slaed5.f(3)

NAME
slaed5.f -

SYNOPSIS

  Functions/Subroutines

subroutine slaed5 (I, D, Z, DELTA, RHO, DLAM)
SLAED5 used by sstedc. Solves the 2-by-2 secular equation.

Function/Subroutine Documentation

  subroutine slaed5 (integerI, real, dimension( 2 )D, real, dimension( 2 )Z, real, dimension( 2 )DELTA, realRHO, realDLAM)

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

    Z

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

    DELTA

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

    RHO

              RHO is REAL
             The scalar in the symmetric updating formula.

    DLAM

              DLAM is REAL
             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 slaed5.f.

Author

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