DPTCON computes the reciprocal of the condition number (in the
 1-norm) of a real symmetric positive definite tridiagonal matrix
 using the factorization A = L*D*L**T or A = U**T*D*U computed by
 DPTTRF.

 Norm(inv(A)) is computed by a direct method, and the reciprocal of
 the condition number is computed as
              RCOND = 1 / (ANORM * norm(inv(A))).

          N is INTEGER
          The order of the matrix A.  N >= 0.

          D is DOUBLE PRECISION array, dimension (N)
          The n diagonal elements of the diagonal matrix D from the
          factorization of A, as computed by DPTTRF.

          E is DOUBLE PRECISION array, dimension (N-1)
          The (n-1) off-diagonal elements of the unit bidiagonal factor
          U or L from the factorization of A,  as computed by DPTTRF.

          ANORM is DOUBLE PRECISION
          The 1-norm of the original matrix A.

          RCOND is DOUBLE PRECISION
          The reciprocal of the condition number of the matrix A,
          computed as RCOND = 1/(ANORM * AINVNM), where AINVNM is the
          1-norm of inv(A) computed in this routine.

          WORK is DOUBLE PRECISION array, dimension (N)

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

  The method used is described in Nicholas J. Higham, "Efficient
  Algorithms for Computing the Condition Number of a Tridiagonal
  Matrix", SIAM J. Sci. Stat. Comput., Vol. 7, No. 1, January 1986.