dsterf()

subroutine dsterf	(	integer	n,
		double precision, dimension( * )	d,
		double precision, dimension( * )	e,
		integer	info )

DSTERF

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Purpose:

!>
!> DSTERF computes all eigenvalues of a symmetric tridiagonal matrix
!> using the Pal-Walker-Kahan variant of the QL or QR algorithm.
!> 

Parameters

[in]	N	!> N is INTEGER !> The order of the matrix. N >= 0. !>
[in,out]	D	!> D is DOUBLE PRECISION array, dimension (N) !> On entry, the n diagonal elements of the tridiagonal matrix. !> On exit, if INFO = 0, the eigenvalues in ascending order. !>
[in,out]	E	!> E is DOUBLE PRECISION array, dimension (N-1) !> On entry, the (n-1) subdiagonal elements of the tridiagonal !> matrix. !> On exit, E has been destroyed. !>
[out]	INFO	!> INFO is INTEGER !> = 0: successful exit !> < 0: if INFO = -i, the i-th argument had an illegal value !> > 0: the algorithm failed to find all of the eigenvalues in !> a total of 30*N iterations; if INFO = i, then i !> elements of E have not converged to zero. !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.