SRC/claein.f(3)

NAME
SRC/claein.f

SYNOPSIS

  Functions/Subroutines
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.

Function/Subroutine Documentation

  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.

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.

Author

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