NAME
SLARRC - 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 SLARRC(
-
JOBT, N, VL, VU, D, E, PIVMIN, EIGCNT, LCNT, RCNT, INFO )
- CHARACTER
-
JOBT
- INTEGER
-
EIGCNT, INFO, LCNT, N, RCNT
- REAL
-
PIVMIN, VL, VU
- REAL
-
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