naginterfaces.library.blas.dsyr

naginterfaces.library.blas.dsyr(uplo, alpha, x, a)

dsyr computes the rank-1 update of a real symmetric matrix.

For full information please refer to the NAG Library document for f06pp

https://support.nag.com/numeric/nl/nagdoc_30/flhtml/f06/f06ppf.html

Parameters

uplostr, length 1

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

$uplo=\text{'U'}$

The upper triangular part of $A$ is stored.

$uplo=\text{'L'}$

The lower triangular part of $A$ is stored.

alphafloat

The scalar $\alpha$.

xfloat, array-like, shape $\left(n\right)$

The $n$-element vector $x$.

afloat, array-like, shape $(n,n)$

The $n\times n$ symmetric matrix $A$.

Returns

afloat, ndarray, shape $(n,n)$

The updated matrix $A$.

Raises

NagValueError

(errno $1$)

On entry, error in parameter $uplo$.

Constraint: $uplo=\text{'U'}$ or $\text{'L'}$.

(errno $2$)

On entry, error in parameter $\text{n}$.

Constraint: $n\ge 0$.

(errno $5$)

On entry, error in parameter $\text{incx}$.

Constraint: $\text{incx}\ne 0$.

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.

dsyr performs the symmetric rank-1 update operation

$$A\leftarrow \alpha x{x}^T+A\text{,}$$

where $A$ is an $n\times n$ real symmetric matrix, $x$ is an $n$-element real vector, and $\alpha$ is a real scalar.