◆ dlangt()

One norm, Frobenius norm, infinity norm, or largest absolute value of any element of a general tridiagonal matrix

Purpose: This routine returns the value of the one norm, the Frobenius norm, the infinity norm, or the largest absolute value of any element of a real tridiagonal matrix A.

Returns: max(abs(Aij)) when norm = 'M',
norm1(A) when norm = '1' or 'O',
normI(A) when norm = 'I', or
normF(A) when norm = 'F' 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(Aij)) is not a consistent matrix norm.

Parameters

[in]	norm	Specifies the value to be returned by dlangt as described above.
[in]	n	Order of the matrix A. (n >= 0) (If n = 0, returns 0)
[in]	dl[]	Array dl[ldl] (ldl >= n - 1) Sub-diagonal elements of tridiagonal matrix A.
[in]	d[]	Array d[ld] (ld >= n) Diagonal elements of tridiagonal matrix A.
[in]	du[]	Array du[ldu] (ldu >= n - 1) Super-diagonal elements of tridiagonal matrix A.