slaein.f man page

slaein.f —

Synopsis

Functions/Subroutines

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

Function/Subroutine Documentation

subroutine slaein (logicalRIGHTV, logicalNOINIT, integerN, real, dimension( ldh, * )H, integerLDH, realWR, realWI, real, dimension( * )VR, real, dimension( * )VI, real, dimension( ldb, * )B, integerLDB, real, dimension( * )WORK, realEPS3, realSMLNUM, realBIGNUM, integerINFO)

SLAEIN computes a specified right or left eigenvector of an upper Hessenberg matrix by inverse iteration.

Purpose:

SLAEIN 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 REAL 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 REAL

WI

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

VR

VR is REAL array, dimension (N)

VI

VI is REAL 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 REAL array, dimension (LDB,N)

LDB

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

WORK

WORK 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.

BIGNUM

BIGNUM is REAL
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

Univ. of Colorado Denver

NAG Ltd.

Date:

September 2012

Definition at line 172 of file slaein.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

slaein(3) is an alias of slaein.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK