lasq6(3) LAPACK lasq6(3)

lasq6 - 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.

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 

          I0 is INTEGER
        First index.

N0

          N0 is INTEGER
        Last index.

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.

PP

          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

          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.

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

Purpose:

 SLASQ6 computes one dqd (shift equal to zero) transform in
 ping-pong form, with protection against underflow and overflow.

Parameters

I0 

          I0 is INTEGER
        First index.

N0

          N0 is INTEGER
        Last index.

Z

          Z is REAL array, dimension ( 4*N )
        Z holds the qd array. EMIN is stored in Z(4*N0) to avoid
        an extra argument.

PP

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

DMIN

          DMIN is REAL
        Minimum value of d.

DMIN1

          DMIN1 is REAL
        Minimum value of d, excluding D( N0 ).

DMIN2

          DMIN2 is REAL
        Minimum value of d, excluding D( N0 ) and D( N0-1 ).

DN

          DN is REAL
        d(N0), the last value of d.

DNM1

          DNM1 is REAL
        d(N0-1).

DNM2

          DNM2 is REAL
        d(N0-2).

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

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