Dune::Amg::KAmgTwoGrid< AMG > Class Template Reference

Two grid operator for AMG with Krylov cycle. More...

#include <dune/istl/paamg/kamg.hh>

Public Types
typedef AMG::Domain	domain_type
	The domain type of the preconditioner.
typedef AMG::Range	range_type
	The range type of the preconditioner.
typedef X::field_type	field_type
	The field type of the preconditioner.

Public Member Functions
virtual SolverCategory::Category	category () const
	Category of the preconditioner (see SolverCategory::Category)
	KAmgTwoGrid (AMG &amg, std::shared_ptr< InverseOperator< Domain, Range > > coarseSolver)
	Constructor. More...
void	pre ([[maybe_unused]] typename AMG::Domain &x, [[maybe_unused]] typename AMG::Range &b)
	Prepare the preconditioner. More...
void	post ([[maybe_unused]] typename AMG::Domain &x)
	Clean up. More...
void	apply (typename AMG::Domain &v, const typename AMG::Range &d)
	Apply one step of the preconditioner to the system A(v)=d. More...
InverseOperator< Domain, Range > *	coarseSolver ()
	Get a pointer to the coarse grid solver. More...
void	setLevelContext (std::shared_ptr< typename AMG::LevelContext > p)
	Set the level context pointer. More...
	~KAmgTwoGrid ()
	Destructor.
virtual void	pre (AMG::Domain &x, AMG::Range &b)=0
	Prepare the preconditioner. More...
virtual void	apply (AMG::Domain &v, const AMG::Range &d)=0
	Apply one step of the preconditioner to the system A(v)=d. More...
virtual void	post (AMG::Domain &x)=0
	Clean up. More...

Detailed Description

template<class AMG>
class Dune::Amg::KAmgTwoGrid< AMG >

Two grid operator for AMG with Krylov cycle.

Template Parameters

AMG	The type of the underlying agglomeration AMG.

Constructor & Destructor Documentation

KAmgTwoGrid()

template<class AMG >

Dune::Amg::KAmgTwoGrid< AMG >::KAmgTwoGrid ( AMG &  amg, std::shared_ptr< InverseOperator< Domain, Range > >  coarseSolver  )

inline

Constructor.

Parameters

amg	The underlying amg. It is used as the storage for the hierarchic data structures.
coarseSolver	The solver used for the coarse grid correction.

Member Function Documentation

apply() [1/2]

virtual void Dune::Preconditioner< AMG::Domain , AMG::Range >::apply ( AMG::Domain &  v, const AMG::Range &  d  )

pure virtualinherited

Apply one step of the preconditioner to the system A(v)=d.

On entry v=0 and d=b-A(x) (although this might not be computed in that way. On exit v contains the update, i.e one step computes \( v = M^{-1} d \) where \( M \) is the approximate inverse of the operator \( A \) characterizing the preconditioner.

Parameters

[out]	v	The update to be computed
	d	The current defect.

apply() [2/2]

template<class AMG >

void Dune::Amg::KAmgTwoGrid< AMG >::apply ( typename AMG::Domain &  v, const typename AMG::Range &  d  )

inline

Apply one step of the preconditioner to the system A(v)=d.

On entry v=0 and d=b-A(x) (although this might not be computed in that way. On exit v contains the update, i.e one step computes \( v = M^{-1} d \) where \( M \) is the approximate inverse of the operator \( A \) characterizing the preconditioner.

Parameters

[out]	v	The update to be computed
	d	The current defect.

References Dune::Amg::postsmooth(), and Dune::Amg::presmooth().

coarseSolver()

template<class AMG >

InverseOperator<Domain,Range>* Dune::Amg::KAmgTwoGrid< AMG >::coarseSolver ( )

inline

Get a pointer to the coarse grid solver.

Returns

The coarse grid solver.

post() [1/2]

template<class AMG >

void Dune::Amg::KAmgTwoGrid< AMG >::post ( [[maybe_unused] ] typename AMG::Domain &  x )

inline

Clean up.

This method is called after the last apply call for the linear system to be solved. Memory may be deallocated safely here. x is the solution of the linear equation.

Parameters

x	The right hand side of the equation.

post() [2/2]

virtual void Dune::Preconditioner< AMG::Domain , AMG::Range >::post ( AMG::Domain &  x )

pure virtualinherited

Clean up.

This method is called after the last apply call for the linear system to be solved. Memory may be deallocated safely here. x is the solution of the linear equation.

Parameters

x	The right hand side of the equation.

pre() [1/2]

template<class AMG >

void Dune::Amg::KAmgTwoGrid< AMG >::pre ( [[maybe_unused] ] typename AMG::Domain &  x, [[maybe_unused] ] typename AMG::Range &  b  )

inline

Prepare the preconditioner.

A solver solves a linear operator equation A(x)=b by applying one or several steps of the preconditioner. The method pre() is called before the first apply operation. b and x are right hand side and solution vector of the linear system respectively. It may. e.g., scale the system, allocate memory or compute a (I)LU decomposition. Note: The ILU decomposition could also be computed in the constructor or with a separate method of the derived method if several linear systems with the same matrix are to be solved.

Note

if a preconditioner is copied (e.g. for a second thread) again the pre() method has to be called to ensure proper memory management.

X x(0.0);
Y b = ...; // rhs
Preconditioner<X,Y> prec(...);
prec.pre(x,b);   // prepare the preconditioner
prec.apply(x,b); // can be called multiple times now...
prec.post(x);    // cleanup internal state

Parameters

x	The left hand side of the equation.
b	The right hand side of the equation.

pre() [2/2]

virtual void Dune::Preconditioner< AMG::Domain , AMG::Range >::pre ( AMG::Domain &  x, AMG::Range &  b  )

pure virtualinherited

Prepare the preconditioner.

A solver solves a linear operator equation A(x)=b by applying one or several steps of the preconditioner. The method pre() is called before the first apply operation. b and x are right hand side and solution vector of the linear system respectively. It may. e.g., scale the system, allocate memory or compute a (I)LU decomposition. Note: The ILU decomposition could also be computed in the constructor or with a separate method of the derived method if several linear systems with the same matrix are to be solved.

Note

if a preconditioner is copied (e.g. for a second thread) again the pre() method has to be called to ensure proper memory management.

X x(0.0);
Y b = ...; // rhs
Preconditioner<X,Y> prec(...);
prec.pre(x,b);   // prepare the preconditioner
prec.apply(x,b); // can be called multiple times now...
prec.post(x);    // cleanup internal state

Parameters

x	The left hand side of the equation.
b	The right hand side of the equation.

setLevelContext()

template<class AMG >

void Dune::Amg::KAmgTwoGrid< AMG >::setLevelContext ( std::shared_ptr< typename AMG::LevelContext >  p )

inline

Set the level context pointer.

Parameters

p	The pointer to set it to.

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

• dune/istl/paamg/amg.hh
• dune/istl/paamg/kamg.hh