redhat man page for dstev

DSTEV(l)								 )								  DSTEV(l)

NAME
       DSTEV - compute all eigenvalues and, optionally, eigenvectors of a real symmetric tridiagonal matrix A

SYNOPSIS
       SUBROUTINE DSTEV( JOBZ, N, D, E, Z, LDZ, WORK, INFO )

	   CHARACTER	 JOBZ

	   INTEGER	 INFO, LDZ, N

	   DOUBLE	 PRECISION D( * ), E( * ), WORK( * ), Z( LDZ, * )

PURPOSE
       DSTEV computes all eigenvalues and, optionally, eigenvectors of a real symmetric tridiagonal matrix A.

ARGUMENTS
       JOBZ    (input) CHARACTER*1
	       = 'N':  Compute eigenvalues only;
	       = 'V':  Compute eigenvalues and eigenvectors.

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

       D       (input/output) DOUBLE PRECISION array, dimension (N)
	       On entry, the n diagonal elements of the tridiagonal matrix A.  On exit, if INFO = 0, the eigenvalues in ascending order.

       E       (input/output) DOUBLE PRECISION array, dimension (N)
	       On  entry,  the (n-1) subdiagonal elements of the tridiagonal matrix A, stored in elements 1 to N-1 of E; E(N) need not be set, but
	       is used by the routine.	On exit, the contents of E are destroyed.

       Z       (output) DOUBLE PRECISION array, dimension (LDZ, N)
	       If JOBZ = 'V', then if INFO = 0, Z contains the orthonormal eigenvectors of the matrix A, with the i-th column  of  Z  holding  the
	       eigenvector associated with D(i).  If JOBZ = 'N', then Z is not referenced.

       LDZ     (input) INTEGER
	       The leading dimension of the array Z.  LDZ >= 1, and if JOBZ = 'V', LDZ >= max(1,N).

       WORK    (workspace) DOUBLE PRECISION array, dimension (max(1,2*N-2))
	       If JOBZ = 'N', WORK is not referenced.

       INFO    (output) INTEGER
	       = 0:  successful exit
	       < 0:  if INFO = -i, the i-th argument had an illegal value
	       > 0:  if INFO = i, the algorithm failed to converge; i off-diagonal elements of E did not converge to zero.

LAPACK version 3.0						   15 June 2000 							  DSTEV(l)