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## ssterf()

subroutine ssterf | ( | integer | n,
|  | real, dimension( * ) | d,
|  | real, dimension( * ) | e,
|  | integer | info )

SSTERF

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

Purpose:

      !>
      !> SSTERF computes all eigenvalues of a symmetric tridiagonal matrix
      !> using the Pal-Walker-Kahan variant of the QL or QR algorithm.
      !>

Parameters

  [in]

  N

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

  [in,out]

  D

      !>          D is REAL array, dimension (N)
      !>          On entry, the n diagonal elements of the tridiagonal matrix.
      !>          On exit, if INFO = 0, the eigenvalues in ascending order.
      !>

  [in,out]

  E

      !>          E is REAL array, dimension (N-1)
      !>          On entry, the (n-1) subdiagonal elements of the tridiagonal
      !>          matrix.
      !>          On exit, E has been destroyed.
      !>

  [out]

  INFO

      !>          INFO is INTEGER
      !>          = 0:  successful exit
      !>          < 0:  if INFO = -i, the i-th argument had an illegal value
      !>          > 0:  the algorithm failed to find all of the eigenvalues in
      !>                a total of 30*N iterations; if INFO = i, then i
      !>                elements of E have not converged to zero.
      !>

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