LAPACK  3.4.0
LAPACK: Linear Algebra PACKage
Functions/Subroutines
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

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

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:
November 2011

Definition at line 181 of file dlasq3.f.

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