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.