slasq4()

subroutine slasq4	(	integer	i0,
		integer	n0,
		real, dimension( * )	z,
		integer	pp,
		integer	n0in,
		real	dmin,
		real	dmin1,
		real	dmin2,
		real	dn,
		real	dn1,
		real	dn2,
		real	tau,
		integer	ttype,
		real	g
	)

SLASQ4 computes an approximation to the smallest eigenvalue using values of d from the previous transform. Used by sbdsqr.

Download SLASQ4 + dependencies [TGZ] [ZIP] [TXT]

Purpose:

 SLASQ4 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 REAL 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 REAL Minimum value of d.
[in]	DMIN1	DMIN1 is REAL Minimum value of d, excluding D( N0 ).
[in]	DMIN2	DMIN2 is REAL Minimum value of d, excluding D( N0 ) and D( N0-1 ).
[in]	DN	DN is REAL d(N)
[in]	DN1	DN1 is REAL d(N-1)
[in]	DN2	DN2 is REAL d(N-2)
[out]	TAU	TAU is REAL This is the shift.
[out]	TTYPE	TTYPE is INTEGER Shift type.
[in,out]	G	G is REAL G is passed as an argument in order to save its value between calls to SLASQ4.

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Further Details:

  CNST1 = 9/16