redhat man page for zlaein

ZLAEIN(l)								 )								 ZLAEIN(l)

NAME
       ZLAEIN - use inverse iteration to find a right or left eigenvector corresponding to the eigenvalue W of a complex upper Hessenberg matrix H

SYNOPSIS
       SUBROUTINE ZLAEIN( RIGHTV, NOINIT, N, H, LDH, W, V, B, LDB, RWORK, EPS3, SMLNUM, INFO )

	   LOGICAL	  NOINIT, RIGHTV

	   INTEGER	  INFO, LDB, LDH, N

	   DOUBLE	  PRECISION EPS3, SMLNUM

	   COMPLEX*16	  W

	   DOUBLE	  PRECISION RWORK( * )

	   COMPLEX*16	  B( LDB, * ), H( LDH, * ), V( * )

PURPOSE
       ZLAEIN uses inverse iteration to find a right or left eigenvector corresponding to the eigenvalue W of a complex upper Hessenberg matrix H.

ARGUMENTS
       RIGHTV	(input) LOGICAL
		= .TRUE. : compute right eigenvector;
		= .FALSE.: compute left eigenvector.

       NOINIT	(input) LOGICAL
		= .TRUE. : no initial vector supplied in V
		= .FALSE.: initial vector supplied in V.

       N       (input) INTEGER
	       The order of the matrix H.  N >= 0.

       H       (input) COMPLEX*16 array, dimension (LDH,N)
	       The upper Hessenberg matrix H.

       LDH     (input) INTEGER
	       The leading dimension of the array H.  LDH >= max(1,N).

       W       (input) COMPLEX*16
	       The eigenvalue of H whose corresponding right or left eigenvector is to be computed.

       V       (input/output) COMPLEX*16 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|.

       B       (workspace) COMPLEX*16 array, dimension (LDB,N)

       LDB     (input) INTEGER
	       The leading dimension of the array B.  LDB >= max(1,N).

       RWORK   (workspace) DOUBLE PRECISION array, dimension (N)

       EPS3    (input) DOUBLE PRECISION
	       A small machine-dependent value which is used to perturb close eigenvalues, and to replace zero pivots.

       SMLNUM  (input) DOUBLE PRECISION
	       A machine-dependent value close to the underflow threshold.

       INFO    (output) INTEGER
	       = 0:  successful exit
	       = 1:  inverse iteration did not converge; V is set to the last iterate.

LAPACK version 3.0						   15 June 2000 							 ZLAEIN(l)