SLAEIN
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.
corresponding to the eigenvalue (WR,WI) of a real upper Hessenberg
matrix H.
Arguments
| RIGHTV |
(input) LOGICAL
= .TRUE. : compute right eigenvector;
= .FALSE.: compute left eigenvector. |
| NOINIT |
(input) LOGICAL
= .TRUE. : no initial vector supplied in (VR,VI).
= .FALSE.: initial vector supplied in (VR,VI). |
| N |
(input) INTEGER
The order of the matrix H. N >= 0.
|
| H |
(input) REAL array, dimension (LDH,N)
The upper Hessenberg matrix H.
|
| LDH |
(input) INTEGER
The leading dimension of the array H. LDH >= max(1,N).
|
| WR |
(input) REAL
|
| WI |
(input) REAL
The real and imaginary parts of the eigenvalue of H whose
corresponding right or left eigenvector is to be computed. |
| VR |
(input/output) REAL array, dimension (N)
|
| VI |
(input/output) 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 |
(workspace) REAL array, dimension (LDB,N)
|
| LDB |
(input) INTEGER
The leading dimension of the array B. LDB >= N+1.
|
| WORK |
(workspace) REAL array, dimension (N)
|
| EPS3 |
(input) REAL
A small machine-dependent value which is used to perturb
close eigenvalues, and to replace zero pivots. |
| SMLNUM |
(input) REAL
A machine-dependent value close to the underflow threshold.
|
| BIGNUM |
(input) REAL
A machine-dependent value close to the overflow threshold.
|
| INFO |
(output) 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. |