Reference documentation for deal.II version Git c9feb145b3 2021-03-01 21:22:52 +0100
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Public Member Functions | Static Public Member Functions | Public Attributes | Protected Attributes | Private Attributes | List of all members
Algorithms::Newton< VectorType > Class Template Reference

#include <deal.II/algorithms/newton.h>

Inheritance diagram for Algorithms::Newton< VectorType >:
[legend]

Public Member Functions

 Newton (OperatorBase &residual, OperatorBase &inverse_derivative)
 
void parse_parameters (ParameterHandler &param)
 
void initialize (OutputOperator< VectorType > &output)
 
virtual void operator() (AnyData &out, const AnyData &in) override
 
virtual void notify (const Event &) override
 
double threshold (double new_value)
 
void clear_events ()
 
template<class Archive >
void serialize (Archive &ar, const unsigned int version)
 
Subscriptor functionality

Classes derived from Subscriptor provide a facility to subscribe to this object. This is mostly used by the SmartPointer class.

void subscribe (std::atomic< bool > *const validity, const std::string &identifier="") const
 
void unsubscribe (std::atomic< bool > *const validity, const std::string &identifier="") const
 
unsigned int n_subscriptions () const
 
template<typename StreamType >
void list_subscribers (StreamType &stream) const
 
void list_subscribers () const
 

Static Public Member Functions

static void declare_parameters (ParameterHandler &param)
 
static ::ExceptionBaseExcInUse (int arg1, std::string arg2, std::string arg3)
 
static ::ExceptionBaseExcNoSubscriber (std::string arg1, std::string arg2)
 

Public Attributes

ReductionControl control
 
bool debug_vectors
 
unsigned int debug
 

Protected Attributes

Event notifications
 

Private Attributes

SmartPointer< OperatorBase, Newton< VectorType > > residual
 
SmartPointer< OperatorBase, Newton< VectorType > > inverse_derivative
 
SmartPointer< OutputOperator< VectorType >, Newton< VectorType > > data_out
 
bool assemble_now
 
unsigned int n_stepsize_iterations
 
double assemble_threshold
 

Detailed Description

template<typename VectorType>
class Algorithms::Newton< VectorType >

Operator class performing Newton's iteration with standard step size control and adaptive matrix generation.

This class performs a Newton iteration up to convergence determined by control. If after an update the norm of the residual has become larger, then step size control is activated and the update is subsequently divided by two until the residual actually becomes smaller (or the minimal scaling factor determined by n_stepsize_iterations is reached).

Since assembling matrices, depending on the implementation, tends to be costly, this method applies an adaptive reassembling strategy. Only if the reduction factor for the residual is more than threshold, the event Algorithms::bad_derivative is submitted to inverse_derivative. It is up to this object to implement reassembling accordingly.

Contents of the AnyData objects

The only value used by the Newton method is the first vector in the parameter out of operator()(). It serves as the start vector of Newton's method and in the end contains the solution. All other vectors of out are ignored by Newton's method and its inner Operator objects. All vectors of in are forwarded to the inner Operator objects, with additional information added as follows.

When calling (*residual)(), the AnyData in given to the Newton iteration is prepended by a vector "Newton iterate", the current value of the Newton iterate, which can be used to evaluate the residual at this point.

For the call to (*inverse_derivative), the vector "Newton residual" is inserted before "Newton iterate".

Definition at line 72 of file newton.h.

Constructor & Destructor Documentation

◆ Newton()

template<typename VectorType >
Algorithms::Newton< VectorType >::Newton ( OperatorBase residual,
OperatorBase inverse_derivative 
)

Constructor, receiving the applications computing the residual and solving the linear problem, respectively.

Member Function Documentation

◆ declare_parameters()

template<typename VectorType >
static void Algorithms::Newton< VectorType >::declare_parameters ( ParameterHandler param)
static

Declare the parameters applicable to Newton's method.

◆ parse_parameters()

template<typename VectorType >
void Algorithms::Newton< VectorType >::parse_parameters ( ParameterHandler param)

Read the parameters in the ParameterHandler.

◆ initialize()

template<typename VectorType >
void Algorithms::Newton< VectorType >::initialize ( OutputOperator< VectorType > &  output)

Initialize the pointer data_out for debugging.

◆ operator()()

template<typename VectorType >
virtual void Algorithms::Newton< VectorType >::operator() ( AnyData out,
const AnyData in 
)
overridevirtual

The actual Newton iteration. The initial value is in out(0), which also contains the result after convergence. Values in in are not used by Newton, but will be handed down to the objects residual and inverse_derivative.

Implements Algorithms::OperatorBase.

◆ notify()

template<typename VectorType >
virtual void Algorithms::Newton< VectorType >::notify ( const Event e)
overridevirtual

Register an event triggered by an outer iteration.

Reimplemented from Algorithms::OperatorBase.

◆ threshold()

template<typename VectorType >
double Algorithms::Newton< VectorType >::threshold ( double  new_value)

Set the maximal residual reduction allowed without triggering assembling in the next step. Return the previous value.

◆ clear_events()

void Algorithms::OperatorBase::clear_events ( )
inherited

Clear all notifications.

Definition at line 49 of file operator.cc.

◆ subscribe()

void Subscriptor::subscribe ( std::atomic< bool > *const  validity,
const std::string &  identifier = "" 
) const
inherited

Subscribes a user of the object by storing the pointer validity. The subscriber may be identified by text supplied as identifier.

Definition at line 136 of file subscriptor.cc.

◆ unsubscribe()

void Subscriptor::unsubscribe ( std::atomic< bool > *const  validity,
const std::string &  identifier = "" 
) const
inherited

Unsubscribes a user from the object.

Note
The identifier and the validity pointer must be the same as the one supplied to subscribe().

Definition at line 156 of file subscriptor.cc.

◆ n_subscriptions()

unsigned int Subscriptor::n_subscriptions ( ) const
inlineinherited

Return the present number of subscriptions to this object. This allows to use this class for reference counted lifetime determination where the last one to unsubscribe also deletes the object.

Definition at line 301 of file subscriptor.h.

◆ list_subscribers() [1/2]

template<typename StreamType >
void Subscriptor::list_subscribers ( StreamType &  stream) const
inlineinherited

List the subscribers to the input stream.

Definition at line 318 of file subscriptor.h.

◆ list_subscribers() [2/2]

void Subscriptor::list_subscribers ( ) const
inherited

List the subscribers to deallog.

Definition at line 204 of file subscriptor.cc.

◆ serialize()

template<class Archive >
void Subscriptor::serialize ( Archive &  ar,
const unsigned int  version 
)
inlineinherited

Read or write the data of this object to or from a stream for the purpose of serialization using the BOOST serialization library.

This function does not actually serialize any of the member variables of this class. The reason is that what this class stores is only who subscribes to this object, but who does so at the time of storing the contents of this object does not necessarily have anything to do with who subscribes to the object when it is restored. Consequently, we do not want to overwrite the subscribers at the time of restoring, and then there is no reason to write the subscribers out in the first place.

Definition at line 310 of file subscriptor.h.

Member Data Documentation

◆ control

template<typename VectorType >
ReductionControl Algorithms::Newton< VectorType >::control

Control object for the Newton iteration.

Definition at line 121 of file newton.h.

◆ residual

template<typename VectorType >
SmartPointer<OperatorBase, Newton<VectorType> > Algorithms::Newton< VectorType >::residual
private

The operator computing the residual.

Definition at line 127 of file newton.h.

◆ inverse_derivative

template<typename VectorType >
SmartPointer<OperatorBase, Newton<VectorType> > Algorithms::Newton< VectorType >::inverse_derivative
private

The operator applying the inverse derivative to the residual.

Definition at line 132 of file newton.h.

◆ data_out

template<typename VectorType >
SmartPointer<OutputOperator<VectorType>, Newton<VectorType> > Algorithms::Newton< VectorType >::data_out
private

The operator handling the output in case the debug_vectors is true. Call the initialize function first.

Definition at line 138 of file newton.h.

◆ assemble_now

template<typename VectorType >
bool Algorithms::Newton< VectorType >::assemble_now
private

This flag is set by the function assemble(), indicating that the matrix must be assembled anew upon start.

Definition at line 144 of file newton.h.

◆ n_stepsize_iterations

template<typename VectorType >
unsigned int Algorithms::Newton< VectorType >::n_stepsize_iterations
private

A flag used to decide how many stepsize iteration should be made. Default is the original value of 21.

Enter zero here to turn off stepsize control.

Note
Controlled by Stepsize iterations in parameter file

Definition at line 154 of file newton.h.

◆ assemble_threshold

template<typename VectorType >
double Algorithms::Newton< VectorType >::assemble_threshold
private

Threshold for re-assembling matrix.

If the quotient of two consecutive residuals is smaller than this threshold, the system matrix is not assembled in this step.

Note
This parameter should be adjusted to the residual gain of the inner solver.

The default values is zero, resulting in reassembling in every Newton step.

Definition at line 168 of file newton.h.

◆ debug_vectors

template<typename VectorType >
bool Algorithms::Newton< VectorType >::debug_vectors

Print residual, update and updated solution after each step into file Newton_NNN?

Definition at line 175 of file newton.h.

◆ debug

template<typename VectorType >
unsigned int Algorithms::Newton< VectorType >::debug

Write debug output to deallog; the higher the number, the more output.

Definition at line 180 of file newton.h.

◆ notifications

Event Algorithms::OperatorBase::notifications
protectedinherited

Accumulate events here. If any of those is set, the function solve() of a terminal application must take care of reassembling the matrix.

Definition at line 97 of file operator.h.


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