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



NAME
       SLANGT

SYNOPSIS
       REAL FUNCTION SLANGT (NORM, N, DL, D, DU)



PURPOSE
            SLANGT  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:
           SLANGT

               SLANGT = ( 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 SLANGT as described
                     above.

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

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

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

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



LAPACK routine                  31 October 2017                      SLANGT(3)