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NAME

        ZDTTRF  - compute an LU factorization of a complex tridiagonal matrix A
        using elimination without partial pivoting
 

SYNOPSIS

        SUBROUTINE ZDTTRF( N, DL, D, DU, INFO )
 
            INTEGER        INFO, N
 
            COMPLEX*16     D( * ), DL( * ), DU( * )
 

PURPOSE

        ZDTTRF computes an LU factorization of a complex tridiagonal  matrix  A
        using elimination without partial pivoting.
 
        The factorization has the form
           A = L * U
        where L is a product of unit lower bidiagonal
        matrices and U is upper triangular with nonzeros in only the main diag‐
        onal and first superdiagonal.
 

ARGUMENTS

        N       (input) INTEGER
                The order of the matrix A.  N >= 0.
 
        DL      (input/output) 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-1) multipliers that define
                the matrix L from the LU factorization of A.
 
        D       (input/output) 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 the upper trian‐
                gular matrix U from the LU factorization of A.
 
        DU      (input/output) 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.
 
        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.  The  factorization
                has  been  completed, but the factor U is exactly singular, and
                division by zero will occur if it is used to solve a system  of
                equations.
 

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