NAG Library Routine Document

C09DAF

1  Purpose

2  Specification

3  Description

4  References

5  Parameters

1:     $\mathrm{N}$ – INTEGERInput

On entry: the number of elements, $n$, in the data array $x$.

Constraint: this must be the same as the value N passed to the initialization routine C09AAF.

2:     $\mathrm{X}\left(\mathbf{N}\right)$ – REAL (KIND=nag_wp) arrayInput

On entry: X contains the input dataset $x_{\mathit{i}}$, for $\mathit{i}=1,2,\dots ,n$.

3:     $\mathrm{LENC}$ – INTEGERInput

On entry: the dimension of the arrays CA and CD as declared in the (sub)program from which C09DAF is called. This must be at least the number, $n_c$, of approximation coefficients, $C_a$, and detail coefficients, $C_d$, of the discrete wavelet transform as returned in NWC by the call to the initialization routine C09AAF. Note that $n_c=n$ for periodic end extension, but this is not the case for other end extension methods which will be available in future releases.

Constraint: $\mathbf{LENC}\ge n_c$, where $n_c$ is the value returned in NWC by the call to the initialization routine C09AAF.

4:     $\mathrm{CA}\left(\mathbf{LENC}\right)$ – REAL (KIND=nag_wp) arrayOutput

On exit: $\mathbf{CA}\left(i\right)$ contains the $i$th approximation coefficient, $C_a\left(\mathit{i}\right)$, for $\mathit{i}=1,2,\dots ,n_c$.

5:     $\mathrm{CD}\left(\mathbf{LENC}\right)$ – REAL (KIND=nag_wp) arrayOutput

On exit: $\mathbf{CD}\left(\mathit{i}\right)$ contains the $\mathit{i}$th detail coefficient, $C_d\left(\mathit{i}\right)$, for $\mathit{i}=1,2,\dots ,n_c$.

6:     $\mathrm{ICOMM}\left(100\right)$ – INTEGER arrayCommunication Array

On entry: contains details of the discrete wavelet transform and the problem dimension as setup in the call to the initialization routine C09AAF.

On exit: contains additional information on the computed transform.

7:     $\mathrm{IFAIL}$ – INTEGERInput/Output

On entry: IFAIL must be set to $0$, $-1\text{ or }1$. If you are unfamiliar with this parameter you should refer to Section 3.3 in the Essential Introduction 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 parameter, 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, N is inconsistent with the value passed to the initialization routine: $\mathbf{N}=〈\mathit{\text{value}}〉$, N should be $〈\mathit{\text{value}}〉$.

$\mathbf{IFAIL}=3$

On entry, array dimension LENC not large enough: $\mathbf{LENC}=〈\mathit{\text{value}}〉$ but must be at least $〈\mathit{\text{value}}〉$.

$\mathbf{IFAIL}=6$

On entry, the initialization routine C09AAF has not been called first or it has not been called with $\mathbf{WTRANS}=\text{'T'}$, or the communication array ICOMM has become corrupted.

$\mathbf{IFAIL}=-99$

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

See Section 3.8 in the Essential Introduction for further information.

$\mathbf{IFAIL}=-399$

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

See Section 3.7 in the Essential Introduction for further information.

$\mathbf{IFAIL}=-999$

Dynamic memory allocation failed.

See Section 3.6 in the Essential Introduction for further information.

7  Accuracy

8  Parallelism and Performance

9  Further Comments

10  Example

10.1  Program Text

Program Text (c09dafe.f90)

10.2  Program Data

Program Data (c09dafe.d)

10.3  Program Results

Program Results (c09dafe.r)