1DLASQ3(1)LAPACK routine (version 3.2)                                 DLASQ3(1)
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NAME

6       DLASQ3 - checks for deflation, computes a shift (TAU) and calls dqds
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SYNOPSIS

9       SUBROUTINE DLASQ3( I0,  N0,  Z,  PP,  DMIN,  SIGMA, DESIG, QMAX, NFAIL,
10                          ITER, NDIV, IEEE, TTYPE, DMIN1, DMIN2, DN, DN1, DN2,
11                          G, TAU )
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13           LOGICAL        IEEE
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15           INTEGER        I0, ITER, N0, NDIV, NFAIL, PP
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17           DOUBLE         PRECISION  DESIG,  DMIN, DMIN1, DMIN2, DN, DN1, DN2,
18                          G, QMAX, SIGMA, TAU
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20           DOUBLE         PRECISION Z( * )
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PURPOSE

23       DLASQ3 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.
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ARGUMENTS

28       I0     (input) INTEGER
29              First index.
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31       N0     (input) INTEGER
32              Last index.
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34       Z      (input) DOUBLE PRECISION array, dimension ( 4*N )
35              Z holds the qd array.
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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.
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42       DMIN   (output) DOUBLE PRECISION
43              Minimum value of d.
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45       SIGMA  (output) DOUBLE PRECISION
46              Sum of shifts used in current segment.
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48       DESIG  (input/output) DOUBLE PRECISION
49              Lower order part of SIGMA
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51       QMAX   (input) DOUBLE PRECISION
52              Maximum value of q.
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54       NFAIL  (output) INTEGER
55              Number of times shift was too big.
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57       ITER   (output) INTEGER
58              Number of iterations.
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60       NDIV   (output) INTEGER
61              Number of divisions.
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63       IEEE   (input) LOGICAL
64              Flag for IEEE or non IEEE arithmetic (passed to DLASQ5).
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66       TTYPE  (input/output) INTEGER
67              Shift type.  DMIN1, DMIN2, DN, DN1, DN2, G,  TAU  (input/output)
68              DOUBLE  PRECISION These are passed as arguments in order to save
69              their values between calls to DLASQ3.
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73 LAPACK routine (version 3.2)    November 2008                       DLASQ3(1)
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