1DLASQ3(1)           LAPACK auxiliary routine (version 3.1)           DLASQ3(1)
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NAME

6       DLASQ3 - 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 )
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12           LOGICAL        IEEE
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14           INTEGER        I0, ITER, N0, NDIV, NFAIL, PP
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16           DOUBLE         PRECISION DESIG, DMIN, QMAX, SIGMA
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18           DOUBLE         PRECISION Z( * )
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PURPOSE

21       DLASQ3 checks for deflation, computes a shift (TAU) and calls dqds.  In
22       case of failure it changes shifts, and tries again until output is pos‐
23       itive.
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ARGUMENTS

27       I0     (input) INTEGER
28              First index.
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30       N0     (input) INTEGER
31              Last index.
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33       Z      (input) DOUBLE PRECISION array, dimension ( 4*N )
34              Z holds the qd array.
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36       PP     (input) INTEGER
37              PP=0 for ping, PP=1 for pong.
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39       DMIN   (output) DOUBLE PRECISION
40              Minimum value of d.
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42       SIGMA  (output) DOUBLE PRECISION
43              Sum of shifts used in current segment.
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45       DESIG  (input/output) DOUBLE PRECISION
46              Lower order part of SIGMA
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48       QMAX   (input) DOUBLE PRECISION
49              Maximum value of q.
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51       NFAIL  (output) INTEGER
52              Number of times shift was too big.
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54       ITER   (output) INTEGER
55              Number of iterations.
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57       NDIV   (output) INTEGER
58              Number of divisions.
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60       TTYPE  (output) INTEGER
61              Shift type.
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63       IEEE   (input) LOGICAL
64              Flag for IEEE or non IEEE arithmetic (passed to DLASQ5).
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68 LAPACK auxiliary routine (versionNo3v.e1m)ber 2006                       DLASQ3(1)