SLASD5 (3)  Linux Manuals
NAME
slasd5.f 
SYNOPSIS
Functions/Subroutines
subroutine slasd5 (I, D, Z, DELTA, RHO, DSIGMA, WORK)
SLASD5 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 slasd5 (integerI, real, dimension( 2 )D, real, dimension( 2 )Z, real, dimension( 2 )DELTA, realRHO, realDSIGMA, real, dimension( 2 )WORK)
SLASD5 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 REAL array, dimension (2) The original eigenvalues. We assume 0 <= D(1) < D(2).
ZZ is REAL array, dimension (2) The components of the updating vector.
DELTADELTA is REAL 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 REAL The scalar in the symmetric updating formula.
DSIGMADSIGMA is REAL The computed sigma_I, the Ith updated eigenvalue.
WORKWORK is REAL 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 slasd5.f.
Author
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