HessenbergDecomposition< _MatrixType > Class Template Reference [QR module]

Reduces a squared matrix to an Hessemberg form. More...

List of all members.

Public Types
enum	{   Size,   SizeMinusOne }
typedef Matrix< Scalar, SizeMinusOne, 1 >	CoeffVectorType
typedef NestByValue < DiagonalCoeffs< MatrixType > >::RealReturnType	DiagonalReturnType
typedef Matrix< RealScalar, Size, 1 >	DiagonalType
typedef _MatrixType	MatrixType
typedef NumTraits< Scalar >::Real	RealScalar
typedef MatrixType::Scalar	Scalar
typedef NestByValue < DiagonalCoeffs< NestByValue < Block< MatrixType, SizeMinusOne, SizeMinusOne > > > >::RealReturnType	SubDiagonalReturnType
typedef Matrix< RealScalar, SizeMinusOne, 1 >	SubDiagonalType
Public Member Functions
void	compute (const MatrixType &matrix)
	HessenbergDecomposition (const MatrixType &matrix)
	HessenbergDecomposition (int size=Size==Dynamic?2:Size)
CoeffVectorType	householderCoefficients (void) const
MatrixType	matrixH (void) const
MatrixType	matrixQ (void) const
const MatrixType &	packedMatrix (void) const
Protected Attributes
CoeffVectorType	m_hCoeffs
MatrixType	m_matrix

---

Detailed Description

template<typename _MatrixType>
class Eigen::HessenbergDecomposition< _MatrixType >

Reduces a squared matrix to an Hessemberg form.

Warning:

This is not considered to be part of the stable public API yet. Changes may happen in future releases. See Experimental parts of Eigen

Parameters:

MatrixType

the type of the matrix of which we are computing the Hessenberg decomposition

This class performs an Hessenberg decomposition of a matrix such that: where is unitary and a Hessenberg matrix.

See also:

class Tridiagonalization, class Qr

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Constructor & Destructor Documentation

HessenbergDecomposition

(

int

size = Size==Dynamic ? 2 : Size

)

[inline]

This constructor initializes a HessenbergDecomposition object for further use with HessenbergDecomposition::compute()

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Member Function Documentation

void compute

(

const MatrixType &

matrix

)

[inline]

Computes or re-compute the Hessenberg decomposition for the matrix matrix.

This method allows to re-use the allocated data.

CoeffVectorType householderCoefficients

(

void

)

const [inline]

Returns:

the householder coefficients allowing to reconstruct the matrix Q from the packed data.

See also:

packedMatrix()

HessenbergDecomposition< MatrixType >::MatrixType matrixH

(

void

)

const

constructs and returns the matrix H. Note that the matrix H is equivalent to the upper part of the packed matrix (including the lower sub-diagonal). Therefore, it might be often sufficient to directly use the packed matrix instead of creating a new one.

HessenbergDecomposition< MatrixType >::MatrixType matrixQ

(

void

)

const

reconstructs and returns the matrix Q

const MatrixType& packedMatrix

(

void

)

const [inline]

Returns:

the internal result of the decomposition.

The returned matrix contains the following information:

• the upper part and lower sub-diagonal represent the Hessenberg matrix H
• the rest of the lower part contains the Householder vectors that, combined with Householder coefficients returned by householderCoefficients(), allows to reconstruct the matrix Q as follow: Q = H_{N-1} ... H_1 H_0 where the matrices H are the Householder transformation: H_i = (I - h_i * v_i * v_i') where h_i == householderCoefficients()[i] and v_i is a Householder vector: v_i = [ 0, ..., 0, 1, M(i+2,i), ..., M(N-1,i) ]

See LAPACK for further details on this packed storage.

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