---
name: "slarrc"
section: "3lapack"
platform: "linux"
package: "liblapack-doc"
version: "3.2.1-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/slarrc/3lapack"
---

# slarrc(3lapack)

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'

## 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