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claein.f(3) LAPACK claein.f(3)

NAME

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.

Date:

December 2016

Definition at line 151 of file claein.f.

Author

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Tue Nov 14 2017 Version 3.8.0