claein.f - Man Page

subroutine claein (rightv, noinit, n, h, ldh, w, v, b, ldb, rwork, eps3, smlnum, info)
CLAEIN computes a specified right or left eigenvector of an upper Hessenberg matrix by inverse iteration.

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

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

RIGHTV

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

NOINIT

          NOINIT is LOGICAL
          = .TRUE. : no initial vector supplied in V
          = .FALSE.: initial vector supplied in V.

N

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

H

          H is COMPLEX array, dimension (LDH,N)
          The upper Hessenberg matrix H.

LDH

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

W

          W is COMPLEX
          The eigenvalue of H whose corresponding right or left
          eigenvector is to be computed.

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|.

B

          B is COMPLEX array, dimension (LDB,N)

LDB

          LDB is INTEGER
          The leading dimension of the array B.  LDB >= max(1,N).

RWORK

          RWORK is REAL array, dimension (N)

EPS3

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

SMLNUM

          SMLNUM is REAL
          A machine-dependent value close to the underflow threshold.

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.

Definition at line 147 of file claein.f.