Provided by: liblapack-doc_3.3.1-1_all

**NAME**

LAPACK-3 - 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 warrants 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 elements 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 (version 3.2) April 2011 DLARRR(3lapack)