Dune::Amg::TwoLevelMethod< FO, CSP, S > Class Template Reference

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

Public Types
typedef CSP	CoarseLevelSolverPolicy
	The type of the policy for constructing the coarse level solver.
typedef CoarseLevelSolverPolicy::CoarseLevelSolver	CoarseLevelSolver
	The type of the coarse level solver.
typedef FO	FineOperatorType
	The linear operator of the finel level system. Has to be derived from AssembledLinearOperator.
typedef FineOperatorType::range_type	FineRangeType
	The type of the range of the fine level operator.
typedef FineOperatorType::domain_type	FineDomainType
	The type of the domain of the fine level operator.
typedef CSP::Operator	CoarseOperatorType
	The linear operator of the finel level system. Has to be derived from AssembledLinearOperator.
typedef CoarseOperatorType::range_type	CoarseRangeType
	The type of the range of the coarse level operator.
typedef CoarseOperatorType::domain_type	CoarseDomainType
	The type of the domain of the coarse level operator.
typedef S	SmootherType
	The type of the fine level smoother.
typedef FO::domain_type	domain_type
	The domain type of the preconditioner.
typedef FO::range_type	range_type
	The range type of the preconditioner.
typedef X::field_type	field_type
	The field type of the preconditioner.

Public Member Functions
	TwoLevelMethod (const FineOperatorType &op, std::shared_ptr< SmootherType > smoother, const LevelTransferPolicy< FineOperatorType, CoarseOperatorType > &policy, CoarseLevelSolverPolicy &coarsePolicy, std::size_t preSteps=1, std::size_t postSteps=1)
	Constructs a two level method. More...
SolverCategory::Category	category () const override
	Category of the preconditioner (see SolverCategory::Category)
virtual void	pre (FO::domain_type &x, FO::range_type &b)=0
	Prepare the preconditioner. More...
virtual void	apply (FO::domain_type &v, const FO::range_type &d)=0
	Apply one step of the preconditioner to the system A(v)=d. More...
virtual void	post (FO::domain_type &x)=0
	Clean up. More...

Detailed Description

template<class FO, class CSP, class S>
class Dune::Amg::TwoLevelMethod< FO, CSP, S >

Template Parameters

FO	The type of the fine level linear operator.
CSP	The type of the coarse level solver policy.
S	The type of the fine level smoother used.

Constructor & Destructor Documentation

TwoLevelMethod()

template<class FO , class CSP , class S >

Dune::Amg::TwoLevelMethod< FO, CSP, S >::TwoLevelMethod ( const FineOperatorType &  op, std::shared_ptr< SmootherType >  smoother, const LevelTransferPolicy< FineOperatorType, CoarseOperatorType > &  policy, CoarseLevelSolverPolicy &  coarsePolicy, std::size_t  preSteps = 1, std::size_t  postSteps = 1  )

inline

Constructs a two level method.

Template Parameters

CoarseSolverPolicy

The policy for constructing the coarse solver, e.g. OneStepAMGCoarseSolverPolicy

Parameters

op	The fine level operator.
smoother	The fine level smoother.
policy	The level transfer policy.
coarsePolicy	The policy for constructing the coarse level solver.
preSteps	The number of smoothing steps to apply before the coarse level correction.
postSteps	The number of smoothing steps to apply after the coarse level correction.

References Dune::Amg::LevelTransferPolicy< FO, CO >::clone(), and Dune::Amg::LevelTransferPolicy< FO, CO >::createCoarseLevelSystem().

Member Function Documentation

apply()

virtual void Dune::Preconditioner< FO::domain_type , FO::range_type >::apply ( FO::domain_type &  v, const FO::range_type &  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.

post()

virtual void Dune::Preconditioner< FO::domain_type , FO::range_type >::post ( FO::domain_type &  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()

virtual void Dune::Preconditioner< FO::domain_type , FO::range_type >::pre ( FO::domain_type &  x, FO::range_type &  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.

---

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

• dune/istl/paamg/twolevelmethod.hh