Sequential ILU preconditioner. More...

#include <dune/istl/preconditioners.hh>

Public Types
typedef std::remove_const< M >::type	matrix_type
	The matrix type the preconditioner is for.

typedef matrix_type::block_type	block_type
	block type of matrix

typedef X	domain_type
	The domain type of the preconditioner.

typedef Y	range_type
	The range type of the preconditioner.

typedef X::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 ILU::CRS< block_type, typename M::allocator_type >	CRS
	type of ILU storage

Public Member Functions
	SeqILU (const M &A, scalar_field_type w, const bool resort=false)
	Constructor. More...

	SeqILU (const M &A, const ParameterTree &config)
	Constructor. More...

	SeqILU (const M &A, int n, scalar_field_type w, const bool resort=false)
	Constructor. More...

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

virtual void	apply (X &v, const Y &d)
	Apply the preconditioner. More...

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

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

Protected Attributes
std::unique_ptr< matrix_type >	ILU_
	The ILU(n) decomposition of the matrix. As storage a BCRSMatrix is used.

CRS	lower_
	The ILU(n) decomposition of the matrix. As storage a CRS structure is used.

const scalar_field_type	w_
	The relaxation factor to use.

const bool	wNotIdentity_
	true if w != 1.0

Detailed Description

template<class M, class X, class Y, int l = 1>
class Dune::SeqILU< M, X, Y, l >

Sequential ILU preconditioner.

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

Template Parameters

M	The matrix type to operate on
X	Type of the update
Y	Type of the defect
l	Ignored. Just there to have the same number of template arguments as other preconditioners.

Constructor & Destructor Documentation

◆ SeqILU() [1/3]

template<class M , class X , class Y , int l = 1>

Dune::SeqILU< M, X, Y, l >::SeqILU	(	const M &	A,
		scalar_field_type	w,
		const bool	resort = `false`
	)

inline

Constructor.

Constructor invoking ILU(0) gets all parameters to operate the prec.

Parameters

A	The matrix to operate on.
w	The relaxation factor.
resort	true if a resort of the computed ILU for improved performance should be done.

◆ SeqILU() [2/3]

template<class M , class X , class Y , int l = 1>

Dune::SeqILU< M, X, Y, l >::SeqILU	(	const M &	A,
		const ParameterTree &	config
	)

inline

Constructor.

Parameters

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

ParameterTree Key	Meaning
n	The order of the ILU decomposition
relaxation	The relaxation factor
resort	True if a resort of the computed ILU for improved performance should be done.

See ISTL_Factory for the ParameterTree layout and examples.

◆ SeqILU() [3/3]

template<class M , class X , class Y , int l = 1>

Dune::SeqILU< M, X, Y, l >::SeqILU	(	const M &	A,
		int	n,
		scalar_field_type	w,
		const bool	resort = `false`
	)

inline

Constructor.

Constructor invoking ILU(n).

Parameters

A	The matrix to operate on.
n	The order of the ILU decomposition.
w	The relaxation factor.
resort	true if a resort of the computed ILU for improved performance should be done.

Member Function Documentation

◆ apply()

template<class M , class X , class Y , int l = 1>

virtual void Dune::SeqILU< M, X, Y, l >::apply	(	X &	v,
		const Y &	d
	)

inlinevirtual

Apply the preconditioner.

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 >.

References Dune::bilu_backsolve(), Dune::SeqILU< M, X, Y, l >::ILU_, Dune::SeqILU< M, X, Y, l >::lower_, Dune::SeqILU< M, X, Y, l >::w_, and Dune::SeqILU< M, X, Y, l >::wNotIdentity_.

◆ post()

template<class M , class X , class Y , int l = 1>

virtual void Dune::SeqILU< M, X, Y, l >::post ( X & x )

inlinevirtual

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 , int l = 1>

virtual void Dune::SeqILU< M, X, Y, l >::pre	(	X &	x,
		Y &	b
	)

inlinevirtual

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