NAG FL Interface
c06prf (fft_​complex_​1d_​multi_​row)

1 Purpose

2 Specification

3 Description

4 References

5 Arguments

1: $\mathbf{direct}$ – Character(1) Input

On entry: if the forward transform as defined in Section 3 is to be computed, direct must be set equal to 'F'.

If the backward transform is to be computed, direct must be set equal to 'B'.

Constraint: $\mathbf{direct}=\text{'F'}$ or $\text{'B'}$.

2: $\mathbf{m}$ – Integer Input

On entry: $m$, the number of sequences to be transformed.

Constraint: $\mathbf{m}\ge 1$.

3: $\mathbf{n}$ – Integer Input

On entry: $n$, the number of complex values in each sequence.

Constraint: $\mathbf{n}\ge 1$.

4: $\mathbf{x}\left(\mathbf{m}\times \mathbf{n}\right)$ – Complex (Kind=nag_wp) array Input/Output

On entry: the complex data must be stored in x as if in a two-dimensional array of dimension $\left(1:\mathbf{m},0:\mathbf{n}-1\right)$; each of the $m$ sequences is stored in a row of each array. In other words, if the elements of the $p$th sequence to be transformed are denoted by $z_{\mathit{j}}^p$, for $\mathit{j}=0,1,\dots ,n-1$, $\mathbf{x}\left(j\times \mathbf{m}+p\right)$ must contain $z_j^p$.

On exit: is overwritten by the complex transforms.

5: $\mathbf{work}\left(*\right)$ – Complex (Kind=nag_wp) array Workspace

Note: the dimension of the array work must be at least $\mathbf{m}\times \mathbf{n}+2\times \mathbf{n}+15$.

The workspace requirements as documented for c06prf may be an overestimate in some implementations.

On exit: the real part of $\mathbf{work}\left(1\right)$ contains the minimum workspace required for the current values of m and n with this implementation.

6: $\mathbf{ifail}$ – Integer Input/Output

On entry: ifail must be set to $0$, $-1\text{ or }1$. If you are unfamiliar with this argument you should refer to Section 4 in the Introduction to the NAG Library FL Interface for details.

For environments where it might be inappropriate to halt program execution when an error is detected, the value $-1\text{ or }1$ is recommended. If the output of error messages is undesirable, then the value $1$ is recommended. Otherwise, if you are not familiar with this argument, the recommended value is $0$. When the value $-\mathbf{1}\text{ or }\mathbf{1}$ is used it is essential to test the value of ifail on exit.

On exit: $\mathbf{ifail}=\mathbf{0}$ unless the routine detects an error or a warning has been flagged (see Section 6).

6 Error Indicators and Warnings

$\mathbf{ifail}=1$

On entry, $\mathbf{m}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{m}\ge 1$.

$\mathbf{ifail}=2$

On entry, $\mathbf{n}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{n}\ge 1$.

$\mathbf{ifail}=3$

On entry, $\mathbf{direct}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{direct}=\text{'F'}$ or $\text{'B'}$.

$\mathbf{ifail}=5$

An internal error has occurred in this routine. Check the routine call and any array sizes. If the call is correct then please contact NAG for assistance.

$\mathbf{ifail}=-99$

An unexpected error has been triggered by this routine. Please contact NAG.

See Section 7 in the Introduction to the NAG Library FL Interface for further information.

$\mathbf{ifail}=-399$

Your licence key may have expired or may not have been installed correctly.

See Section 8 in the Introduction to the NAG Library FL Interface for further information.

$\mathbf{ifail}=-999$

Dynamic memory allocation failed.

See Section 9 in the Introduction to the NAG Library FL Interface for further information.

7 Accuracy

8 Parallelism and Performance

9 Further Comments

10 Example

10.1 Program Text

10.2 Program Data

10.3 Program Results