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Tempus::StepperForwardEuler< Scalar > Class Template Reference

Forward Euler time stepper. More...

#include <Tempus_StepperForwardEuler_decl.hpp>

Inheritance diagram for Tempus::StepperForwardEuler< Scalar >:
Tempus::StepperExplicit< Scalar > Tempus::Stepper< Scalar >

Public Member Functions

 StepperForwardEuler ()
 Default constructor.
 
 StepperForwardEuler (const Teuchos::RCP< const Thyra::ModelEvaluator< Scalar > > &appModel, bool useFSAL, std::string ICConsistency, bool ICConsistencyCheck, const Teuchos::RCP< StepperForwardEulerAppAction< Scalar > > &stepperFEAppAction)
 Constructor.
 
virtual void setAppAction (Teuchos::RCP< StepperForwardEulerAppAction< Scalar > > appAction)
 
virtual Teuchos::RCP< StepperForwardEulerAppAction< Scalar > > getAppAction () const
 
virtual void setInitialConditions (const Teuchos::RCP< SolutionHistory< Scalar > > &solutionHistory)
 Set the initial conditions, make them consistent, and set needed memory.
 
virtual void takeStep (const Teuchos::RCP< SolutionHistory< Scalar > > &solutionHistory)
 Take the specified timestep, dt, and return true if successful.
 
virtual Teuchos::RCP< Tempus::StepperState< Scalar > > getDefaultStepperState ()
 Get a default (initial) StepperState.
 
virtual Scalar getOrder () const
 
virtual Scalar getOrderMin () const
 
virtual Scalar getOrderMax () const
 
virtual void setUseFSAL (bool a)
 
virtual OrderODE getOrderODE () const
 
- Public Member Functions inherited from Tempus::StepperExplicit< Scalar >
void setStepperExplicitValues (Teuchos::RCP< Teuchos::ParameterList > pl)
 Set StepperExplicit member data from the ParameterList.
 
virtual void setModel (const Teuchos::RCP< const Thyra::ModelEvaluator< Scalar > > &appModel)
 Set model.
 
virtual Teuchos::RCP< const Thyra::ModelEvaluator< Scalar > > getModel () const
 Return the application ModelEvaluator.
 
virtual Scalar getInitTimeStep (const Teuchos::RCP< SolutionHistory< Scalar > > &) const
 
virtual void setSolver (Teuchos::RCP< Thyra::NonlinearSolverBase< Scalar > > solver)
 Set solver.
 
virtual Teuchos::RCP< Thyra::NonlinearSolverBase< Scalar > > getSolver () const
 Get solver.
 
virtual void setInitialGuess (Teuchos::RCP< const Thyra::VectorBase< Scalar > >)
 Pass initial guess to Newton solver (only relevant for implicit solvers)
 
virtual bool isExplicit () const
 
virtual bool isImplicit () const
 
virtual bool isExplicitImplicit () const
 
virtual bool isOneStepMethod () const
 
virtual bool isMultiStepMethod () const
 
virtual void evaluateExplicitODE (Teuchos::RCP< Thyra::VectorBase< Scalar > > xDot, Teuchos::RCP< const Thyra::VectorBase< Scalar > > x, const Scalar time, const Teuchos::RCP< ExplicitODEParameters< Scalar > > &p)
 Evaluate xDot = f(x,t).
 
virtual void evaluateExplicitODE (Teuchos::RCP< Thyra::VectorBase< Scalar > > xDotDot, Teuchos::RCP< const Thyra::VectorBase< Scalar > > x, Teuchos::RCP< const Thyra::VectorBase< Scalar > > xDot, const Scalar time, const Teuchos::RCP< ExplicitODEParameters< Scalar > > &p)
 Evaluate xDotDot = f(x, xDot, t).
 
- Public Member Functions inherited from Tempus::Stepper< Scalar >
virtual std::string description () const
 
void setStepperValues (const Teuchos::RCP< Teuchos::ParameterList > pl)
 Set Stepper member data from ParameterList.
 
virtual Teuchos::RCP< const Teuchos::ParameterList > getValidParameters () const
 
Teuchos::RCP< Teuchos::ParameterList > getValidParametersBasic () const
 Add basic parameters to Steppers ParameterList.
 
virtual void initialize ()
 Initialize after construction and changing input parameters.
 
virtual bool isInitialized ()
 True if stepper's member data is initialized.
 
virtual void checkInitialized ()
 Check initialization, and error out on failure.
 
void setStepperName (std::string s)
 Set the stepper name.
 
std::string getStepperName () const
 Get the stepper name.
 
std::string getStepperType () const
 Get the stepper type. The stepper type is used as an identifier for the stepper, and can only be set by the derived Stepper class.
 
void setUseFSALTrueOnly (bool a)
 
void setUseFSALFalseOnly (bool a)
 
bool getUseFSAL () const
 
void setICConsistency (std::string s)
 
std::string getICConsistency () const
 
void setICConsistencyCheck (bool c)
 
bool getICConsistencyCheck () const
 
virtual Teuchos::RCP< Thyra::VectorBase< Scalar > > getStepperX ()
 Get Stepper x.
 
virtual Teuchos::RCP< Thyra::VectorBase< Scalar > > getStepperXDot ()
 Get Stepper xDot.
 
virtual Teuchos::RCP< Thyra::VectorBase< Scalar > > getStepperXDotDot ()
 Get Stepper xDotDot.
 
virtual Teuchos::RCP< Thyra::VectorBase< Scalar > > getStepperXDotDot (Teuchos::RCP< SolutionState< Scalar > > state)
 Get xDotDot from SolutionState or Stepper storage.
 

Overridden from Teuchos::Describable

Teuchos::RCP< StepperForwardEulerAppAction< Scalar > > stepperFEAppAction_
 
virtual void describe (Teuchos::FancyOStream &out, const Teuchos::EVerbosityLevel verbLevel) const
 
virtual bool isValidSetup (Teuchos::FancyOStream &out) const
 

Additional Inherited Members

- Protected Member Functions inherited from Tempus::Stepper< Scalar >
virtual void setStepperX (Teuchos::RCP< Thyra::VectorBase< Scalar > > x)
 Set x for Stepper storage.
 
virtual void setStepperXDot (Teuchos::RCP< Thyra::VectorBase< Scalar > > xDot)
 Set xDot for Stepper storage.
 
virtual void setStepperXDotDot (Teuchos::RCP< Thyra::VectorBase< Scalar > > xDotDot)
 Set x for Stepper storage.
 
void setStepperType (std::string s)
 Set the stepper type.
 
- Protected Attributes inherited from Tempus::StepperExplicit< Scalar >
Teuchos::RCP< const Thyra::ModelEvaluator< Scalar > > appModel_
 Explicit ODE ModelEvaluator.
 
Thyra::ModelEvaluatorBase::InArgs< Scalar > inArgs_
 
Thyra::ModelEvaluatorBase::OutArgs< Scalar > outArgs_
 
- Protected Attributes inherited from Tempus::Stepper< Scalar >
bool useFSAL_ = false
 Use First-Same-As-Last (FSAL) principle.
 
bool isInitialized_ = false
 True if stepper's member data is initialized.
 

Detailed Description

template<class Scalar>
class Tempus::StepperForwardEuler< Scalar >

Forward Euler time stepper.

For the explicit ODE system,

\[
  \dot{x} = \bar{f}(x,t),
\]

the Forward Euler stepper can be written as

\[
  x_{n} = x_{n-1} + \Delta t\, \bar{f}(x_{n-1},t_{n-1})
\]

Forward Euler is an explicit time stepper (i.e., no solver used). Note that the time derivative by definition is

\[
  \dot{x}_{n} = \bar{f}(x_{n},t_{n}),
\]

Algorithm The single-timestep algorithm for Forward Euler is

\begin{center}
  \parbox{5in}{
  \rule{5in}{0.4pt} \\
  {\bf Algorithm} Forward Euler \\
  \rule{5in}{0.4pt} \vspace{-15pt}
  \begin{enumerate}
    \setlength{\itemsep}{0pt} \setlength{\parskip}{0pt} \setlength{\parsep}{0pt}
    \item {\it appAction.execute(solutionHistory, stepper, BEGIN\_STEP)}
    \item {\bf if (Not ``Use FSAL'' or (previous step failed)) then}
    \item \quad  {\it appAction.execute(solutionHistory, stepper, BEFORE\_EXPLICIT\_EVAL)}
    \item \quad  $\dot{x}_{n-1} \leftarrow \bar{f}(x_{n-1},t_{n-1})$
    \item {\bf endif}
    \item $x_{n} \leftarrow x_{n-1} + \Delta t\, \dot{x}_{n-1}$
          \hfill {\it * Forward Euler update.}
    \item {\it appAction.execute(solutionHistory, stepper, END\_STEP)}
    \item {\bf if (``Use FSAL'') then}
    \item \quad  {\it appAction.execute(solutionHistory, stepper, BEFORE\_EXPLICIT\_EVAL)}
    \item \quad  $\dot{x}_n \leftarrow \bar{f}(x_{n},t_{n})$
    \item {\bf endif}
    \item {\it appAction.execute(solutionHistory, stepper, END\_STEP)}
  \end{enumerate}
  \vspace{-10pt} \rule{5in}{0.4pt}
  }
\end{center}

Note that with useFSAL=false $x_n$ and $\dot{x}_{n-1}$ are not at the same time level at the end of the time step (i.e., they are not sync'ed).

To have them at the same time level, we can use the First-Same-As-Last (FSAL) principle where the function evaulation from the last time step can be used as the first function evalulation of the current step.

The default for Forward Euler is to use FSAL (useFSAL=true), but will also work with useFSAL=false. Using useFSAL=true does assume that the solution, $x$, and its time derivative, $\dot{x}$, are consistent at the initial conditions (ICs), i.e., $\dot{x}_{0} = \bar{f}(x_{0},t_{0})$. This can be ensured by setting setICConsistency("Consistent"), and checked with setICConsistencyCheck(true).

Definition at line 79 of file Tempus_StepperForwardEuler_decl.hpp.

Constructor & Destructor Documentation

◆ StepperForwardEuler() [1/2]

template<class Scalar >
Tempus::StepperForwardEuler< Scalar >::StepperForwardEuler ( )

Default constructor.

Definition at line 20 of file Tempus_StepperForwardEuler_impl.hpp.

◆ StepperForwardEuler() [2/2]

template<class Scalar >
Tempus::StepperForwardEuler< Scalar >::StepperForwardEuler ( const Teuchos::RCP< const Thyra::ModelEvaluator< Scalar > > & appModel,
bool useFSAL,
std::string ICConsistency,
bool ICConsistencyCheck,
const Teuchos::RCP< StepperForwardEulerAppAction< Scalar > > & stepperFEAppAction )

Constructor.

Definition at line 31 of file Tempus_StepperForwardEuler_impl.hpp.

Member Function Documentation

◆ setAppAction()

template<class Scalar >
void Tempus::StepperForwardEuler< Scalar >::setAppAction ( Teuchos::RCP< StepperForwardEulerAppAction< Scalar > > appAction)
virtual

Definition at line 52 of file Tempus_StepperForwardEuler_impl.hpp.

◆ getAppAction()

template<class Scalar >
virtual Teuchos::RCP< StepperForwardEulerAppAction< Scalar > > Tempus::StepperForwardEuler< Scalar >::getAppAction ( ) const
inlinevirtual

Definition at line 101 of file Tempus_StepperForwardEuler_decl.hpp.

◆ setInitialConditions()

template<class Scalar >
void Tempus::StepperForwardEuler< Scalar >::setInitialConditions ( const Teuchos::RCP< SolutionHistory< Scalar > > & solutionHistory)
virtual

Set the initial conditions, make them consistent, and set needed memory.

Reimplemented from Tempus::StepperExplicit< Scalar >.

Definition at line 67 of file Tempus_StepperForwardEuler_impl.hpp.

◆ takeStep()

template<class Scalar >
void Tempus::StepperForwardEuler< Scalar >::takeStep ( const Teuchos::RCP< SolutionHistory< Scalar > > & solutionHistory)
virtual

Take the specified timestep, dt, and return true if successful.

Implements Tempus::Stepper< Scalar >.

Definition at line 84 of file Tempus_StepperForwardEuler_impl.hpp.

◆ getDefaultStepperState()

template<class Scalar >
Teuchos::RCP< Tempus::StepperState< Scalar > > Tempus::StepperForwardEuler< Scalar >::getDefaultStepperState ( )
virtual

Get a default (initial) StepperState.

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.

Implements Tempus::Stepper< Scalar >.

Definition at line 174 of file Tempus_StepperForwardEuler_impl.hpp.

◆ getOrder()

template<class Scalar >
virtual Scalar Tempus::StepperForwardEuler< Scalar >::getOrder ( ) const
inlinevirtual

Implements Tempus::Stepper< Scalar >.

Definition at line 114 of file Tempus_StepperForwardEuler_decl.hpp.

◆ getOrderMin()

template<class Scalar >
virtual Scalar Tempus::StepperForwardEuler< Scalar >::getOrderMin ( ) const
inlinevirtual

Implements Tempus::Stepper< Scalar >.

Definition at line 115 of file Tempus_StepperForwardEuler_decl.hpp.

◆ getOrderMax()

template<class Scalar >
virtual Scalar Tempus::StepperForwardEuler< Scalar >::getOrderMax ( ) const
inlinevirtual

Implements Tempus::Stepper< Scalar >.

Definition at line 116 of file Tempus_StepperForwardEuler_decl.hpp.

◆ setUseFSAL()

template<class Scalar >
virtual void Tempus::StepperForwardEuler< Scalar >::setUseFSAL ( bool a)
inlinevirtual

Reimplemented from Tempus::Stepper< Scalar >.

Definition at line 117 of file Tempus_StepperForwardEuler_decl.hpp.

◆ getOrderODE()

template<class Scalar >
virtual OrderODE Tempus::StepperForwardEuler< Scalar >::getOrderODE ( ) const
inlinevirtual

Implements Tempus::Stepper< Scalar >.

Definition at line 118 of file Tempus_StepperForwardEuler_decl.hpp.

◆ describe()

template<class Scalar >
void Tempus::StepperForwardEuler< Scalar >::describe ( Teuchos::FancyOStream & out,
const Teuchos::EVerbosityLevel verbLevel ) const
virtual

Reimplemented from Tempus::StepperExplicit< Scalar >.

Definition at line 184 of file Tempus_StepperForwardEuler_impl.hpp.

◆ isValidSetup()

template<class Scalar >
bool Tempus::StepperForwardEuler< Scalar >::isValidSetup ( Teuchos::FancyOStream & out) const
virtual

Reimplemented from Tempus::StepperExplicit< Scalar >.

Definition at line 202 of file Tempus_StepperForwardEuler_impl.hpp.

Member Data Documentation

◆ stepperFEAppAction_

template<class Scalar >
Teuchos::RCP<StepperForwardEulerAppAction<Scalar> > Tempus::StepperForwardEuler< Scalar >::stepperFEAppAction_
protected

Definition at line 131 of file Tempus_StepperForwardEuler_decl.hpp.


The documentation for this class was generated from the following files: