SRC/dptcon.f(3)            Library Functions Manual            SRC/dptcon.f(3)

NAME
       SRC/dptcon.f

SYNOPSIS
   Functions/Subroutines
       subroutine dptcon (n, d, e, anorm, rcond, work, info)
           DPTCON

Function/Subroutine Documentation
   subroutine dptcon (integer n, double precision, dimension( * ) d, double
       precision, dimension( * ) e, double precision anorm, double precision
       rcond, double precision, dimension( * ) work, integer info)
       DPTCON

       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))).

       Parameters
           N

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

           D

                     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

                     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

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

           RCOND

                     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

                     WORK is DOUBLE PRECISION array, dimension (N)

           INFO

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

       Author
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       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.

       Definition at line 117 of file dptcon.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

LAPACK                          Version 3.12.0                 SRC/dptcon.f(3)