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

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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 ( 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]
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:
[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.
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.

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