2. EL 6 ELS
  3. lapack
  4. slaed9(l)

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SLAED9(1) LAPACK routine (version 3.2) SLAED9(1)

NAME

SLAED9 - finds the roots of the secular equation, as defined by the values in D, Z, and RHO, between KSTART and KSTOP

SYNOPSIS

K, KSTART, KSTOP, N, D, Q, LDQ, RHO, DLAMDA, W, S, LDS, INFO )

INTEGER INFO, K, KSTART, KSTOP, LDQ, LDS, N REAL RHO REAL D( * ), DLAMDA( * ), Q( LDQ, * ), S( LDS, * ), W( * )

PURPOSE

SLAED9 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 SLAED4 and then stores the new matrix of eigenvectors for use in calculating the next level of Z vectors.

ARGUMENTS

The number of terms in the rational function to be solved by SLAED4. K >= 0.
KSTOP (input) INTEGER The updated eigenvalues Lambda(I), KSTART <= I <= KSTOP are to be computed. 1 <= KSTART <= KSTOP <= K.
The number of rows and columns in the Q matrix. N >= K (delation may result in N > K).
D(I) contains the updated eigenvalues for KSTART <= I <= KSTOP.
The leading dimension of the array Q. LDQ >= max( 1, N ).
The value of the parameter in the rank one update equation. RHO >= 0 required.
The first K elements of this array contain the old roots of the deflated updating problem. These are the poles of the secular equation.
The first K elements of this array contain the components of the deflation-adjusted updating vector.
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.
The leading dimension of S. LDS >= max( 1, K ).
= 0: successful exit.
< 0: if INFO = -i, the i-th argument had an illegal value.
> 0: if INFO = 1, an eigenvalue did not converge

FURTHER DETAILS

Based on contributions by
Jeff Rutter, Computer Science Division, University of California
at Berkeley, USA

November 2008 LAPACK routine (version 3.2)