# dlarrc.f

Section: LAPACK (3)
Updated: Tue Nov 14 2017
Page Index

dlarrc.f

## SYNOPSIS

### Functions/Subroutines

subroutine dlarrc (JOBT, N, VL, VU, D, E, PIVMIN, EIGCNT, LCNT, RCNT, INFO)
DLARRC computes the number of eigenvalues of the symmetric tridiagonal matrix.

## Function/Subroutine Documentation

### subroutine dlarrc (character JOBT, integer N, double precision VL, double precision VU, double precision, dimension( * ) D, double precision, dimension( * ) E, double precision PIVMIN, integer EIGCNT, integer LCNT, integer RCNT, integer INFO)

DLARRC computes the number of eigenvalues of the symmetric tridiagonal matrix.

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'.
```

Parameters:

JOBT

```          JOBT is CHARACTER*1
= 'T':  Compute Sturm count for matrix T.
= 'L':  Compute Sturm count for matrix L D L^T.
```

N

```          N is INTEGER
The order of the matrix. N > 0.
```

VL

```          VL is DOUBLE PRECISION
The lower bound for the eigenvalues.
```

VU

```          VU is DOUBLE PRECISION
The upper bound for the eigenvalues.
```

D

```          D is 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

```          E is 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

```          PIVMIN is DOUBLE PRECISION
The minimum pivot in the Sturm sequence for T.
```

EIGCNT

```          EIGCNT is INTEGER
The number of eigenvalues of the symmetric tridiagonal matrix T
that are in the interval (VL,VU]
```

LCNT

```          LCNT is INTEGER
```

RCNT

```          RCNT is INTEGER
The left and right negcounts of the interval.
```

INFO

```          INFO is INTEGER
```

Author:

Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Date:

June 2016

Contributors:

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

Definition at line 139 of file dlarrc.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.