slaein (3)  Linux Manuals
NAME
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.
NOINITNOINIT is LOGICAL = .TRUE. : no initial vector supplied in (VR,VI). = .FALSE.: initial vector supplied in (VR,VI).
NN is INTEGER The order of the matrix H. N >= 0.
HH is REAL array, dimension (LDH,N) The upper Hessenberg matrix H.
LDHLDH is INTEGER The leading dimension of the array H. LDH >= max(1,N).
WRWR is REAL
WIWI is REAL The real and imaginary parts of the eigenvalue of H whose corresponding right or left eigenvector is to be computed.
VRVR is REAL array, dimension (N)
VIVI 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.
BB is REAL array, dimension (LDB,N)
LDBLDB is INTEGER The leading dimension of the array B. LDB >= N+1.
WORKWORK is REAL array, dimension (N)
EPS3EPS3 is REAL A small machinedependent value which is used to perturb close eigenvalues, and to replace zero pivots.
SMLNUMSMLNUM is REAL A machinedependent value close to the underflow threshold.
BIGNUMBIGNUM is REAL A machinedependent value close to the overflow threshold.
INFOINFO 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
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