Developer Reference for Intel® oneAPI Math Kernel Library for Fortran
?langb
Returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value of any element of general band matrix.
Syntax
valslangb ( norm , n , kl , ku , ab , ldab , work )
valdlangb ( norm , n , kl , ku , ab , ldab , work )
valclangb ( norm , n , kl , ku , ab , ldab , work )
valzlangb ( norm , n , kl , ku , ab , ldab , work )
Include Files
mkl.fi
Description
slangb dlangb clangb zlangb
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.
Input Parameters
- norm
-
CHARACTER*1 . Specifies the value to be returned by the routine: = ‘M’ or ‘m’: val = max(abs(A_{ij})) , 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).
- n
-
INTEGER . The order of the matrix A . n≥ 0 . When n = 0 , ?langb is set to zero.
- kl
-
INTEGER . The number of sub-diagonals of the matrix A . kl≥ 0 .
- ku
-
INTEGER . The number of super-diagonals of the matrix A . ku≥ 0 .
- ab
-
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) for max(1,j-ku) ≤ i ≤ min(n,j+kl) .
- ldab
-
INTEGER . The leading dimension of the array ab . ldab≥kl+ku+1 .
- work
-
REAL for slangb / clangb DOUBLE PRECISION for dlangb / zlangb Workspace array, DIMENSION ( max(1,lwork) ), where lwork≥n when norm = 'I' ; otherwise, work is not referenced.
Output Parameters
- val
-
REAL for slangb / clangb DOUBLE PRECISION for dlangb / zlangb Value returned by the function.