LAPACK

NAME¶

lasq6 - lasq6: dqds step

SYNOPSIS¶

Functions¶

subroutine dlasq6 (i0, n0, z, pp, dmin, dmin1, dmin2, dn, dnm1, dnm2)
DLASQ6 computes one dqd transform in ping-pong form. Used by sbdsqr and sstegr. subroutine slasq6 (i0, n0, z, pp, dmin, dmin1, dmin2, dn, dnm1, dnm2)
SLASQ6 computes one dqd transform in ping-pong form. Used by sbdsqr and sstegr.

Detailed Description¶

Function Documentation¶

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.

Purpose:

!>
!> DLASQ6 computes one dqd (shift equal to zero) transform in
!> ping-pong form, with protection against underflow and overflow.
!>

Parameters

!>          I0 is INTEGER
!>        First index.
!>

!>          N0 is INTEGER
!>        Last index.
!>

!>          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.
!>

!>          PP is INTEGER
!>        PP=0 for ping, PP=1 for pong.
!>

DMIN

!>          DMIN is DOUBLE PRECISION
!>        Minimum value of d.
!>

DMIN1

!>          DMIN1 is DOUBLE PRECISION
!>        Minimum value of d, excluding D( N0 ).
!>

DMIN2

!>          DMIN2 is DOUBLE PRECISION
!>        Minimum value of d, excluding D( N0 ) and D( N0-1 ).
!>

!>          DN is DOUBLE PRECISION
!>        d(N0), the last value of d.
!>

DNM1

!>          DNM1 is DOUBLE PRECISION
!>        d(N0-1).
!>

DNM2

!>          DNM2 is DOUBLE PRECISION
!>        d(N0-2).
!>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

subroutine slasq6 (integer i0, integer n0, real, dimension( * ) z, integer pp, real dmin, real dmin1, real dmin2, real dn, real dnm1, real dnm2)¶

SLASQ6 computes one dqd transform in ping-pong form. Used by sbdsqr and sstegr.