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LAPACK version 3.0
dlasq4(3)

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

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

      INTEGER	     I0, N0, N0IN, PP, TTYPE

      DOUBLE	     PRECISION DMIN, DMIN1, DMIN2, DN, DN1, DN2, TAU

      DOUBLE	     PRECISION Z( * )

DESCRIPTION
  DLASQ4 computes an approximation TAU to the smallest eigenvalue using
  values of d from the previous transform.  I0	  (input) INTEGER
	First index.

  N0	(input) INTEGER
	Last index.

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

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

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

  DMIN	(input) DOUBLE PRECISION
	Minimum value of d.

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

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

  DN	(input) DOUBLE PRECISION
	d(N)

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

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

  TAU	(output) DOUBLE PRECISION
	This is the shift.

  TTYPE (output) INTEGER
	Shift type.

FURTHER DETAILS