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## sgttrs()

subroutine sgttrs | ( | character | trans,
|  | integer | n,
|  | integer | nrhs,
|  | real, dimension( * ) | dl,
|  | real, dimension( * ) | d,
|  | real, dimension( * ) | du,
|  | real, dimension( * ) | du2,
|  | integer, dimension( * ) | ipiv,
|  | real, dimension( ldb, * ) | b,
|  | integer | ldb,
|  | integer | info )

SGTTRS

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

Purpose:

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

Parameters

  [in]

  TRANS

      !>          TRANS is CHARACTER*1
      !>          Specifies the form of the system of equations.
      !>          = 'N':  A * X = B  (No transpose)
      !>          = 'T':  A**T* X = B  (Transpose)
      !>          = 'C':  A**T* X = B  (Conjugate transpose = 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 REAL array, dimension (N-1)
      !>          The (n-1) multipliers that define the matrix L from the
      !>          LU factorization of A.
      !>

  [in]

  D

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

  [in]

  DU

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

  [in]

  DU2

      !>          DU2 is REAL 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 REAL 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).
      !>

  [out]

  INFO

      !>          INFO is INTEGER
      !>          = 0:  successful exit
      !>          < 0:  if INFO = -i, the i-th argument had an illegal value
      !>

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