NAG FL Interface
c06fcf (fft_​complex_​1d_​sep)

1 Purpose

2 Specification

3 Description

4 References

5 Arguments

1: $\mathbf{x}\left(\mathbf{n}\right)$ – Real (Kind=nag_wp) array Input/Output

On entry: if x is declared with bounds $(0:\mathbf{n}-1)$ in the subroutine from which c06fcf is called, $\mathbf{x}\left(\mathit{j}\right)$ must contain $x_{\mathit{j}}$, the real part of $z_{\mathit{j}}$, for $\mathit{j}=0,1,\dots ,n-1$.

On exit: the real parts $a_k$ of the components of the discrete Fourier transform. If x is declared with bounds $(0:\mathbf{n}-1)$ in the subroutine from which c06fcf is called, for $0\le k\le n-1$, $a_k$ is contained in $\mathbf{x}\left(k\right)$.

2: $\mathbf{y}\left(\mathbf{n}\right)$ – Real (Kind=nag_wp) array Input/Output

On entry: if y is declared with bounds $(0:\mathbf{n}-1)$ in the subroutine from which c06fcf is called, $\mathbf{y}\left(\mathit{j}\right)$ must contain $y_{\mathit{j}}$, the imaginary part of $z_{\mathit{j}}$, for $\mathit{j}=0,1,\dots ,n-1$.

On exit: the imaginary parts $b_k$ of the components of the discrete Fourier transform. If y is declared with bounds $(0:\mathbf{n}-1)$ in the subroutine from which c06fcf is called, then for $0\le k\le n-1$, $b_k$ is contained in $\mathbf{y}\left(k\right)$.

3: $\mathbf{n}$ – Integer Input

On entry: $n$, the number of data values.

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

4: $\mathbf{work}\left(\mathbf{n}\right)$ – Real (Kind=nag_wp) array Workspace

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

On entry: ifail must be set to $0$, $-1$ or $1$ to set behaviour on detection of an error; these values have no effect when no error is detected.

A value of $0$ causes the printing of an error message and program execution will be halted; otherwise program execution continues. A value of $-1$ means that an error message is printed while a value of $1$ means that it is not.

If halting is not appropriate, the value $-1$ or $1$ is recommended. If message printing is undesirable, then the value $1$ is recommended. Otherwise, the value $0$ is recommended. When the value $-\mathbf{1}$ 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

$\mathbf{ifail}=3$

On entry, $\mathbf{n}=⟨\mathit{\text{value}}⟩$.
Constraint: $\mathbf{n}>1$.

$\mathbf{ifail}=-99$

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