SLAED5 (3) Linux Manual Page

slaed5.f –

Synopsis

Functions/Subroutines

subroutine slaed5 (I, D, Z, DELTA, RHO, DLAM)
SLAED5 used by sstedc. Solves the 2-by-2 secular equation.

Function/Subroutine Documentation

subroutine slaed5 (integerI, real, dimension( 2 )D, real, dimension( 2 )Z, real, dimension( 2 )DELTA, realRHO, realDLAM)

SLAED5 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 REAL array, dimension (2)

 The original eigenvalues. We assume D(1) < D(2).

Z

 Z is REAL array, dimension (2)

 The components of the updating vector.

DELTA

 DELTA is REAL array, dimension (2)

 The vector DELTA contains the information necessary

 to construct the eigenvectors.

RHO

 RHO is REAL

 The scalar in the symmetric updating formula.

DLAM

 DLAM is REAL

 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 slaed5.f.

Author

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