LAPACK 3.12.0
LAPACK: Linear Algebra PACKage
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◆ claein()

subroutine claein ( logical rightv,
logical noinit,
integer n,
complex, dimension( ldh, * ) h,
integer ldh,
complex w,
complex, dimension( * ) v,
complex, dimension( ldb, * ) b,
integer ldb,
real, dimension( * ) rwork,
real eps3,
real smlnum,
integer info )

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

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

Purpose:
!>
!> CLAEIN 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 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
!>          The eigenvalue of H whose corresponding right or left
!>          eigenvector is to be computed.
!>
[in,out]V
!>          V is COMPLEX 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 array, dimension (LDB,N)
!>
[in]LDB
!>          LDB is INTEGER
!>          The leading dimension of the array B.  LDB >= max(1,N).
!>
[out]RWORK
!>          RWORK is REAL array, dimension (N)
!>
[in]EPS3
!>          EPS3 is REAL
!>          A small machine-dependent value which is used to perturb
!>          close eigenvalues, and to replace zero pivots.
!>
[in]SMLNUM
!>          SMLNUM is REAL
!>          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.