NAG Library Routine Document

f06fcf (ddscl)

1

Purpose

2

Specification

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Description

4

References

5

Arguments

1:     $\mathbf{n}$ – IntegerInput

On entry: $n$, the number of elements in $d$ and $x$.

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

Note: the dimension of the array d must be at least $\max \left(1,1+\left(\mathbf{n}-1\right)\times \left|\mathbf{incd}\right|\right)$.

On entry: the vector $d$.

If $\mathbf{incd}>0$, $d_{\mathit{i}}$ must be stored in $\mathbf{d}\left(\left(\mathit{i}-1\right)\times \mathbf{incd}+1\right)$, for $\mathit{i}=1,2,\dots ,\mathbf{n}$.

If $\mathbf{incd}<0$, $d_{\mathit{i}}$ must be stored in $\mathbf{d}\left(1-\left(\mathbf{n}-\mathit{i}\right)\times \mathbf{incd}\right)$, for $\mathit{i}=1,2,\dots ,\mathbf{n}$.

3:     $\mathbf{incd}$ – IntegerInput

On entry: the increment in the subscripts of d between successive elements of $d$.

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

Note: the dimension of the array x must be at least $\max \left(1,1+\left(\mathbf{n}-1\right)\times \left|\mathbf{incx}\right|\right)$.

On entry: the array x must contain the $n$-element vector $x$.

If $\mathbf{incx}>0$, $x_{\mathit{i}}$ must be stored in $\mathbf{x}\left(1+\left(\mathit{i}-1\right)\times \mathbf{incx}\right)$, for $\mathit{i}=1,2,\dots ,\mathbf{n}$.

If $\mathbf{incx}<0$, $x_{\mathit{i}}$ must be stored in $\mathbf{x}\left(1-\left(\mathbf{n}-\mathit{i}\right)\times \mathbf{incx}\right)$, for $\mathit{i}=1,2,\dots ,\mathbf{n}$.

On exit: the updated vector $x$ stored in the array elements used to supply the original vector $x$.

Intermediate elements of x are unchanged.

5:     $\mathbf{incx}$ – IntegerInput

On entry: the increment in the subscripts of x between successive elements of $x$.

6

Error Indicators and Warnings

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Accuracy

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Parallelism and Performance

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Further Comments

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Example