SRC/dlasq4.f(3)

NAME
SRC/dlasq4.f

SYNOPSIS

  Functions/Subroutines
subroutine dlasq4 (i0, n0, z, pp, n0in, dmin, dmin1, dmin2, dn, dn1, dn2, tau, ttype, g)
DLASQ4 computes an approximation to the smallest eigenvalue using values of d from the previous transform. Used by sbdsqr.

Function/Subroutine Documentation

  subroutine dlasq4 (integer i0, integer n0, double precision, dimension( * ) z, integer pp, integer n0in, double precision dmin, double precision dmin1, double precision dmin2, double precision dn, double precision dn1, double precision dn2, double precision tau, integer ttype, double precision g)

DLASQ4 computes an approximation to the smallest eigenvalue using values of d from the previous transform. Used by sbdsqr.

Purpose:

     DLASQ4 computes an approximation TAU to the smallest eigenvalue
     using values of d from the previous transform.

Parameters
    I0

              I0 is INTEGER
            First index.

    N0

              N0 is INTEGER
            Last index.

    Z

              Z is DOUBLE PRECISION array, dimension ( 4*N0 )
            Z holds the qd array.

    PP

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

    N0IN

              N0IN is INTEGER
            The value of N0 at start of EIGTEST.

    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(N)

    DN1

              DN1 is DOUBLE PRECISION
            d(N-1)

    DN2

              DN2 is DOUBLE PRECISION
            d(N-2)

    TAU

              TAU is DOUBLE PRECISION
            This is the shift.

    TTYPE

              TTYPE is INTEGER
            Shift type.

    G

              G is DOUBLE PRECISION
            G is passed as an argument in order to save its value between
            calls to DLASQ4.

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Further Details:

      CNST1 = 9/16

Definition at line 149 of file dlasq4.f.

Author

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