Reference documentation for deal.II version 9.3.0
MGTransferBase< VectorType > Class Template Referenceabstract

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

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

virtual ~MGTransferBase () override=default

virtual void prolongate (const unsigned int to_level, VectorType &dst, const VectorType &src) const =0

virtual void prolongate_and_add (const unsigned int to_level, VectorType &dst, const VectorType &src) const

virtual void restrict_and_add (const unsigned int from_level, VectorType &dst, const VectorType &src) const =0

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 MGTransferBase< VectorType >

Base class used to declare the operations needed by a concrete class implementing prolongation and restriction of vectors in the multigrid context. This class is abstract and has no implementation of these operations.

There are several derived classes, reflecting the fact that vector types and numbering of the fine-grid discretization and of the multi-level implementation are independent.

If you use multigrid for a single PDE or for your complete system of equations, you will use MGTransferPrebuilt together with Multigrid. The vector types used on the fine grid as well as for the multilevel operations may be Vector or BlockVector. In both cases, MGTransferPrebuilt will operate on all components of the solution.

Note
For the following, it is important to realize the difference between a solution component and a solution block. The distinction only applies if vector valued elements are used, but is quite important then. This is reflected in the fact that it is not possible right now to use transfer classes based on MGTransferComponentBase for genuine vector valued elements, but descendants of MGTransferBlockBase would have to be applied. In the following text, we will use the term block, but remark that it might refer to components as well.
Todo:
update the following documentation, since it does not reflect the latest changes in structure.

For mixed systems, it may be required to do multigrid only for a single component or for some components. The classes MGTransferSelect and MGTransferBlock handle these cases.

MGTransferSelect is used if you use multigrid (on Vector objects) for a single component, possibly grouped using mg_target_component.

The class MGTransferBlock handles the case where your multigrid method operates on BlockVector objects. These can contain all or a consecutive set of the blocks of the complete system. Since most smoothers cannot operate on block structures, it is not clear whether this case is really useful. Therefore, a tested implementation of this case will be supplied when needed.

Definition at line 171 of file mg_base.h.

## ◆ ~MGTransferBase()

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

Destructor. Does nothing here, but needs to be declared virtual anyway.

## ◆ prolongate()

template<typename VectorType>
 virtual void MGTransferBase< VectorType >::prolongate ( const unsigned int to_level, VectorType & dst, const VectorType & src ) const
pure virtual

Prolongate a vector from level to_level-1 to level to_level. The previous content of dst is overwritten.

• src is a vector with as many elements as there are degrees of freedom on the coarser level involved.
• dst has as many elements as there are degrees of freedom on the finer level.

template<typename VectorType>
 void MGTransferBase< VectorType >::prolongate_and_add ( const unsigned int to_level, VectorType & dst, const VectorType & src ) const
virtual

Prolongate a vector from level to_level-1 to level to_level, summing into the previous content of dst.

• src is a vector with as many elements as there are degrees of freedom on the coarser level involved.
• dst has as many elements as there are degrees of freedom on the finer level.

Reimplemented in MGTransferBlockMatrixFree< dim, Number >, and MGTransferMatrixFree< dim, Number >.

Definition at line 47 of file mg_base.cc.

template<typename VectorType>
 virtual void MGTransferBase< VectorType >::restrict_and_add ( const unsigned int from_level, VectorType & dst, const VectorType & src ) const
pure virtual

Restrict a vector from level from_level to level from_level-1 and add this restriction to dst. If the region covered by cells on level from_level is smaller than that of level from_level-1 (local refinement), then some degrees of freedom in dst are active and will not be altered. For the other degrees of freedom, the result of the restriction is added.

• src is a vector with as many elements as there are degrees of freedom on the finer level
• dst has as many elements as there are degrees of freedom on the coarser level.

## ◆ 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: