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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