Stateful owner of the outer-Krylov solver path. More...

#include <CD_EllipticSolverChain.H>

Inheritance diagram for EllipticSolverChain::KrylovSolver< T >:

[legend]

Public Types
using	Vec = Vector< LevelData< T > * >
	Multilevel data type.

Public Member Functions
	KrylovSolver () noexcept=default
	Default constructor. Must call define() before use.

	~KrylovSolver () noexcept
	Destructor. Frees the persistent work vectors and custom solvers.

void	define (AMRMultiGrid< LevelData< T > > *a_mg, const Vector< RefCountedPtr< LevelData< BaseFab< bool > > > > &a_validCells, const Vector< Real > &a_dx, const int a_lbase, const int a_lmax, const int a_numVCycles)
	Define the multigrid-preconditioner adapter and reset the persistent work. Call once per regrid.

bool	solve (Vec &a_phi, const Vec &a_rhs, const bool a_zeroPhi, const SolverType a_type, const Settings &a_settings)
	Solve L(phi) = rhs with the chosen outer Krylov method preconditioned by the multigrid cycle.

int	lastKrylovIterations () const
	Iteration count of the most recent Krylov solve (GMRES/BiCGStab).

void	snapshotGuess (Vec &a_phi, const Vec &a_rhs)
	Snapshot the chain's starting guess and its residual for the fallback warm-start rule.

bool	keepOrRestore (Vec &a_phi, const Vec &a_rhs)
	Warm-start rule applied between fallback attempts.

Protected Member Functions
void	allocateWork (const Vec &a_template)
	Lazily allocate the persistent residual-correction vectors r0/dphi from a template hierarchy.

void	freeWork ()
	Free the persistent work vectors and undefine the custom solvers.

Protected Attributes
AMRMultiGrid< LevelData< T > > *	m_mg = nullptr
	Multigrid solver (not owned).

AMRMultigridKrylovOp< T >	m_op
	Multigrid-cycle-as-preconditioner adapter.

KrylovBiCGStab< T >	m_bicg
	Custom BiCGStab solver (lazily defined on first BiCGStab solve).

KrylovGMRES< T >	m_gmres
	Custom GMRES solver (lazily defined on first GMRES solve).

int	m_lastKrylovIters = -1
	Iteration count of the most recent Krylov solve, or -1 if none has run.

int	m_lbase = 0
	Coarsest level.

int	m_lmax = 0
	Finest level.

bool	m_isDefined = false
	Whether define() has been called.

bool	m_workAllocated = false
	Whether r0/dphi are allocated for the current grid.

Vec	m_r0
	Persistent initial residual.

Vec	m_dphi
	Persistent correction.

Vec	m_phiInit
	Snapshot of the chain's starting guess (the initial-residual solution) for the warm-start rule.

Real	m_initResidual = 0.0
	Residual of the snapshot (the initial residual of the fallback chain).

Detailed Description

template<class T>
class EllipticSolverChain::KrylovSolver< T >

Stateful owner of the outer-Krylov solver path.

Holds the multigrid-cycle adapter (AMRMultigridKrylovOp), the chombo-discharge BiCGStab/GMRES solvers, and the persistent residual-correction work vectors. define() is called once per regrid; solve() reuses the adapter, the (lazily defined) custom solvers and the work vectors across all subsequent solves, so there is no per-solve work-vector allocation. solve() runs in residual-correction form so the inhomogeneous boundary/jump contribution enters only through the initial residual r0 = rhs - L(phi); the matvec and preconditioner are applied with homogeneous boundary conditions, and warm starts are honoured.

Note: T is the FAB type (EBCellFAB or MFCellFAB).

Member Function Documentation

◆ allocateWork()

template<class T >

void EllipticSolverChain::KrylovSolver< T >::allocateWork ( const Vec & a_template )

protected

Lazily allocate the persistent residual-correction vectors r0/dphi from a template hierarchy.

Parameters

[in] a_template A hierarchy whose layout the work vectors mirror (e.g. the rhs).

◆ define()

template<class T >

void EllipticSolverChain::KrylovSolver< T >::define	(	AMRMultiGrid< LevelData< T > > *	a_mg,
		const Vector< RefCountedPtr< LevelData< BaseFab< bool > > > > &	a_validCells,
		const Vector< Real > &	a_dx,
		const int	a_lbase,
		const int	a_lmax,
		const int	a_numVCycles
	)

Define the multigrid-preconditioner adapter and reset the persistent work. Call once per regrid.

Parameters

[in]	a_mg	Fully set-up multigrid solver (reused for matvec and preconditioning)
[in]	a_validCells	Per-level valid-cell mask (true where not covered by a finer level), e.g. from AmrMesh::getValidCells
[in]	a_dx	Grid spacing on each level (index 0..a_lmax)
[in]	a_lbase	Coarsest level in the solve
[in]	a_lmax	Finest level in the solve
[in]	a_numVCycles	Number of multigrid cycles per preconditioner invocation (cycle type from gmg_cycle; normally a V-cycle)

◆ keepOrRestore()

template<class T >

bool EllipticSolverChain::KrylovSolver< T >::keepOrRestore	(	Vec &	a_phi,
		const Vec &	a_rhs
	)

Warm-start rule applied between fallback attempts.

If the just-failed attempt left a residual smaller than the snapshot's initial residual, a_phi is kept (the failed solve is a better warm start); otherwise a_phi is restored to the snapshot (the initial-residual solution). snapshotGuess() must have been called first.

Parameters

[in,out]	a_phi	Current solution; restored to the snapshot if it did not improve on the initial residual.
[in]	a_rhs	Right-hand side, used to evaluate the current residual.

Returns: True if the current solution was kept, false if it was restored.

◆ lastKrylovIterations()

template<class T >

int EllipticSolverChain::KrylovSolver< T >::lastKrylovIterations ( ) const

inline

Iteration count of the most recent Krylov solve (GMRES/BiCGStab).

Returns: Number of iterations, or -1 if no Krylov solve has run.

◆ snapshotGuess()

template<class T >

void EllipticSolverChain::KrylovSolver< T >::snapshotGuess	(	Vec &	a_phi,
		const Vec &	a_rhs
	)

Snapshot the chain's starting guess and its residual for the fallback warm-start rule.

Call once, before the first attempt in a fallback chain. Stores a copy of the starting solution (the "initial-residual solution") so keepOrRestore() can fall back to it.

Parameters

[in,out]	a_phi	The starting guess (after any zeroing the host has applied); its ghost cells may be filled.
[in]	a_rhs	Right-hand side, used to evaluate the initial residual.

◆ solve()

template<class T >

bool EllipticSolverChain::KrylovSolver< T >::solve	(	Vec &	a_phi,
		const Vec &	a_rhs,
		const bool	a_zeroPhi,
		const SolverType	a_type,
		const Settings &	a_settings
	)

Solve L(phi) = rhs with the chosen outer Krylov method preconditioned by the multigrid cycle.

Parameters

[in,out]	a_phi	Solution (in: initial guess unless a_zeroPhi; out: solution)
[in]	a_rhs	Right-hand side
[in]	a_zeroPhi	If true, start from phi = 0
[in]	a_type	Which Krylov method to run (GMRES or BiCGStab)
[in]	a_settings	Outer-Krylov settings (tolerance, iterations, restart, verbosity)

Returns: True if the Krylov solver reported convergence.

The documentation for this class was generated from the following files:

Source/Elliptic/CD_EllipticSolverChain.H
Source/Elliptic/CD_EllipticSolverChainImplem.H

Public Types

Public Member Functions

Protected Member Functions

Protected Attributes

Detailed Description

Member Function Documentation

◆ allocateWork()

◆ define()

◆ keepOrRestore()

◆ lastKrylovIterations()

◆ snapshotGuess()

◆ solve()