sequential ILDL preconditioner More...

#include <dune/istl/preconditioners.hh>

Public Types
typedef std::remove_const_t< M >	matrix_type
	type of matrix the preconditioner is for

typedef X	domain_type
	domain type of the preconditioner

typedef Y	range_type
	range type of the preconditioner

typedef X::field_type	field_type
	field type of the preconditioner

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

Public Member Functions
	SeqILDL (const matrix_type &A, const ParameterTree &config)
	Constructor. More...

	SeqILDL (const matrix_type &A, scalar_field_type relax=scalar_field_type(1))
	constructor More...

void	pre (X &x, Y &b) override
	Prepare the preconditioner. More...

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

void	post (X &x) override
	Clean up. More...

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

Detailed Description

template<class M, class X, class Y>
class Dune::SeqILDL< M, X, Y >

sequential ILDL preconditioner

Author: Martin Nolte

Wraps the naked ISTL generic ILDL preconditioner into the solver framework.

Template Parameters

M	type of matrix to operate on
X	type of update
Y	type of defect

Constructor & Destructor Documentation

◆ SeqILDL() [1/2]

template<class M , class X , class Y >

Dune::SeqILDL< M, X, Y >::SeqILDL	(	const matrix_type &	A,
		const ParameterTree &	config
	)

inline

Constructor.

Parameters

A	The matrix to operate on.
configuration	ParameterTree containing preconditioner parameters.

ParameterTree Key	Meaning
relaxation	relaxation factor

See ISTL_Factory for the ParameterTree layout and examples.

◆ SeqILDL() [2/2]

template<class M , class X , class Y >

Dune::SeqILDL< M, X, Y >::SeqILDL	(	const matrix_type &	A,
		scalar_field_type	relax = `scalar_field_type( 1 )`
	)

inlineexplicit

constructor

The constructor copies the matrix A and computes its ILDL decomposition.

Parameters

[in]	A	matrix to operate on
[in]	relax	relaxation factor

Member Function Documentation

◆ apply()

template<class M , class X , class Y >

void Dune::SeqILDL< M, X, Y >::apply	(	X &	v,
		const Y &	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< X, Y >.

◆ category()

template<class M , class X , class Y >

SolverCategory::Category Dune::SeqILDL< M, X, Y >::category ( ) const

inlineoverridevirtual

Category of the preconditioner (see SolverCategory::Category)

Implements Dune::Preconditioner< X, Y >.

References Dune::SolverCategory::sequential.

◆ post()

template<class M , class X , class Y >

void Dune::SeqILDL< M, X, Y >::post ( X & 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< X, Y >.

References DUNE_UNUSED_PARAMETER.

◆ pre()

template<class M , class X , class Y >

void Dune::SeqILDL< M, X, Y >::pre	(	X &	x,
		Y &	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 mangement.

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