DLAED5(3)      LAPACK routine of NEC Numeric Library Collection      DLAED5(3)



NAME
       DLAED5

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



PURPOSE
            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)
                     I is INTEGER
                    The index of the eigenvalue to be computed.  I = 1 or I = 2.

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

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

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

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

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



LAPACK routine                  31 October 2017                      DLAED5(3)