SLAED5
November 2006
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.
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.
Arguments
| I |
(input) INTEGER
The index of the eigenvalue to be computed. I = 1 or I = 2.
|
| D |
(input) REAL array, dimension (2)
The original eigenvalues. We assume D(1) < D(2).
|
| Z |
(input) REAL array, dimension (2)
The components of the updating vector.
|
| DELTA |
(output) REAL array, dimension (2)
The vector DELTA contains the information necessary
to construct the eigenvectors. |
| RHO |
(input) REAL
The scalar in the symmetric updating formula.
|
| DLAM |
(output) REAL
The computed lambda_I, the I-th updated eigenvalue.
|
Further Details
Based on contributions by
Ren-Cang Li, Computer Science Division, University of California
at Berkeley, USA
Ren-Cang Li, Computer Science Division, University of California
at Berkeley, USA