dlasd0()

subroutine dlasd0	(	integer	n,
		integer	sqre,
		double precision, dimension( * )	d,
		double precision, dimension( * )	e,
		double precision, dimension( ldu, * )	u,
		integer	ldu,
		double precision, dimension( ldvt, * )	vt,
		integer	ldvt,
		integer	smlsiz,
		integer, dimension( * )	iwork,
		double precision, dimension( * )	work,
		integer	info )

DLASD0 computes the singular values of a real upper bidiagonal n-by-m matrix B with diagonal d and off-diagonal e. Used by sbdsdc.

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Purpose:

!>
!> Using a divide and conquer approach, DLASD0 computes the singular
!> value decomposition (SVD) of a real upper bidiagonal N-by-M
!> matrix B with diagonal D and offdiagonal E, where M = N + SQRE.
!> The algorithm computes orthogonal matrices U and VT such that
!> B = U * S * VT. The singular values S are overwritten on D.
!>
!> A related subroutine, DLASDA, computes only the singular values,
!> and optionally, the singular vectors in compact form.
!> 

Parameters

[in]	N	!> N is INTEGER !> On entry, the row dimension of the upper bidiagonal matrix. !> This is also the dimension of the main diagonal array D. !>
[in]	SQRE	!> SQRE is INTEGER !> Specifies the column dimension of the bidiagonal matrix. !> = 0: The bidiagonal matrix has column dimension M = N; !> = 1: The bidiagonal matrix has column dimension M = N+1; !>
[in,out]	D	!> D is DOUBLE PRECISION array, dimension (N) !> On entry D contains the main diagonal of the bidiagonal !> matrix. !> On exit D, if INFO = 0, contains its singular values. !>
[in,out]	E	!> E is DOUBLE PRECISION array, dimension (M-1) !> Contains the subdiagonal entries of the bidiagonal matrix. !> On exit, E has been destroyed. !>
[in,out]	U	!> U is DOUBLE PRECISION array, dimension (LDU, N) !> On exit, U contains the left singular vectors, !> if U passed in as (N, N) Identity. !>
[in]	LDU	!> LDU is INTEGER !> On entry, leading dimension of U. !>
[in,out]	VT	!> VT is DOUBLE PRECISION array, dimension (LDVT, M) !> On exit, VT**T contains the right singular vectors, !> if VT passed in as (M, M) Identity. !>
[in]	LDVT	!> LDVT is INTEGER !> On entry, leading dimension of VT. !>
[in]	SMLSIZ	!> SMLSIZ is INTEGER !> On entry, maximum size of the subproblems at the !> bottom of the computation tree. !>
[out]	IWORK	!> IWORK is INTEGER array, dimension (8*N) !>
[out]	WORK	!> WORK is DOUBLE PRECISION array, dimension (3*M**2+2*M) !>
[out]	INFO	!> INFO is INTEGER !> = 0: successful exit. !> < 0: if INFO = -i, the i-th argument had an illegal value. !> > 0: if INFO = 1, a singular value did not converge !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Contributors:

Ming Gu and Huan Ren, Computer Science Division, University of California at Berkeley, USA