# naginterfaces.library.sparse.direct_​real_​gen_​norm¶

naginterfaces.library.sparse.direct_real_gen_norm(norm, n, icolzp, irowix, a)[source]

direct_real_gen_norm computes the -norm, the -norm or the maximum absolute value of the elements of a real, square, sparse matrix which is held in compressed column (Harwell–Boeing) format.

For full information please refer to the NAG Library document for f11ml

https://www.nag.com/numeric/nl/nagdoc_28.7/flhtml/f11/f11mlf.html

Parameters
normstr, length 1

Specifies the value to be returned in .

or

The -norm of the matrix is computed, that is .

The -norm of the matrix is computed, that is .

The value (not a norm).

nint

, the order of the matrix .

icolzpint, array-like, shape

The new column index array of sparse matrix . See the F11 Introduction.

irowixint, array-like, shape

The row index array of sparse matrix . See the F11 Introduction.

afloat, array-like, shape

The array of nonzero values in the sparse matrix .

Returns
anormfloat

The computed quantity relating the matrix.

Raises
NagValueError
(errno )

On entry, .

Constraint: .

(errno )

On entry, .

Constraint: , , or .

Notes

direct_real_gen_norm computes various quantities relating to norms of a real, sparse matrix presented in compressed column (Harwell–Boeing) format.