slasq3.f File Reference

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Functions/Subroutines
subroutine	slasq3 (I0, N0, Z, PP, DMIN, SIGMA, DESIG, QMAX, NFAIL, ITER, NDIV, IEEE, TTYPE, DMIN1, DMIN2, DN, DN1, DN2, G, TAU)
	SLASQ3 checks for deflation, computes a shift and calls dqds. Used by sbdsqr.

---

Function/Subroutine Documentation

subroutine slasq3	(	integer	I0,
		integer	N0,
		real, dimension( * )	Z,
		integer	PP,
		real	DMIN,
		real	SIGMA,
		real	DESIG,
		real	QMAX,
		integer	NFAIL,
		integer	ITER,
		integer	NDIV,
		logical	IEEE,
		integer	TTYPE,
		real	DMIN1,
		real	DMIN2,
		real	DN,
		real	DN1,
		real	DN2,
		real	G,
		real	TAU
	)

SLASQ3 checks for deflation, computes a shift and calls dqds. Used by sbdsqr.

Download SLASQ3 + dependencies [TGZ] [ZIP] [TXT]

Purpose:

 SLASQ3 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 REAL 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 REAL Minimum value of d.
[out]	SIGMA	SIGMA is REAL Sum of shifts used in current segment.
[in,out]	DESIG	DESIG is REAL Lower order part of SIGMA
[in]	QMAX	QMAX is REAL 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 SLASQ5).
[in,out]	TTYPE	TTYPE is INTEGER Shift type.
[in,out]	DMIN1	DMIN1 is REAL
[in,out]	DMIN2	DMIN2 is REAL
[in,out]	DN	DN is REAL
[in,out]	DN1	DN1 is REAL
[in,out]	DN2	DN2 is REAL
[in,out]	G	G is REAL
[in,out]	TAU	TAU is REAL These are passed as arguments in order to save their values between calls to SLASQ3.

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

September 2012

Definition at line 181 of file slasq3.f.

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