dlaein.f File Reference

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Functions/Subroutines
subroutine	dlaein (RIGHTV, NOINIT, N, H, LDH, WR, WI, VR, VI, B, LDB, WORK, EPS3, SMLNUM, BIGNUM, INFO)
	DLAEIN computes a specified right or left eigenvector of an upper Hessenberg matrix by inverse iteration.

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Function/Subroutine Documentation

subroutine dlaein	(	logical	RIGHTV,
		logical	NOINIT,
		integer	N,
		double precision, dimension( ldh, * )	H,
		integer	LDH,
		double precision	WR,
		double precision	WI,
		double precision, dimension( * )	VR,
		double precision, dimension( * )	VI,
		double precision, dimension( ldb, * )	B,
		integer	LDB,
		double precision, dimension( * )	WORK,
		double precision	EPS3,
		double precision	SMLNUM,
		double precision	BIGNUM,
		integer	INFO
	)

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

Download DLAEIN + dependencies [TGZ] [ZIP] [TXT]

Purpose:

 DLAEIN 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 DOUBLE PRECISION 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 DOUBLE PRECISION
[in]	WI	WI is DOUBLE PRECISION 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 DOUBLE PRECISION array, dimension (N)
[in,out]	VI	VI is DOUBLE PRECISION 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 DOUBLE PRECISION array, dimension (LDB,N)
[in]	LDB	LDB is INTEGER The leading dimension of the array B. LDB >= N+1.
[out]	WORK	WORK is DOUBLE PRECISION array, dimension (N)
[in]	EPS3	EPS3 is DOUBLE PRECISION A small machine-dependent value which is used to perturb close eigenvalues, and to replace zero pivots.
[in]	SMLNUM	SMLNUM is DOUBLE PRECISION A machine-dependent value close to the underflow threshold.
[in]	BIGNUM	BIGNUM is DOUBLE PRECISION 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 dlaein.f.

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