SLASQ4(3)      LAPACK routine of NEC Numeric Library Collection      SLASQ4(3)



NAME
       SLASQ4

SYNOPSIS
       SUBROUTINE SLASQ4 (I0, N0, Z, PP, N0IN, DMIN, DMIN1, DMIN2, DN, DN1,
           DN2, TAU, TTYPE, G)



PURPOSE
            SLASQ4 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 REAL 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 REAL
                   Minimum value of d.

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

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

           DN        (input)
                     DN is REAL
                   d(N)

           DN1       (input)
                     DN1 is REAL
                   d(N-1)

           DN2       (input)
                     DN2 is REAL
                   d(N-2)

           TAU       (output)
                     TAU is REAL
                   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 SLASQ4.






FURTHER DETAILS
             CNST1 = 9/16



LAPACK routine                  31 October 2017                      SLASQ4(3)