TrilinosWrappers::PreconditionAMG::AdditionalData Struct Reference

#include <trilinos_precondition.h>

Public Member Functions
	AdditionalData (const bool elliptic=true, const bool higher_order_elements=false, const unsigned int n_cycles=1, const bool w_cyle=false, const double aggregation_threshold=1e-4, const std::vector< std::vector< bool > > &constant_modes=std::vector< std::vector< bool > >(1), const unsigned int smoother_sweeps=2, const unsigned int smoother_overlap=0, const bool output_details=false)

Public Attributes
bool	elliptic
bool	higher_order_elements
unsigned int	n_cycles
bool	w_cycle
double	aggregation_threshold
std::vector< std::vector< bool > >	constant_modes
unsigned int	smoother_sweeps
unsigned int	smoother_overlap
bool	output_details

Detailed Description

A data structure that is used to control details of how the algebraic multigrid is set up. The flags detailed in here are then passed to the Trilinos ML implementation. A structure of the current type are passed to the constructor of PreconditionAMG.

Definition at line 1293 of file trilinos_precondition.h.

Constructor & Destructor Documentation

TrilinosWrappers::PreconditionAMG::AdditionalData::AdditionalData	(	const bool	elliptic = true,
		const bool	higher_order_elements = false,
		const unsigned int	n_cycles = 1,
		const bool	w_cyle = false,
		const double	aggregation_threshold = 1e-4,
		const std::vector< std::vector< bool > > &	constant_modes = std::vector< std::vector< bool > >(1),
		const unsigned int	smoother_sweeps = 2,
		const unsigned int	smoother_overlap = 0,
		const bool	output_details = false
	)

Constructor. By default, we pretend to work on elliptic problems with linear finite elements on a scalar equation.

Member Data Documentation

bool TrilinosWrappers::PreconditionAMG::AdditionalData::elliptic

Determines whether the AMG preconditioner should be optimized for elliptic problems (ML option smoothed aggregation SA, using a Chebyshev smoother) or for non-elliptic problems (ML option non-symmetric smoothed aggregation NSSA, smoother is SSOR with underrelaxation).

Definition at line 1322 of file trilinos_precondition.h.

bool TrilinosWrappers::PreconditionAMG::AdditionalData::higher_order_elements

Determines whether the matrix that the preconditioner is built upon is generated from linear or higher-order elements.

Definition at line 1330 of file trilinos_precondition.h.

unsigned int TrilinosWrappers::PreconditionAMG::AdditionalData::n_cycles

Defines how many multigrid cycles should be performed by the preconditioner.

Definition at line 1337 of file trilinos_precondition.h.

bool TrilinosWrappers::PreconditionAMG::AdditionalData::w_cycle

Defines whether a w-cycle should be used instead of the standard setting of a v-cycle.

Definition at line 1344 of file trilinos_precondition.h.

double TrilinosWrappers::PreconditionAMG::AdditionalData::aggregation_threshold

This threshold tells the AMG setup how the coarsening should be performed. In the AMG used by ML, all points that strongly couple with the tentative coarse-level point form one aggregate. The term strong coupling is controlled by the variable aggregation_threshold, meaning that all elements that are not smaller than aggregation_threshold times the diagonal element do couple strongly.

Definition at line 1362 of file trilinos_precondition.h.

std::vector<std::vector<bool> > TrilinosWrappers::PreconditionAMG::AdditionalData::constant_modes

Specifies the constant modes (near null space) of the matrix. This parameter tells AMG whether we work on a scalar equation (where the near null space only consists of ones) or on a vector-valued equation.

Definition at line 1373 of file trilinos_precondition.h.

unsigned int TrilinosWrappers::PreconditionAMG::AdditionalData::smoother_sweeps

Determines how many sweeps of the smoother should be performed. When the flag elliptic is set to true, i.e., for elliptic or almost elliptic problems, the polynomial degree of the Chebyshev smoother is set to smoother_sweeps. The term sweeps refers to the number of matrix-vector products performed in the Chebyshev case. In the non-elliptic case, smoother_sweeps sets the number of SSOR relaxation sweeps for post-smoothing to be performed.

Definition at line 1393 of file trilinos_precondition.h.

unsigned int TrilinosWrappers::PreconditionAMG::AdditionalData::smoother_overlap

Determines the overlap in the SSOR/Chebyshev error smoother when run in parallel.

Definition at line 1400 of file trilinos_precondition.h.

bool TrilinosWrappers::PreconditionAMG::AdditionalData::output_details

If this flag is set to true, then internal information from the ML preconditioner is printed to screen. This can be useful when debugging the preconditioner.

Definition at line 1410 of file trilinos_precondition.h.

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

• include/deal.II/lac/trilinos_precondition.h