Forward Euler time stepper. More...

#include <Tempus_StepperForwardEuler_decl.hpp>

Inheritance diagram for Tempus::StepperForwardEuler< 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...

	StepperForwardEuler (const Teuchos::RCP< const Thyra::ModelEvaluator< Scalar > > &appModel, bool useFSAL, std::string ICConsistency, bool ICConsistencyCheck, const Teuchos::RCP< StepperForwardEulerAppAction< Scalar > > &stepperFEAppAction)
	Constructor. More...

Teuchos::RCP< const Teuchos::ParameterList >	getValidParameters () const

virtual bool	isValidSetup (Teuchos::FancyOStream &out) 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	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. 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 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)
	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	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 >
virtual void	setNonConstModel (const Teuchos::RCP< Thyra::ModelEvaluator< Scalar > > &)

virtual void	initialize ()
	Initialize after construction and changing input parameters. More...

virtual bool	isInitialized ()
	True if stepper's member data is initialized. More...

virtual void	checkInitialized ()
	Check initialization, and error out on failure. More...

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 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 std::string	description () const

virtual void	createSubSteppers (std::vector< Teuchos::RCP< const Thyra::ModelEvaluator< Scalar > > >)

Protected Attributes
Teuchos::RCP < StepperForwardEulerObserver < Scalar > >	stepperFEObserver_

Teuchos::RCP < StepperForwardEulerAppAction < Scalar > >	stepperFEAppAction_

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_

Protected Attributes inherited from Tempus::Stepper< Scalar >
bool	isInitialized_ = false
	True if stepper's member data is initialized. More...

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. 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...

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 55 of file Tempus_StepperForwardEuler_decl.hpp.

Constructor & Destructor Documentation

template<class Scalar >

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

Default constructor.

Requires subsequent setModel() and initialize() calls before calling takeStep().

Definition at line 19 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 33 of file Tempus_StepperForwardEuler_impl.hpp.

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 55 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

Reimplemented from Tempus::StepperExplicit< Scalar >.

Definition at line 239 of file Tempus_StepperForwardEuler_impl.hpp.

template<class Scalar >

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

inlinevirtual

Definition at line 97 of file Tempus_StepperForwardEuler_decl.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 230 of file Tempus_StepperForwardEuler_impl.hpp.

template<class Scalar >

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

inlinevirtual

Get Observer.

Reimplemented from Tempus::Stepper< Scalar >.

Definition at line 90 of file Tempus_StepperForwardEuler_decl.hpp.

template<class Scalar >

virtual Scalar Tempus::StepperForwardEuler< Scalar >::getOrder ( ) const

inlinevirtual

Implements Tempus::Stepper< Scalar >.