dlasq3.f File Reference

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Functions/Subroutines
subroutine	dlasq3 (I0, N0, Z, PP, DMIN, SIGMA, DESIG, QMAX, NFAIL, ITER, NDIV, IEEE, TTYPE, DMIN1, DMIN2, DN, DN1, DN2, G, TAU)
	DLASQ3 checks for deflation, computes a shift and calls dqds. Used by sbdsqr.

---

Function/Subroutine Documentation

subroutine dlasq3	(	integer	I0,
		integer	N0,
		double precision, dimension( * )	Z,
		integer	PP,
		double precision	DMIN,
		double precision	SIGMA,
		double precision	DESIG,
		double precision	QMAX,
		integer	NFAIL,
		integer	ITER,
		integer	NDIV,
		logical	IEEE,
		integer	TTYPE,
		double precision	DMIN1,
		double precision	DMIN2,
		double precision	DN,
		double precision	DN1,
		double precision	DN2,
		double precision	G,
		double precision	TAU
	)

DLASQ3 checks for deflation, computes a shift and calls dqds. Used by sbdsqr.

Download DLASQ3 + dependencies [TGZ] [ZIP] [TXT]

Purpose:

 DLASQ3 checks for deflation, computes a shift (TAU) and calls dqds.
 In case of failure it changes shifts, and tries again until output
 is positive.

Parameters:

[in]	I0	I0 is INTEGER First index.
[in,out]	N0	N0 is INTEGER Last index.
[in]	Z	Z is DOUBLE PRECISION array, dimension ( 4*N ) Z holds the qd array.
[in,out]	PP	PP is INTEGER PP=0 for ping, PP=1 for pong. PP=2 indicates that flipping was applied to the Z array and that the initial tests for deflation should not be performed.
[out]	DMIN	DMIN is DOUBLE PRECISION Minimum value of d.
[out]	SIGMA	SIGMA is DOUBLE PRECISION Sum of shifts used in current segment.
[in,out]	DESIG	DESIG is DOUBLE PRECISION Lower order part of SIGMA
[in]	QMAX	QMAX is DOUBLE PRECISION Maximum value of q.
[out]	NFAIL	NFAIL is INTEGER Number of times shift was too big.
[out]	ITER	ITER is INTEGER Number of iterations.
[out]	NDIV	NDIV is INTEGER Number of divisions.
[in]	IEEE	IEEE is LOGICAL Flag for IEEE or non IEEE arithmetic (passed to DLASQ5).
[in,out]	TTYPE	TTYPE is INTEGER Shift type.
[in,out]	DMIN1	DMIN1 is DOUBLE PRECISION
[in,out]	DMIN2	DMIN2 is DOUBLE PRECISION
[in,out]	DN	DN is DOUBLE PRECISION
[in,out]	DN1	DN1 is DOUBLE PRECISION
[in,out]	DN2	DN2 is DOUBLE PRECISION
[in,out]	G	G is DOUBLE PRECISION
[in,out]	TAU	TAU is DOUBLE PRECISION These are passed as arguments in order to save their values between calls to DLASQ3.

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

September 2012

Definition at line 181 of file dlasq3.f.

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