StepperBackwardEuler::setPredictor()\n");
 
  if (predictorStepper_->getModel() == Teuchos::null)
    predictorStepper_->setModel(this->wrapperModel_->getAppModel());
  predictorStepper_->initialize();
 
  this->isInitialized_ = false;
}
 
template <class Scalar>
void StepperBackwardEuler<Scalar>::setAppAction(
    Teuchos::RCP<StepperBackwardEulerAppAction<Scalar> > appAction)
{
  if (appAction == Teuchos::null) {
    // Create default appAction
    stepperBEAppAction_ =
        Teuchos::rcp(new StepperBackwardEulerModifierDefault<Scalar>());
  }
  else {
    stepperBEAppAction_ = appAction;
  }
  this->isInitialized_ = false;
}
 
template <class Scalar>
void StepperBackwardEuler<Scalar>::setModel(
    const Teuchos::RCP<const Thyra::ModelEvaluator<Scalar> >& appModel)
{
  StepperImplicit<Scalar>::setModel(appModel);
 
  if (predictorStepper_ != Teuchos::null) {
    // If predictor's model is not set, set it to the stepper model.
    if (predictorStepper_->getModel() == Teuchos::null) {
      predictorStepper_->setModel(appModel);
      predictorStepper_->initialize();
    }
  }
 
  this->isInitialized_ = false;
}
 
template <class Scalar>
void StepperBackwardEuler<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);
}
 
template <class Scalar>
void StepperBackwardEuler<Scalar>::takeStep(
    const Teuchos::RCP<SolutionHistory<Scalar> >& solutionHistory)
{
  this->checkInitialized();
 
  using Teuchos::RCP;
 
  TEMPUS_FUNC_TIME_MONITOR("Tempus::StepperBackwardEuler::takeStep()");
  {
    TEUCHOS_TEST_FOR_EXCEPTION(
        solutionHistory->getNumStates() < 2, std::logic_error,
        "Error - StepperBackwardEuler<Scalar>::takeStep(...)\n"
            << "Need at least two SolutionStates for Backward 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<StepperBackwardEuler<Scalar> > thisStepper = Teuchos::rcpFromRef(*this);
    stepperBEAppAction_->execute(
        solutionHistory, thisStepper,
        StepperBackwardEulerAppAction<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<Thyra::VectorBase<Scalar> > x          = workingState->getX();
    if (workingState->getXDot() != Teuchos::null)
      this->setStepperXDot(workingState->getXDot());
    RCP<Thyra::VectorBase<Scalar> > xDot = this->getStepperXDot();
 
    computePredictor(solutionHistory);
    if (workingState->getSolutionStatus() == Status::FAILED) return;
 
    const Scalar time = workingState->getTime();
    const Scalar dt   = workingState->getTimeStep();
 
    // Setup TimeDerivative
    Teuchos::RCP<TimeDerivative<Scalar> > timeDer = Teuchos::rcp(
        new StepperBackwardEulerTimeDerivative<Scalar>(Scalar(1.0) / dt, xOld));
 
    const Scalar alpha = Scalar(1.0) / dt;
    const Scalar beta  = Scalar(1.0);
    auto p             = Teuchos::rcp(
                    new ImplicitODEParameters<Scalar>(timeDer, dt, alpha, beta));
 
    stepperBEAppAction_->execute(
        solutionHistory, thisStepper,
        StepperBackwardEulerAppAction<Scalar>::ACTION_LOCATION::BEFORE_SOLVE);
 
    const Thyra::SolveStatus<Scalar> sStatus =
        this->solveImplicitODE(x, xDot, time, p);
 
    stepperBEAppAction_->execute(
        solutionHistory, thisStepper,
        StepperBackwardEulerAppAction<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);
    stepperBEAppAction_->execute(
        solutionHistory, thisStepper,
        StepperBackwardEulerAppAction<Scalar>::ACTION_LOCATION::END_STEP);
  }
  return;
}
 
template <class Scalar>
void StepperBackwardEuler<Scalar>::computePredictor(
    const Teuchos::RCP<SolutionHistory<Scalar> >& solutionHistory)
{
  if (predictorStepper_ == Teuchos::null) return;
  predictorStepper_->takeStep(solutionHistory);
 
  if (solutionHistory->getWorkingState()->getSolutionStatus() ==
      Status::FAILED) {
    Teuchos::RCP<Teuchos::FancyOStream> out = this->getOStream();
    Teuchos::OSTab ostab(out, 1, "StepperBackwardEuler::computePredictor");
    *out << "Warning - predictorStepper has failed." << std::endl;
  }
  else {
    // Reset status to WORKING since this is the predictor
    solutionHistory->getWorkingState()->setSolutionStatus(Status::WORKING);
  }
}

template <class Scalar>
Teuchos::RCP<Tempus::StepperState<Scalar> >
StepperBackwardEuler<Scalar>::getDefaultStepperState()
{
  Teuchos::RCP<Tempus::StepperState<Scalar> > stepperState =
      rcp(new StepperState<Scalar>(this->getStepperType()));
  return stepperState;
}
 
template <class Scalar>
void StepperBackwardEuler<Scalar>::describe(
    Teuchos::FancyOStream& out, const Teuchos::EVerbosityLevel verbLevel) const
{
  out.setOutputToRootOnly(0);
  out << std::endl;
  Stepper<Scalar>::describe(out, verbLevel);
  StepperImplicit<Scalar>::describe(out, verbLevel);
 
  out << "--- StepperBackwardEuler ---\n";
  out << "  predictorStepper_                  = " << predictorStepper_
      << std::endl;
  if (predictorStepper_ != Teuchos::null) {
    out << "  predictorStepper_->isInitialized() = "
        << Teuchos::toString(predictorStepper_->isInitialized()) << std::endl;
    out << "  predictor stepper type             = "
        << predictorStepper_->description() << std::endl;
  }
  out << "  stepperBEAppAction_                = " << stepperBEAppAction_
      << std::endl;
  out << "----------------------------" << std::endl;
}
 
template <class Scalar>
bool StepperBackwardEuler<Scalar>::isValidSetup(
    Teuchos::FancyOStream& out) const
{
  out.setOutputToRootOnly(0);
  bool isValidSetup = true;
 
  if (!Stepper<Scalar>::isValidSetup(out)) isValidSetup = false;
  if (!StepperImplicit<Scalar>::isValidSetup(out)) isValidSetup = false;
 
  if (predictorStepper_ != Teuchos::null) {
    if (!predictorStepper_->isInitialized()) {
      isValidSetup = false;
      out << "The predictor stepper is not initialized!\n";
    }
  }
 
  if (stepperBEAppAction_ == Teuchos::null) {
    isValidSetup = false;
    out << "The Backward Euler AppAction is not set!\n";
  }
 
  return isValidSetup;
}
 
template <class Scalar>
Teuchos::RCP<const Teuchos::ParameterList>
StepperBackwardEuler<Scalar>::getValidParameters() const
{
  auto pl = this->getValidParametersBasicImplicit();
  if (predictorStepper_ == Teuchos::null)
    pl->set("Predictor Stepper Type", "None");
  else
    pl->set("Predictor Stepper Type", predictorStepper_->getStepperType());
  return pl;
}
 
template <class Scalar>
int StepperBackwardEuler<Scalar>::stencilLength() const
{
  return 2;
}
 
template <class Scalar>
void StepperBackwardEuler<Scalar>::computeStepResidual(
    Thyra::VectorBase<Scalar>& residual,
    const Teuchos::Array<Teuchos::RCP<const Thyra::VectorBase<Scalar> > >& x,
    const Teuchos::Array<Scalar>& t, const Thyra::VectorBase<Scalar>& p,
    const int param_index) const
{
  typedef Thyra::ModelEvaluatorBase MEB;
  MEB::OutArgs<Scalar> outArgs = this->wrapperModel_->createOutArgs();
  outArgs.set_f(Teuchos::rcpFromRef(residual));
  computeStepResidDerivImpl(outArgs, x, t, p, param_index);
}
 
template <class Scalar>
void StepperBackwardEuler<Scalar>::computeStepJacobian(
    Thyra::LinearOpBase<Scalar>& jacobian,
    const Teuchos::Array<Teuchos::RCP<const Thyra::VectorBase<Scalar> > >& x,
    const Teuchos::Array<Scalar>& t, const Thyra::VectorBase<Scalar>& p,
    const int param_index, const int deriv_index) const
{
  typedef Thyra::ModelEvaluatorBase MEB;
  MEB::OutArgs<Scalar> outArgs = this->wrapperModel_->createOutArgs();
  TEUCHOS_ASSERT(outArgs.supports(MEB::OUT_ARG_W_op));
  outArgs.set_W_op(Teuchos::rcpFromRef(jacobian));
  computeStepResidDerivImpl(outArgs, x, t, p, param_index, deriv_index);
}
 
template <class Scalar>
void StepperBackwardEuler<Scalar>::computeStepParamDeriv(
    Thyra::LinearOpBase<Scalar>& deriv,
    const Teuchos::Array<Teuchos::RCP<const Thyra::VectorBase<Scalar> > >& x,
    const Teuchos::Array<Scalar>& t, const Thyra::VectorBase<Scalar>& p,
    const int param_index) const
{
  typedef Thyra::ModelEvaluatorBase MEB;
  MEB::OutArgs<Scalar> outArgs = this->wrapperModel_->createOutArgs();
  TEUCHOS_ASSERT(outArgs.supports(MEB::OUT_ARG_DfDp, param_index)
                     .supports(MEB::DERIV_LINEAR_OP));
  outArgs.set_DfDp(param_index,
                   MEB::Derivative<Scalar>(Teuchos::rcpFromRef(deriv)));
  computeStepResidDerivImpl(outArgs, x, t, p, param_index);
}
 
template <class Scalar>
void StepperBackwardEuler<Scalar>::computeStepSolver(
    Thyra::LinearOpWithSolveBase<Scalar>& jacobian_solver,
    const Teuchos::Array<Teuchos::RCP<const Thyra::VectorBase<Scalar> > >& x,
    const Teuchos::Array<Scalar>& t, const Thyra::VectorBase<Scalar>& p,
    const int param_index) const
{
  typedef Thyra::ModelEvaluatorBase MEB;
  MEB::OutArgs<Scalar> outArgs = this->wrapperModel_->createOutArgs();
  TEUCHOS_ASSERT(outArgs.supports(MEB::OUT_ARG_W));
  outArgs.set_W(Teuchos::rcpFromRef(jacobian_solver));
  computeStepResidDerivImpl(outArgs, x, t, p, param_index, 0);
}
 
template <class Scalar>
void StepperBackwardEuler<Scalar>::computeStepResidDerivImpl(
    const Thyra::ModelEvaluatorBase::OutArgs<Scalar>& outArgs,
    const Teuchos::Array<Teuchos::RCP<const Thyra::VectorBase<Scalar> > >& x,
    const Teuchos::Array<Scalar>& t, const Thyra::VectorBase<Scalar>& p,
    const int param_index, const int deriv_index) const
{
  using Teuchos::RCP;
  typedef Thyra::ModelEvaluatorBase MEB;
 
  TEUCHOS_ASSERT(x.size() == 2);
  TEUCHOS_ASSERT(t.size() == 2);
  RCP<const Thyra::VectorBase<Scalar> > xn = x[0];
  RCP<const Thyra::VectorBase<Scalar> > xo = x[1];
  const Scalar tn                          = t[0];
  const Scalar to                          = t[1];
  const Scalar dt                          = tn - to;
 
  // compute x_dot
  RCP<Thyra::VectorBase<Scalar> > x_dot         = xn->clone_v();
  Teuchos::RCP<TimeDerivative<Scalar> > timeDer = Teuchos::rcp(
      new StepperBackwardEulerTimeDerivative<Scalar>(Scalar(1.0) / dt, xo));
  timeDer->compute(xn, x_dot);
 
  // evaluate model
  MEB::InArgs<Scalar> inArgs = this->wrapperModel_->createInArgs();
  inArgs.set_x(xn);
  if (inArgs.supports(MEB::IN_ARG_x_dot)) inArgs.set_x_dot(x_dot);
  if (inArgs.supports(MEB::IN_ARG_t)) inArgs.set_t(tn);
  if (inArgs.supports(MEB::IN_ARG_step_size)) inArgs.set_step_size(dt);
  inArgs.set_p(param_index, Teuchos::rcpFromRef(p));
  TEUCHOS_ASSERT(inArgs.supports(MEB::IN_ARG_alpha));
  TEUCHOS_ASSERT(inArgs.supports(MEB::IN_ARG_beta));
  if (deriv_index == 0) {
    // df/dx_n = df/dx_dot * dx_dot/dx_n + df/dx_n = 1/dt*df/dx_dot + df/dx_n
    inArgs.set_alpha(Scalar(1.0) / dt);
    inArgs.set_beta(Scalar(1.0));
  }
  else if (deriv_index == 1) {
    // df/dx_{n-1} = df/dx_dot * dx_dot/dx_{n-1} = -1/dt*df/dx_dot
    inArgs.set_alpha(Scalar(-1.0) / dt);
    inArgs.set_beta(Scalar(0.0));
  }
  this->wrapperModel_->getAppModel()->evalModel(inArgs, outArgs);
}
 
// Nonmember constructor - ModelEvaluator and ParameterList
// ------------------------------------------------------------------------
template <class Scalar>
Teuchos::RCP<StepperBackwardEuler<Scalar> > createStepperBackwardEuler(
    const Teuchos::RCP<const Thyra::ModelEvaluator<Scalar> >& model,
    Teuchos::RCP<Teuchos::ParameterList> pl)
{
  auto stepper = Teuchos::rcp(new StepperBackwardEuler<Scalar>());
 
  stepper->setStepperImplicitValues(pl);
 
  if (pl != Teuchos::null) {
    std::string predictorName =
        pl->get<std::string>("Predictor Stepper Type", "None");
    stepper->setPredictor(predictorName);
  }
 
  if (model != Teuchos::null) {
    stepper->setModel(model);
    stepper->initialize();
  }
 
  return stepper;
}
 
}  // namespace Tempus
#endif  // Tempus_StepperBackwardEuler_impl_hpp