1SLASQ3(1)LAPACK routine (version 3.2)                                 SLASQ3(1)
2
3
4

NAME

6       SLASQ3 - checks for deflation, computes a shift (TAU) and calls dqds
7

SYNOPSIS

9       SUBROUTINE SLASQ3( I0,  N0,  Z,  PP,  DMIN,  SIGMA, DESIG, QMAX, NFAIL,
10                          ITER, NDIV, IEEE, TTYPE, DMIN1, DMIN2, DN, DN1, DN2,
11                          G, TAU )
12
13           LOGICAL        IEEE
14
15           INTEGER        I0, ITER, N0, NDIV, NFAIL, PP
16
17           REAL           DESIG,  DMIN,  DMIN1,  DMIN2, DN, DN1, DN2, G, QMAX,
18                          SIGMA, TAU
19
20           REAL           Z( * )
21

PURPOSE

23       SLASQ3 checks for deflation, computes a shift (TAU) and calls dqds.  In
24       case of failure it changes shifts, and tries again until output is pos‐
25       itive.
26

ARGUMENTS

28       I0     (input) INTEGER
29              First index.
30
31       N0     (input) INTEGER
32              Last index.
33
34       Z      (input) REAL array, dimension ( 4*N )
35              Z holds the qd array.
36
37       PP     (input/output) INTEGER
38              PP=0 for ping, PP=1 for pong.  PP=2 indicates that flipping  was
39              applied  to the Z array and that the initial tests for deflation
40              should not be performed.
41
42       DMIN   (output) REAL
43              Minimum value of d.
44
45       SIGMA  (output) REAL
46              Sum of shifts used in current segment.
47
48       DESIG  (input/output) REAL
49              Lower order part of SIGMA
50
51       QMAX   (input) REAL
52              Maximum value of q.
53
54       NFAIL  (output) INTEGER
55              Number of times shift was too big.
56
57       ITER   (output) INTEGER
58              Number of iterations.
59
60       NDIV   (output) INTEGER
61              Number of divisions.
62
63       IEEE   (input) LOGICAL
64              Flag for IEEE or non IEEE arithmetic (passed to SLASQ5).
65
66       TTYPE  (input/output) INTEGER
67              Shift type.  DMIN1, DMIN2, DN, DN1, DN2, G,  TAU  (input/output)
68              REAL These are passed as arguments in order to save their values
69              between calls to SLASQ3.
70
71
72
73 LAPACK routine (version 3.2)    November 2008                       SLASQ3(1)
Impressum