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## slarrc()

subroutine slarrc | ( | character | jobt,
|  | integer | n,
|  | real | vl,
|  | real | vu,
|  | real, dimension( * ) | d,
|  | real, dimension( * ) | e,
|  | real | pivmin,
|  | integer | eigcnt,
|  | integer | lcnt,
|  | integer | rcnt,
|  | integer | info )

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

Download SLARRC + dependencies [TGZ] [ZIP] [TXT]

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

  [in]

  JOBT

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

  [in]

  N

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

  [in]

  VL

      !>          VL is REAL
      !>          The lower bound for the eigenvalues.
      !>

  [in]

  VU

      !>          VU is REAL
      !>          The upper bound for the eigenvalues.
      !>

  [in]

  D

      !>          D is REAL 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.
      !>

  [in]

  E

      !>          E is REAL 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.
      !>

  [in]

  PIVMIN

      !>          PIVMIN is REAL
      !>          The minimum pivot in the Sturm sequence for T.
      !>

  [out]

  EIGCNT

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

  [out]

  LCNT

      !>          LCNT is INTEGER
      !>

  [out]

  RCNT

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

  [out]

  INFO

      !>          INFO is INTEGER
      !>

Author
  Univ. of Tennessee
  Univ. of California Berkeley
  Univ. of Colorado Denver
  NAG Ltd.

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