SRC/claein.f(3) Library Functions Manual SRC/claein.f(3)

SRC/claein.f


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.

Generated automatically by Doxygen for LAPACK from the source code.

Version 3.12.0 LAPACK