DLARRR(1) LAPACK auxiliary routine (version 3.2) DLARRR(1)NAME
DLARRR - tests to decide whether the symmetric tridiagonal matrix T
warrants expensive computations which guarantee high relative accuracy
in the eigenvalues
SYNOPSIS
SUBROUTINE DLARRR( N, D, E, INFO )
INTEGER N, INFO
DOUBLE PRECISION D( * ), E( * )
PURPOSE
Perform tests to decide whether the symmetric tridiagonal matrix T war‐
rants expensive computations which guarantee high relative accuracy in
the eigenvalues.
ARGUMENTS
N (input) INTEGER
The order of the matrix. N > 0.
D (input) DOUBLE PRECISION array, dimension (N)
The N diagonal elements of the tridiagonal matrix T.
E (input/output) DOUBLE PRECISION array, dimension (N)
On entry, the first (N-1) entries contain the subdiagonal ele‐
ments of the tridiagonal matrix T; E(N) is set to ZERO.
INFO (output) INTEGER
INFO = 0(default) : the matrix warrants computations preserving
relative accuracy. INFO = 1 : the matrix warrants
computations guaranteeing only absolute accuracy.
FURTHER DETAILS
Based on contributions by
Beresford Parlett, University of California, Berkeley, USA
Jim Demmel, University of California, Berkeley, USA
Inderjit Dhillon, University of Texas, Austin, USA
Osni Marques, LBNL/NERSC, USA
Christof Voemel, University of California, Berkeley, USA
LAPACK auxiliary routine (versioNovember 2008 DLARRR(1)
