dlaed5.f(3) LAPACK dlaed5.f(3)NAMEdlaed5.f-
SYNOPSIS
Functions/Subroutines
subroutine dlaed5 (I, D, Z, DELTA, RHO, DLAM)
DLAED5 used by sstedc. Solves the 2-by-2 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 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
I is INTEGER
The index of the eigenvalue to be computed. I = 1 or I = 2.
D
D is DOUBLE PRECISION array, dimension (2)
The original eigenvalues. We assume D(1) < D(2).
Z
Z is DOUBLE PRECISION array, dimension (2)
The components of the updating vector.
DELTA
DELTA is DOUBLE PRECISION array, dimension (2)
The vector DELTA contains the information necessary
to construct the eigenvectors.
RHO
RHO is DOUBLE PRECISION
The scalar in the symmetric updating formula.
DLAM
DLAM is DOUBLE PRECISION
The computed lambda_I, the I-th updated eigenvalue.
Author:
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
September 2012
Contributors:
Ren-Cang Li, Computer Science Division, University of California at
Berkeley, USA
Definition at line 109 of file dlaed5.f.
Author
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Version 3.4.2 Sat Nov 16 2013 dlaed5.f(3)