DLANGT(3)      LAPACK routine of NEC Numeric Library Collection      DLANGT(3)



NAME
       DLANGT

SYNOPSIS
       DOUBLE PRECISION FUNCTION DLANGT (NORM, N, DL, D, DU)



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.




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

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

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

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

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



LAPACK routine                  31 October 2017                      DLANGT(3)