NAG Library Routine Document

f06etf (daxpyi)

1

Purpose

2

Specification

3

Description

4

References

5

Arguments

1:     $\mathbf{nz}$ – IntegerInput

On entry: the number of nonzeros in the sparse vector $x$.

2:     $\mathbf{a}$ – Real (Kind=nag_wp)Input

On entry: the scalar $\alpha$.

3:     $\mathbf{x}\left(*\right)$ – Real (Kind=nag_wp) arrayInput

Note: the dimension of the array x must be at least $\max \left(1,\mathbf{nz}\right)$.

On entry: the nonzero elements of the sparse vector $x$.

4:     $\mathbf{indx}\left(*\right)$ – Integer arrayInput

Note: the dimension of the array indx must be at least $\max \left(1,\mathbf{nz}\right)$.

On entry: $\mathbf{indx}\left(\mathit{i}\right)$ must contain the index of $\mathbf{x}\left(\mathit{i}\right)$ in the sparse vector $x$, for $\mathit{i}=1,2,\dots ,\mathbf{nz}$.

Constraint: the indices must be distinct.

5:     $\mathbf{y}\left(*\right)$ – Real (Kind=nag_wp) arrayInput/Output

Note: the dimension of the array y must be at least ${\displaystyle \underset{\mathit{k}}{\max }}\left\{\mathbf{indx}\left(\mathit{k}\right)\right\}$.

On entry: the vector $y$. Only elements corresponding to indices in indx are accessed.

On exit: the updated vector $y$.

6

Error Indicators and Warnings

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Accuracy

8

Parallelism and Performance

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Further Comments

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Example