dlarrc.f

Section: LAPACK (3)
Updated: Tue Nov 14 2017
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NAME

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

          VL is DOUBLE PRECISION
          The lower bound for the eigenvalues.

          VU is DOUBLE PRECISION
          The upper bound for the eigenvalues.

          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 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

Univ. of Colorado Denver

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

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