claein-f(3)

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 (logicalRIGHTV, logicalNOINIT, integerN, complex, dimension( ldh, * )H, integerLDH, complexW, complex, dimension( * )V, complex, dimension( ldb, * )B, integerLDB, real, dimension( * )RWORK, realEPS3, realSMLNUM, integerINFO)

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

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

 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 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:

September 2012

Definition at line 149 of file claein.f.

Author

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