DLASD5 (3)  Linux Manuals
NAME
dlasd5.f 
SYNOPSIS
Functions/Subroutines
subroutine dlasd5 (I, D, Z, DELTA, RHO, DSIGMA, WORK)
DLASD5 computes the square root of the ith eigenvalue of a positive symmetric rankone modification of a 2by2 diagonal matrix. Used by sbdsdc.
Function/Subroutine Documentation
subroutine dlasd5 (integerI, double precision, dimension( 2 )D, double precision, dimension( 2 )Z, double precision, dimension( 2 )DELTA, double precisionRHO, double precisionDSIGMA, double precision, dimension( 2 )WORK)
DLASD5 computes the square root of the ith eigenvalue of a positive symmetric rankone modification of a 2by2 diagonal matrix. Used by sbdsdc.
Purpose:

This subroutine computes the square root of the Ith eigenvalue of a positive symmetric rankone modification of a 2by2 diagonal matrix diag( D ) * diag( D ) + RHO * Z * transpose(Z) . The diagonal entries in the array D are assumed to satisfy 0 <= 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 0 <= D(1) < D(2).
ZZ is DOUBLE PRECISION array, dimension ( 2 ) The components of the updating vector.
DELTADELTA is DOUBLE PRECISION array, dimension ( 2 ) Contains (D(j)  sigma_I) in its jth component. The vector DELTA contains the information necessary to construct the eigenvectors.
RHORHO is DOUBLE PRECISION The scalar in the symmetric updating formula.
DSIGMADSIGMA is DOUBLE PRECISION The computed sigma_I, the Ith updated eigenvalue.
WORKWORK is DOUBLE PRECISION array, dimension ( 2 ) WORK contains (D(j) + sigma_I) in its jth component.
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 117 of file dlasd5.f.
Author
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