.TH DLANSB 1 "November 2006" " LAPACK auxiliary routine (version 3.1) " " LAPACK auxiliary routine (version 3.1) "
.SH NAME
DLANSB - 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 symmetric band matrix A, with k super-diagonals
.SH SYNOPSIS
.TP 17
DOUBLE PRECISION
FUNCTION DLANSB( NORM, UPLO, N, K, AB, LDAB,
WORK )
.TP 17
.ti +4
CHARACTER
NORM, UPLO
.TP 17
.ti +4
INTEGER
K, LDAB, N
.TP 17
.ti +4
DOUBLE
PRECISION AB( LDAB, * ), WORK( * )
.SH PURPOSE
DLANSB 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 symmetric band matrix A, with k super-diagonals.
.SH DESCRIPTION
DLANSB returns the value
.br
DLANSB = ( max(abs(A(i,j))), NORM = \(aqM\(aq or \(aqm\(aq
.br
(
.br
( norm1(A), NORM = \(aq1\(aq, \(aqO\(aq or \(aqo\(aq
.br
(
.br
( normI(A), NORM = \(aqI\(aq or \(aqi\(aq
.br
(
.br
( normF(A), NORM = \(aqF\(aq, \(aqf\(aq, \(aqE\(aq or \(aqe\(aq
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.
.SH ARGUMENTS
.TP 8
NORM (input) CHARACTER*1
Specifies the value to be returned in DLANSB as described
above.
.TP 8
UPLO (input) CHARACTER*1
Specifies whether the upper or lower triangular part of the
band matrix A is supplied.
= \(aqU\(aq: Upper triangular part is supplied
.br
= \(aqL\(aq: Lower triangular part is supplied
.TP 8
N (input) INTEGER
The order of the matrix A. N >= 0. When N = 0, DLANSB is
set to zero.
.TP 8
K (input) INTEGER
The number of super-diagonals or sub-diagonals of the
band matrix A. K >= 0.
.TP 8
AB (input) DOUBLE PRECISION array, dimension (LDAB,N)
The upper or lower triangle of the symmetric 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 = \(aqU\(aq, AB(k+1+i-j,j) = A(i,j) for max(1,j-k)<=i<=j;
if UPLO = \(aqL\(aq, AB(1+i-j,j) = A(i,j) for j<=i<=min(n,j+k).
.TP 8
LDAB (input) INTEGER
The leading dimension of the array AB. LDAB >= K+1.
.TP 8
WORK (workspace) DOUBLE PRECISION array, dimension (MAX(1,LWORK)),
where LWORK >= N when NORM = \(aqI\(aq or \(aq1\(aq or \(aqO\(aq; otherwise,
WORK is not referenced.