LAPACK  3.4.2
LAPACK: Linear Algebra PACKage
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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.

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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.
Author:
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
September 2012

Definition at line 149 of file claein.f.

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