LAPACK 3.12.0
LAPACK: Linear Algebra PACKage
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◆ dlasq6()

subroutine dlasq6 ( integer i0,
integer n0,
double precision, dimension( * ) z,
integer pp,
double precision dmin,
double precision dmin1,
double precision dmin2,
double precision dn,
double precision dnm1,
double precision dnm2 )

DLASQ6 computes one dqd transform in ping-pong form. Used by sbdsqr and sstegr.

Download DLASQ6 + dependencies [TGZ] [ZIP] [TXT]

Purpose:
!>
!> DLASQ6 computes one dqd (shift equal to zero) transform in
!> ping-pong form, with protection against underflow and overflow.
!>
Parameters
[in]I0
!>          I0 is INTEGER
!>        First index.
!>
[in]N0
!>          N0 is INTEGER
!>        Last index.
!>
[in]Z
!>          Z is DOUBLE PRECISION 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.
!>
[out]DMIN
!>          DMIN is DOUBLE PRECISION
!>        Minimum value of d.
!>
[out]DMIN1
!>          DMIN1 is DOUBLE PRECISION
!>        Minimum value of d, excluding D( N0 ).
!>
[out]DMIN2
!>          DMIN2 is DOUBLE PRECISION
!>        Minimum value of d, excluding D( N0 ) and D( N0-1 ).
!>
[out]DN
!>          DN is DOUBLE PRECISION
!>        d(N0), the last value of d.
!>
[out]DNM1
!>          DNM1 is DOUBLE PRECISION
!>        d(N0-1).
!>
[out]DNM2
!>          DNM2 is DOUBLE PRECISION
!>        d(N0-2).
!>
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.