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# CentOS 7.0 - man page for dlaein (centos section 3)

```dlaein.f(3)						LAPACK						  dlaein.f(3)

NAME
dlaein.f -

SYNOPSIS
Functions/Subroutines
subroutine dlaein (RIGHTV, NOINIT, N, H, LDH, WR, WI, VR, VI, B, LDB, WORK, EPS3, SMLNUM, BIGNUM, INFO)
DLAEIN computes a specified right or left eigenvector of an upper Hessenberg matrix by inverse iteration.

Function/Subroutine Documentation
subroutine dlaein (logicalRIGHTV, logicalNOINIT, integerN, double precision, dimension( ldh, * )H, integerLDH,
double precisionWR, double precisionWI, double precision, dimension( * )VR, double precision, dimension( *
)VI, double precision, dimension( ldb, * )B, integerLDB, double precision, dimension( * )WORK, double
precisionEPS3, double precisionSMLNUM, double precisionBIGNUM, integerINFO)
DLAEIN computes a specified right or left eigenvector of an upper Hessenberg matrix by inverse iteration.

Purpose:

DLAEIN uses inverse iteration to find a right or left eigenvector
corresponding to the eigenvalue (WR,WI) of a real 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 (VR,VI).
= .FALSE.: initial vector supplied in (VR,VI).

N

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

H

H is DOUBLE PRECISION array, dimension (LDH,N)
The upper Hessenberg matrix H.

LDH

LDH is INTEGER
The leading dimension of the array H.  LDH >= max(1,N).

WR

WR is DOUBLE PRECISION

WI

WI is DOUBLE PRECISION
The real and imaginary parts of the eigenvalue of H whose
corresponding right or left eigenvector is to be computed.

VR

VR is DOUBLE PRECISION array, dimension (N)

VI

VI is DOUBLE PRECISION array, dimension (N)
On entry, if NOINIT = .FALSE. and WI = 0.0, VR must contain
a real starting vector for inverse iteration using the real
eigenvalue WR; if NOINIT = .FALSE. and WI.ne.0.0, VR and VI
must contain the real and imaginary parts of a complex
starting vector for inverse iteration using the complex
eigenvalue (WR,WI); otherwise VR and VI need not be set.
On exit, if WI = 0.0 (real eigenvalue), VR contains the
computed real eigenvector; if WI.ne.0.0 (complex eigenvalue),
VR and VI contain the real and imaginary parts of the
computed complex eigenvector. The eigenvector is 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|.
VI is not referenced if WI = 0.0.

B

B is DOUBLE PRECISION array, dimension (LDB,N)

LDB

LDB is INTEGER
The leading dimension of the array B.  LDB >= N+1.

WORK

WORK is DOUBLE PRECISION array, dimension (N)

EPS3

EPS3 is DOUBLE PRECISION
A small machine-dependent value which is used to perturb
close eigenvalues, and to replace zero pivots.

SMLNUM

SMLNUM is DOUBLE PRECISION
A machine-dependent value close to the underflow threshold.

BIGNUM

BIGNUM is DOUBLE PRECISION
A machine-dependent value close to the overflow threshold.

INFO

INFO is INTEGER
= 0:  successful exit
= 1:  inverse iteration did not converge; VR is set to the
last iterate, and so is VI if WI.ne.0.0.

Author:
Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Date:
September 2012

Definition at line 172 of file dlaein.f.

Author
Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2					   Tue Sep 25 2012					  dlaein.f(3)```

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