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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. More...
 
 StepperForwardEuler (const Teuchos::RCP< const Thyra::ModelEvaluator< Scalar > > &appModel, const Teuchos::RCP< StepperObserver< Scalar > > &obs, bool useFSAL, std::string ICConsistency, bool ICConsistencyCheck)
 Constructor. More...
 
Teuchos::RCP< const
Teuchos::ParameterList > 		getValidParameters () const
 
Basic stepper methods
virtual void setObserver (Teuchos::RCP< StepperObserver< Scalar > > obs=Teuchos::null)
 Set Observer. More...
 
virtual Teuchos::RCP
< StepperObserver< Scalar > > 		getObserver () const
 Get Observer. More...
 
virtual void initialize ()
 Initialize during construction and after changing input parameters. More...
 
virtual void setInitialConditions (const Teuchos::RCP< SolutionHistory< Scalar > > &solutionHistory)
 Set the initial conditions, make them consistent, and set needed memory. More...
 
virtual void takeStep (const Teuchos::RCP< SolutionHistory< Scalar > > &solutionHistory)
 Take the specified timestep, dt, and return true if successful. More...
 
virtual Teuchos::RCP
< Tempus::StepperState< Scalar > > 		getDefaultStepperState ()
 Get a default (initial) StepperState. More...
 
virtual Scalar getOrder () const
 
virtual Scalar getOrderMin () const
 
virtual Scalar getOrderMax () const
 
virtual OrderODE getOrderODE () const
 
Overridden from Teuchos::Describable
virtual void describe (Teuchos::FancyOStream &out, const Teuchos::EVerbosityLevel verbLevel) const
 
- Public Member Functions inherited from Tempus::StepperExplicit< Scalar >
virtual void setModel (const Teuchos::RCP< const Thyra::ModelEvaluator< Scalar > > &appModel)
 
virtual void setNonConstModel (const Teuchos::RCP< Thyra::ModelEvaluator< Scalar > > &appModel)
 
virtual Teuchos::RCP< const
Thyra::ModelEvaluator< Scalar > > 		getModel ()
 
virtual Scalar getInitTimeStep (const Teuchos::RCP< SolutionHistory< Scalar > > &) const
 
virtual void setSolver (Teuchos::RCP< Thyra::NonlinearSolverBase< Scalar > > solver=Teuchos::null)
 Set solver. More...
 
virtual Teuchos::RCP
< Thyra::NonlinearSolverBase
< Scalar > > 		getSolver () const
 Get solver. More...
 
virtual void setInitialGuess (Teuchos::RCP< const Thyra::VectorBase< Scalar > >)
 Pass initial guess to Newton solver (only relevant for implicit solvers) More...
 
virtual bool isExplicit () const
 
virtual bool isImplicit () const
 
virtual bool isExplicitImplicit () const
 
virtual bool isOneStepMethod () const
 
virtual bool isMultiStepMethod () const
 
virtual void setStepperX (Teuchos::RCP< Thyra::VectorBase< Scalar > > x)
 Set x for Stepper storage. More...
 
virtual void setStepperXDot (Teuchos::RCP< Thyra::VectorBase< Scalar > > xDot)
 Set xDot for Stepper storage. More...
 
virtual void setStepperXDotDot (Teuchos::RCP< Thyra::VectorBase< Scalar > > xDotDot)
 Set x for Stepper storage. More...
 
virtual Teuchos::RCP
< Thyra::VectorBase< Scalar > > 		getStepperX (Teuchos::RCP< SolutionState< Scalar > > state)
 Get x from SolutionState or Stepper storage. More...
 
virtual Teuchos::RCP
< Thyra::VectorBase< Scalar > > 		getStepperXDot (Teuchos::RCP< SolutionState< Scalar > > state)
 Get xDot from SolutionState or Stepper storage. More...
 
virtual Teuchos::RCP
< Thyra::VectorBase< Scalar > > 		getStepperXDotDot (Teuchos::RCP< SolutionState< Scalar > > state)
 Get xDotDot from SolutionState or Stepper storage. More...
 
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). More...
 
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). More...
 
- Public Member Functions inherited from Tempus::Stepper< Scalar >
void setStepperType (std::string s)
 
std::string getStepperType () const
 
void setUseFSAL (bool a)
 
bool getUseFSAL () const
 
virtual bool getUseFSALDefault () const
 
void setICConsistency (std::string s)
 
std::string getICConsistency () const
 
virtual std::string getICConsistencyDefault () const
 
void setICConsistencyCheck (bool c)
 
bool getICConsistencyCheck () const
 
virtual bool getICConsistencyCheckDefault () const
 
virtual std::string description () const
 
virtual void createSubSteppers (std::vector< Teuchos::RCP< const Thyra::ModelEvaluator< Scalar > > >)
 

Protected Attributes

Teuchos::RCP
< StepperForwardEulerObserver
< Scalar > > 		stepperFEObserver_
 
- Protected Attributes inherited from Tempus::StepperExplicit< Scalar >
Teuchos::RCP< const
Thyra::ModelEvaluator< Scalar > > 		appModel_
 Explicit ODE ModelEvaluator. More...
 
Thyra::ModelEvaluatorBase::InArgs
< Scalar > 		inArgs_
 
Thyra::ModelEvaluatorBase::OutArgs
< Scalar > 		outArgs_
 
Teuchos::RCP< StepperObserver
< Scalar > > 		stepperObserver_
 
Teuchos::RCP
< Thyra::VectorBase< Scalar > > 		stepperX_
 
Teuchos::RCP
< Thyra::VectorBase< Scalar > > 		stepperXDot_
 
Teuchos::RCP
< Thyra::VectorBase< Scalar > > 		stepperXDotDot_
 

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 simply,

  • $\dot{x}_{n-1} \leftarrow \bar{f}(x_{n-1},t_{n-1})$
  • $x_{n} \leftarrow x_{n-1} + \Delta t\, \dot{x}_{n-1}$

Note that $x_n$ 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-Step-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. For the Forward Euler, the FSAL algorithm is

  • $x_{n} \leftarrow x_{n-1} + \Delta t\, \dot{x}_{n-1}$
  • $\dot{x}_n \leftarrow \bar{f}(x_{n},t_{n})$

The default for Forward Euler is to use FSAL (useFSAL=true).

Definition at line 53 of file Tempus_StepperForwardEuler_decl.hpp.

Constructor & Destructor Documentation

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

Default constructor.

Definition at line 20 of file Tempus_StepperForwardEuler_impl.hpp.

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

Constructor.

Definition at line 32 of file Tempus_StepperForwardEuler_impl.hpp.

Member Function Documentation

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

Definition at line 188 of file Tempus_StepperForwardEuler_impl.hpp.

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 179 of file Tempus_StepperForwardEuler_impl.hpp.

template<class Scalar >
virtual Teuchos::RCP<StepperObserver<Scalar> > Tempus::StepperForwardEuler< Scalar >::getObserver ( ) const
inlinevirtual

Get Observer.

Implements Tempus::Stepper< Scalar >.

Definition at line 77 of file Tempus_StepperForwardEuler_decl.hpp.

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

Implements Tempus::Stepper< Scalar >.

Definition at line 93 of file Tempus_StepperForwardEuler_decl.hpp.

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

Implements Tempus::Stepper< Scalar >.

Definition at line 95 of file Tempus_StepperForwardEuler_decl.hpp.

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

Implements Tempus::Stepper< Scalar >.

Definition at line 94 of file Tempus_StepperForwardEuler_decl.hpp.

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

Implements Tempus::Stepper< Scalar >.

Definition at line 97 of file Tempus_StepperForwardEuler_decl.hpp.

template<class Scalar >
Teuchos::RCP< const Teuchos::ParameterList > Tempus::StepperForwardEuler< Scalar >::getValidParameters ( ) const
virtual

Implements Tempus::Stepper< Scalar >.

Definition at line 199 of file Tempus_StepperForwardEuler_impl.hpp.

template<class Scalar >
void Tempus::StepperForwardEuler< Scalar >::initialize ( )
virtual

Initialize during construction and after changing input parameters.

Implements Tempus::Stepper< Scalar >.

Definition at line 74 of file Tempus_StepperForwardEuler_impl.hpp.

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 83 of file Tempus_StepperForwardEuler_impl.hpp.

template<class Scalar >
void Tempus::StepperForwardEuler< Scalar >::setObserver ( Teuchos::RCP< StepperObserver< Scalar > >  obs = Teuchos::null)
virtual

Set Observer.

Implements Tempus::Stepper< Scalar >.

Definition at line 54 of file Tempus_StepperForwardEuler_impl.hpp.

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 98 of file Tempus_StepperForwardEuler_impl.hpp.

Member Data Documentation

template<class Scalar >
Teuchos::RCP<StepperForwardEulerObserver<Scalar> > Tempus::StepperForwardEuler< Scalar >::stepperFEObserver_
protected

Definition at line 110 of file Tempus_StepperForwardEuler_decl.hpp.

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