dspev()

subroutine dspev	(	character	jobz,
		character	uplo,
		integer	n,
		double precision, dimension( * )	ap,
		double precision, dimension( * )	w,
		double precision, dimension( ldz, * )	z,
		integer	ldz,
		double precision, dimension( * )	work,
		integer	info )

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

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Purpose:

!>
!> DSPEV computes all the eigenvalues and, optionally, eigenvectors of a
!> real symmetric matrix A in packed storage.
!> 

Parameters

[in]	JOBZ	!> JOBZ is CHARACTER*1 !> = 'N': Compute eigenvalues only; !> = 'V': Compute eigenvalues and eigenvectors. !>
[in]	UPLO	!> UPLO is CHARACTER*1 !> = 'U': Upper triangle of A is stored; !> = 'L': Lower triangle of A is stored. !>
[in]	N	!> N is INTEGER !> The order of the matrix A. N >= 0. !>
[in,out]	AP	!> AP is DOUBLE PRECISION array, dimension (N*(N+1)/2) !> On entry, the upper or lower triangle of the symmetric matrix !> A, packed columnwise in a linear array. The j-th column of A !> is stored in the array AP as follows: !> if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j; !> if UPLO = 'L', AP(i + (j-1)*(2*n-j)/2) = A(i,j) for j<=i<=n. !> !> On exit, AP is overwritten by values generated during the !> reduction to tridiagonal form. If UPLO = 'U', the diagonal !> and first superdiagonal of the tridiagonal matrix T overwrite !> the corresponding elements of A, and if UPLO = 'L', the !> diagonal and first subdiagonal of T overwrite the !> corresponding elements of A. !>
[out]	W	!> W is DOUBLE PRECISION array, dimension (N) !> If INFO = 0, the eigenvalues in ascending order. !>
[out]	Z	!> Z is 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 W(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 DOUBLE PRECISION array, dimension (3*N) !>
[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 an intermediate tridiagonal !> form did not converge to zero. !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.