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## cgtts2()

subroutine cgtts2 | ( | integer | itrans,
|  | integer | n,
|  | integer | nrhs,
|  | complex, dimension( * ) | dl,
|  | complex, dimension( * ) | d,
|  | complex, dimension( * ) | du,
|  | complex, dimension( * ) | du2,
|  | integer, dimension( * ) | ipiv,
|  | complex, dimension( ldb, * ) | b,
|  | integer | ldb )

CGTTS2 solves a system of linear equations with a tridiagonal matrix using the LU factorization computed by sgttrf.

Download CGTTS2 + dependencies [TGZ] [ZIP] [TXT]

Purpose:

      !>
      !> CGTTS2 solves one of the systems of equations
      !>    A * X = B,  A**T * X = B,  or  A**H * X = B,
      !> with a tridiagonal matrix A using the LU factorization computed
      !> by CGTTRF.
      !>

Parameters

  [in]

  ITRANS

      !>          ITRANS is INTEGER
      !>          Specifies the form of the system of equations.
      !>          = 0:  A * X = B     (No transpose)
      !>          = 1:  A**T * X = B  (Transpose)
      !>          = 2:  A**H * X = B  (Conjugate transpose)
      !>

  [in]

  N

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

  [in]

  NRHS

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

  [in]

  DL

      !>          DL is COMPLEX array, dimension (N-1)
      !>          The (n-1) multipliers that define the matrix L from the
      !>          LU factorization of A.
      !>

  [in]

  D

      !>          D is COMPLEX array, dimension (N)
      !>          The n diagonal elements of the upper triangular matrix U from
      !>          the LU factorization of A.
      !>

  [in]

  DU

      !>          DU is COMPLEX array, dimension (N-1)
      !>          The (n-1) elements of the first super-diagonal of U.
      !>

  [in]

  DU2

      !>          DU2 is COMPLEX array, dimension (N-2)
      !>          The (n-2) elements of the second super-diagonal of U.
      !>

  [in]

  IPIV

      !>          IPIV is INTEGER array, dimension (N)
      !>          The pivot indices; for 1 <= i <= n, row i of the matrix was
      !>          interchanged with row IPIV(i).  IPIV(i) will always be either
      !>          i or i+1; IPIV(i) = i indicates a row interchange was not
      !>          required.
      !>

  [in,out]

  B

      !>          B is COMPLEX array, dimension (LDB,NRHS)
      !>          On entry, the matrix of right hand side vectors B.
      !>          On exit, B is overwritten by 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.