zlaein()

subroutine zlaein	(	logical	rightv,
		logical	noinit,
		integer	n,
		complex*16, dimension( ldh, * )	h,
		integer	ldh,
		complex*16	w,
		complex*16, dimension( * )	v,
		complex*16, dimension( ldb, * )	b,
		integer	ldb,
		double precision, dimension( * )	rwork,
		double precision	eps3,
		double precision	smlnum,
		integer	info )

ZLAEIN computes a specified right or left eigenvector of an upper Hessenberg matrix by inverse iteration.

Download ZLAEIN + dependencies [TGZ] [ZIP] [TXT]

Purpose:

!>
!> ZLAEIN uses inverse iteration to find a right or left eigenvector
!> corresponding to the eigenvalue W of a complex upper Hessenberg
!> matrix H.
!> 

Parameters

[in]	RIGHTV	!> RIGHTV is LOGICAL !> = .TRUE. : compute right eigenvector; !> = .FALSE.: compute left eigenvector. !>
[in]	NOINIT	!> NOINIT is LOGICAL !> = .TRUE. : no initial vector supplied in V !> = .FALSE.: initial vector supplied in V. !>
[in]	N	!> N is INTEGER !> The order of the matrix H. N >= 0. !>
[in]	H	!> H is COMPLEX*16 array, dimension (LDH,N) !> The upper Hessenberg matrix H. !>
[in]	LDH	!> LDH is INTEGER !> The leading dimension of the array H. LDH >= max(1,N). !>
[in]	W	!> W is COMPLEX*16 !> The eigenvalue of H whose corresponding right or left !> eigenvector is to be computed. !>
[in,out]	V	!> V is COMPLEX*16 array, dimension (N) !> On entry, if NOINIT = .FALSE., V must contain a starting !> vector for inverse iteration; otherwise V need not be set. !> On exit, V contains the computed eigenvector, normalized so !> that the component of largest magnitude has magnitude 1; here !> the magnitude of a complex number (x,y) is taken to be !> |x| + |y|. !>
[out]	B	!> B is COMPLEX*16 array, dimension (LDB,N) !>
[in]	LDB	!> LDB is INTEGER !> The leading dimension of the array B. LDB >= max(1,N). !>
[out]	RWORK	!> RWORK is DOUBLE PRECISION array, dimension (N) !>
[in]	EPS3	!> EPS3 is DOUBLE PRECISION !> A small machine-dependent value which is used to perturb !> close eigenvalues, and to replace zero pivots. !>
[in]	SMLNUM	!> SMLNUM is DOUBLE PRECISION !> A machine-dependent value close to the underflow threshold. !>
[out]	INFO	!> INFO is INTEGER !> = 0: successful exit !> = 1: inverse iteration did not converge; V is set to the !> last iterate. !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.