# dlaed9 (3) - Linux Manuals

dlaed9.f -

## SYNOPSIS

### Functions/Subroutines

subroutine dlaed9 (K, KSTART, KSTOP, N, D, Q, LDQ, RHO, DLAMDA, W, S, LDS, INFO)
DLAED9 used by sstedc. Finds the roots of the secular equation and updates the eigenvectors. Used when the original matrix is dense.

## Function/Subroutine Documentation

### subroutine dlaed9 (integerK, integerKSTART, integerKSTOP, integerN, double precision, dimension( * )D, double precision, dimension( ldq, * )Q, integerLDQ, double precisionRHO, double precision, dimension( * )DLAMDA, double precision, dimension( * )W, double precision, dimension( lds, * )S, integerLDS, integerINFO)

DLAED9 used by sstedc. Finds the roots of the secular equation and updates the eigenvectors. Used when the original matrix is dense.

Purpose:

DLAED9 finds the roots of the secular equation, as defined by the
values in D, Z, and RHO, between KSTART and KSTOP.  It makes the
appropriate calls to DLAED4 and then stores the new matrix of
eigenvectors for use in calculating the next level of Z vectors.

Parameters:

K

K is INTEGER
The number of terms in the rational function to be solved by
DLAED4.  K >= 0.

KSTART

KSTART is INTEGER

KSTOP

KSTOP is INTEGER
The updated eigenvalues Lambda(I), KSTART <= I <= KSTOP
are to be computed.  1 <= KSTART <= KSTOP <= K.

N

N is INTEGER
The number of rows and columns in the Q matrix.
N >= K (delation may result in N > K).

D

D is DOUBLE PRECISION array, dimension (N)
D(I) contains the updated eigenvalues
for KSTART <= I <= KSTOP.

Q

Q is DOUBLE PRECISION array, dimension (LDQ,N)

LDQ

LDQ is INTEGER
The leading dimension of the array Q.  LDQ >= max( 1, N ).

RHO

RHO is DOUBLE PRECISION
The value of the parameter in the rank one update equation.
RHO >= 0 required.

DLAMDA

DLAMDA is DOUBLE PRECISION array, dimension (K)
The first K elements of this array contain the old roots
of the deflated updating problem.  These are the poles
of the secular equation.

W

W is DOUBLE PRECISION array, dimension (K)
The first K elements of this array contain the components
of the deflation-adjusted updating vector.

S

S is DOUBLE PRECISION array, dimension (LDS, K)
Will contain the eigenvectors of the repaired matrix which
will be stored for subsequent Z vector calculation and
multiplied by the previously accumulated eigenvectors
to update the system.

LDS

LDS is INTEGER
The leading dimension of S.  LDS >= max( 1, K ).

INFO

INFO is INTEGER
= 0:  successful exit.
< 0:  if INFO = -i, the i-th argument had an illegal value.
> 0:  if INFO = 1, an eigenvalue did not converge

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

September 2012

Contributors:

Jeff Rutter, Computer Science Division, University of California at Berkeley, USA

Definition at line 156 of file dlaed9.f.

## Author

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