SLAED5(3)      LAPACK routine of NEC Numeric Library Collection      SLAED5(3)



NAME
       SLAED5

SYNOPSIS
       SUBROUTINE SLAED5 (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 REAL array, dimension (2)
                    The original eigenvalues.  We assume D(1) < D(2).

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

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

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

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



LAPACK routine                  31 October 2017                      SLAED5(3)