dlasq6()

subroutine dlasq6	(	integer	I0,
		integer	N0,
		double precision, dimension( * )	Z,
		integer	PP,
		double precision	DMIN,
		double precision	DMIN1,
		double precision	DMIN2,
		double precision	DN,
		double precision	DNM1,
		double precision	DNM2
	)

DLASQ6 computes one dqd transform in ping-pong form. Used by sbdsqr and sstegr.

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Purpose:

 DLASQ6 computes one dqd (shift equal to zero) transform in
 ping-pong form, with protection against underflow and overflow.

Parameters

[in]	I0	I0 is INTEGER First index.
[in]	N0	N0 is INTEGER Last index.
[in]	Z	Z is DOUBLE PRECISION array, dimension ( 4*N ) Z holds the qd array. EMIN is stored in Z(4*N0) to avoid an extra argument.
[in]	PP	PP is INTEGER PP=0 for ping, PP=1 for pong.
[out]	DMIN	DMIN is DOUBLE PRECISION Minimum value of d.
[out]	DMIN1	DMIN1 is DOUBLE PRECISION Minimum value of d, excluding D( N0 ).
[out]	DMIN2	DMIN2 is DOUBLE PRECISION Minimum value of d, excluding D( N0 ) and D( N0-1 ).
[out]	DN	DN is DOUBLE PRECISION d(N0), the last value of d.
[out]	DNM1	DNM1 is DOUBLE PRECISION d(N0-1).
[out]	DNM2	DNM2 is DOUBLE PRECISION d(N0-2).

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.