Tempus_StepperDIRK_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_StepperDIRK_impl_hpp
#define Tempus_StepperDIRK_impl_hpp
 
#include "Thyra_VectorStdOps.hpp"
 
#include "Tempus_WrapperModelEvaluatorBasic.hpp"
 
namespace Tempus {
 
template <class Scalar>
void StepperDIRK<Scalar>::setupDefault()
{
  this->setUseEmbedded(false);
  this->setZeroInitialGuess(false);
  this->setStageNumber(-1);
 
  this->setAppAction(Teuchos::null);
  this->setDefaultSolver();
}
 
template <class Scalar>
void StepperDIRK<Scalar>::setup(
    const Teuchos::RCP<const Thyra::ModelEvaluator<Scalar> >& appModel,
    const Teuchos::RCP<Thyra::NonlinearSolverBase<Scalar> >& solver,
    bool useFSAL, std::string ICConsistency, bool ICConsistencyCheck,
    bool useEmbedded, bool zeroInitialGuess,
    const Teuchos::RCP<StepperRKAppAction<Scalar> >& stepperRKAppAction)
{
  this->setUseFSAL(useFSAL);
  this->setICConsistency(ICConsistency);
  this->setICConsistencyCheck(ICConsistencyCheck);
  this->setUseEmbedded(useEmbedded);
  this->setZeroInitialGuess(zeroInitialGuess);
 
  this->setStageNumber(-1);
  this->setErrorNorm();
  this->setAppAction(stepperRKAppAction);
  this->setSolver(solver);
 
  if (appModel != Teuchos::null) {
    this->setModel(appModel);
    this->initialize();
  }
}
 
template <class Scalar>
Teuchos::RCP<Teuchos::ParameterList>
StepperDIRK<Scalar>::getValidParametersBasicDIRK() const
{
  auto pl = this->getValidParametersBasicImplicit();
  pl->template set<bool>(
      "Use Embedded", this->getUseEmbedded(),
      "'Whether to use Embedded Stepper (if available) or not\n"
      "  'true' - Stepper will compute embedded solution and is adaptive.\n"
      "  'false' - Stepper is not embedded(adaptive).\n");
  pl->template set<std::string>("Description", this->getDescription());
  pl->template set<bool>("Reset Initial Guess", this->getResetInitialGuess());
 
  return pl;
}
 
template <class Scalar>
void StepperDIRK<Scalar>::initialize()
{
  TEUCHOS_TEST_FOR_EXCEPTION(this->tableau_ == Teuchos::null, std::logic_error,
                             "Error - Need to set the tableau, before calling "
                             "StepperDIRK::initialize()\n");
 
  TEUCHOS_TEST_FOR_EXCEPTION(
      this->wrapperModel_ == Teuchos::null, std::logic_error,
      "Error - Need to set the model, setModel(), before calling "
      "StepperDIRK::initialize()\n");
 
  StepperImplicit<Scalar>::initialize();
}
 
template <class Scalar>
void StepperDIRK<Scalar>::setModel(
    const Teuchos::RCP<const Thyra::ModelEvaluator<Scalar> >& appModel)
{
  StepperImplicit<Scalar>::setModel(appModel);
 
  // Set the stage vectors
  const int numStages = this->tableau_->numStages();
  stageXDot_.resize(numStages);
  for (int i = 0; i < numStages; ++i) {
    stageXDot_[i] = Thyra::createMember(this->wrapperModel_->get_f_space());
    assign(stageXDot_[i].ptr(), Teuchos::ScalarTraits<Scalar>::zero());
  }
  xTilde_ = Thyra::createMember(this->wrapperModel_->get_x_space());
  assign(xTilde_.ptr(), Teuchos::ScalarTraits<Scalar>::zero());
 
  this->setEmbeddedMemory();
  this->setErrorNorm();
 
  this->isInitialized_ = false;
}
 
template <class Scalar>
void StepperDIRK<Scalar>::setEmbeddedMemory()
{
  if (this->getModel() == Teuchos::null)
    return;  // Embedded memory will be set when setModel() is called.
 
  if (this->tableau_->isEmbedded() && this->getUseEmbedded()) {
    this->ee_    = Thyra::createMember(this->wrapperModel_->get_f_space());
    this->abs_u0 = Thyra::createMember(this->wrapperModel_->get_f_space());
    this->abs_u  = Thyra::createMember(this->wrapperModel_->get_f_space());
    this->sc     = Thyra::createMember(this->wrapperModel_->get_f_space());
  }
  else {
    this->ee_    = Teuchos::null;
    this->abs_u0 = Teuchos::null;
    this->abs_u  = Teuchos::null;
    this->sc     = Teuchos::null;
  }
}
 
template <class Scalar>
void StepperDIRK<Scalar>::setInitialConditions(
    const Teuchos::RCP<SolutionHistory<Scalar> >& solutionHistory)
{
  this->setStepperXDot(stageXDot_.back());
  StepperImplicit<Scalar>::setInitialConditions(solutionHistory);
}
 
template <class Scalar>
void StepperDIRK<Scalar>::takeStep(
    const Teuchos::RCP<SolutionHistory<Scalar> >& solutionHistory)
{
  this->checkInitialized();
 
  using Teuchos::RCP;
 
  TEMPUS_FUNC_TIME_MONITOR("Tempus::StepperDIRK::takeStep()");
  {
    TEUCHOS_TEST_FOR_EXCEPTION(
        solutionHistory->getNumStates() < 2, std::logic_error,
        "Error - StepperDIRK<Scalar>::takeStep(...)\n"
            << "Need at least two SolutionStates for DIRK.\n"
            << "  Number of States = " << solutionHistory->getNumStates()
            << "\nTry setting in \"Solution History\" "
            << "\"Storage Type\" = \"Undo\"\n"
            << "  or \"Storage Type\" = \"Static\" and "
            << "\"Storage Limit\" = \"2\"\n");
 
    RCP<SolutionState<Scalar> > currentState =
        solutionHistory->getCurrentState();
    RCP<SolutionState<Scalar> > workingState =
        solutionHistory->getWorkingState();
    const Scalar dt   = workingState->getTimeStep();
    const Scalar time = currentState->getTime();
 
    const int numStages                       = this->tableau_->numStages();
    Teuchos::SerialDenseMatrix<int, Scalar> A = this->tableau_->A();
    Teuchos::SerialDenseVector<int, Scalar> b = this->tableau_->b();
    Teuchos::SerialDenseVector<int, Scalar> c = this->tableau_->c();
 
    // Reset non-zero initial guess.
    if (this->getResetInitialGuess() && (!this->getZeroInitialGuess()))
      Thyra::assign(workingState->getX().ptr(), *(currentState->getX()));
 
    RCP<StepperDIRK<Scalar> > thisStepper = Teuchos::rcpFromRef(*this);
    this->stepperRKAppAction_->execute(
        solutionHistory, thisStepper,
        StepperRKAppAction<Scalar>::ACTION_LOCATION::BEGIN_STEP);
 
    // Compute stage solutions
    bool pass = true;
    Thyra::SolveStatus<Scalar> sStatus;
    for (int i = 0; i < numStages; ++i) {
      this->setStageNumber(i);
 
      Thyra::assign(xTilde_.ptr(), *(currentState->getX()));
      for (int j = 0; j < i; ++j) {
        if (A(i, j) != Teuchos::ScalarTraits<Scalar>::zero()) {
          Thyra::Vp_StV(xTilde_.ptr(), dt * A(i, j), *(stageXDot_[j]));
        }
      }
      this->setStepperXDot(stageXDot_[i]);
 
      this->stepperRKAppAction_->execute(
          solutionHistory, thisStepper,
          StepperRKAppAction<Scalar>::ACTION_LOCATION::BEGIN_STAGE);
 
      Scalar ts = time + c(i) * dt;
 
      // Check if stageXDot_[i] is needed.
      bool isNeeded = false;
      for (int k = i + 1; k < numStages; ++k)
        if (A(k, i) != 0.0) isNeeded = true;
      if (b(i) != 0.0) isNeeded = true;
      if (this->tableau_->isEmbedded() && this->getUseEmbedded() &&
          this->tableau_->bstar()(i) != 0.0)
        isNeeded = true;
      if (isNeeded == false) {
        assign(stageXDot_[i].ptr(), Teuchos::ScalarTraits<Scalar>::zero());
      }
      else if (A(i, i) == Teuchos::ScalarTraits<Scalar>::zero()) {
        // Explicit stage for the ImplicitODE_DAE
        if (i == 0 && this->getUseFSAL() &&
            workingState->getNConsecutiveFailures() == 0) {
          // Reuse last evaluation for first step
          RCP<Thyra::VectorBase<Scalar> > tmp = stageXDot_[0];
          stageXDot_[0]                       = stageXDot_.back();
          stageXDot_.back()                   = tmp;
          this->setStepperXDot(stageXDot_[0]);
        }
        else {
          // Calculate explicit stage
          typedef Thyra::ModelEvaluatorBase MEB;
          MEB::InArgs<Scalar> inArgs   = this->wrapperModel_->createInArgs();
          MEB::OutArgs<Scalar> outArgs = this->wrapperModel_->createOutArgs();
          inArgs.set_x(xTilde_);
          if (inArgs.supports(MEB::IN_ARG_t)) inArgs.set_t(ts);
          if (inArgs.supports(MEB::IN_ARG_x_dot))
            inArgs.set_x_dot(Teuchos::null);
          outArgs.set_f(stageXDot_[i]);
 
          this->wrapperModel_->getAppModel()->evalModel(inArgs, outArgs);
        }
      }
      else {
        // Implicit stage for the ImplicitODE_DAE
        const Scalar alpha = 1.0 / (dt * A(i, i));
        const Scalar beta  = 1.0;
 
        // Setup TimeDerivative
        Teuchos::RCP<TimeDerivative<Scalar> > timeDer = Teuchos::rcp(
            new StepperDIRKTimeDerivative<Scalar>(alpha, xTilde_.getConst()));
 
        auto p = Teuchos::rcp(new ImplicitODEParameters<Scalar>(
            timeDer, dt, alpha, beta, SOLVE_FOR_X, i));
 
        this->stepperRKAppAction_->execute(
            solutionHistory, thisStepper,
            StepperRKAppAction<Scalar>::ACTION_LOCATION::BEFORE_SOLVE);
 
        sStatus =
            this->solveImplicitODE(workingState->getX(), stageXDot_[i], ts, p);
 
        if (sStatus.solveStatus != Thyra::SOLVE_STATUS_CONVERGED) pass = false;
 
        this->stepperRKAppAction_->execute(
            solutionHistory, thisStepper,
            StepperRKAppAction<Scalar>::ACTION_LOCATION::AFTER_SOLVE);
 
        timeDer->compute(workingState->getX(), stageXDot_[i]);
      }
      this->stepperRKAppAction_->execute(
          solutionHistory, thisStepper,
          StepperRKAppAction<Scalar>::ACTION_LOCATION::BEFORE_EXPLICIT_EVAL);
      this->stepperRKAppAction_->execute(
          solutionHistory, thisStepper,
          StepperRKAppAction<Scalar>::ACTION_LOCATION::END_STAGE);
    }
    // reset the stage number
    this->setStageNumber(-1);
 
    // Sum for solution: x_n = x_n-1 + Sum{ dt*b(i) * f(i) }
    Thyra::assign((workingState->getX()).ptr(), *(currentState->getX()));
    for (int i = 0; i < numStages; ++i) {
      if (b(i) != Teuchos::ScalarTraits<Scalar>::zero()) {
        Thyra::Vp_StV((workingState->getX()).ptr(), dt * b(i),
                      *(stageXDot_[i]));
      }
    }
 
    if (this->tableau_->isEmbedded() && this->getUseEmbedded()) {
      const Scalar tolRel = workingState->getTolRel();
      const Scalar tolAbs = workingState->getTolAbs();
 
      // update the tolerance
      this->stepperErrorNormCalculator_->setRelativeTolerance(tolRel);
      this->stepperErrorNormCalculator_->setAbsoluteTolerance(tolAbs);
 
      // just compute the error weight vector
      // (all that is needed is the error, and not the embedded solution)
      Teuchos::SerialDenseVector<int, Scalar> errWght = b;
      errWght -= this->tableau_->bstar();
 
      // compute local truncation error estimate: | u^{n+1} - \hat{u}^{n+1} |
      // Sum for solution: ee_n = Sum{ (b(i) - bstar(i)) * dt*f(i) }
      assign(this->ee_.ptr(), Teuchos::ScalarTraits<Scalar>::zero());
      for (int i = 0; i < numStages; ++i) {
        if (errWght(i) != Teuchos::ScalarTraits<Scalar>::zero()) {
          Thyra::Vp_StV(this->ee_.ptr(), dt * errWght(i), *(stageXDot_[i]));
        }
      }
 
      Scalar err = this->stepperErrorNormCalculator_->computeWRMSNorm(
          currentState->getX(), workingState->getX(), this->ee_);
      workingState->setErrorRel(err);
 
      // test if step should be rejected
      if (std::isinf(err) || std::isnan(err) || err > Teuchos::as<Scalar>(1.0))
        pass = false;
    }
 
    if (pass)
      workingState->setSolutionStatus(Status::PASSED);
    else
      workingState->setSolutionStatus(Status::FAILED);
 
    workingState->setOrder(this->getOrder());
    workingState->computeNorms(currentState);
    this->stepperRKAppAction_->execute(
        solutionHistory, thisStepper,
        StepperRKAppAction<Scalar>::ACTION_LOCATION::END_STEP);
  }
  return;
}

template <class Scalar>
Teuchos::RCP<Tempus::StepperState<Scalar> >
StepperDIRK<Scalar>::getDefaultStepperState()
{
  Teuchos::RCP<Tempus::StepperState<Scalar> > stepperState =
      rcp(new StepperState<Scalar>(this->getStepperType()));
  return stepperState;
}
 
template <class Scalar>
void StepperDIRK<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 << "--- StepperDIRK ---\n";
  out << "  tableau_            = " << this->tableau_ << std::endl;
  if (this->tableau_ != Teuchos::null) this->tableau_->describe(out, verbLevel);
  out << "  stepperRKAppAction_ = " << this->stepperRKAppAction_ << std::endl;
  out << "  xTilde_             = " << xTilde_ << std::endl;
  out << "  stageXDot_.size()   = " << stageXDot_.size() << std::endl;
  const int numStages = stageXDot_.size();
  for (int i = 0; i < numStages; ++i)
    out << "    stageXDot_[" << i << "] = " << stageXDot_[i] << std::endl;
  out << "  useEmbedded_        = " << Teuchos::toString(this->useEmbedded_)
      << std::endl;
  out << "  ee_                 = " << this->ee_ << std::endl;
  out << "  abs_u0              = " << this->abs_u0 << std::endl;
  out << "  abs_u               = " << this->abs_u << std::endl;
  out << "  sc                  = " << this->sc << std::endl;
  out << "-------------------" << std::endl;
}
 
template <class Scalar>
bool StepperDIRK<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 (this->tableau_ == Teuchos::null) {
    isValidSetup = false;
    out << "The tableau is not set!\n";
  }
 
  if (this->stepperRKAppAction_ == Teuchos::null) {
    isValidSetup = false;
    out << "The AppAction is not set!\n";
  }
 
  return isValidSetup;
}
 
template <class Scalar>
Teuchos::RCP<const Teuchos::ParameterList>
StepperDIRK<Scalar>::getValidParameters() const
{
  return this->getValidParametersBasicDIRK();
}
 
}  // namespace Tempus
#endif  // Tempus_StepperDIRK_impl_hpp