# CentOS 7.0 - man page for dlantb (centos section 3)

```dlantb.f(3)							      LAPACK							       dlantb.f(3)

NAME
dlantb.f -

SYNOPSIS
Functions/Subroutines
DOUBLE PRECISION function dlantb (NORM, UPLO, DIAG, N, K, AB, LDAB, WORK)
DLANTB returns the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a
triangular band matrix.

Function/Subroutine Documentation
DOUBLE PRECISION function dlantb (characterNORM, characterUPLO, characterDIAG, integerN, integerK, double precision, dimension( ldab, * )AB,
integerLDAB, double precision, dimension( * )WORK)
DLANTB returns the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a
triangular band matrix.

Purpose:

DLANTB  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 triangular band matrix A,  with ( k + 1 ) diagonals.

Returns:
DLANTB

DLANTB = ( 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 DLANTB as described
above.

UPLO

UPLO is CHARACTER*1
Specifies whether the matrix A is upper or lower triangular.
= 'U':  Upper triangular
= 'L':  Lower triangular

DIAG

DIAG is CHARACTER*1
Specifies whether or not the matrix A is unit triangular.
= 'N':  Non-unit triangular
= 'U':  Unit triangular

N

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

K

K is INTEGER
The number of super-diagonals of the matrix A if UPLO = 'U',
or the number of sub-diagonals of the matrix A if UPLO = 'L'.
K >= 0.

AB

AB is DOUBLE PRECISION array, dimension (LDAB,N)
The upper or lower triangular band matrix A, stored in the
first k+1 rows of AB.  The j-th column of A is stored
in the j-th column of the array AB as follows:
if UPLO = 'U', AB(k+1+i-j,j) = A(i,j) for max(1,j-k)<=i<=j;
if UPLO = 'L', AB(1+i-j,j)   = A(i,j) for j<=i<=min(n,j+k).
Note that when DIAG = 'U', the elements of the array AB
corresponding to the diagonal elements of the matrix A are
not referenced, but are assumed to be one.

LDAB

LDAB is INTEGER
The leading dimension of the array AB.  LDAB >= K+1.

WORK

WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK)),
where LWORK >= N when NORM = 'I'; otherwise, WORK is not
referenced.

Author:
Univ. of Tennessee

Univ. of California Berkeley