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NAME
     dlangb - return the value of the one norm, or the  Frobenius
     norm,  or the infinity norm, or the element of largest abso-
     lute value of an n by n band matrix A, with kl sub-diagonals
     and ku super-diagonals

SYNOPSIS
     DOUBLE PRECISION FUNCTION DLANGB( NORM, N, KL, KU, AB, LDAB,
               WORK )

     CHARACTER NORM

     INTEGER KL, KU, LDAB, N

     DOUBLE PRECISION AB( LDAB, * ), WORK( * )



     #include <sunperf.h>

     double dlangb(char norm, int n, int kl, int ku, double *dab,
               int ldab ) ;

PURPOSE
     DLANGB  returns the value of the one norm,  or the Frobenius
     norm,  or  the   infinity  norm,  or the element of  largest
     absolute value  of an n by n band matrix  A,  with  kl  sub-
     diagonals and ku super-diagonals.


DESCRIPTION
     DLANGB returns the value

        DLANGB = ( 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  matrix norm.


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

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

     KL        (input) INTEGER
               The number of sub-diagonals of the matrix  A.   KL
               >= 0.

     KU        (input) INTEGER
               The number of super-diagonals of the matrix A.  KU
               >= 0.

     AB        (input) DOUBLE PRECISION array, dimension (LDAB,N)
               The band matrix A, stored in rows  1  to  KL+KU+1.
               The  j-th column of A is stored in the j-th column
               of the array  AB  as  follows:   AB(ku+1+i-j,j)  =
               A(i,j) for max(1,j-ku)<=i<=min(n,j+kl).

     LDAB      (input) INTEGER
               The leading dimension of the array  AB.   LDAB  >=
               KL+KU+1.

     WORK      (workspace)  DOUBLE  PRECISION  array,   dimension
               (LWORK),
               where LWORK >= N when NORM = 'I'; otherwise,  WORK
               is not referenced.

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