dlaein.f3

!>
!> DLAEIN uses inverse iteration to find a right or left eigenvector
!> corresponding to the eigenvalue (WR,WI) of a real upper Hessenberg
!> matrix H.
!> 

RIGHTV

!>          RIGHTV is LOGICAL
!>          = .TRUE. : compute right eigenvector;
!>          = .FALSE.: compute left eigenvector.
!> 

NOINIT

!>          NOINIT is LOGICAL
!>          = .TRUE. : no initial vector supplied in (VR,VI).
!>          = .FALSE.: initial vector supplied in (VR,VI).
!> 

N

!>          N is INTEGER
!>          The order of the matrix H.  N >= 0.
!> 

H

!>          H is DOUBLE PRECISION array, dimension (LDH,N)
!>          The upper Hessenberg matrix H.
!> 

LDH

!>          LDH is INTEGER
!>          The leading dimension of the array H.  LDH >= max(1,N).
!> 

WR

!>          WR is DOUBLE PRECISION
!> 

WI

!>          WI is DOUBLE PRECISION
!>          The real and imaginary parts of the eigenvalue of H whose
!>          corresponding right or left eigenvector is to be computed.
!> 

VR

!>          VR is DOUBLE PRECISION array, dimension (N)
!> 

VI

!>          VI is DOUBLE PRECISION array, dimension (N)
!>          On entry, if NOINIT = .FALSE. and WI = 0.0, VR must contain
!>          a real starting vector for inverse iteration using the real
!>          eigenvalue WR; if NOINIT = .FALSE. and WI.ne.0.0, VR and VI
!>          must contain the real and imaginary parts of a complex
!>          starting vector for inverse iteration using the complex
!>          eigenvalue (WR,WI); otherwise VR and VI need not be set.
!>          On exit, if WI = 0.0 (real eigenvalue), VR contains the
!>          computed real eigenvector; if WI.ne.0.0 (complex eigenvalue),
!>          VR and VI contain the real and imaginary parts of the
!>          computed complex eigenvector. The eigenvector is 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|.
!>          VI is not referenced if WI = 0.0.
!> 

B

!>          B is DOUBLE PRECISION array, dimension (LDB,N)
!> 

LDB

!>          LDB is INTEGER
!>          The leading dimension of the array B.  LDB >= N+1.
!> 

WORK

!>          WORK is DOUBLE PRECISION array, dimension (N)
!> 

EPS3

!>          EPS3 is DOUBLE PRECISION
!>          A small machine-dependent value which is used to perturb
!>          close eigenvalues, and to replace zero pivots.
!> 

SMLNUM

!>          SMLNUM is DOUBLE PRECISION
!>          A machine-dependent value close to the underflow threshold.
!> 

BIGNUM

!>          BIGNUM is DOUBLE PRECISION
!>          A machine-dependent value close to the overflow threshold.
!> 

INFO

!>          INFO is INTEGER
!>          = 0:  successful exit
!>          = 1:  inverse iteration did not converge; VR is set to the
!>                last iterate, and so is VI if WI.ne.0.0.
!> 

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.