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LAPACK version 3.0
dlaed5(3)

PURPOSE
  DLAED5 - subroutine computes the I-th eigenvalue of a symmetric rank-one
  modification of a 2-by-2 diagonal matrix  diag( D ) + RHO * Z *
  transpose(Z)

SYNTAX
  SUBROUTINE DLAED5( I, D, Z, DELTA, RHO, DLAM )

      INTEGER	     I

      DOUBLE	     PRECISION DLAM, RHO

      DOUBLE	     PRECISION D( 2 ), DELTA( 2 ), Z( 2 )

DESCRIPTION
  This subroutine computes the I-th eigenvalue of a symmetric rank-one
  modification of a 2-by-2 diagonal matrix diag( D ) + RHO * Z * transpose(Z)
  .  The diagonal elements in the array D are assumed to satisfy

	     D(i) < D(j)  for  i < j .

  We also assume RHO > 0 and that the Euclidean norm of the vector Z is one.

ARGUMENTS
  I	 (input) INTEGER
	 The index of the eigenvalue to be computed.  I = 1 or I = 2.

  D	 (input) DOUBLE PRECISION array, dimension (2)
	 The original eigenvalues.  We assume D(1) < D(2).

  Z	 (input) DOUBLE PRECISION array, dimension (2)
	 The components of the updating vector.

  DELTA	 (output) DOUBLE PRECISION array, dimension (2)
	 The vector DELTA contains the information necessary to construct the
	 eigenvectors.

  RHO	 (input) DOUBLE PRECISION
	 The scalar in the symmetric updating formula.

  DLAM	 (output) DOUBLE PRECISION
	 The computed lambda_I, the I-th updated eigenvalue.

FURTHER DETAILS
  Based on contributions by
     Ren-Cang Li, Computer Science Division, University of California
     at Berkeley, USA