DLARRC(1) LAPACK auxiliary routine (version 3.2) DLARRC(1)NAME
DLARRC - the number of eigenvalues of the symmetric tridiagonal matrix
T that are in the interval (VL,VU] if JOBT = 'T', and of L D L^T if
JOBT = 'L'
SYNOPSIS
SUBROUTINE DLARRC( JOBT, N, VL, VU, D, E, PIVMIN, EIGCNT, LCNT, RCNT,
INFO )
CHARACTER JOBT
INTEGER EIGCNT, INFO, LCNT, N, RCNT
DOUBLE PRECISION PIVMIN, VL, VU
DOUBLE PRECISION D( * ), E( * )
PURPOSE
Find the number of eigenvalues of the symmetric tridiagonal matrix T
that are in the interval (VL,VU] if JOBT = 'T', and of L D L^T if JOBT
= 'L'.
ARGUMENTS
JOBT (input) CHARACTER*1
= 'T': Compute Sturm count for matrix T.
= 'L': Compute Sturm count for matrix L D L^T.
N (input) INTEGER
The order of the matrix. N > 0.
VL (input) DOUBLE PRECISION
VU (input) DOUBLE PRECISION The lower and upper bounds for
the eigenvalues.
D (input) DOUBLE PRECISION array, dimension (N)
JOBT = 'T': The N diagonal elements of the tridiagonal matrix
T.
JOBT = 'L': The N diagonal elements of the diagonal matrix D.
E (input) DOUBLE PRECISION array, dimension (N)
JOBT = 'T': The N-1 offdiagonal elements of the matrix T.
JOBT = 'L': The N-1 offdiagonal elements of the matrix L.
PIVMIN (input) DOUBLE PRECISION
The minimum pivot in the Sturm sequence for T.
EIGCNT (output) INTEGER
The number of eigenvalues of the symmetric tridiagonal matrix T
that are in the interval (VL,VU]
LCNT (output) INTEGER
RCNT (output) INTEGER The left and right negcounts of the
interval.
INFO (output) INTEGER
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 DLARRC(1)