◆ dlansy()

One norm, Frobenius norm, infinity norm, or largest absolute value of any element of a real symmetric matrix

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

Returns: (anorm, info)

anorm (float):
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.

info (int):
= 0: Successful exit.
= -1: The argument norm had an illegal value. (norm <> 'M', '1', 'O', 'I', 'F' nor 'E')
= -2: The argument uplo had an illegal value. (uplo <> 'U' nor 'L')
= -3: The argument n had an illegal value. (n < 0)
= -4: The argument a is invalid.

Parameters

[in]	norm	Specifies the value to be returned by Dlansy as described above. Note that normI(A) = norm1(A) since A is symmetric.
[in]	uplo	Specifies whether the upper or lower triangular part of the symmetric matrix A is to be referenced. = 'U': Only the upper triangular part is to be referenced. = 'L': Only the lower triangular part is to be referenced.
[in]	n	Order of the matrix A. (n >= 0) (If n = 0, returns 0)
[in]	a	Numpy ndarray (2-dimensional, float, n x n) n x n symmetric matrix A. Only the upper or lower triangular part is to be referenced in accordance with uplo.