Reference documentation for deal.II version Git 39b7d3efb0 2021-05-07 15:49:09 -0400
MGSmootherBase< VectorType > Class Template Referenceabstract

#include <deal.II/multigrid/mg_base.h>

Inheritance diagram for MGSmootherBase< VectorType >:
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## Public Member Functions

virtual ~MGSmootherBase () override=default

virtual void clear ()=0

virtual void smooth (const unsigned int level, VectorType &u, const VectorType &rhs) const =0

virtual void apply (const unsigned int level, VectorType &u, const VectorType &rhs) 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)

## Detailed Description

### template<typename VectorType> class MGSmootherBase< VectorType >

Base class for multigrid smoothers. Does nothing but defining the interface used by multigrid methods.

The smoother interface provides two methods, a smooth() method and an apply() method. The multigrid preconditioner interfaces distinguish between the two for efficiency reasons: Upon entry to the preconditioner operations, the vector u needs to be set to zero and smoothing starts by a simple application of the smoother on the rhs vector. This method is provided by the apply() method of this class. It is the same as first setting u to zero and then calling smooth(), but for many classes the separate apply() interface is more efficient because it can skip one matrix-vector product.

In the multigrid preconditioner interfaces, the apply() method is used for the pre-smoothing operation because the previous content in the solution vector needs to be overwritten for a new incoming residual. On the other hand, all subsequent operations need to smooth the content already present in the vector u given the right hand side, which is done by smooth().

Definition at line 251 of file mg_base.h.

## ◆ ~MGSmootherBase()

template<typename VectorType>
 virtual MGSmootherBase< VectorType >::~MGSmootherBase ( )
overridevirtualdefault

Virtual destructor.

## ◆ clear()

template<typename VectorType>
 virtual void MGSmootherBase< VectorType >::clear ( )
pure virtual

## ◆ smooth()

template<typename VectorType>
 virtual void MGSmootherBase< VectorType >::smooth ( const unsigned int level, VectorType & u, const VectorType & rhs ) const
pure virtual

Smoothing function that smooths the content in u given the right hand side vector rhs. This is the function used in multigrid methods.

## ◆ apply()

template<typename VectorType>
 void MGSmootherBase< VectorType >::apply ( const unsigned int level, VectorType & u, const VectorType & rhs ) const
virtual

As opposed to the smooth() function, this function applies the action of the smoothing, overwriting the previous content in the vector u. This function must be equivalent to the following code

u = 0;
smooth(level, u, rhs);

but can usually be implemented more efficiently than the former. If a particular smoother does not override the apply() method, the default implementation as described here is used.

In the multigrid preconditioner interfaces, the apply() method is used for the pre-smoothing operation because the previous content in the solution vector needs to be overwritten for a new incoming residual. On the other hand, all subsequent operations need to smooth the content already present in the vector u given the right hand side, which is done by smooth().

Definition at line 35 of file mg_base.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.

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