Detailed Description

template<typename _MatrixType, typename _Preconditioner = DiagonalPreconditioner<typename _MatrixType::Scalar>>
class Eigen::DGMRES< _MatrixType, _Preconditioner >

A Restarted GMRES with deflation. This class implements a modification of the GMRES solver for sparse linear systems. The basis is built with modified Gram-Schmidt. At each restart, a few approximated eigenvectors corresponding to the smallest eigenvalues are used to build a preconditioner for the next cycle. This preconditioner for deflation can be combined with any other preconditioner, the IncompleteLUT for instance. The preconditioner is applied at right of the matrix and the combination is multiplicative.

Template Parameters

_MatrixType	the type of the sparse matrix A, can be a dense or a sparse matrix.
_Preconditioner	the type of the preconditioner. Default is DiagonalPreconditioner Typical usage : * SparseMatrix<double> A; * VectorXd x, b; * //Fill A and b ... * DGMRES<SparseMatrix<double> > solver; * solver.set_restart(30); // Set restarting value * solver.setEigenv(1); // Set the number of eigenvalues to deflate * solver.compute(A); * x = solver.solve(b); *

References : [1] D. NUENTSA WAKAM and F. PACULL, Memory Efficient Hybrid Algebraic Solvers for Linear Systems Arising from Compressible Flows, Computers and Fluids, In Press, http://dx.doi.org/10.1016/j.compfluid.2012.03.023 [2] K. Burrage and J. Erhel, On the performance of various adaptive preconditioned GMRES strategies, 5(1998), 101-121. [3] J. Erhel, K. Burrage and B. Pohl, Restarted GMRES preconditioned by deflation,J. Computational and Applied Mathematics, 69(1996), 303-318.

Inherits IterativeSolverBase< DGMRES< _MatrixType, _Preconditioner > >.

Public Member Functions
int	deflSize ()

	DGMRES ()

template<typename MatrixDerived >
	DGMRES (const EigenBase< MatrixDerived > &A)

int	restart ()

void	set_restart (const int restart)

void	setEigenv (const int neig)

void	setMaxEigenv (const int maxNeig)

template<typename Rhs , typename Guess >
const internal::solve_retval_with_guess < DGMRES, Rhs, Guess >	solveWithGuess (const MatrixBase< Rhs > &b, const Guess &x0) const

Protected Member Functions
template<typename Rhs , typename Dest >
void	dgmres (const MatrixType &mat, const Rhs &rhs, Dest &x, const Preconditioner &precond) const
	Perform several cycles of restarted GMRES with modified Gram Schmidt,. More...

template<typename Dest >
int	dgmresCycle (const MatrixType &mat, const Preconditioner &precond, Dest &x, DenseVector &r0, RealScalar &beta, const RealScalar &normRhs, int &nbIts) const
	Perform one restart cycle of DGMRES. More...

Constructor & Destructor Documentation

DGMRES ( )

inline

Default constructor.

Referenced by DGMRES< _MatrixType, _Preconditioner >::solveWithGuess().

DGMRES ( const EigenBase< MatrixDerived > & A )

inlineexplicit

Initialize the solver with matrix A for further Ax=b solving.

This constructor is a shortcut for the default constructor followed by a call to compute().

Warning: this class stores a reference to the matrix A as well as some precomputed values that depend on it. Therefore, if A is changed this class becomes invalid. Call compute() to update it with the new matrix A, or modify a copy of A.

Member Function Documentation

int deflSize ( )

inline

Get the size of the deflation subspace size

void dgmres	(	const MatrixType &	mat,
		const Rhs &	rhs,
		Dest &	x,
		const Preconditioner &	precond
	)		const

protected

Perform several cycles of restarted GMRES with modified Gram Schmidt,.

A right preconditioner is used combined with deflation.

int dgmresCycle	(	const MatrixType &	mat,
		const Preconditioner &	precond,
		Dest &	x,
		DenseVector &	r0,
		RealScalar &	beta,
		const RealScalar &	normRhs,
		int &	nbIts
	)		const

protected

Perform one restart cycle of DGMRES.

Parameters

mat	The coefficient matrix
precond	The preconditioner
x	the new approximated solution
r0	The initial residual vector
beta	The norm of the residual computed so far
normRhs	The norm of the right hand side vector
nbIts	The number of iterations