MGSmootherBase< VectorType > Class Template Reference

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

Inheritance diagram for MGSmootherBase< VectorType >:

Public Member Functions
virtual	~MGSmootherBase ()=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
Public Member Functions inherited from Subscriptor
	Subscriptor ()
	Subscriptor (const Subscriptor &)
	Subscriptor (Subscriptor &&) noexcept
virtual	~Subscriptor ()
Subscriptor &	operator= (const Subscriptor &)
Subscriptor &	operator= (Subscriptor &&) noexcept
void	subscribe (const char *identifier=nullptr) const
void	unsubscribe (const char *identifier=nullptr) const
unsigned int	n_subscriptions () const
void	list_subscribers () const
template<class Archive >
void	serialize (Archive &ar, const unsigned int version)

Additional Inherited Members
Static Public Member Functions inherited from Subscriptor
static ::ExceptionBase &	ExcInUse (int arg1, std::string arg2, std::string arg3)
static ::ExceptionBase &	ExcNoSubscriber (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().

Author

Guido Kanschat, 2002

Definition at line 234 of file mg_base.h.

Constructor & Destructor Documentation

~MGSmootherBase()

template<typename VectorType>

virtual MGSmootherBase< VectorType >::~MGSmootherBase ( )

virtualdefault

Virtual destructor.

Member Function Documentation

clear()

template<typename VectorType>

virtual void MGSmootherBase< VectorType >::clear ( )

pure virtual

Release matrices.

Implemented in MGSmootherPrecondition< MatrixType, PreconditionerType, VectorType >, MGSmootherRelaxation< MatrixType, RelaxationType, VectorType >, mg::SmootherRelaxation< RelaxationType, VectorType >, MGSmootherIdentity< VectorType >, and MGSmootherBlock< MatrixType, RelaxationType, number >.

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.

Implemented in MGSmootherPrecondition< MatrixType, PreconditionerType, VectorType >, MGSmootherRelaxation< MatrixType, RelaxationType, VectorType >, mg::SmootherRelaxation< RelaxationType, VectorType >, MGSmootherIdentity< VectorType >, and MGSmootherBlock< MatrixType, RelaxationType, number >.

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().

Reimplemented in MGSmootherPrecondition< MatrixType, PreconditionerType, VectorType >, MGSmootherRelaxation< MatrixType, RelaxationType, VectorType >, and mg::SmootherRelaxation< RelaxationType, VectorType >.

Definition at line 32 of file mg_base.cc.

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

• deal.II/multigrid/mg_base.h
• source/multigrid/mg_base.cc