DLASQ4(3)      LAPACK routine of NEC Numeric Library Collection      DLASQ4(3)



NAME
       DLASQ4

SYNOPSIS
       SUBROUTINE DLASQ4 (I0, N0, Z, PP, N0IN, DMIN, DMIN1, DMIN2, DN, DN1,
           DN2, TAU, TTYPE, G)



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




ARGUMENTS
           I0        (input)
                     I0 is INTEGER
                   First index.

           N0        (input)
                     N0 is INTEGER
                   Last index.

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

           PP        (input)
                     PP is INTEGER
                   PP=0 for ping, PP=1 for pong.

           N0IN      (input)
                     N0IN is INTEGER
                   The value of N0 at start of EIGTEST.

           DMIN      (input)
                     DMIN is DOUBLE PRECISION
                   Minimum value of d.

           DMIN1     (input)
                     DMIN1 is DOUBLE PRECISION
                   Minimum value of d, excluding D( N0 ).

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

           DN        (input)
                     DN is DOUBLE PRECISION
                   d(N)

           DN1       (input)
                     DN1 is DOUBLE PRECISION
                   d(N-1)

           DN2       (input)
                     DN2 is DOUBLE PRECISION
                   d(N-2)

           TAU       (output)
                     TAU is DOUBLE PRECISION
                   This is the shift.

           TTYPE     (output)
                     TTYPE is INTEGER
                   Shift type.

           G         (input/output)
                     G is REAL
                   G is passed as an argument in order to save its value between
                   calls to DLASQ4.






FURTHER DETAILS
             CNST1 = 9/16



LAPACK routine                  31 October 2017                      DLASQ4(3)