lasq6 - Man Page

lasq6: dqds step

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.

Definition at line 117 of file dlasq6.f.

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.