Provided by: liblapack-doc_3.3.1-1_all bug

NAME

       LAPACK-3  -  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

SYNOPSIS

       SUBROUTINE DPTCON( N, D, E, ANORM, RCOND, WORK, INFO )

           INTEGER        INFO, N

           DOUBLE         PRECISION ANORM, RCOND

           DOUBLE         PRECISION D( * ), E( * ), WORK( * )

PURPOSE

       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))).

ARGUMENTS

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

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

        E       (input) 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   (input) DOUBLE PRECISION
                The 1-norm of the original matrix A.

        RCOND   (output) 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    (workspace) DOUBLE PRECISION array, dimension (N)

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

FURTHER DETAILS

        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.

 LAPACK routine (version 3.3.1)             April 2011                            DPTCON(3lapack)