 LAPACK  3.4.2 LAPACK: Linear Algebra PACKage
claein.f File Reference

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## Functions/Subroutines

subroutine claein (RIGHTV, NOINIT, N, H, LDH, W, V, B, LDB, RWORK, EPS3, SMLNUM, INFO)
CLAEIN computes a specified right or left eigenvector of an upper Hessenberg matrix by inverse iteration.

## Function/Subroutine Documentation

 subroutine claein ( logical RIGHTV, logical NOINIT, integer N, complex, dimension( ldh, * ) H, integer LDH, complex W, complex, dimension( * ) V, complex, dimension( ldb, * ) B, integer LDB, real, dimension( * ) RWORK, real EPS3, real SMLNUM, integer INFO )

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

Purpose:
``` CLAEIN uses inverse iteration to find a right or left eigenvector
corresponding to the eigenvalue W of a complex upper Hessenberg
matrix H.```
Parameters:
 [in] RIGHTV ``` RIGHTV is LOGICAL = .TRUE. : compute right eigenvector; = .FALSE.: compute left eigenvector.``` [in] NOINIT ``` NOINIT is LOGICAL = .TRUE. : no initial vector supplied in V = .FALSE.: initial vector supplied in V.``` [in] N ``` N is INTEGER The order of the matrix H. N >= 0.``` [in] H ``` H is COMPLEX 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] W ``` W is COMPLEX The eigenvalue of H whose corresponding right or left eigenvector is to be computed.``` [in,out] V ``` V is COMPLEX array, dimension (N) On entry, if NOINIT = .FALSE., V must contain a starting vector for inverse iteration; otherwise V need not be set. On exit, V contains the computed eigenvector, 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|.``` [out] B ` B is COMPLEX array, dimension (LDB,N)` [in] LDB ``` LDB is INTEGER The leading dimension of the array B. LDB >= max(1,N).``` [out] RWORK ` RWORK 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.``` [out] INFO ``` INFO is INTEGER = 0: successful exit = 1: inverse iteration did not converge; V is set to the last iterate.```
Date:
September 2012

Definition at line 149 of file claein.f.

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