Turns an InverseOperator into a Preconditioner. More...

#include <dune/istl/preconditioners.hh>

Public Types
typedef O::domain_type	domain_type
	The domain type of the preconditioner.

typedef O::range_type	range_type
	The range type of the preconditioner.

typedef range_type::field_type	field_type
	The field type of the preconditioner.

typedef Simd::Scalar< field_type >	scalar_field_type
	scalar type underlying the field_type

typedef FieldTraits< scalar_field_type >::real_type	real_field_type
	real scalar type underlying the field_type

typedef O	InverseOperator
	type of the wrapped inverse operator

Public Member Functions
	InverseOperator2Preconditioner (InverseOperator &inverse_operator)
	Construct the preconditioner from the solver. More...

void	pre (domain_type &, range_type &) override
	Prepare the preconditioner. More...

void	apply (domain_type &v, const range_type &d) override
	Apply one step of the preconditioner to the system A(v)=d. More...

void	post (domain_type &) override
	Clean up. More...

SolverCategory::Category	category () const override
	Category of the preconditioner (see SolverCategory::Category)

Detailed Description

template<class O, int c = -1>
class Dune::InverseOperator2Preconditioner< O, c >

Turns an InverseOperator into a Preconditioner.

Template Parameters

O	The type of the inverse operator to wrap.

Constructor & Destructor Documentation

◆ InverseOperator2Preconditioner()

template<class O , int c = -1>

Dune::InverseOperator2Preconditioner< O, c >::InverseOperator2Preconditioner ( InverseOperator & inverse_operator )

inline

Construct the preconditioner from the solver.

Parameters

inverse_operator The inverse operator to wrap.

References Dune::SolverCategory::category(), and DUNE_THROW.

Member Function Documentation

◆ apply()

template<class O , int c = -1>

void Dune::InverseOperator2Preconditioner< O, c >::apply	(	domain_type &	v,
		const range_type &	d
	)

inlineoverridevirtual

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.

Implements Dune::Preconditioner< O::domain_type, O::range_type >.

◆ post()

template<class O , int c = -1>

void Dune::InverseOperator2Preconditioner< O, c >::post ( domain_type & x )

inlineoverridevirtual

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.

Implements Dune::Preconditioner< O::domain_type, O::range_type >.

◆ pre()

template<class O , int c = -1>

void Dune::InverseOperator2Preconditioner< O, c >::pre	(	domain_type &	x,
		range_type &	b
	)

inlineoverridevirtual

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