NAME

       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*N )
                   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 REAL
                   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.

       Date:
           September 2012

       Further Details:

             CNST1 = 9/16

Author

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