Returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value of any element of general band matrix.
val = slangb( norm, n, kl, ku, ab, ldab, work )
val = dlangb( norm, n, kl, ku, ab, ldab, work )
val = clangb( norm, n, kl, ku, ab, ldab, work )
val = zlangb( norm, n, kl, ku, ab, ldab, work )
The function returns the value of the 1-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.
CHARACTER*1. Specifies the value to be returned by the routine:
= 'M' or 'm':
val = max(abs(Aij)), largest absolute value of the matrix A.
= '1' or 'O' or 'o':
val = norm1(A), 1-norm of the matrix A (maximum column sum),
= 'I' or 'i':
val = normI(A), infinity norm of the matrix A (maximum row sum),
= 'F', 'f', 'E' or 'e':
val = normF(A), Frobenius norm of the matrix A (square root of sum of squares).
INTEGER. The order of the matrix A.
n ≥ 0. When
n = 0, ?langb is set to zero.
INTEGER. The number of sub-diagonals of the matrix A.
kl ≥ 0.
INTEGER. The number of super-diagonals of the matrix A.
ku ≥ 0.
REAL for slangb
DOUBLE PRECISION for dlangb
COMPLEX for clangb
DOUBLE COMPLEX for zlangb
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)
max(1,j-ku) ≤ i ≤ min(n,j+kl).
INTEGER. The leading dimension of the array ab.
ldab ≥ kl+ku+1.
REAL for slangb/clangb
DOUBLE PRECISION for dlangb/zlangb
Workspace array, DIMENSION (
lwork ≥ nwhen
norm = 'I'; otherwise, work is not referenced.