Detailed Description

Fixed time stepping algorithm.

This algorithm returns time step size defined by a user priori.

Definition at line 27 of file FixedTimeStepping.h.

#include <FixedTimeStepping.h>

Inheritance diagram for NumLib::FixedTimeStepping:

Collaboration diagram for NumLib::FixedTimeStepping:

Public Member Functions
	FixedTimeStepping (double t0, double tn, double dt)

	FixedTimeStepping (double t0, double tn, const std::vector< double > &vec_all_dt)

std::tuple< bool, double >	next (double solution_error, int number_iterations) override

bool	accepted () const override
	return if current time step is accepted or not More...

Public Member Functions inherited from NumLib::TimeStepAlgorithm
	TimeStepAlgorithm (const double t0, const double t_end)

	TimeStepAlgorithm (const double t0, const double t_end, const double dt)

	TimeStepAlgorithm (const double t0, const double t_end, const std::vector< double > &all_step_sizes)

virtual	~TimeStepAlgorithm ()=default

double	begin () const
	return the beginning of time steps More...

double	end () const
	return the end of time steps More...

const TimeStep	getTimeStep () const
	return current time step More...

void	resetCurrentTimeStep (const double dt)
	reset the current step size from the previous time More...

virtual void	setAcceptedOrNot (const bool accepted)

const std::vector< double > &	getTimeStepSizeHistory () const
	return a history of time step sizes More...

virtual bool	isSolutionErrorComputationNeeded () const

virtual bool	canReduceTimestepSize () const
	Query the timestepper if further time step size reduction is possible. More...

Static Private Member Functions
static double	computeEnd (double t_initial, double t_end, const std::vector< double > &dt_vector)
	determine true end time More...

Additional Inherited Members
Protected Attributes inherited from NumLib::TimeStepAlgorithm
const double	_t_initial
	initial time More...

const double	_t_end
	end time More...

TimeStep	_ts_prev
	previous time step information More...

TimeStep	_ts_current
	current time step information More...

std::vector< double >	_dt_vector
	a vector of time step sizes More...

Constructor & Destructor Documentation

◆ FixedTimeStepping() [1/2]

NumLib::FixedTimeStepping::FixedTimeStepping	(	double	t0,
		double	tn,
		double	dt
	)

Constructor with homogeneous time step size

A user provides a single time step size \(\Delta t\). Total number of time steps is calculated by

\[ n=\frac{t_{\rm n} - t_0}{\Delta t} \]

.

Parameters

t0	start time
tn	finish time
dt	uniform time step size

Definition at line 29 of file FixedTimeStepping.cpp.

     : TimeStepAlgorithm(t0, tn, dt)
 {
 }

◆ FixedTimeStepping() [2/2]

NumLib::FixedTimeStepping::FixedTimeStepping	(	double	t0,
		double	tn,
		const std::vector< double > &	vec_all_dt
	)

Constructor with user-specified time step sizes

A user can specify \(\Delta t\) for each time step (i.e. \(\Delta t_1, \Delta t_2, ..., \Delta t_n\)). Time at \(m\) th step is given as

\[ t_{m}=\sum_{i=1}^m \Delta t_i + t_0 \]

.

Parameters

t0	start time
tn	finish time
vec_all_dt	a vector of all time steps

Definition at line 22 of file FixedTimeStepping.cpp.

     : TimeStepAlgorithm(t0, computeEnd(t0, tn, vec_all_dt), vec_all_dt)
 {
 }

Member Function Documentation

◆ accepted()

bool NumLib::FixedTimeStepping::accepted ( ) const

inlineoverridevirtual

return if current time step is accepted or not

Implements NumLib::TimeStepAlgorithm.

Definition at line 64 of file FixedTimeStepping.h.

64 { return true; }

◆ computeEnd()

double NumLib::FixedTimeStepping::computeEnd	(	double	t_initial,
		double	t_end,
		const std::vector< double > &	dt_vector
	)

staticprivate

determine true end time

Definition at line 54 of file FixedTimeStepping.cpp.

 {
     double t_sum =
         t_initial + std::accumulate(dt_vector.begin(), dt_vector.end(), 0.);
     return std::min(t_end, t_sum);
 }

◆ next()

std::tuple< bool, double > NumLib::FixedTimeStepping::next	(	double	solution_error,
		int	number_iterations
	)

overridevirtual

Move to the next time step

Parameters

solution_error	Solution error \(e_n\) between two successive time steps.
number_iterations	Number of non-linear iterations used.

Returns: A step acceptance flag and the computed step size.

Implements NumLib::TimeStepAlgorithm.

Definition at line 34 of file FixedTimeStepping.cpp.

 {
     // check if last time step
     if (_ts_current.steps() == _dt_vector.size() ||
         std::abs(_ts_current.current() - _t_end) <
             std::numeric_limits<double>::epsilon())
     {
         return std::make_tuple(false, 0.0);
     }
  
     double dt = _dt_vector[_ts_current.steps()];
     if (_ts_current.current() + dt > _t_end)
     {  // upper bound by t_end
         dt = _t_end - _ts_current.current();
     }
  
     return std::make_tuple(true, dt);
 }

References NumLib::TimeStepAlgorithm::_dt_vector, NumLib::TimeStepAlgorithm::_t_end, NumLib::TimeStepAlgorithm::_ts_current, NumLib::TimeStep::current(), and NumLib::TimeStep::steps().

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

NumLib/TimeStepping/Algorithms/FixedTimeStepping.h
NumLib/TimeStepping/Algorithms/FixedTimeStepping.cpp

Detailed Description

Public Member Functions

Static Private Member Functions

Additional Inherited Members

Constructor & Destructor Documentation

◆ FixedTimeStepping() [1/2]

◆ FixedTimeStepping() [2/2]

Member Function Documentation

◆ accepted()

◆ computeEnd()

◆ next()