This information is part of the Modelica Standard Library maintained by the Modelica Association.

Lapack documentation
    Purpose
    =======

    DGTSV  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'*X = B  may be solved by interchanging the
    order of the arguments DU and DL.

    Arguments
    =========

    N       (input) INTEGER
            The order of the matrix A.  N >= 0.

    NRHS    (input) INTEGER
            The number of right hand sides, i.e., the number of columns
            of the matrix B.  NRHS >= 0.

    DL      (input/output) DOUBLE PRECISION array, dimension (N-1)
            On entry, DL must contain the (n-1) sub-diagonal elements of
            A.

            On exit, DL is overwritten by the (n-2) elements of the
            second super-diagonal of the upper triangular matrix U from
            the LU factorization of A, in DL(1), ..., DL(n-2).

    D       (input/output) DOUBLE PRECISION 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.

    DU      (input/output) DOUBLE PRECISION array, dimension (N-1)
            On entry, DU must contain the (n-1) super-diagonal elements
            of A.

            On exit, DU is overwritten by the (n-1) elements of the first
            super-diagonal of U.

    B       (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)
            On entry, the N by NRHS matrix of right hand side matrix B.
            On exit, if INFO = 0, the N by NRHS solution matrix X.

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

    INFO    (output) 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.