dlasq4()

subroutine dlasq4	(	integer	i0,
		integer	n0,
		double precision, dimension( * )	z,
		integer	pp,
		integer	n0in,
		double precision	dmin,
		double precision	dmin1,
		double precision	dmin2,
		double precision	dn,
		double precision	dn1,
		double precision	dn2,
		double precision	tau,
		integer	ttype,
		double precision	g )

DLASQ4 computes an approximation to the smallest eigenvalue using values of d from the previous transform. Used by sbdsqr.

Download DLASQ4 + dependencies [TGZ] [ZIP] [TXT]

Purpose:

!>
!> DLASQ4 computes an approximation TAU to the smallest eigenvalue
!> using values of d from the previous transform.
!> 

Parameters

[in]	I0	!> I0 is INTEGER !> First index. !>
[in]	N0	!> N0 is INTEGER !> Last index. !>
[in]	Z	!> Z is DOUBLE PRECISION array, dimension ( 4*N0 ) !> Z holds the qd array. !>
[in]	PP	!> PP is INTEGER !> PP=0 for ping, PP=1 for pong. !>
[in]	N0IN	!> N0IN is INTEGER !> The value of N0 at start of EIGTEST. !>
[in]	DMIN	!> DMIN is DOUBLE PRECISION !> Minimum value of d. !>
[in]	DMIN1	!> DMIN1 is DOUBLE PRECISION !> Minimum value of d, excluding D( N0 ). !>
[in]	DMIN2	!> DMIN2 is DOUBLE PRECISION !> Minimum value of d, excluding D( N0 ) and D( N0-1 ). !>
[in]	DN	!> DN is DOUBLE PRECISION !> d(N) !>
[in]	DN1	!> DN1 is DOUBLE PRECISION !> d(N-1) !>
[in]	DN2	!> DN2 is DOUBLE PRECISION !> d(N-2) !>
[out]	TAU	!> TAU is DOUBLE PRECISION !> This is the shift. !>
[out]	TTYPE	!> TTYPE is INTEGER !> Shift type. !>
[in,out]	G	!> G is DOUBLE PRECISION !> G is passed as an argument in order to save its value between !> calls to DLASQ4. !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Further Details:

!>
!>  CNST1 = 9/16
!>