NAME

       dlaed5.f -

SYNOPSIS

   Functions/Subroutines
       subroutine dlaed5 (I, D, Z, DELTA, RHO, DLAM)
           DLAED5 used by sstedc. Solves the 2-by-2 secular equation.

Function/Subroutine Documentation

   subroutine dlaed5 (integerI, double precision, dimension( 2 )D, double precision, dimension( 2
       )Z, double precision, dimension( 2 )DELTA, double precisionRHO, double precisionDLAM)
       DLAED5 used by sstedc. Solves the 2-by-2 secular equation.

       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.

       Parameters:
           I

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

           D

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

           Z

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

           DELTA

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

           RHO

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

           DLAM

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

       Author:
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Date:
           September 2012

       Contributors:
           Ren-Cang Li, Computer Science Division, University of California at Berkeley, USA

       Definition at line 109 of file dlaed5.f.

Author

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