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## dptts2()

subroutine dptts2 | ( | integer | n,
|  | integer | nrhs,
|  | double precision, dimension( * ) | d,
|  | double precision, dimension( * ) | e,
|  | double precision, dimension( ldb, * ) | b,
|  | integer | ldb )

DPTTS2 solves a tridiagonal system of the form AX=B using the L D LH factorization computed by spttrf.

Download DPTTS2 + dependencies [TGZ] [ZIP] [TXT]

Purpose:

      !>
      !> DPTTS2 solves a tridiagonal system of the form
      !>    A * X = B
      !> using the L*D*L**T factorization of A computed by DPTTRF.  D is a
      !> diagonal matrix specified in the vector D, L is a unit bidiagonal
      !> matrix whose subdiagonal is specified in the vector E, and X and B
      !> are N by NRHS matrices.
      !>

Parameters

  [in]

  N

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

  [in]

  NRHS

      !>          NRHS is INTEGER
      !>          The number of right hand sides, i.e., the number of columns
      !>          of the matrix B.  NRHS >= 0.
      !>

  [in]

  D

      !>          D is DOUBLE PRECISION array, dimension (N)
      !>          The n diagonal elements of the diagonal matrix D from the
      !>          L*D*L**T factorization of A.
      !>

  [in]

  E

      !>          E is DOUBLE PRECISION array, dimension (N-1)
      !>          The (n-1) subdiagonal elements of the unit bidiagonal factor
      !>          L from the L*D*L**T factorization of A.  E can also be regarded
      !>          as the superdiagonal of the unit bidiagonal factor U from the
      !>          factorization A = U**T*D*U.
      !>

  [in,out]

  B

      !>          B is DOUBLE PRECISION array, dimension (LDB,NRHS)
      !>          On entry, the right hand side vectors B for the system of
      !>          linear equations.
      !>          On exit, the solution vectors, X.
      !>

  [in]

  LDB

      !>          LDB is INTEGER
      !>          The leading dimension of the array B.  LDB >= max(1,N).
      !>

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