naginterfaces.library.blas.zaxpyi

naginterfaces.library.blas.zaxpyi(a, x, indx, y)

zaxpyi adds a scaled sparse complex vector to an unscaled complex vector.

For full information please refer to the NAG Library document for f06gt

https://support.nag.com/numeric/nl/nagdoc_30.2/flhtml/f06/f06gtf.html

Parameters

acomplex

The scalar $\alpha$.

xcomplex, array-like, shape $\left(\text{nz}\right)$

The compressed vector $x$. $x$ contains $x_i$ for $i\in J$.

indxint, array-like, shape $\left(\text{nz}\right)$

The indices of the elements in the compressed vector $x$.

ycomplex, array-like, shape $(max\left(indx\right))$

The vector $y$. Only elements corresponding to indices in $indx$ are accessed.

Returns

ycomplex, ndarray, shape $(max\left(indx\right))$

The updated vector $y$.

Raises

NagValueError

(errno $4$)

On entry, error in parameter $indx$.

Constraint: the indices must be distinct.

Notes

No equivalent traditional C interface for this routine exists in the NAG Library.

zaxpyi performs the operation

$$y\leftarrow \alpha x+y$$

where $x$ is a sparse complex vector stored in compressed form, and $y$ is a complex vector in full storage form.

References

Dodson, D S, Grimes, R G and Lewis, J G, 1991, Sparse extensions to the Fortran basic linear algebra subprograms, ACM Trans. Math. Software (17), 253–263