Provided by: liblapack-doc_3.3.1-1_all NAME

LAPACK-3 - 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

SYNOPSIS

REAL FUNCTION CLANTB( NORM, UPLO, DIAG, N, K, AB, LDAB, WORK )

CHARACTER DIAG, NORM, UPLO

INTEGER   K, LDAB, N

REAL      WORK( * )

COMPLEX   AB( LDAB, * )

PURPOSE

CLANTB   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.

DESCRIPTION

CLANTB returns the value
CLANTB = ( 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) CHARACTER*1
Specifies the value to be returned in CLANTB as described
above.

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

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

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

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

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

LAPACK auxiliary routine (version 3.2)     April 2011                            CLANTB(3lapack)