naginterfaces.library.blas.dsbmv

naginterfaces.library.blas.dsbmv(uplo, k, alpha, a, x, beta, y=None)[source]

dsbmv computes the matrix-vector product for a real symmetric band matrix.

For full information please refer to the NAG Library document for f06pd

https://www.nag.com/numeric/nl/nagdoc_28.5/flhtml/f06/f06pdf.html

Parameters
uplostr, length 1

Specifies whether the upper or lower triangular part of is stored.

The upper triangular part of is stored.

The lower triangular part of is stored.

kint

, the number of subdiagonals or superdiagonals of the matrix .

alphafloat

The scalar .

afloat, array-like, shape

The symmetric band matrix .

xfloat, array-like, shape

The -element vector .

betafloat

The scalar .

yNone or float, array-like, shape , optional

The -element vector , if need not be set.

Returns
yfloat, ndarray, shape

The updated vector .

Raises
NagValueError
(errno )

On entry, error in parameter .

Constraint: or .

(errno )

On entry, error in parameter .

Constraint: .

(errno )

On entry, error in parameter .

Constraint: .

(errno )

On entry, error in parameter .

Constraint: .

(errno )

On entry, error in parameter .

Constraint: .

Notes

In the NAG Library the traditional C interface for this routine uses a different algorithmic base. Please contact NAG if you have any questions about compatibility.

dsbmv performs the matrix-vector operation

where is an real symmetric band matrix with subdiagonals and superdiagonals, and are -element real vectors, and and are real scalars.