# dlasd5.f(3) [centos man page]

```dlasd5.f(3)							      LAPACK							       dlasd5.f(3)

NAME
dlasd5.f -

SYNOPSIS
Functions/Subroutines
subroutine dlasd5 (I, D, Z, DELTA, RHO, DSIGMA, WORK)
DLASD5 computes the square root of the i-th eigenvalue of a positive symmetric rank-one modification of a 2-by-2 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 i-th eigenvalue of a positive symmetric rank-one modification of a 2-by-2 diagonal matrix. Used by
sbdsdc.

Purpose:

This subroutine computes the square root of the I-th eigenvalue
of a positive symmetric rank-one modification of a 2-by-2 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.

D

D is DOUBLE PRECISION array, dimension ( 2 )
The original eigenvalues.  We assume 0 <= 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 )
Contains (D(j) - sigma_I) in its  j-th component.
The vector DELTA contains the information necessary
to construct the eigenvectors.

RHO

RHO is DOUBLE PRECISION
The scalar in the symmetric updating formula.

DSIGMA

DSIGMA is DOUBLE PRECISION
The computed sigma_I, the I-th updated eigenvalue.

WORK

WORK is DOUBLE PRECISION array, dimension ( 2 )
WORK contains (D(j) + sigma_I) in its  j-th component.

Author:
Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Date:
September 2012

Contributors:
Ren-Cang Li, Computer Science Division, University of California at Berkeley, USA

Definition at line 117 of file dlasd5.f.

Author
Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2							  Tue Sep 25 2012						       dlasd5.f(3)```

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```dlaed5.f(3)							      LAPACK							       dlaed5.f(3)

NAME
dlaed5.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

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
Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2							  Tue Sep 25 2012						       dlaed5.f(3)```
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