Reference documentation for deal.II version GIT c415589cf0 2022-08-14 18:50:02+00:00
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 Types

using map_value_type = decltype(counter_map)::value_type

using map_iterator = decltype(counter_map)::iterator

## Private Member Functions

void check_no_subscribers () const noexcept

## Private Attributes

size_type n_rows

size_type n_columns

std::atomic< unsigned int > counter

std::map< std::string, unsigned int > counter_map

std::vector< std::atomic< bool > * > validity_pointers

const std::type_info * object_info

## Static Private Attributes

static std::mutex mutex

## Detailed Description

This preconditioner implements the identity operator. This class can be used you if you want to use a linear solver without preconditioning, because all linear solvers require the usage of a preconditioner.

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());
SymmetricTensor< 2, dim, Number > e(const Tensor< 2, dim, Number > &F)

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 82 of file precondition.h.

## ◆ size_type

Declare type for container size.

Definition at line 88 of file precondition.h.

## ◆ map_value_type

 using Subscriptor::map_value_type = decltype(counter_map)::value_type
privateinherited

The data type used in counter_map.

Definition at line 230 of file subscriptor.h.

## ◆ map_iterator

 using Subscriptor::map_iterator = decltype(counter_map)::iterator
privateinherited

The iterator type used in counter_map.

Definition at line 235 of file subscriptor.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 ( )

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

## ◆ 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 300 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 317 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 309 of file subscriptor.h.

## ◆ check_no_subscribers()

 void Subscriptor::check_no_subscribers ( ) const
privatenoexceptinherited

Check that there are no objects subscribing to this object. If this check passes then it is safe to destroy the current object. It this check fails then this function will either abort or print an error message to deallog (by using the AssertNothrow mechanism), but will not throw an exception.

Note
Since this function is just a consistency check it does nothing in release mode.
If this function is called when there is an uncaught exception then, rather than aborting, this function prints an error message to the standard error stream and returns.

Definition at line 53 of file subscriptor.cc.

## ◆ n_rows

 size_type PreconditionIdentity::n_rows
private

The dimension of the range space.

Definition at line 177 of file precondition.h.

## ◆ n_columns

 size_type PreconditionIdentity::n_columns
private

The dimension of the domain space.

Definition at line 182 of file precondition.h.

## ◆ counter

 std::atomic Subscriptor::counter
mutableprivateinherited

Store the number of objects which subscribed to this object. Initially, this number is zero, and upon destruction it shall be zero again (i.e. all objects which subscribed should have unsubscribed again).

The creator (and owner) of an object is counted in the map below if HE manages to supply identification.

We use the mutable keyword in order to allow subscription to constant objects also.

This counter may be read from and written to concurrently in multithreaded code: hence we use the std::atomic class template.

Definition at line 219 of file subscriptor.h.

## ◆ counter_map

 std::map Subscriptor::counter_map
mutableprivateinherited

In this map, we count subscriptions for each different identification string supplied to subscribe().

Definition at line 225 of file subscriptor.h.

## ◆ validity_pointers

 std::vector *> Subscriptor::validity_pointers
mutableprivateinherited

In this vector, we store pointers to the validity bool in the SmartPointer objects that subscribe to this class.

Definition at line 241 of file subscriptor.h.

## ◆ object_info

 const std::type_info* Subscriptor::object_info
mutableprivateinherited

Pointer to the typeinfo object of this object, from which we can later deduce the class name. Since this information on the derived class is neither available in the destructor, nor in the constructor, we obtain it in between and store it here.

Definition at line 249 of file subscriptor.h.

## ◆ mutex

 std::mutex Subscriptor::mutex
staticprivateinherited

A mutex used to ensure data consistency when printing out the list of subscribers.

Definition at line 271 of file subscriptor.h.

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