PreconditionChebyshev< MatrixType, VectorType, PreconditionerType >::AdditionalData Struct Reference

#include <deal.II/lac/precondition.h>

Public Member Functions
	AdditionalData (const unsigned int degree=1, const double smoothing_range=0., const bool nonzero_starting=false, const unsigned int eig_cg_n_iterations=8, const double eig_cg_residual=1e-2, const double max_eigenvalue=1)

Public Attributes
unsigned int	degree
double	smoothing_range
bool	nonzero_starting
unsigned int	eig_cg_n_iterations
double	eig_cg_residual
double	max_eigenvalue
VectorType	matrix_diagonal_inverse
std::shared_ptr< PreconditionerType >	preconditioner

Detailed Description

template<typename MatrixType = SparseMatrix<double>, typename VectorType = Vector<double>, typename PreconditionerType = DiagonalMatrix<VectorType>>
struct PreconditionChebyshev< MatrixType, VectorType, PreconditionerType >::AdditionalData

Standardized data struct to pipe additional parameters to the preconditioner.

Definition at line 1020 of file precondition.h.

Constructor & Destructor Documentation

AdditionalData()

template<typename MatrixType = SparseMatrix<double>, typename VectorType = Vector<double>, typename PreconditionerType = DiagonalMatrix<VectorType>>

PreconditionChebyshev< MatrixType, VectorType, PreconditionerType >::AdditionalData::AdditionalData	(	const unsigned int	degree = 1,
		const double	smoothing_range = 0.,
		const bool	nonzero_starting = false,
		const unsigned int	eig_cg_n_iterations = 8,
		const double	eig_cg_residual = 1e-2,
		const double	max_eigenvalue = 1
	)

Constructor.

Member Data Documentation

degree

template<typename MatrixType = SparseMatrix<double>, typename VectorType = Vector<double>, typename PreconditionerType = DiagonalMatrix<VectorType>>

unsigned int PreconditionChebyshev< MatrixType, VectorType, PreconditionerType >::AdditionalData::degree

This determines the degree of the Chebyshev polynomial. The degree of the polynomial gives the number of matrix-vector products to be performed for one application of the vmult() operation. Degree one corresponds to a damped Jacobi method.

If the degree is set to numbers::invalid_unsigned_int, the algorithm will automatically determine the number of necessary iterations based on the usual Chebyshev error formula as mentioned in the discussion of the main class.

Definition at line 1043 of file precondition.h.

smoothing_range

template<typename MatrixType = SparseMatrix<double>, typename VectorType = Vector<double>, typename PreconditionerType = DiagonalMatrix<VectorType>>

double PreconditionChebyshev< MatrixType, VectorType, PreconditionerType >::AdditionalData::smoothing_range

This sets the range between the largest eigenvalue in the matrix and the smallest eigenvalue to be treated. If the parameter is set to a number less than 1, an estimate for the largest and for the smallest eigenvalue will be calculated internally. For a smoothing range larger than one, the Chebyshev polynomial will act in the interval \([\lambda_\mathrm{max}/ \tt{smoothing\_range}, \lambda_\mathrm{max}]\), where \(\lambda_\mathrm{max}\) is an estimate of the maximum eigenvalue of the matrix. A choice of smoothing_range between 5 and 20 is useful in case the preconditioner is used as a smoother in multigrid.

Definition at line 1056 of file precondition.h.

nonzero_starting

template<typename MatrixType = SparseMatrix<double>, typename VectorType = Vector<double>, typename PreconditionerType = DiagonalMatrix<VectorType>>

bool PreconditionChebyshev< MatrixType, VectorType, PreconditionerType >::AdditionalData::nonzero_starting

When this flag is set to true, it enables the method vmult(dst, src) to use non-zero data in the vector dst, appending to it the Chebyshev corrections. This can be useful in some situations (e.g. when used for high-frequency error smoothing in a multigrid algorithm), but not the way the solver classes expect a preconditioner to work (where one ignores the content in dst for the preconditioner application).

Deprecated:

For non-zero starting, use the step() and Tstep() interfaces, whereas vmult() provides the preconditioner interface.

Definition at line 1070 of file precondition.h.

eig_cg_n_iterations

template<typename MatrixType = SparseMatrix<double>, typename VectorType = Vector<double>, typename PreconditionerType = DiagonalMatrix<VectorType>>

unsigned int PreconditionChebyshev< MatrixType, VectorType, PreconditionerType >::AdditionalData::eig_cg_n_iterations

Maximum number of CG iterations performed for finding the maximum eigenvalue. If set to zero, no computations are performed. Instead, the user must supply a largest eigenvalue via the variable PreconditionChebyshev::AdditionalData::max_eigenvalue.

Definition at line 1078 of file precondition.h.

eig_cg_residual

template<typename MatrixType = SparseMatrix<double>, typename VectorType = Vector<double>, typename PreconditionerType = DiagonalMatrix<VectorType>>

double PreconditionChebyshev< MatrixType, VectorType, PreconditionerType >::AdditionalData::eig_cg_residual

Tolerance for CG iterations performed for finding the maximum eigenvalue.

Definition at line 1084 of file precondition.h.

max_eigenvalue

template<typename MatrixType = SparseMatrix<double>, typename VectorType = Vector<double>, typename PreconditionerType = DiagonalMatrix<VectorType>>

double PreconditionChebyshev< MatrixType, VectorType, PreconditionerType >::AdditionalData::max_eigenvalue

Maximum eigenvalue to work with. Only in effect if eig_cg_n_iterations is set to zero, otherwise this parameter is ignored.

Definition at line 1091 of file precondition.h.

matrix_diagonal_inverse

template<typename MatrixType = SparseMatrix<double>, typename VectorType = Vector<double>, typename PreconditionerType = DiagonalMatrix<VectorType>>

VectorType PreconditionChebyshev< MatrixType, VectorType, PreconditionerType >::AdditionalData::matrix_diagonal_inverse

Stores the inverse of the diagonal of the underlying matrix.

Deprecated:

Set the variable preconditioner defined below instead.

Definition at line 1098 of file precondition.h.

preconditioner

template<typename MatrixType = SparseMatrix<double>, typename VectorType = Vector<double>, typename PreconditionerType = DiagonalMatrix<VectorType>>

std::shared_ptr<PreconditionerType> PreconditionChebyshev< MatrixType, VectorType, PreconditionerType >::AdditionalData::preconditioner

Stores the preconditioner object that the Chebyshev is wrapped around.

Definition at line 1103 of file precondition.h.

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

• deal.II/lac/precondition.h