dlangb.f3
Usage
Functions/Subroutines
double precision function dlangb (norm, n, kl, ku, ab, ldab, work)
DLANGB returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value of any element of general band matrix.
Function/Subroutine Documentation
double precision function dlangb (character norm, integer n, integer kl, integer ku, double precision, dimension( ldab, * ) ab, integer ldab, double precision, dimension( * ) work)
DLANGB returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value of any element of general band matrix.
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. !>
Returns
DLANGB
!> !> 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 consistent matrix norm. !>
Parameters
NORM
!> NORM is CHARACTER*1 !> Specifies the value to be returned in DLANGB as described !> above. !>
N
!> N is INTEGER !> The order of the matrix A. N >= 0. When N = 0, DLANGB is !> set to zero. !>
KL
!> KL is INTEGER !> The number of sub-diagonals of the matrix A. KL >= 0. !>
KU
!> KU is INTEGER !> The number of super-diagonals of the matrix A. KU >= 0. !>
AB
!> AB is 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
!> LDAB is INTEGER !> The leading dimension of the array AB. LDAB >= KL+KU+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
Univ. of Colorado Denver
NAG Ltd.
Definition at line 122 of file dlangb.f.
Releases
4 releases since Debian 7 (Wheezy); the text changed 3 times.