Reference documentation for deal.II version Git 4fbb5374f0 2021-01-22 15:02:13 -0500
PreconditionIdentity Class Reference

#include <deal.II/lac/precondition.h>

Inheritance diagram for PreconditionIdentity:
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## Public Types

using size_type = types::global_dof_index

## Public Member Functions

PreconditionIdentity ()

template<typename MatrixType >

template<class VectorType >
void vmult (VectorType &, const VectorType &) const

template<class VectorType >
void Tvmult (VectorType &, const VectorType &) const

template<class VectorType >
void vmult_add (VectorType &, const VectorType &) const

template<class VectorType >
void Tvmult_add (VectorType &, const VectorType &) const

void clear ()

size_type m () const

size_type n () const

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 ::ExceptionBaseExcInUse (int arg1, std::string arg2, std::string arg3)

static ::ExceptionBaseExcNoSubscriber (std::string arg1, std::string arg2)

## Private Attributes

size_type n_rows

size_type n_columns

## Detailed Description

No preconditioning. This class helps you, if you want to use a linear solver without preconditioning. All solvers in LAC require a preconditioner. Therefore, you must use the identity provided here to avoid preconditioning. It can be used in the following way:

SolverControl solver_control (1000, 1e-12);
SolverCG<> cg (solver_control);
cg.solve (system_matrix, solution, system_rhs, PreconditionIdentity());

See the step-3 tutorial program for an example and additional explanations.

Alternatively, the IdentityMatrix class can be used to precondition in this way.

Definition at line 79 of file precondition.h.

## ◆ size_type

Declare type for container size.

Definition at line 85 of file precondition.h.

## ◆ PreconditionIdentity()

 PreconditionIdentity::PreconditionIdentity ( )

Constructor, sets the domain and range sizes to their defaults.

## ◆ initialize()

template<typename MatrixType >
 void PreconditionIdentity::initialize ( const MatrixType & matrix, const AdditionalData & additional_data = AdditionalData() )

The matrix argument is ignored and here just for compatibility with more complex preconditioners.

## ◆ vmult()

template<class VectorType >
 void PreconditionIdentity::vmult ( VectorType & , const VectorType & ) const

Apply preconditioner.

## ◆ Tvmult()

template<class VectorType >
 void PreconditionIdentity::Tvmult ( VectorType & , const VectorType & ) const

Apply transpose preconditioner. Since this is the identity, this function is the same as vmult().

template<class VectorType >
 void PreconditionIdentity::vmult_add ( VectorType & , const VectorType & ) const

Apply preconditioner, adding to the previous value.

template<class VectorType >
 void PreconditionIdentity::Tvmult_add ( VectorType & , const VectorType & ) const

Apply transpose preconditioner, adding. Since this is the identity, this function is the same as vmult_add().

## ◆ clear()

 void PreconditionIdentity::clear ( )
inline

This function is only present to provide the interface of a preconditioner to be handed to a smoother. This does nothing.

Definition at line 148 of file precondition.h.

## ◆ m()

 size_type PreconditionIdentity::m ( ) const

Return the dimension of the codomain (or range) space. Note that the matrix is of dimension $$m \times n$$.

Note
This function should only be called if the preconditioner has been initialized.

## ◆ n()

 size_type PreconditionIdentity::n ( ) const

Return the dimension of the domain space. Note that the matrix is of dimension $$m \times n$$.

Note
This function should only be called if the preconditioner has been initialized.

## ◆ 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.

## ◆ n_rows

 size_type PreconditionIdentity::n_rows
private

The dimension of the range space.

Definition at line 175 of file precondition.h.

## ◆ n_columns

 size_type PreconditionIdentity::n_columns
private

The dimension of the domain space.

Definition at line 180 of file precondition.h.

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