sstev()

subroutine sstev	(	character	jobz,
		integer	n,
		real, dimension( * )	d,
		real, dimension( * )	e,
		real, dimension( ldz, * )	z,
		integer	ldz,
		real, dimension( * )	work,
		integer	info )

SSTEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for OTHER matrices

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Purpose:

!>
!> SSTEV computes all eigenvalues and, optionally, eigenvectors of a
!> real symmetric tridiagonal matrix A.
!> 

Parameters

[in]	JOBZ	!> JOBZ is CHARACTER*1 !> = 'N': Compute eigenvalues only; !> = 'V': Compute eigenvalues and eigenvectors. !>
[in]	N	!> N is INTEGER !> The order of the matrix. N >= 0. !>
[in,out]	D	!> D is REAL array, dimension (N) !> On entry, the n diagonal elements of the tridiagonal matrix !> A. !> On exit, if INFO = 0, the eigenvalues in ascending order. !>
[in,out]	E	!> E is REAL array, dimension (N-1) !> On entry, the (n-1) subdiagonal elements of the tridiagonal !> matrix A, stored in elements 1 to N-1 of E. !> On exit, the contents of E are destroyed. !>
[out]	Z	!> Z is REAL 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. !>
[in]	LDZ	!> LDZ is INTEGER !> The leading dimension of the array Z. LDZ >= 1, and if !> JOBZ = 'V', LDZ >= max(1,N). !>
[out]	WORK	!> WORK is REAL array, dimension (max(1,2*N-2)) !> If JOBZ = 'N', WORK is not referenced. !>
[out]	INFO	!> INFO is 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. !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.