NAME

       dgtcon.f -

SYNOPSIS

   Functions/Subroutines
       subroutine dgtcon (NORM, N, DL, D, DU, DU2, IPIV, ANORM, RCOND, WORK, IWORK, INFO)
           DGTCON

Function/Subroutine Documentation

   subroutine dgtcon (characterNORM, integerN, double precision, dimension( * )DL, double
       precision, dimension( * )D, double precision, dimension( * )DU, double precision,
       dimension( * )DU2, integer, dimension( * )IPIV, double precisionANORM, double
       precisionRCOND, double precision, dimension( * )WORK, integer, dimension( * )IWORK,
       integerINFO)
       DGTCON

       Purpose:

            DGTCON estimates the reciprocal of the condition number of a real
            tridiagonal matrix A using the LU factorization as computed by
            DGTTRF.

            An estimate is obtained for norm(inv(A)), and the reciprocal of the
            condition number is computed as RCOND = 1 / (ANORM * norm(inv(A))).

       Parameters:
           NORM

                     NORM is CHARACTER*1
                     Specifies whether the 1-norm condition number or the
                     infinity-norm condition number is required:
                     = '1' or 'O':  1-norm;
                     = 'I':         Infinity-norm.

           N

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

           DL

                     DL is DOUBLE PRECISION array, dimension (N-1)
                     The (n-1) multipliers that define the matrix L from the
                     LU factorization of A as computed by DGTTRF.

           D

                     D is DOUBLE PRECISION array, dimension (N)
                     The n diagonal elements of the upper triangular matrix U from
                     the LU factorization of A.

           DU

                     DU is DOUBLE PRECISION array, dimension (N-1)
                     The (n-1) elements of the first superdiagonal of U.

           DU2

                     DU2 is DOUBLE PRECISION array, dimension (N-2)
                     The (n-2) elements of the second superdiagonal of U.

           IPIV

                     IPIV is INTEGER array, dimension (N)
                     The pivot indices; for 1 <= i <= n, row i of the matrix was
                     interchanged with row IPIV(i).  IPIV(i) will always be either
                     i or i+1; IPIV(i) = i indicates a row interchange was not
                     required.

           ANORM

                     ANORM is DOUBLE PRECISION
                     If NORM = '1' or 'O', the 1-norm of the original matrix A.
                     If NORM = 'I', the infinity-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 an
                     estimate of the 1-norm of inv(A) computed in this routine.

           WORK

                     WORK is DOUBLE PRECISION array, dimension (2*N)

           IWORK

                     IWORK is INTEGER 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.

       Date:
           September 2012

       Definition at line 146 of file dgtcon.f.

Author

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