LAPACK  3.7.0
LAPACK: Linear Algebra PACKage

§ slasq5()

subroutine slasq5 ( integer  I0,
integer  N0,
real, dimension( * )  Z,
integer  PP,
real  TAU,
real  SIGMA,
real  DMIN,
real  DMIN1,
real  DMIN2,
real  DN,
real  DNM1,
real  DNM2,
logical  IEEE,
real  EPS 
)

SLASQ5 computes one dqds transform in ping-pong form. Used by sbdsqr and sstegr.

Download SLASQ5 + dependencies [TGZ] [ZIP] [TXT]

Purpose:
 SLASQ5 computes one dqds transform in ping-pong form, one
 version for IEEE machines another for non IEEE machines.
Parameters
[in]I0
          I0 is INTEGER
        First index.
[in]N0
          N0 is INTEGER
        Last index.
[in]Z
          Z is REAL array, dimension ( 4*N )
        Z holds the qd array. EMIN is stored in Z(4*N0) to avoid
        an extra argument.
[in]PP
          PP is INTEGER
        PP=0 for ping, PP=1 for pong.
[in]TAU
          TAU is REAL
        This is the shift.
[in]SIGMA
          SIGMA is REAL
        This is the accumulated shift up to this step.
[out]DMIN
          DMIN is REAL
        Minimum value of d.
[out]DMIN1
          DMIN1 is REAL
        Minimum value of d, excluding D( N0 ).
[out]DMIN2
          DMIN2 is REAL
        Minimum value of d, excluding D( N0 ) and D( N0-1 ).
[out]DN
          DN is REAL
        d(N0), the last value of d.
[out]DNM1
          DNM1 is REAL
        d(N0-1).
[out]DNM2
          DNM2 is REAL
        d(N0-2).
[in]IEEE
          IEEE is LOGICAL
        Flag for IEEE or non IEEE arithmetic.
[in]EPS
         EPS is REAL
        This is the value of epsilon used.
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date
December 2016