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LAPACK 3.12.0
LAPACK: Linear Algebra PACKage
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LAPACK 3.12.0
LAPACK: Linear Algebra PACKage
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| subroutine slaein | ( | logical | rightv, |
| logical | noinit, | ||
| integer | n, | ||
| real, dimension( ldh, * ) | h, | ||
| integer | ldh, | ||
| real | wr, | ||
| real | wi, | ||
| real, dimension( * ) | vr, | ||
| real, dimension( * ) | vi, | ||
| real, dimension( ldb, * ) | b, | ||
| integer | ldb, | ||
| real, dimension( * ) | work, | ||
| real | eps3, | ||
| real | smlnum, | ||
| real | bignum, | ||
| integer | info | ||
| ) |
SLAEIN computes a specified right or left eigenvector of an upper Hessenberg matrix by inverse iteration.
Download SLAEIN + dependencies [TGZ] [ZIP] [TXT]
SLAEIN uses inverse iteration to find a right or left eigenvector corresponding to the eigenvalue (WR,WI) of a real upper Hessenberg matrix H.
| [in] | RIGHTV | RIGHTV is LOGICAL
= .TRUE. : compute right eigenvector;
= .FALSE.: compute left eigenvector. |
| [in] | NOINIT | NOINIT is LOGICAL
= .TRUE. : no initial vector supplied in (VR,VI).
= .FALSE.: initial vector supplied in (VR,VI). |
| [in] | N | N is INTEGER
The order of the matrix H. N >= 0. |
| [in] | H | H is REAL array, dimension (LDH,N)
The upper Hessenberg matrix H. |
| [in] | LDH | LDH is INTEGER
The leading dimension of the array H. LDH >= max(1,N). |
| [in] | WR | WR is REAL |
| [in] | WI | WI is REAL
The real and imaginary parts of the eigenvalue of H whose
corresponding right or left eigenvector is to be computed. |
| [in,out] | VR | VR is REAL array, dimension (N) |
| [in,out] | 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. |
| [out] | B | B is REAL array, dimension (LDB,N) |
| [in] | LDB | LDB is INTEGER
The leading dimension of the array B. LDB >= N+1. |
| [out] | WORK | WORK is REAL array, dimension (N) |
| [in] | EPS3 | EPS3 is REAL
A small machine-dependent value which is used to perturb
close eigenvalues, and to replace zero pivots. |
| [in] | SMLNUM | SMLNUM is REAL
A machine-dependent value close to the underflow threshold. |
| [in] | BIGNUM | BIGNUM is REAL
A machine-dependent value close to the overflow threshold. |
| [out] | 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. |
1.9.8