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## cgtsv()

subroutine cgtsv | ( | integer | n,
|  | integer | nrhs,
|  | complex, dimension( * ) | dl,
|  | complex, dimension( * ) | d,
|  | complex, dimension( * ) | du,
|  | complex, dimension( ldb, * ) | b,
|  | integer | ldb,
|  | integer | info )

CGTSV computes the solution to system of linear equations A * X = B for GT matrices

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

Purpose:

      !>
      !> CGTSV  solves the equation
      !>
      !>    A*X = B,
      !>
      !> where A is an N-by-N tridiagonal matrix, by Gaussian elimination with
      !> partial pivoting.
      !>
      !> Note that the equation  A**T *X = B  may be solved by interchanging the
      !> order of the arguments DU and DL.
      !>

Parameters

  [in]

  N

      !>          N is INTEGER
      !>          The order of the 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,out]

  DL

      !>          DL is COMPLEX array, dimension (N-1)
      !>          On entry, DL must contain the (n-1) subdiagonal elements of
      !>          A.
      !>          On exit, DL is overwritten by the (n-2) elements of the
      !>          second superdiagonal of the upper triangular matrix U from
      !>          the LU factorization of A, in DL(1), ..., DL(n-2).
      !>

  [in,out]

  D

      !>          D is COMPLEX array, dimension (N)
      !>          On entry, D must contain the diagonal elements of A.
      !>          On exit, D is overwritten by the n diagonal elements of U.
      !>

  [in,out]

  DU

      !>          DU is COMPLEX array, dimension (N-1)
      !>          On entry, DU must contain the (n-1) superdiagonal elements
      !>          of A.
      !>          On exit, DU is overwritten by the (n-1) elements of the first
      !>          superdiagonal of U.
      !>

  [in,out]

  B

      !>          B is COMPLEX array, dimension (LDB,NRHS)
      !>          On entry, the N-by-NRHS right hand side matrix B.
      !>          On exit, if INFO = 0, the N-by-NRHS solution matrix 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
      !>          > 0:  if INFO = i, U(i,i) is exactly zero, and the solution
      !>                has not been computed.  The factorization has not been
      !>                completed unless i = N.
      !>

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