Tempus_StepperHHTAlpha_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_StepperHHTAlpha_impl_hpp
#define Tempus_StepperHHTAlpha_impl_hpp

#include "Teuchos_VerboseObjectParameterListHelpers.hpp"

#include "Tempus_StepperHHTAlphaModifierDefault.hpp"

//#define VERBOSE_DEBUG_OUTPUT
//#define DEBUG_OUTPUT

namespace Tempus {


template<class Scalar>
void StepperHHTAlpha<Scalar>::
predictVelocity(Thyra::VectorBase<Scalar>& vPred,
                const Thyra::VectorBase<Scalar>& v,
                const Thyra::VectorBase<Scalar>& a,
                const Scalar dt) const
{
#ifdef VERBOSE_DEBUG_OUTPUT
  *out_ << "DEBUG: " << __PRETTY_FUNCTION__ << "\n";
#endif
  //vPred = v + dt*(1.0-gamma_)*a
  Thyra::V_StVpStV(Teuchos::ptrFromRef(vPred), 1.0, v, dt*(1.0-gamma_), a);
}

template<class Scalar>
void StepperHHTAlpha<Scalar>::
predictDisplacement(Thyra::VectorBase<Scalar>& dPred,
                    const Thyra::VectorBase<Scalar>& d,
                    const Thyra::VectorBase<Scalar>& v,
                    const Thyra::VectorBase<Scalar>& a,
                    const Scalar dt) const
{
#ifdef VERBOSE_DEBUG_OUTPUT
  *out_ << "DEBUG: " << __PRETTY_FUNCTION__ << "\n";
#endif
  //dPred = dt*v + dt*dt/2.0*(1.0-2.0*beta_)*a
  Scalar aConst = dt*dt/2.0*(1.0-2.0*beta_);
  Thyra::V_StVpStV(Teuchos::ptrFromRef(dPred), dt, v, aConst, a);
  //dPred += d;
  Thyra::Vp_V(Teuchos::ptrFromRef(dPred), d, 1.0);
}


template<class Scalar>
void StepperHHTAlpha<Scalar>::
predictVelocity_alpha_f(Thyra::VectorBase<Scalar>& vPred,
                        const Thyra::VectorBase<Scalar>& v) const
{
#ifdef VERBOSE_DEBUG_OUTPUT
  *out_ << "DEBUG: " << __PRETTY_FUNCTION__ << "\n";
#endif
  //vPred = (1-alpha_f)*vPred + alpha_f*v
  Thyra::V_StVpStV(Teuchos::ptrFromRef(vPred), 1.0-alpha_f_, vPred, alpha_f_, v);
}


template<class Scalar>
void StepperHHTAlpha<Scalar>::
predictDisplacement_alpha_f(Thyra::VectorBase<Scalar>& dPred,
                            const Thyra::VectorBase<Scalar>& d) const
{
#ifdef VERBOSE_DEBUG_OUTPUT
  *out_ << "DEBUG: " << __PRETTY_FUNCTION__ << "\n";
#endif
  //dPred = (1-alpha_f)*dPred + alpha_f*d
  Thyra::V_StVpStV(Teuchos::ptrFromRef(dPred), 1.0-alpha_f_, dPred, alpha_f_, d);
}

template<class Scalar>
void StepperHHTAlpha<Scalar>::
correctAcceleration(Thyra::VectorBase<Scalar>& a_n_plus1,
                    const Thyra::VectorBase<Scalar>& a_n) const
{
#ifdef VERBOSE_DEBUG_OUTPUT
  *out_ << "DEBUG: " << __PRETTY_FUNCTION__ << "\n";
#endif
  Scalar c = 1.0/(1.0-alpha_m_);
  //a_n_plus1 = 1.0/(1.0-alpha_m_)*a_n_plus1 - alpha_m/(1.0-alpha_m)*a_n = (1-alpha_f)*vPred + alpha_f*v
  Thyra::V_StVpStV(Teuchos::ptrFromRef(a_n_plus1), c, a_n_plus1, -c*alpha_m_, a_n);
}



template<class Scalar>
void StepperHHTAlpha<Scalar>::
correctVelocity(Thyra::VectorBase<Scalar>& v,
                const Thyra::VectorBase<Scalar>& vPred,
                const Thyra::VectorBase<Scalar>& a,
                const Scalar dt) const
{
#ifdef VERBOSE_DEBUG_OUTPUT
  *out_ << "DEBUG: " << __PRETTY_FUNCTION__ << "\n";
#endif
  //v = vPred + dt*gamma_*a
  Thyra::V_StVpStV(Teuchos::ptrFromRef(v), 1.0, vPred, dt*gamma_, a);
}

template<class Scalar>
void StepperHHTAlpha<Scalar>::
correctDisplacement(Thyra::VectorBase<Scalar>& d,
                    const Thyra::VectorBase<Scalar>& dPred,
                    const Thyra::VectorBase<Scalar>& a,
                    const Scalar dt) const
{
#ifdef VERBOSE_DEBUG_OUTPUT
  *out_ << "DEBUG: " << __PRETTY_FUNCTION__ << "\n";
#endif
  //d = dPred + beta_*dt*dt*a
  Thyra::V_StVpStV(Teuchos::ptrFromRef(d), 1.0, dPred, beta_*dt*dt, a);
}



template<class Scalar>
void StepperHHTAlpha<Scalar>::setBeta(Scalar beta)
{
  if (schemeName_ != "Newmark Beta User Defined") {
    out_->setOutputToRootOnly(0);
    *out_ << "\nWARNING: schemeName != 'Newmark Beta User Defined' (= '"
          << schemeName_ << "').\n"
          << " Leaving as beta = " << beta_ << "!\n";
    return;
  }

  beta_ = beta;

  if (beta_ == 0.0) {
    out_->setOutputToRootOnly(0);
    *out_ << "\nWARNING: Running (implicit implementation of) Newmark "
          << "Implicit a-Form Stepper with Beta = 0.0, which \n"
          << "specifies an explicit scheme.  Mass lumping is not possible, "
          << "so this will be slow!  To run explicit \n"
          << "implementation of Newmark Implicit a-Form Stepper, please "
          << "re-run with 'Stepper Type' = 'Newmark Explicit a-Form'.\n"
          << "This stepper allows for mass lumping when called through "
          << "Piro::TempusSolver.\n";
  }

  TEUCHOS_TEST_FOR_EXCEPTION( (beta_ > 1.0) || (beta_ < 0.0),
    std::logic_error,
    "\nError in 'Newmark Implicit a-Form' stepper: invalid value of Beta = "
    << beta_ << ".  Please select Beta >= 0 and <= 1. \n");

  this->isInitialized_ = false;
}


template<class Scalar>
void StepperHHTAlpha<Scalar>::setGamma(Scalar gamma)
{
  if (schemeName_ != "Newmark Beta User Defined") {
    out_->setOutputToRootOnly(0);
    *out_ << "\nWARNING: schemeName != 'Newmark Beta User Defined' (= '"
          << schemeName_ << "').\n"
          << " Leaving as gamma = " << gamma_ << "!\n";
    return;
  }

  gamma_ = gamma;

  TEUCHOS_TEST_FOR_EXCEPTION( (gamma_ > 1.0) || (gamma_ < 0.0),
    std::logic_error,
    "\nError in 'Newmark Implicit a-Form' stepper: invalid value of Gamma ="
    <<gamma_ << ".  Please select Gamma >= 0 and <= 1. \n");

  this->isInitialized_ = false;
}


template<class Scalar>
void StepperHHTAlpha<Scalar>::setAlphaF(Scalar alpha_f)
{
  alpha_f_ = alpha_f;

  TEUCHOS_TEST_FOR_EXCEPTION( (alpha_f_ > 1.0) || (alpha_f_ < 0.0),
    std::logic_error,
    "\nError in 'HHT-Alpha' stepper: invalid value of Alpha_f = "
    << alpha_f_ << ".  Please select Alpha_f >= 0 and <= 1. \n");

  this->isInitialized_ = false;
}


template<class Scalar>
void StepperHHTAlpha<Scalar>::setAlphaM(Scalar alpha_m)
{
  alpha_m_ = alpha_m;

  TEUCHOS_TEST_FOR_EXCEPTION( (alpha_m_ >= 1.0) || (alpha_m_ < 0.0),
    std::logic_error,
    "\nError in 'HHT-Alpha' stepper: invalid value of Alpha_m = "
    << alpha_m_ << ".  Please select Alpha_m >= 0 and < 1. \n");

  this->isInitialized_ = false;
}


template<class Scalar>
void StepperHHTAlpha<Scalar>::setSchemeName(
  std::string schemeName)
{
  schemeName_ = schemeName;

  if (schemeName_ == "Newmark Beta Average Acceleration") {
    beta_= 0.25; gamma_ = 0.5;
  }
  else if (schemeName_ == "Newmark Beta Linear Acceleration") {
    beta_= 0.25; gamma_ = 1.0/6.0;
  }
  else if (schemeName_ == "Newmark Beta Central Difference") {
    beta_=  0.0; gamma_ = 0.5;
  }
  else if (schemeName_ == "Newmark Beta User Defined") {
    beta_= 0.25; gamma_ = 0.5; // Use defaults until setBeta and setGamma calls.
  }
  else {
    TEUCHOS_TEST_FOR_EXCEPTION(true,
       std::logic_error,
       "\nError in Tempus::StepperHHTAlpha!  "
       <<"Invalid Scheme Name = " << schemeName_ <<".  \n"
       <<"Valid Scheme Names are: 'Newmark Beta Average Acceleration', "
       <<"'Newmark Beta Linear Acceleration', \n"
       <<"'Newmark Beta Central Difference' and 'Newmark Beta User Defined'.\n");
  }

  this->isInitialized_ = false;
}

template<class Scalar>
StepperHHTAlpha<Scalar>::StepperHHTAlpha() :
  out_(Teuchos::VerboseObjectBase::getDefaultOStream())
{
#ifdef VERBOSE_DEBUG_OUTPUT
  *out_ << "DEBUG: " << __PRETTY_FUNCTION__ << "\n";
#endif

  this->setStepperName(        "HHT-Alpha");
  this->setStepperType(        "HHT-Alpha");
  this->setUseFSAL(            false);
  this->setICConsistency(      "None");
  this->setICConsistencyCheck( false);
  this->setZeroInitialGuess(   false);
  this->setSchemeName(         "Newmark Beta Average Acceleration");
  this->setAlphaF(             0.0);
  this->setAlphaM(             0.0);
  this->setAppAction(Teuchos::null);
  this->setDefaultSolver();
}

template<class Scalar>
StepperHHTAlpha<Scalar>::StepperHHTAlpha(
  const Teuchos::RCP<const Thyra::ModelEvaluator<Scalar> >& appModel,
  const Teuchos::RCP<Thyra::NonlinearSolverBase<Scalar> >& solver,
  bool useFSAL,
  std::string ICConsistency,
  bool ICConsistencyCheck,
  bool zeroInitialGuess,
  std::string schemeName,
  Scalar beta,
  Scalar gamma,
  Scalar alpha_f,
  Scalar alpha_m,
  const Teuchos::RCP<StepperHHTAlphaAppAction<Scalar> >& stepperHHTAlphaAppAction)
  : out_(Teuchos::VerboseObjectBase::getDefaultOStream())
{
  this->setStepperName(        "HHT-Alpha");
  this->setStepperType(        "HHT-Alpha");
  this->setUseFSAL(            useFSAL);
  this->setICConsistency(      ICConsistency);
  this->setICConsistencyCheck( ICConsistencyCheck);
  this->setZeroInitialGuess(   zeroInitialGuess);
  this->setSchemeName(         schemeName);
  if (schemeName == "Newmark Beta User Defined") {
    this->setBeta(               beta);
    this->setGamma(              gamma);
  }
  this->setAlphaF(             alpha_f);
  this->setAlphaM(             alpha_m);
  this->setAppAction(stepperHHTAlphaAppAction);
  this->setSolver(solver);

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

template<class Scalar>
void StepperHHTAlpha<Scalar>::setAppAction(
  Teuchos::RCP<StepperHHTAlphaAppAction<Scalar> > appAction)
{
  if (appAction == Teuchos::null) {
  // Create default appAction
  stepperHHTAlphaAppAction_ =
    Teuchos::rcp(new StepperHHTAlphaModifierDefault<Scalar>());
  }
  else {
    stepperHHTAlphaAppAction_ = appAction;
  }
}

template<class Scalar>
void StepperHHTAlpha<Scalar>::setModel(
  const Teuchos::RCP<const Thyra::ModelEvaluator<Scalar> >& appModel)
{
#ifdef VERBOSE_DEBUG_OUTPUT
  *out_ << "DEBUG: " << __PRETTY_FUNCTION__ << "\n";
#endif
  validSecondOrderODE_DAE(appModel);
  Teuchos::RCP<WrapperModelEvaluatorSecondOrder<Scalar> > wrapperModel =
    Teuchos::rcp(new WrapperModelEvaluatorSecondOrder<Scalar>(appModel,
                                                      "HHT-Alpha"));
  this->wrapperModel_ = wrapperModel;

  TEUCHOS_TEST_FOR_EXCEPTION(this->solver_ == Teuchos::null, std::logic_error,
    "Error - Solver is not set!\n");
  if (this->wrapperModel_ != Teuchos::null)
    this->solver_->setModel(this->wrapperModel_);

  this->isInitialized_ = false;
}


template<class Scalar>
void StepperHHTAlpha<Scalar>::takeStep(
  const Teuchos::RCP<SolutionHistory<Scalar> >& solutionHistory)
{
#ifdef VERBOSE_DEBUG_OUTPUT
  *out_ << "DEBUG: " << __PRETTY_FUNCTION__ << "\n";
#endif
  this->checkInitialized();

  using Teuchos::RCP;

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

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

    Teuchos::RCP<WrapperModelEvaluatorSecondOrder<Scalar> > wrapperModel =
      Teuchos::rcp_dynamic_cast<WrapperModelEvaluatorSecondOrder<Scalar> >(
        this->wrapperModel_);

    //Get values of d, v and a from previous step
    RCP<const Thyra::VectorBase<Scalar> > d_old = currentState->getX();
    RCP<const Thyra::VectorBase<Scalar> > v_old = currentState->getXDot();
    RCP<Thyra::VectorBase<Scalar> > a_old = currentState->getXDotDot();

#ifdef DEBUG_OUTPUT
    //IKT, 3/21/17, debug output: pring d_old, v_old, a_old to check for
    // correctness.
    *out_ << "IKT d_old = " << Thyra::max(*d_old) << "\n";
    *out_ << "IKT v_old = " << Thyra::max(*v_old) << "\n";
#endif

    //Get new values of d, v and a from current workingState
    //(to be updated here)
    RCP<Thyra::VectorBase<Scalar> > d_new = workingState->getX();
    RCP<Thyra::VectorBase<Scalar> > v_new = workingState->getXDot();
    RCP<Thyra::VectorBase<Scalar> > a_new = workingState->getXDotDot();

    //Get time and dt
    const Scalar time = currentState->getTime();
    const Scalar dt   = workingState->getTimeStep();
    //Update time
    Scalar t = time+dt;

    //Compute initial acceleration, a_old, using initial displacement (d_old) and initial
    //velocity (v_old) if in 1st time step
    if (time == solutionHistory->minTime()) {
      RCP<Thyra::VectorBase<Scalar> > d_init = Thyra::createMember(d_old->space());
      RCP<Thyra::VectorBase<Scalar> > v_init = Thyra::createMember(v_old->space());
      RCP<Thyra::VectorBase<Scalar> > a_init = Thyra::createMember(a_old->space());
      Thyra::copy(*d_old, d_init.ptr());
      Thyra::copy(*v_old, v_init.ptr());
      if (this->initialGuess_ != Teuchos::null) { //set initial guess for Newton, if provided
        //Throw an exception if initial_guess is not compatible with solution
        bool is_compatible = (a_init->space())->isCompatible(*this->initialGuess_->space());
        TEUCHOS_TEST_FOR_EXCEPTION(
            is_compatible != true, std::logic_error,
              "Error in Tempus::NemwarkImplicitAForm takeStep(): user-provided initial guess'!\n"
              << "for Newton is not compatible with solution vector!\n");
        Thyra::copy(*this->initialGuess_, a_init.ptr());
      }
      else { //if no initialGuess_ provide, set 0 initial guess
        Thyra::put_scalar(0.0, a_init.ptr());
      }
      wrapperModel->initializeNewmark(v_init,d_init,0.0,time,beta_,gamma_);
      const Thyra::SolveStatus<Scalar> sStatus=this->solveImplicitODE(a_init);

      workingState->setSolutionStatus(sStatus);  // Converged --> pass.
      Thyra::copy(*a_init, a_old.ptr());
    }
#ifdef DEBUG_OUTPUT
    //IKT, 3/30/17, debug output: pring a_old to check for correctness.
    *out_ << "IKT a_old = " << Thyra::max(*a_old) << "\n";
#endif

    //allocate d and v predictors
    RCP<Thyra::VectorBase<Scalar> > d_pred =Thyra::createMember(d_old->space());
    RCP<Thyra::VectorBase<Scalar> > v_pred =Thyra::createMember(v_old->space());

    //compute displacement and velocity predictors
    predictDisplacement(*d_pred, *d_old, *v_old, *a_old, dt);
    predictVelocity(*v_pred, *v_old, *a_old, dt);

    //compute second displacement and velocity predictors (those that are functions of alpha_f)
    predictDisplacement_alpha_f(*d_pred, *d_old);
    predictVelocity_alpha_f(*v_pred, *v_old);

    //inject d_pred, v_pred, a and other relevant data into wrapperModel
    wrapperModel->initializeNewmark(v_pred,d_pred,dt,t,beta_,gamma_);


    stepperHHTAlphaAppAction_->execute(solutionHistory, thisStepper,
      StepperHHTAlphaAppAction<Scalar>::ACTION_LOCATION::BEFORE_SOLVE);

    //Solve for new acceleration
    const Thyra::SolveStatus<Scalar> sStatus = this->solveImplicitODE(a_new);

    stepperHHTAlphaAppAction_->execute(solutionHistory, thisStepper,
      StepperHHTAlphaAppAction<Scalar>::ACTION_LOCATION::AFTER_SOLVE);

    //correct acceleration (function of alpha_m)
    correctAcceleration(*a_new, *a_old);

    //correct velocity and displacement
    correctVelocity(*v_new, *v_pred, *a_new, dt);
    correctDisplacement(*d_new, *d_pred, *a_new, dt);

    workingState->setSolutionStatus(sStatus);  // Converged --> pass.
    workingState->setOrder(this->getOrder());
    workingState->computeNorms(currentState);

    stepperHHTAlphaAppAction_->execute(solutionHistory, thisStepper,
      StepperHHTAlphaAppAction<Scalar>::ACTION_LOCATION::END_STEP);
  }
  return;
}



template<class Scalar>
Teuchos::RCP<Tempus::StepperState<Scalar> >
StepperHHTAlpha<Scalar>::
getDefaultStepperState()
{
#ifdef VERBOSE_DEBUG_OUTPUT
  *out_ << "DEBUG: " << __PRETTY_FUNCTION__ << "\n";
#endif
  Teuchos::RCP<Tempus::StepperState<Scalar> > stepperState =
    rcp(new StepperState<Scalar>(this->getStepperType()));
  return stepperState;
}


template<class Scalar>
void StepperHHTAlpha<Scalar>::describe(
   Teuchos::FancyOStream               &out,
   const Teuchos::EVerbosityLevel      verbLevel) const
{

#ifdef VERBOSE_DEBUG_OUTPUT
  *out_ << "DEBUG: " << __PRETTY_FUNCTION__ << "\n";
#endif

  out << std::endl;
  Stepper<Scalar>::describe(out, verbLevel);
  StepperImplicit<Scalar>::describe(out, verbLevel);

  auto l_out = Teuchos::fancyOStream( out.getOStream() );
  l_out->setOutputToRootOnly(0);
  *l_out << "--- StepperHHTAlpha ---\n";
  *l_out << "  schemeName_ = " << schemeName_ << std::endl;
  *l_out << "  beta_       = " << beta_       << std::endl;
  *l_out << "  gamma_      = " << gamma_      << std::endl;
  *l_out << "  alpha_f_    = " << alpha_f_    << std::endl;
  *l_out << "  alpha_m_    = " << alpha_m_    << std::endl;
  *l_out << "-----------------------" << std::endl;
}


template<class Scalar>
bool StepperHHTAlpha<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->wrapperModel_->getAppModel() == Teuchos::null) {
    isValidSetup = false;
    out << "The application ModelEvaluator is not set!\n";
  }

  if (this->wrapperModel_ == Teuchos::null) {
    isValidSetup = false;
    out << "The wrapper ModelEvaluator is not set!\n";
  }

  if (this->solver_ == Teuchos::null) {
    isValidSetup = false;
    out << "The solver is not set!\n";
  }

  return isValidSetup;
}


template<class Scalar>
Teuchos::RCP<const Teuchos::ParameterList>
StepperHHTAlpha<Scalar>::getValidParameters() const
{
#ifdef VERBOSE_DEBUG_OUTPUT
  *out_ << "DEBUG: " << __PRETTY_FUNCTION__ << "\n";
#endif
  auto pl = this->getValidParametersBasicImplicit();

  auto hhtalphaPL = Teuchos::parameterList("HHT-Alpha Parameters");
  hhtalphaPL->set<std::string>("Scheme Name", schemeName_);
  hhtalphaPL->set<double>     ("Beta",    beta_);
  hhtalphaPL->set<double>     ("Gamma",   gamma_ );
  hhtalphaPL->set<double>     ("Alpha_f", alpha_f_ );
  hhtalphaPL->set<double>     ("Alpha_m", alpha_m_ );
  pl->set("HHT-Alpha Parameters", *hhtalphaPL);

  return pl;
}


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

  if (pl != Teuchos::null) {
    if (pl->isSublist("HHT-Alpha Parameters")) {
      auto hhtalphaPL = pl->sublist("HHT-Alpha Parameters", true);
      std::string schemeName =
        hhtalphaPL.get<std::string>("Scheme Name", "Newmark Beta Average Acceleration");
      stepper->setSchemeName(schemeName);
      if (schemeName == "Newmark Beta User Defined") {
        stepper->setBeta (hhtalphaPL.get<double>("Beta",  0.25));
        stepper->setGamma(hhtalphaPL.get<double>("Gamma", 0.5 ));
      }
      stepper->setAlphaF(hhtalphaPL.get<double>("Alpha_f",  0.0));
      stepper->setAlphaM(hhtalphaPL.get<double>("Alpha_m",  0.0));
    } else {
      stepper->setSchemeName("Newmark Beta Average Acceleration");
      stepper->setAlphaF(0.0);
      stepper->setAlphaM(0.0);
    }
  }

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

  return stepper;
}


} // namespace Tempus
#endif // Tempus_StepperHHTAlpha_impl_hpp