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

NAME

       LAPACK-3  -  computes  the  L*D*L**T  factorization  of a real symmetric positive definite
       tridiagonal matrix A

SYNOPSIS

       SUBROUTINE DPTTRF( N, D, E, INFO )

           INTEGER        INFO, N

           DOUBLE         PRECISION D( * ), E( * )

PURPOSE

       DPTTRF  computes  the  L*D*L**T  factorization  of  a  real  symmetric  positive  definite
       tridiagonal matrix A.  The factorization may also
        be regarded as having the form A = U**T*D*U.

ARGUMENTS

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

        D       (input/output) DOUBLE PRECISION array, dimension (N)
                On entry, the n diagonal elements of the tridiagonal matrix
                A.  On exit, the n diagonal elements of the diagonal matrix
                D from the L*D*L**T factorization of A.

        E       (input/output) DOUBLE PRECISION array, dimension (N-1)
                On entry, the (n-1) subdiagonal elements of the tridiagonal
                matrix A.  On exit, the (n-1) subdiagonal elements of the
                unit bidiagonal factor L from the L*D*L**T factorization of A.
                E can also be regarded as the superdiagonal of the unit
                bidiagonal factor U from the U**T*D*U factorization of A.

        INFO    (output) INTEGER
                = 0: successful exit
                < 0: if INFO = -k, the k-th argument had an illegal value
                > 0: if INFO = k, the leading minor of order k is not
                positive definite; if k < N, the factorization could not
                be completed, while if k = N, the factorization was
                completed, but D(N) <= 0.

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