Dune::Fem::TimeProvider< Communication > Class Template Reference

manager for global simulation time of time-dependent solutions More...

#include <dune/fem/solver/timeprovider.hh>

Public Member Functions
	TimeProvider (const ParameterReader &parameter=Parameter::container())
	default constructor More...
	TimeProvider (const double startTime, const CommunicationType &comm=MPIManager::comm())
	constructor taking start time More...
	TimeProvider (const double startTime, const double cfl, const CommunicationType &comm=MPIManager::comm())
	constructor taking start time and CFL constant More...
void	init ()
	init dt with time step estimate
void	init (const double timeStep)
	init dt with provided time step More...
void	next ()
	goto next time step More...
void	next (const double timeStep)
	goto next time step More...
double	factor () const
	return the global factor number More...
void	restore (const double time, const int timeStep)
	restore time and timestep from outside (i.e. from former calculation) More...
virtual void	backup () const
	backup persistent object
virtual void	restore ()
	restore persistent object
double	time () const
	obtain the current time More...
int	timeStep () const
	obtain number of the current time step More...
double	deltaT () const
	obtain the size of the current time step More...
double	inverseDeltaT () const
	obtain the size of the inverse of the current time step More...
double	timeStepEstimate () const
	obtain current estimate on time step More...
void	provideTimeStepEstimate (const double dtEstimate)
	set time step estimate to minimum of given value and internal time step estiamte More...
void	provideTimeStepUpperBound (const double upperBound)
	set upper bound for time step to minimum of given value and internal bound More...
void	invalidateTimeStep ()
	count current time step a not valid
bool	timeStepValid () const
	return if this time step should be used

Protected Member Functions
virtual void	insertSubData ()
	insert possible sub data of object
virtual void	removeSubData ()
	remove possible sub data of object

Detailed Description

template<class Communication = typename MPIManager::Communication>
class Dune::Fem::TimeProvider< Communication >

manager for global simulation time of time-dependent solutions

When calculating possibly multiple time-dependent solutions, it is often necessary to use the same time in all calculations. This means that we have to use the same time step for all our calculations. A TimeProvider keeps track of this information in a simple and unified way.

An example of a time loop could look as follows:

// create time provider
TimeProvider tp( startTime );
 
SpaceOperator spaceOperator;
typedef SpaceOperator::DestinationType DestinationType;
OdeSolver<DestinationType> odeSolver(spaceOperator,tp,order);
 
DestinationType U;
initialize(U);
 
// set the initial time step estimate
odeSolver.initialize( U );
 
// time loop
for( tp.init(); tp.time() < endTime; tp.next() )
{
  // do calculation
  odeSolver.solve(U);
}

Within the time loop, both tp.time() and tp.deltaT() are fixed and cannot be altered and an the next time step should be fixed in the loop, e.g., in the method solve of the ode solver an upper estimate for the next time step is provided; if more than one time step restriction has to be imposed, the minimum is taken for the next time step. By calling the method provideTimeStepEstimate(maxDt) in the body of the loop an upper estimate for the next time step can be supplied; to fix the next time step (ignoring the estimates) an optinal argument can be passed to the next method on the Dune::Fem::TimeProvider.

Obviously, we need to provide an initial estimate. In the above example, this is done by the initialize method of the ODE solver. In tp.init(), the first time step (deltaT) is set based on the estimate and this value can also be fixed independent of the estimate through an optional argument. The following loop would fix the time step to 1e-3

for( tp.init(1e-3); tp.time() < endTime; tp.next(1e-3) )
{
  // do calculation
  odeSolver.solve(U);
}

In order to allow the user to influence the calculation of the next time step from the estimate, the time provider also maintains an additional factor (which is constant during the entire simulation). Therefore the actual time step used, is calculated as follows:

\[ \mathrm{deltaT} = \mathrm{factor} * \mathrm{timeStepEstimate}. \]

Therefore in the above example 1e-3 might not be the acctual time step depending on the value of the factor in the TimeProvider. The default value for this factor is equal to one but can be changed either during the construction of the Dune::TimeProvider or by using the parameter fem.timeprovider.factor. A further parameter read by the Dune::TimeProvider is fem.timeprovider.starttime defining the starting time of the simulation (default is zero).

The most general implementation is given in the class Dune::Fem::TimeProvider< Communication< C > > which takes a Dune::Communication instance in the constructor which is used in parallel computations is syncronize the time step. It defaults to Dune::Fem::MPIManager::comm() and also works for serial runs.

If the communication manager from a given grid is to be used the class Dune::Fem::GridTimeProvider using the GridType as template argument can be used instead, with the same functionality.

DUNE-FEM parameter:

fem.timeprovider.factor
multiplication factor to use for each time step; defaults to 1.

fem.timeprovider.starttime
time used for initializing the starting time defaults to zero.

fem.timeprovider.updatestep
only do the update of the time step size every 'updatestep' to avoid the expensive communication to achieve this (for testing only); defaults to 1

Constructor & Destructor Documentation

TimeProvider() [1/3]

template<class Communication = typename MPIManager::Communication>

Dune::Fem::TimeProvider< Communication >::TimeProvider ( const ParameterReader &  parameter = Parameter::container() )

inlineexplicit

default constructor

Parameters

[in]

comm

collective communication (default Dune::Fem::MPIManager::comm())

TimeProvider() [2/3]

template<class Communication = typename MPIManager::Communication>

Dune::Fem::TimeProvider< Communication >::TimeProvider ( const double  startTime, const CommunicationType &  comm = MPIManager::comm()  )

inlineexplicit

constructor taking start time

Parameters

[in]	startTime	initial time
[in]	comm	collective communication (default Dune::Fem::MPIManager::comm())

TimeProvider() [3/3]

template<class Communication = typename MPIManager::Communication>

Dune::Fem::TimeProvider< Communication >::TimeProvider ( const double  startTime, const double  cfl, const CommunicationType &  comm = MPIManager::comm()  )

inline

constructor taking start time and CFL constant

Parameters

[in]	startTime	initial time
[in]	cfl	CFL constant
[in]	comm	collective communication (default Dune::Fem::MPIManager::comm())

Member Function Documentation

deltaT()

double Dune::Fem::TimeProviderBase::deltaT ( ) const

inlineinherited

obtain the size of the current time step

Returns

the size of the current time step

References Dune::Fem::TimeProviderBase::timeStepValid().

factor()

template<class Communication = typename MPIManager::Communication>

double Dune::Fem::TimeProvider< Communication >::factor ( ) const

inline

return the global factor number

Returns

time step factor

init()

template<class Communication = typename MPIManager::Communication>

void Dune::Fem::TimeProvider< Communication >::init ( const double  timeStep )

inline

init dt with provided time step

Parameters

[in]

timeStep

value of the first time step (is multiplied with factor)

References Dune::Fem::TimeProviderBase::timeStep().

inverseDeltaT()

double Dune::Fem::TimeProviderBase::inverseDeltaT ( ) const

inlineinherited

obtain the size of the inverse of the current time step

Returns

the size of the inverse of the current time step

References Dune::Fem::TimeProviderBase::timeStepValid().

next() [1/2]

template<class Communication = typename MPIManager::Communication>

void Dune::Fem::TimeProvider< Communication >::next ( )

inline

goto next time step

Sets the size of the next time step to the current time step estimate and sets the estimate to infinity.

next() [2/2]

template<class Communication = typename MPIManager::Communication>

void Dune::Fem::TimeProvider< Communication >::next ( const double  timeStep )

inline

goto next time step

Sets the size of the next time step to the provided time step value and sets the estimate to infinity.

Parameters

[in]

timeStep

value of the next time step (is multiplied with factor)

References Dune::Fem::TimeProviderBase::timeStep().

provideTimeStepEstimate()

void Dune::Fem::TimeProviderBase::provideTimeStepEstimate ( const double  dtEstimate )

inlineinherited

set time step estimate to minimum of given value and internal time step estiamte

Parameters

[in]

dtEstimate

time step size estimate

References Dune::Hybrid::min.

provideTimeStepUpperBound()

void Dune::Fem::TimeProviderBase::provideTimeStepUpperBound ( const double  upperBound )

inlineinherited

set upper bound for time step to minimum of given value and internal bound

Parameters

[in]

upperBound

time step size estimate

References Dune::Hybrid::min.

restore()

template<class Communication = typename MPIManager::Communication>

void Dune::Fem::TimeProvider< Communication >::restore ( const double  time, const int  timeStep  )

inline

restore time and timestep from outside (i.e. from former calculation)

Parameters

[in]	time	new time
[in]	timeStep	new time step counter

References Dune::Fem::TimeProviderBase::time(), and Dune::Fem::TimeProviderBase::timeStep().

time()

double Dune::Fem::TimeProviderBase::time ( ) const

inlineinherited

obtain the current time

Returns

the current time

Referenced by Dune::Fem::TimeProvider< Communication >::restore(), and Dune::Fem::DataOutput< GridImp, DataImp >::write().

timeStep()

int Dune::Fem::TimeProviderBase::timeStep ( ) const

inlineinherited

obtain number of the current time step

Returns

the current time step counter

References Dune::Fem::TimeProviderBase::timeStepValid().

Referenced by Dune::Fem::TimeProvider< Communication >::init(), Dune::Fem::TimeProvider< Communication >::next(), Dune::Fem::TimeProvider< Communication >::restore(), and Dune::Fem::CheckPointer< GridImp >::willWrite().

timeStepEstimate()

double Dune::Fem::TimeProviderBase::timeStepEstimate ( ) const

inlineinherited

obtain current estimate on time step

Returns

the current estimate for the time step

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

• dune/fem/solver/timeprovider.hh