Detailed Description

Forward Euler scheme.

Definition at line 307 of file TimeDiscretization.h.

#include <TimeDiscretization.h>

Inheritance diagram for NumLib::ForwardEuler:

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Collaboration diagram for NumLib::ForwardEuler:

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Public Member Functions
	ForwardEuler ()

	~ForwardEuler () override

void	setInitialState (const double t0, GlobalVector const &x0) override
	Sets the initial condition. More...

double	getRelativeChangeFromPreviousTimestep (GlobalVector const &x, MathLib::VecNormType norm_type) override

void	pushState (const double, GlobalVector const &x, InternalMatrixStorage const &) override

void	popState (GlobalVector &x) override

void	nextTimestep (const double t, const double delta_t) override

double	getCurrentTime () const override

GlobalVector const &	getCurrentX (const GlobalVector &) const override

double	getNewXWeight () const override
	Returns $\alpha = \partial \hat x / \partial x_N$ . More...

void	getWeightedOldX (GlobalVector &y) const override
	Returns . More...

bool	isLinearTimeDisc () const override

double	getDxDx () const override

GlobalVector const &	getXOld () const
	Returns the solution from the preceding timestep. More...

Public Member Functions inherited from NumLib::TimeDiscretization
	TimeDiscretization ()=default

void	getXdot (GlobalVector const &x_at_new_timestep, GlobalVector &xdot) const

virtual	~TimeDiscretization ()=default

virtual bool	needsPreload () const

Private Attributes
double	_t = std::numeric_limits<double>::quiet_NaN()
	More...

double	_t_old

double	_delta_t
	the timestep size More...

GlobalVector &	_x_old
	the solution from the preceding timestep More...

Additional Inherited Members
Protected Member Functions inherited from NumLib::TimeDiscretization
double	computeRelativeChangeFromPreviousTimestep (GlobalVector const &x, GlobalVector const &x_old, MathLib::VecNormType norm_type)

Protected Attributes inherited from NumLib::TimeDiscretization
std::unique_ptr< GlobalVector >	_dx
	Used to store $u_{n+1}-u_{n}$ . More...

Constructor & Destructor Documentation

◆ ForwardEuler()

NumLib::ForwardEuler::ForwardEuler ( )

inline

Definition at line 310 of file TimeDiscretization.h.

                    : _x_old(NumLib::GlobalVectorProvider::provider.getVector())
     {
     }

◆ ~ForwardEuler()

NumLib::ForwardEuler::~ForwardEuler ( )

inlineoverride

Definition at line 314 of file TimeDiscretization.h.

References NumLib::GlobalVectorProvider::provider, and NumLib::VectorProvider::releaseVector().

     {
         NumLib::GlobalVectorProvider::provider.releaseVector(_x_old);
     }

Member Function Documentation

◆ getCurrentTime()

double NumLib::ForwardEuler::getCurrentTime ( ) const

inlineoverridevirtual

Returns $ t_C $ , i.e., the time at which the equation will be assembled.

Implements NumLib::TimeDiscretization.

Definition at line 347 of file TimeDiscretization.h.

     {
         return _t_old;  // forward Euler does assembly at the preceding timestep
     }

◆ getCurrentX()

GlobalVector const& NumLib::ForwardEuler::getCurrentX ( const GlobalVector & x_at_new_timestep ) const

inlineoverridevirtual

Returns $ x_C $ , i.e., the state at which the equation will be assembled.

This method is overridden in the ForwardEuler scheme.

Reimplemented from NumLib::TimeDiscretization.

Definition at line 352 of file TimeDiscretization.h.

     {
         return _x_old;
     }

◆ getDxDx()

double NumLib::ForwardEuler::getDxDx ( ) const

inlineoverridevirtual

Returns $\partial x_C / \partial x_N$ .

The ForwardEuler scheme overrides this.

Reimplemented from NumLib::TimeDiscretization.

Definition at line 369 of file TimeDiscretization.h.

369 { return 0.0; }

◆ getNewXWeight()

double NumLib::ForwardEuler::getNewXWeight ( ) const

inlineoverridevirtual

Returns $\alpha = \partial \hat x / \partial x_N$ .

Implements NumLib::TimeDiscretization.

Definition at line 358 of file TimeDiscretization.h.

358 { return 1.0 / _delta_t; }

NumLib::ForwardEuler::_delta_t

double _delta_t

the timestep size

Definition: TimeDiscretization.h:377

◆ getRelativeChangeFromPreviousTimestep()

double NumLib::ForwardEuler::getRelativeChangeFromPreviousTimestep	(	GlobalVector const &	x,
		MathLib::VecNormType	norm_type
	)

overridevirtual

Get the relative change of solutions between two successive time steps by $e_n = \|u^{n+1}-u^{n}\|/\|u^{n+1}\|$ .

Parameters

x	The solution at the current timestep.
norm_type	The type of global vector norm.

Implements NumLib::TimeDiscretization.

Definition at line 62 of file TimeDiscretization.cpp.

References NumLib::TimeDiscretization::computeRelativeChangeFromPreviousTimestep().

 {
     return computeRelativeChangeFromPreviousTimestep(x, _x_old, norm_type);
 }

◆ getWeightedOldX()

void NumLib::ForwardEuler::getWeightedOldX ( GlobalVector & y ) const

inlineoverridevirtual

Returns $ x_O $ .

Implements NumLib::TimeDiscretization.

Definition at line 359 of file TimeDiscretization.h.

References MathLib::LinAlg::copy(), and MathLib::LinAlg::scale().

     {
         namespace LinAlg = MathLib::LinAlg;
 
         // y = x_old / delta_t
         LinAlg::copy(_x_old, y);
         LinAlg::scale(y, 1.0 / _delta_t);
     }

◆ getXOld()

GlobalVector const& NumLib::ForwardEuler::getXOld ( ) const

inline

Returns the solution from the preceding timestep.

Definition at line 371 of file TimeDiscretization.h.

371 { return _x_old; }

NumLib::ForwardEuler::_x_old

GlobalVector & _x_old

the solution from the preceding timestep

Definition: TimeDiscretization.h:379

◆ isLinearTimeDisc()

bool NumLib::ForwardEuler::isLinearTimeDisc ( ) const

inlineoverridevirtual

Tell whether this scheme inherently requires a nonlinear solver or not.

The ForwardEuler scheme is inherently linear in that sense, the others are not.

Reimplemented from NumLib::TimeDiscretization.

Definition at line 368 of file TimeDiscretization.h.

368 { return true; }

◆ nextTimestep()

void NumLib::ForwardEuler::nextTimestep	(	const double	t,
		const double	delta_t
	)

inlineoverridevirtual

Indicate that the computation of a new timestep is being started now.

Warning: Currently changing timestep sizes are not supported. Thus, delta_t must not change throughout the entire time integration process! This is not checked by this code!

Implements NumLib::TimeDiscretization.

Definition at line 340 of file TimeDiscretization.h.

     {
         _t_old = _t;
         _t = t;
         _delta_t = delta_t;
     }

◆ popState()

void NumLib::ForwardEuler::popState ( GlobalVector & x )

inlineoverridevirtual

Restores the given vector x to its old value. Used only for repeating of the time step with new time step size when the current time step is rejected. The restored x is only used as an initial guess for linear solver in the first Picard nonlinear iteration.

Parameters

x	The solution at the current time step, which is going to be reset to its previous value.

Implements NumLib::TimeDiscretization.

Definition at line 335 of file TimeDiscretization.h.

References MathLib::LinAlg::copy().

     {
         MathLib::LinAlg::copy(_x_old, x);
     }

◆ pushState()

void NumLib::ForwardEuler::pushState	(	const double	t,
		GlobalVector const &	x,
		InternalMatrixStorage const &	strg
	)

inlineoverridevirtual

Indicate that the current timestep is done and that you will proceed to the next one.

Warning: Do not use this method for setting the initial condition, rather use setInitialState()!

Parameters

t	The current timestep.
x	The solution at the current timestep.
strg	Trigger storing some internal state. Currently only used by the CrankNicolson scheme.

Implements NumLib::TimeDiscretization.

Definition at line 329 of file TimeDiscretization.h.

References MathLib::LinAlg::copy().

     {
         MathLib::LinAlg::copy(x, _x_old);
     }

◆ setInitialState()

void NumLib::ForwardEuler::setInitialState	(	const double	t0,
		GlobalVector const &	x0
	)

inlineoverridevirtual

Sets the initial condition.

Implements NumLib::TimeDiscretization.

Definition at line 319 of file TimeDiscretization.h.

References MathLib::LinAlg::copy().

     {
         _t = t0;
         _t_old = t0;
         MathLib::LinAlg::copy(x0, _x_old);
     }

Member Data Documentation

◆ _delta_t

double NumLib::ForwardEuler::_delta_t

private

Initial value:

=

std::numeric_limits<double>::quiet_NaN()

the timestep size

Definition at line 377 of file TimeDiscretization.h.

◆ _t

double NumLib::ForwardEuler::_t = std::numeric_limits<double>::quiet_NaN()

private

$ t_C $

Definition at line 373 of file TimeDiscretization.h.

◆ _t_old

double NumLib::ForwardEuler::_t_old

private

Initial value:

=

std::numeric_limits<double>::quiet_NaN()

the time of the preceding timestep

Definition at line 374 of file TimeDiscretization.h.

◆ _x_old

GlobalVector& NumLib::ForwardEuler::_x_old

private

the solution from the preceding timestep

Definition at line 379 of file TimeDiscretization.h.

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

NumLib/ODESolver/TimeDiscretization.h
NumLib/ODESolver/TimeDiscretization.cpp

Detailed Description

Public Member Functions

Private Attributes

Additional Inherited Members

Constructor & Destructor Documentation

◆ ForwardEuler()

◆ ~ForwardEuler()

Member Function Documentation

◆ getCurrentTime()

◆ getCurrentX()

◆ getDxDx()

◆ getNewXWeight()

◆ getRelativeChangeFromPreviousTimestep()

◆ getWeightedOldX()

◆ getXOld()

◆ isLinearTimeDisc()

◆ nextTimestep()

◆ popState()

◆ pushState()

◆ setInitialState()

Member Data Documentation

◆ _delta_t

◆ _t

◆ _t_old

◆ _x_old