claed0()

subroutine claed0	(	integer	qsiz,
		integer	n,
		real, dimension( * )	d,
		real, dimension( * )	e,
		complex, dimension( ldq, * )	q,
		integer	ldq,
		complex, dimension( ldqs, * )	qstore,
		integer	ldqs,
		real, dimension( * )	rwork,
		integer, dimension( * )	iwork,
		integer	info )

CLAED0 used by CSTEDC. Computes all eigenvalues and corresponding eigenvectors of an unreduced symmetric tridiagonal matrix using the divide and conquer method.

Download CLAED0 + dependencies [TGZ] [ZIP] [TXT]

Purpose:

!>
!> Using the divide and conquer method, CLAED0 computes all eigenvalues
!> of a symmetric tridiagonal matrix which is one diagonal block of
!> those from reducing a dense or band Hermitian matrix and
!> corresponding eigenvectors of the dense or band matrix.
!> 

Parameters

[in]	QSIZ	!> QSIZ is INTEGER !> The dimension of the unitary matrix used to reduce !> the full matrix to tridiagonal form. QSIZ >= N if ICOMPQ = 1. !>
[in]	N	!> N is INTEGER !> The dimension of the symmetric tridiagonal matrix. N >= 0. !>
[in,out]	D	!> D is REAL array, dimension (N) !> On entry, the diagonal elements of the tridiagonal matrix. !> On exit, the eigenvalues in ascending order. !>
[in,out]	E	!> E is REAL array, dimension (N-1) !> On entry, the off-diagonal elements of the tridiagonal matrix. !> On exit, E has been destroyed. !>
[in,out]	Q	!> Q is COMPLEX array, dimension (LDQ,N) !> On entry, Q must contain an QSIZ x N matrix whose columns !> unitarily orthonormal. It is a part of the unitary matrix !> that reduces the full dense Hermitian matrix to a !> (reducible) symmetric tridiagonal matrix. !>
[in]	LDQ	!> LDQ is INTEGER !> The leading dimension of the array Q. LDQ >= max(1,N). !>
[out]	IWORK	!> IWORK is INTEGER array, !> the dimension of IWORK must be at least !> 6 + 6*N + 5*N*lg N !> ( lg( N ) = smallest integer k !> such that 2^k >= N ) !>
[out]	RWORK	!> RWORK is REAL array, !> dimension (1 + 3*N + 2*N*lg N + 3*N**2) !> ( lg( N ) = smallest integer k !> such that 2^k >= N ) !>
[out]	QSTORE	!> QSTORE is COMPLEX array, dimension (LDQS, N) !> Used to store parts of !> the eigenvector matrix when the updating matrix multiplies !> take place. !>
[in]	LDQS	!> LDQS is INTEGER !> The leading dimension of the array QSTORE. !> LDQS >= max(1,N). !>
[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 compute an eigenvalue while !> working on the submatrix lying in rows and columns !> INFO/(N+1) through mod(INFO,N+1). !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.