dlaed5.f (3)  Linux Man Pages
NAME
dlaed5.f 
SYNOPSIS
Functions/Subroutines
subroutine dlaed5 (I, D, Z, DELTA, RHO, DLAM)
DLAED5 used by sstedc. Solves the 2by2 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 2by2 secular equation.
Purpose:

This subroutine computes the Ith eigenvalue of a symmetric rankone modification of a 2by2 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.
DD is DOUBLE PRECISION array, dimension (2) The original eigenvalues. We assume D(1) < D(2).
ZZ is DOUBLE PRECISION array, dimension (2) The components of the updating vector.
DELTADELTA is DOUBLE PRECISION array, dimension (2) The vector DELTA contains the information necessary to construct the eigenvectors.
RHORHO is DOUBLE PRECISION The scalar in the symmetric updating formula.
DLAMDLAM is DOUBLE PRECISION The computed lambda_I, the Ith updated eigenvalue.
Author:

Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
 September 2012
Contributors:
 RenCang Li, Computer Science Division, University of California at Berkeley, USA
Definition at line 109 of file dlaed5.f.
Author
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