Class mgrid::LinearMultigrid

ClassList > mgrid > LinearMultigrid

Linear full-multigrid (FMG) solver. More...

• #include <multigrid_linear.hpp>

Inherits the following classes: mgrid::MultigridBase

Public Attributes inherited from mgrid::MultigridBase

See mgrid::MultigridBase

Type	Name
int	coarsestLevel Level index of the coarsest grid (always 0).
int	finestLevel Level index of the finest grid.

Public Functions

Type	Name
	LinearMultigrid (const Settings & settings) Builds the solver state from settings .
virtual void	multigrid () override Runs the full-multigrid cycle.
	~LinearMultigrid () override Defaulted polymorphic destructor.

Public Functions inherited from mgrid::MultigridBase

See mgrid::MultigridBase

Type	Name
	MultigridBase (const Settings & settings) Builds the solver state from settings .
virtual double	differential_operator (Level level, int i, int j) = 0 Evaluates the discrete PDE operator at one grid point.
void	evaluate_operator (Level level, FDArray & result) Evaluates the discrete operator over result .
void	evaluate_residual (Level level, FDArray & result) Evaluates the residual source - operator(solution) overresult .
virtual std::string	filename (std::string root="") = 0 Builds the output file name for this problem.
bool	fully_periodic () const True when both axes of the grid hierarchy wrap periodically.
FDArray &	get_result () The current solution on the finest grid.
void	initial_guess (T arg) Sets the finest-level initial guess and flags it as provided.
virtual void	multigrid () Runs the multigrid cycle.
void	relax (Level level, unsigned long n) Smooths solution[level] with a fixed number of sweeps.
void	relax (Level level, double tolerance) Smooths solution[level] until the relative change falls belowtolerance ormaxIterations sweeps have run.
virtual void	relaxation_updater (Level level, int i, int j) = 0 Applies one in-place relaxation update at a single grid point.
virtual void	solve () Solves the problem.
FDArray &	source_term () Accesses the finest-level source term.
void	source_term (T arg) Sets the finest-level source term and flags it as provided.
virtual void	write (int numOfVariables, std::string root="") Writes the finest-level solution (and optional derived fields) to a netCDF-4 file.
virtual	~MultigridBase () = default Defaulted polymorphic destructor.

Protected Attributes inherited from mgrid::MultigridBase

See mgrid::MultigridBase

Type	Name
const double	aspect Domain aspect ratio.
const int	cycleType FMG cycle type (V / W / three).
bool	initialIsSet = {false} Has an initial guess been provided?
const unsigned long	maxIterations Cap on relax-to-tolerance sweeps.
int	nxfine = {0}
int	nzfine = {0} Finest-grid extents (rows, columns).
const unsigned long	postRelax Post-correction relaxation sweeps.
const unsigned long	preRelax Pre-correction relaxation sweeps.
const double	residualTolerance Convergence tolerance for the solver.
Stack	solution
Stack	source
bool	sourceIsSet = {false} Has a source term been provided?
Stack	temp Solution, source and scratch grid hierarchies.

Protected Functions inherited from mgrid::MultigridBase

See mgrid::MultigridBase

Type	Name
void	mark_source_set () Flags the source term as set without touching its array.
virtual void	on_cycle_end (double residual_norm)

Detailed Description

Drives a constant-coefficient linear PDE to its discrete solution with a full-multigrid cycle: the right-hand side is restricted down the hierarchy, the coarsest level is solved, and each successively finer level is reached by interpolation followed by Settings::mgCycleType correction cycles (V / W / three). A concrete subclass supplies the discrete PDE by overriding differential_operator, relaxation_updater and filename; this class only implements the cycle.

Note:

Modernised from the 2011 mgrid::LinearMultigrid: the finestLevel / coarsestLevel locals that shadowed the MultigridBase members are dropped (the base's members, set from solution in the constructor, are used directly) and not is spelled !. The cycle body is otherwise transcribed verbatim from multigrid_linear.cpp.

Public Functions Documentation

function LinearMultigrid

Builds the solver state from settings .

inline explicit mgrid::LinearMultigrid::LinearMultigrid (
    const Settings & settings
) 

Parameters:

• settings solver configuration, forwarded to MultigridBase.

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function multigrid

Runs the full-multigrid cycle.

virtual void mgrid::LinearMultigrid::multigrid () override

Note:

No-op unless a source term has been provided. Restricts the right-hand side to the coarsest level, solves it, then sweeps up the hierarchy running a full-multigrid V/W cycle (per Settings::mgCycleType) at each level before a final post-correction smooth on the finest grid.

Implements mgrid::MultigridBase::multigrid

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function ~LinearMultigrid

Defaulted polymorphic destructor.

mgrid::LinearMultigrid::~LinearMultigrid () override

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The documentation for this class was generated from the following file include/multigrid/multigrid_linear.hpp