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

NAME
       SRC/dlangt.f

SYNOPSIS
   Functions/Subroutines
       double precision function dlangt (norm, n, dl, d, du)
           DLANGT returns the value of the 1-norm, Frobenius norm,
           infinity-norm, or the largest absolute value of any element of a
           general tridiagonal matrix.

Function/Subroutine Documentation
   double precision function dlangt (character norm, integer n, double
       precision, dimension( * ) dl, double precision, dimension( * ) d,
       double precision, dimension( * ) du)
       DLANGT returns the value of the 1-norm, Frobenius norm, infinity-norm,
       or the largest absolute value of any element of a general tridiagonal
       matrix.

       Purpose:


            DLANGT  returns the value of the one norm,  or the Frobenius norm, or
            the  infinity norm,  or the  element of  largest absolute value  of a
            real tridiagonal matrix A.

       Returns
           DLANGT

               DLANGT = ( max(abs(A(i,j))), NORM = 'M' or 'm'
                        (
                        ( norm1(A),         NORM = '1', 'O' or 'o'
                        (
                        ( normI(A),         NORM = 'I' or 'i'
                        (
                        ( normF(A),         NORM = 'F', 'f', 'E' or 'e'

            where  norm1  denotes the  one norm of a matrix (maximum column sum),
            normI  denotes the  infinity norm  of a matrix  (maximum row sum) and
            normF  denotes the  Frobenius norm of a matrix (square root of sum of
            squares).  Note that  max(abs(A(i,j)))  is not a consistent matrix norm.

       Parameters
           NORM

                     NORM is CHARACTER*1
                     Specifies the value to be returned in DLANGT as described
                     above.

           N

                     N is INTEGER
                     The order of the matrix A.  N >= 0.  When N = 0, DLANGT is
                     set to zero.

           DL

                     DL is DOUBLE PRECISION array, dimension (N-1)
                     The (n-1) sub-diagonal elements of A.

           D

                     D is DOUBLE PRECISION array, dimension (N)
                     The diagonal elements of A.

           DU

                     DU is DOUBLE PRECISION array, dimension (N-1)
                     The (n-1) super-diagonal elements of A.

       Author
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Definition at line 105 of file dlangt.f.

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

LAPACK                          Version 3.12.0                 SRC/dlangt.f(3)