NAME

SRC/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 (integer i, real, dimension( 2 ) d, real, dimension( 2 ) z, real, dimension( 2 ) delta, real rho, real dlam)

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 is INTEGER


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



          D is REAL array, dimension (2)


         The original eigenvalues.  We assume D(1) < D(2).



          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.

Contributors:

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

Definition at line 107 of file slaed5.f.

Author

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