LAPACK

NAME¶

lasq5 - lasq5: dqds step

SYNOPSIS¶

Functions¶

subroutine dlasq5 (i0, n0, z, pp, tau, sigma, dmin, dmin1, dmin2, dn, dnm1, dnm2, ieee, eps)
DLASQ5 computes one dqds transform in ping-pong form. Used by sbdsqr and sstegr. subroutine slasq5 (i0, n0, z, pp, tau, sigma, dmin, dmin1, dmin2, dn, dnm1, dnm2, ieee, eps)
SLASQ5 computes one dqds transform in ping-pong form. Used by sbdsqr and sstegr.

Detailed Description¶

Function Documentation¶

subroutine dlasq5 (integer i0, integer n0, double precision, dimension( * ) z, integer pp, double precision tau, double precision sigma, double precision dmin, double precision dmin1, double precision dmin2, double precision dn, double precision dnm1, double precision dnm2, logical ieee, double precision eps)¶

DLASQ5 computes one dqds transform in ping-pong form. Used by sbdsqr and sstegr.

Purpose:



 DLASQ5 computes one dqds transform in ping-pong form, one


 version for IEEE machines another for non IEEE machines.

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.

TAU



          TAU is DOUBLE PRECISION


        This is the shift.

SIGMA



          SIGMA is DOUBLE PRECISION


        This is the accumulated shift up to this step.

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).

IEEE



          IEEE is LOGICAL


        Flag for IEEE or non IEEE arithmetic.

EPS



          EPS is DOUBLE PRECISION


        This is the value of epsilon used.

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

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.