Provided by: liblapack-doc_3.3.1-1_all bug

NAME

       LAPACK-3  -  subroutine  compute  the  square  root  of  the I-th eigenvalue of a positive
       symmetric rank-one modification of a 2-by-2 diagonal matrix   diag( D ) * diag( D ) +  RHO
       The diagonal entries in the array D are assumed to satisfy   0 <= D(i) < D(j) for i < j

SYNOPSIS

       SUBROUTINE DLASD5( I, D, Z, DELTA, RHO, DSIGMA, WORK )

           INTEGER        I

           DOUBLE         PRECISION DSIGMA, RHO

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

PURPOSE

       This  subroutine  computes  the square root of the I-th eigenvalue of a positive symmetric
       rank-one modification of a 2-by-2 diagonal matrix
        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 0 <= D(1) < D(2).

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

        DELTA  (output) DOUBLE PRECISION array, dimension ( 2 )
               Contains (D(j) - sigma_I) in its  j-th component.
               The vector DELTA contains the information necessary
               to construct the eigenvectors.

        RHO    (input) DOUBLE PRECISION
               The scalar in the symmetric updating formula.
               DSIGMA (output) DOUBLE PRECISION
               The computed sigma_I, the I-th updated eigenvalue.

        WORK   (workspace) DOUBLE PRECISION array, dimension ( 2 )
               WORK contains (D(j) + sigma_I) in its  j-th component.

FURTHER DETAILS

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

 LAPACK auxiliary routine (version 3.2)     April 2011                            DLASD5(3lapack)